- A KINETIC STUDY OF THE CLEAVAGE OF THE IRON-CARBON ? BOND IN η5-C5H5Fe(CO)2R BY HALOGENATED ACETIC ACIDS
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The rates of the reaction of η5-C5H5Fe(CO)2R (R = alkyl and aryl) with CF3CO2H to give η5-C5H5Fe(CO)2OC(O)CF3 and RH were investigated in organic solvents, mostly at 25 deg C, by infrared spectroscopic, manometric and volumetric techniques.When R = alkyl, the cleavage in CH2Cl2 is first order in η5-C5H5Fe(CO)2R and first order in the CF3CO2H monomer at acid concentrations 0.1 M, but first order in η5-C5H5Fe(CO)2R and second order in the CF3CO2H monomer at lower acid concentrations.The dependence of the second-order rate constant on R follows the order C6H5 > CH2Si(CH3)3 (>110) > CH3 (32) > n-C4H9 (15) > C2H5 (11) > CH2C(CH3)3 (6.2) > CH2CH2C6H5 (5.3) > CH(CH3)C6H5 (ca. 1.2) CH2C6H5 (1.0) > CH(CH3)2.The isotope effect, kH/kD, for the cleavage of η5-C5H5Fe(CO)2CH3 by CF3CO2H and CF3CO2D is 4.7.Solvent influence on the rate of the Fe-CH3 bond scission in CH2Cl2, CH2ClCH2Cl and C6H6 is very small.A mechanism is proposed which involves the formation of an Fe-H-OC(O)CF3 hydrogen-bridged 1/1 adduct of the reactants in a reversible step.This adduct then affords 5-C5H5Fe(CO)2(R)H> with the assistance of a second molecule of CF3CO2H.Reductive elimination of RH and coordination to iron of CF3CO2- complete the reaction.The corresponding cleavage of a given Fe-R bond by CHCl2CO2H is substantially slower than that by CF3CO2H; for the aryl complexes it follows the order R = p-C6H4CH3 > p-C6H4F > C6H5 > p-C6H4Cl, with ρ ca. -5.4.
- Luca, Nancy De,Wojcicki, Andrew
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- Reaction Studies on Heterodinuclear Alkanediyl Complexes: Some Examples of Metalloselectivity
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The reactions of some heterobimetallic alkanediyl complexes of the type with tertiary phosphines, trityl hexafluorophosphate (Ph3CPF6) and halogens were investigated.The reactions of with PPh3 were metalloselective, with the phosphine always attacking the expected metal site, which could be predicted from the reactivities of the corresponding monometallic alkyl or homodinuclear alkanediyl species.The alkanediyl chain length was found not to influence the site of nucleophilic attack.The reactions of with Ph3CPF6 gave the complexes PF6, where the β-CH unit is believed to be weakly bonded to both metal centres.The reaction of (n = 4 or 6) with the trityl salt was not metalloselective, and gave a mixture of equal amounts of n-2>Ru(CO)2(cp)>PF6 and n-2CHCH2>Ru(CO)2(cp)>PF6.In contrast, gave only W(CO)3(cp)>PF6.Metalloselectivity was observed for the reaction of with HCl, which gave cleavage of the W-C bond.In contrast, the reaction of with I2 resulted in cleavage of both metal-alkyl bonds.The reactions of with PPh3 to give Mo(CO)3(cp)> and Mo(PPh3)(CO)2(cp)> are also reported.
- Friedrich, Holger B.,Moss, John R.
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- Fe:Co/TiO2 bimetallic catalysts for the Fischer-Tropsch reaction: Part 4: A study of nitrate and carbonyl derived FT catalysts
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A series of Fe:Co bimetallic catalysts supported on TiO2 were prepared by precipitation from nitrate salts and by impregnation from metal carbonyl complexes. These Fe:Co materials were characterized by a range of techniques including BET, temperature programmed reduction (TPR) and CO chemisorption, and their Fischer-Tropsch (FT) activity was evaluated in a series of fixed bed reactors (220 °C, 10 bar, 2H2:1CO, 350 h -1, 200 h). Important observations from the study are (i) both preparation technique yield catalysts in which the Fe:Co/TiO2 has lower activity than the equivalent Co/TiO2 catalyst and (ii) selectivity patterns are similar to a Co/TiO2 catalyst but indicate the impact of Fe on the system. Methane levels produced with the precipitated catalysts are high (20 wt%) while levels for the most active carbonyl bimetallic catalysts are lower (10 wt%). The impregnated catalysts produced from metal carbonyl precursors proved to be the better long chain hydrocarbon producers and olefin producers than the precipitated catalysts produced from metal nitrate precursors.
- Duvenhage,Coville
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- Indium monohalide insertion reactions into metal-metal bonds. Crystal structure of 2>
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The reaction between InCl and affords 2>, 6a which has been characterised as a THF adduct 2>, 10, by X-ray crystallography.An additional complex, 2>-, 11, is also formed in this reaction.Similar products are reported for reactions involving (M = Cr, W).The reaction between InCl and affords 2>, 17, and >, whilst that between InI and affords 2>, 19.
- Clarkson, L. M.,Norman, N. C.,Farrugia, L. J.
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- The Carbalkoxymethyl Ligand on (η-C5H5)(CO)FeCH2CO2CH3 as a CO-Derived C2 Template for Generating C2 Organic Ligands and Molecules
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The carbalkoxymethyl ligand on Cp(CO)FeCH2CO2R (7) (R = CH3, CH2CH3) serves as a C2 template for generating other C2-coordinated ligands and organic molecules.In this study 7 is procured by acid isomerization of the alkoxyacetyl complexes Cp(CO)FeCOCH2OR (5), which are obtained by P(OCH3)3-induced CO-insertion on Cp(CO)2FeCH2OR. (Overall, the carbalkoxymethyl ligand on 7 derives from two CO groups on Cp(CO)3Fe(1+)).A mechanism for this alkoxyacetyl-carbalkoxymethyl ligand isomerization is advanced whereby protonation of 5 generates a ligated ketene intermediate that regioselectively adds alcohol and gives 7.In excess acid either 5 or 7 quantitatively releases acetic acid ester, a selective generation of this C2 organic from CO.The carbalkoxymethyl ligand on 7 is activated as a hydride acceptor by converting it to the (dialkoxycarbenio)methyl salt Cp(CO)FeCH2C(OR)2(1+) (8). (Interestingly, 8 cannot be generated from the alkoxycarbene system Cp(CO)FeC(OR)CH2OR(1+) (6).) BH4(1-) converts 8 into a mixture of η2-ethylene and η1-ethyl complexes of Cp(CO)Fe, whereas (sec-Bu)3BH(1-)Li(1+) generates the corresponding η2-ethyl vinyl ether and η1-formylethyl compounds.The conversion of these latter two into acetaldehyde is discussed.
- Crawford, Edward J.,Lambert, Carol,Menard, Kevin P.,Cutler, Alan R.
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- Two heterodinuclear NiFe-based sulfenate complexes mimicking an S-oxygenated intermediate of an O2-tolerant [NiFe]-H2ase: Synthesis, structures, and reactivity
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The synthetic modelling of the S-oxygenated intermediate of an O2-tolerant [NiFe]-H2ase has proven to be greatly challenging. Treatment of 1,4-bis(2-mercapto-2-methylpropyl)-1,4-diazacycloheptane with Ni(acac)2 gave dithiolate complex [1,4-bis(2-mercapto-
- Song, Li-Cheng,Chen, Wei,Feng, Li
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- Photoinduced Carbon Monoxide Release from Half-Sandwich Iron(II) Carbonyl Complexes by Visible Irradiation: Kinetic Analysis and Mechanistic Investigation
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Three half-sandwich iron(II) complexes, [Fe(η5-Cp)(cis-CO)2X] (X-=Cl-, Br-, I-), were synthesized and characterized. The kinetics of the CO-releasing behaviour of these complexes upon illumination by visible irradiation in various media was investigated. Our results indicated that the CO release was significantly affected by the auxiliary ligands. Of the three light sources used (blue, green, and red), blue light exhibited the highest efficiency. In the photoinduced CO release, the solvents and exogenous nucleophiles in the media were involved, which allowed their CO-releasing reaction to comply with pseudo first-order model rather than the characteristic zero-order model for a photochemical reaction. In aqueous media (D2O), an intermediate bearing the core of {FeII(cis-CO)2} involving cleavage of cyclopentadiene was detected. Despite the non-absorption of the red light, its illumination combined with nucleophilic substitution did cause considerable CO release. Assessment of the cytotoxicity of the three complexes indicated that they showed good biocompatibility.
- Jiang, Xiujuan,Chen, Limei,Wang, Xiu,Long, Li,Xiao, Zhiyin,Liu, Xiaoming
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- THE REACTIONS OF 4-n(CNMe)n> (n=0-4) COMPLEXES WITH HALOGENS AND MERCURY(II) SALTS
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Halogens, X2, and HgY2 (X=Cl, Br, I; Y=X, F, NO3, BF4) cleave the metal-metal bonds in 4-n(CNMe)n> complexes (n=0-4).Typically, e.g. when n=2, X2 electrophiles give (a) and X (b) in relative yields which depend on X, the reaction solvent and n, but HgY2 give equimolar amounts of (c) and only.Hg(CN)2 reacts more slowly than other HgY2, and does not react at all.It is suggested that the reactions which give rise to products of type (a), (b) or (c) are all two-electron oxidations which proceed by way of adducts containing μ-CA->X2 or μ-CA->HgX2 groups (CA=CO or CNMe).One of these adducts has been isolated, namely 2>*CHCl3.
- Kumar, Rajesh,Manning, A. R.,Murray, Paul T.
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- Further reactions of (MLn=Fe(η-C5H5)(CO)2, Re(CO)5) with organic electrophiles
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Reaction of FpC(S)SMLn (Fp=Fe(η-C5H5)(CO)2; MLn=Fp (1a), Re(CO)5 (1b)) with MeC(O)Cl affords Cl and LnMSC(O)Me (3); 1a reacts with (CF3CO)2O to yield CF3CO2 and FpSC(O)CF3 (5).In both cases the reactions have been shown to occur via the unstable S-acylated intermediates SMLn>+ (R=CF3, Me).Alkylation of 1a with RBr (R=Me, Et, CH2Ph, CH2CHCH2) or CF3SO2OR (R=Me, Et) followed by treatment of the stable S-alkylated derivatives + with I- provides a useful alternative method for the synthesis of a variety of FpC(S)SR.
- Busetto, L.,Bordoni, S.,Zanotti, V.
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- Probing the electron transfer mechanism of the half-sandwich iron(II)-carbonyl complexes and their catalysis on proton reduction
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The electrochemical behaviors of three half-sandwich iron(II) complexes, [CpFe(CO)2X] (Cp = cyclopentadienyl, 1: X = Cl; 2: X = Br; 3: X = I) were investigated. For the three complexes, two reduction processes at ca. ?1.3 V and ?2.0 V were observed. They are assigned to the reductions of Fe(II) → Fe(I) couple and the reduction of the dimer, [CpFe (μ-CO)(CO)]2 (Fp2), which formed via the dimerization of the neutral intermediate “CpFe(CO)2” (Fp) generated from the first reduction, respectively. Our results ruled out the possibility of two-electron reduction for the first process. Using stop-flow infrared spectroscopic technique (SFIS) allowed us to trace the rapid chemical reactions and the first-order reaction rate constants for the formations of both Fp and Fp2 were derived as 0.27 and 0.43 s?1, respectively. Both complexes 1 and Fp2 could be reduced by LiHBEt3. In the reduction, ligand exchange reaction occurred between the chloride and hydride, which was evidenced by the observation the absorption bands of [CpFe(CO)2H] (FpH). Their reduction reactions abided first-order model for the complex and the reducing agent. By assuming that equal moles of the complex and the reducing agent were used in the reduction, a rate equation was established. Again, the SFIS technique was employed to follow the reductions and linear plots were observed to give the rate constants as 14 and 18 mol?1 L s?1, respectively. The catalysis on proton reduction of the complexes was also examined. Sufficient experimental evidences in our work and the analysis of literature data suggested strongly that the catalytic species was not the neutral species Fp. Instead the anion, FpX?, was responsible for the catalysis. The poor performance in catalysis of these complexes resulted from the competing reaction coupled to the first reduction, loss of the halide upon reduction. The resultant neutral species, Fp dimerized rapidly into Fp2.
- Rong, Bingying,Zhong, Wei,Gu, Erxing,Long, Li,Song, Lijuan,Liu, Xiaoming
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- Synthesis and solvent induced halide exchange of the electron rich, half sandwich complexes [FeI(dppe)Cp] and [MoX(dppe)(η7-C 7H7)] (X = Br, Cl; Dppe = Ph2PCH 2CH2PPh2)
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Improved synthetic routes to [FeI(dppe)Cp], and [MoX(dppe) (η7-C7H7)] (X = Br, Cl) are described. [FeI(CO)2Cp] reacts with dppe in refluxing toluene to give multi-gram quantities of [FeI(dppe)Cp], 3 without the
- El-Tarhuni, Sarah,Ho, Monica,Kawser, Mohammed H.,Shi, Saiqin,Whiteley, Mark W.
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- Synthesis, characterization and reactions of the transition metal halogenoalkyl carbocation complexes [Cp(CO)2M{η2-CH2CH(CH2)nX}]PF6 (n = 1-8, 10, M = Fe; n = 3, 4 M = Ru; X = Br, I)
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The halogenoalkyl complexes [Cp(CO)2M{(CH2)nX}] (n = 3-10, 12, M = Fe; n = 5, 6, M = Ru, X = Br, I) react with Ph3CPF6 in dry CH2Cl2 to give the corresponding carbocation complex
- Changamu, Evans O.,Friedrich, Holger B.
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- Monosubstituted nitrogen donors as ligands in cyclopentadienyliron complexes: synthesis, reactivity, ligand properties, and crystal structure of SbF6
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Cationic complexes BF4, with L a monosubstituted nitrile, RCN, or a pyridine C5H4NR' have been prepared by oxidative cleavage of 2 with BF4 in the presence of an excess of L.The coordinated nitriles act as relatively weak donors and the donor strength dependence of R as observed by NMR and IR spectroscopy is in good agreement with Taft's inductive factor δ* for the uncoordinated ligand.These constants correlate roughly with the charge on the nitrogen atom of the uncoordinated RCN ligand as found by AM1 calculations.For the st ronger donor ligands C5H4NR' there is no overall dependence of their donor strength, but for systems with substituents in the same ring position there is a correlation of the δ13C CO shift of the complex with the pKa value of the uncoordinated pyridine ligand.The lability of the coordinated nitrile has been demonstrated by ligand replacement with anionic nucleophiles (X- = I and CN) or Group Vb donor ligands ER3 (E = P, R = C6H5, OCH3, OC6H5; E = As, Sb, R = C6H5) to give the related C5H5Fe(CO)2X and BF4 complexes in high yields.Related substitutions are only found with X- in the pyridine series.When L = C5H4NR' with R' = 3-4-CN or 4-N(CH3)2, a nonseparable mixture of isomeric complexes involving coordination of the pyridine-nitrogen or of the pyridine substituent R' are obtained.The observed ratio between these isomers depends on the pKa value of the uncoordinated pyridine and on the reaction conditions.
- Schumann, Hans,Speis, Martin,Bosman, W. P.,Smits, J. M. M.,Beurskens, Paul T.
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- Electrochemical Reduction Mechanism of [(η5-C5H5)Fe(dppf)(CO)]+(dppf = 1,1′-Bis(diphenylphosphino)ferrocene)
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The complex [CpFe(dppf)(CO)][B(ArF)4] [1][B(ArF)4] (Cp = cyclopentadienyl, dppf = 1,1′-bis(diphenylphosphino)ferrocene, and [B(ArF)4]- = tetrakis[3,5-bis(trifluoromethyl)phenyl]borate) was made by removal of one carbonyl ligand from the dicarbonyl complex
- Pan, Yixian,Schnierle, Marc,Auweiler, Daniel,Ringenberg, Mark R.
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- Reactions of tin(IV) halides with (n=1 or 2)
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The reactions of (I) and (II) with thin(IV) Lewis acids E=SnX4 or RSnX3 (X=Cl, Br, or I; R=alkyl, Ph, Fe(η-C5H5)(CO)2 or Fe(η-C5H5)(CO)(CNMe) proceed by way of often isolable adducts and .II but not I also forms adducts with 2SnX2>.On the basis of IR spectroscopy it is concluded that these adducts have the > structure with N->Sn bonds (L=CO or CNMe).They are more or less unstable; some break down in the solid state, some in the benzene solution, and all in acetone solution to give mono-iron complexes, in reactions which appear to be largely if not completely regiospecific.Thus when E=SnX4 the products are and where L=CO (from I) or CNMe (from II) which appear to form in ca. equal amounts and in high yields.Small amounts of + - and are also formed from I when X=Br or I, but the second do not appear to be primary products.A previously proposed mechanistic scheme is used to account for the course of these reactions.
- Donegan, Pacelli,Manning, A.R.
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- Reaction of Bidentate Isonitrile Ligands with Iron Carbonyls
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Reaction of the bidentate isonitriles CN(CH2)nNC ( n =2, 3, 4, or 6) with (cp = η-cyclopentadienyl) yields exclusively 2> derivatives which are fluxional in solution and exist in three isomeric forms (bridged-bridged, bridged-terminal, and terminal-terminal with respect to the bonding mode of the bidentate isonitrile).The proportion of the isomers containing terminally bound isonitrile increases with the length of the alkyl chain.The complexes may be protonated to yield 2>2 salts (n = 2 or 6) and may be cleaved with I2 to give and 2nNC>> (n = 2 or 6).Reaction ofCN(CH2)nNC (n = 2 or 6 with or yields exclusively 2nNC>>
- Howell, James A. S.,Rowan, Anthony J.
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- Facile conversion of (η5-C5R5)M(CO)2 - halide complexes to halomethyl, alkoxymethyl, and cyanomethyl derivatives (R = H, CH3; M = Fe, Ru; halide = Cl, Br, I)
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The CpM(CO)2-X complexes (M = Fe, Ru; X = Cl, Br; Cp = η5-C5H5, Cp* = η5-C5Me5) are completely converted to the corresponding halomethyl derivatives over a 20-30 min period when ethereal diazomethane is added dropwise in the presence of Cu powder.Product work-up involves only simple extraction of the crude product with hexane followed by recrystallization at -40 deg C.Formation of iodomethyl derivatives from iodide precursors requires considerably longer CH2N2 addition times and cannot be completely freed of the starting iodide complexes.Fortunately, iodomethyl complexes can be prepared in 80-95percent isolated yield by treating the chloromethyl or bromomethyl derivatives with NaI in acetone/Et2O.The CpFe(CO)2CH2I and Cp*Fe(CO)2CH2I complexes are the most sensitive, decomposing rapidly to polymethylene and the parent iodide complexes upon standing at room temperature.Metathetical reactions of the halomethyl complexes to give alkoxymethyl and cyanomethyl derivatives are described.
- Hubbard, John L.,McVicar, William K.
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- Oxidation of Iron Complex with NHC Ligand with Molecular Iodine
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Abstract: Complex (η5-C5H5)2Fe2(CO)4 (I) reacts with 1,3-dimethylimidazolium-2-carboxylate Me2ImCO2 to give asymmetric binuclear carbene iron complex (η5-C5H5)2Fe2(CO)3(Me2Im) (II) (Me2Im = 1,3-dimethylimidazol-2-ylidene). The oxidation of compound II with elemental iodine proceeds via two mechanisms, symmetrical and asymmetrical, to form four products: (η5-C5H5Fe(CO)2(Me2Im)I (III), (η5-C5H5)Fe(CO)2I (IV), (η5-C5H5Fe(CO)2(Me2Im)I3 (V), and ferrocene (VI). In each case, two pairs of reaction products have formed, two of which include NHC ligand: neutral iron(III) complex and ionic complex V. Optimal synthesis conditions to obtain preferably one of these complexes have been found. Geometry and transition state energy of supposed reaction mechanism have been calculated by quantum chemistry methods.
- Shapovalov,Tikhonova,Skabitskii,Kolos,Sakharov,Torubaev, Yu. V.
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p. 1418 - 1423
(2019/12/25)
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- Syntheses, structural elucidation and reactions of allylamino compounds of the type, [η5-C5R5(CO) 2Fe(NH2CH2CHCH2)]BF4
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The reaction of 3-aminoprop-1-ene (allylamine) with the etherate complexes [(η5-C5R5)(CO)2Fe(L)] + (R = H; L = Et2O; R = CH3; L = THF) have been investigated and found to give air stable allylamino complexes [(η5-C5R5)(CO)2Fe(NH 2CH2CHCH2)]+ (R = H (3) or CH 3 (4)) with the vinyl functionality pendant on the alkyl chain. These complexes have been isolated as the tetrafluoroborate salts. They undergo halogenation reactions on the pendant vinyl group to give high yields of the dihalopropylamino complexes [(η5-C5H 5)(CO)2Fe{NH2CH2CH(X)CH 2X}]+ (X = Cl (5), Br (6)) and [{η5-C 5(CH3)5}(CO)2Fe{NH 2CH2CH(Br)CH2Br}]+, (7), respectively. Complexes 3 and 4 also react with the etherate complexes [(η5-C5R5)(CO)2Fe(L)] + to yield dinuclear complexes of the type, [(η5- C5R5)(CO)2Fe(NH2CH 2CHCH2)Fe(CO)2(η5-C 5R5′)]2+ (R not necessarily equal to R′), in which the two iron moieties are in different electronic environments. The NMR and IR data of the dinuclear complexes show that the allylamine ligand bridges the two metal systems. It is coordinated to the metal on one end via the nitrogen of the amine functionality in a η1- fashion and on the other end via the vinylic functionality in a η2-fashion forming a chiral metallacyclopropane type structure. The reaction of the dinuclear salt [{(η5-C5H 5)(CO)2Fe}2(NH2CH 2CHCH2)](BF4)2 with NaI in acetone gives [(η5-C5H5)(CO)2Fe(NH 2CH2CHCH2)]I and [(η5-C 5H5)Fe(CO)2I] indicating that the iodide displaces the η2-coordinated metal center. All these compounds have been fully characterized. The molecular structures of [3][BF4], [4][BF4] and [7][BF4] have been determined by single crystal X-ray diffraction.
- M'Thiruaine, Cyprian M.,Friedrich, Holger B.,Changamu, Evans O.,Omondi, Bernard
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- The intriguing substitution behavior of CO with bidentate phosphine ligands induced by a gem-dialkyl effect
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The reaction of the complexes [FeCpX(CO)2] (X = Cl, Br, I) into either [FeCp(CO)(PP)]X or [FeCpX(PP)] (PP = a bidentate diphosphine ligand) is shown to be highly dependent of the phosphine ligand used. Diphosphine ligands that form stable chelates favor formation of the neutral complex, whereas diphosphine ligands that form less stable chelates favor formation of the cationic complex. Thus, with the use of dppdmp (= 1,3-bis(diphenylphosphino)-2, 2-dimethylpropane) the [FeCpX(PP)] complexes (X = Cl, Br, I) are selectively formed, induced by a gem-dialkyl effect. Apart from the bidentate phosphine ligand, the halide ion present in the iron complex has a significant influence on the course of the substitution reaction.
- Van Rijn, Jimmy A.,Gouré, Eric,Siegler, Maxime A.,Spek, Anthony L.,Drent, Eite,Bouwman, Elisabeth
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p. 1899 - 1903
(2011/06/19)
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- Microwave synthesis of benchmark organo-iron complexes
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Microwave-assisted reaction techniques have been applied to the formation of a variety of organo-iron species. The species synthesized include ferrocene and acetyferrocene, piano stool complexes such as CpFe(CO)2I, CpFe(PPh3)(CO)I, a
- Garringer, Sean M.,Hesse, Andrew J.,Magers, John R.,Pugh, Kristapher R.,O'Reilly, Stacy A.,Wilson, Anne M.
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p. 6841 - 6844
(2010/04/01)
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- A study of β-hydride abstraction from alkanediyl homobimetallic complexes [{Cp(CO)2Fe}2{μ-(CnH2n)}] (n = 4-10, Cp = η5-C5H5)
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The alkyl-bridged iron(II) complexes [{Cp(CO)2Fe}2{μ-(CnH2n)}] (n = 6-10, Cp = η5-C5H5) undergo both single and double hydride abstraction when reacted with one equivalent of Ph3CPF6 to give both the monocationic complexes, [{Cp(CO)2Fe}2{μ-(CnH2n-1)}]PF6, and the dicationic complexes, [{Cp(CO)2Fe}2{μ-(CnH2n-2)}](PF6)2. The ratios of monocationic to dicationic complexes decrease with the increase in the value of n. The complexes where n = 4 and 5 undergo only single hydride abstraction under similar conditions. When reacted with two equivalents of Ph3CPF6, the complexes where n = 6-10 undergo double hydride abstraction to give dicationic complexes only. In contrast, the complex where n = 5 gives equal amounts of the monocationic and the dicationic complexes, while the complex where n = 4 only gives the monocationic complex. 1H and 13C NMR data show that in the monocationic complexes one metal is σ-bonded to the carbenium ion moiety while the other is bonded in a η2-fashion forming a chiral metallacylopropane type structure. In the dicationic complexes both metals are bonded in the η2-fashion. The monocationic complexes where n = 4-6, react with methanol to give η1-alkenyl complexes[Cp(CO)2Fe(CH2)nCH{double bond, long}CH2] (n = 2-4) as the major products and σ-bonded ether products [{Cp(CO)2Fe}2{μ-(CH2)nCH(OCH3)CH2}] as the minor products. The complex where n = 8 reacted with iso-propanol to give the η1-alkenyl complex [Cp(CO)2Fe(CH2)6CH{double bond, long}CH2]. The dicationic complexes where n = 5, 8 and 9 were reacted with NaI to give the respective α, ω-dienes and [Cp(CO)2FeI].
- Changamu, Evans O.,Friedrich, Holger B.
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p. 1138 - 1149
(2007/10/03)
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- Silylene-bridged dinuclear iron complexes [Cp(OC)2Fe]2SiX2 (X = H, F, Cl, Br, I). Synthesis, molecular structure, vibrational spectroscopy, and theoretical studies
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The μ2-silylene-bridged iron complexes [Cp(OC)2Fe]2SiX2 (X = F (2), Br (4), I (5)) have been prepared from the μ2-SiH2 functional precursor [Cp(OC)2Fe]2SiH2 (1) by hydrogen/halogen exchange, using HBF4, CBr4, and CH2I2, respectively. The fluoro- and bromo-substituted derivatives 2 and 4 are converted upon UV irradiation to the carbonyl-and dihalosilylene-bridged dinuclear complexes [Cp(OC)Fe]2(μ2-CO)(μ2-SiX2) (X = F (6), Br (7)) via CO elimination. All new compounds have been characterized spectroscopically, and, in addition, the molecular structure of 2, 4, and the previously reported chloro derivative Cp(OC)2Fe]2SiCl2 (3) has been determined by single-crystal X-ray diffraction methods. For 1-5, the Fourier transform infrared and Raman spectra have been recorded and discussed, together with density functional theory calculations, which support the experimental results of the structural and vibrational analysis. The computed geometries, harmonic vibrational wavenumbers, and their corresponding Raman scattering activities are in good agreement with the experimental data. A significant dependence of the CO and Fe-Si stretching modes on the X substituents of the μ2-silylene bridge has been observed and discussed.
- Voegler, Matthias,Pavel, Ioana,Hofmann, Marco,Moigno, Damien,Nieger, Martin,Kiefer, Wolfgang,Malisch, Wolfgang
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p. 3274 - 3284
(2008/10/08)
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- The synthesis, characterization and some reactions of cationic η2-(α,ω-diene) complexes of iron
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The cationic iron η2-(α,ω-diene) complexes of the type. [(η5-C5H5)Fe(CO)2{η 2-(α,ω-diene)}]PF6, (diene = 1,3-butadiene: 1.4-pentadiene; 1.5-hexadiene; and 1.7-octadiene) were prepared by the reaction of η1-alkenyl compounds of the type [(η5C5H5)Fe(CO)2(η 1-alkenyl)] with the so-called trityl salt. (Ph3CPF6). The reactions of the η2-diene complexes with a number of nucleophiles give a range of products resulting from nucleophillic addition to the coordinated diene and/or displacement of the diene. The reaction with triethylamine results in deprotonation leading to the formation of [(η5-C5H5)Fe(CO)2(η 1-allyl)] complexes.
- Dooling, Dalene,Joorst, Genevieve,Mapolie, Selwyn F.
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p. 467 - 476
(2008/10/08)
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- Synthesis and Properties of s-Alkyl-Substituted Silanediyl-Bridged and Silanetriyl-Bridged Diiron Complexes,Cp2(CO)2Fe 2(μ-CO)[μ-Si(X)CHR2] and Cp2(CO) 2Fe2(μ-CO)[μ-Si(DMAP)CHR2]+I -(X = H, I; R = Et, Ph; DMAP = 4-(Dimethylamino)pyridine)
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Photolysis of 2 molar amounts of CpFe(CO)2SiMe3 (= FpSiMe3 1) with s-alkylsilanes R2CHSiH3 (2a: R = Et; 2b: R = Ph) produces the silylene (or silanediyl)-bridged diiron complexes Cp2(CO)2Fe2(μ-CO)[μ-Si(H)CHR2] (3a: R = Et; 3b: R = Ph) which exist mainly in cis-form. The treatment of cis-3 with an excess amount of CH2I2 stereoselectively affords the iodosilylene-bridged diiron complexes Cp2(CO)2Fe2(μ-CO)[μ-Si(I)CHR2] (4a: R = Et; 4b: R = Ph) in cis-form. The reaction of complexes 4 with 4-(dimethylamino)pyridine (=DMAP) gives the base-stabilized silylyne (or silanetriyl)-bridged diiron complexes Cp2(CO)2Fe2(μ-CO)[μ-Si(DMAP)CHR 2]+I- (5a: R = Et; 5b: R = Ph) in 35 and 43% yields, respectively. The cis-trans isomerization of complexes 3 was studied under thermal and photochemical reaction conditions. The molar ratios of the cis and trans isomers of complexes 3 in the thermal equilibrium at 50 °C were 95 : 5 (3a) and 78 : 22 (3b), respectively, and in the photostationary state at 10 °C were 80 : 20 and 30 : 70, respectively. The structures of complexes 3b and 4b have been characterized by X-ray diffraction.
- Luh, Lung-Shiang,Wen, Yuh-Sheng,Tobita, Hiromi,Ogino, Hiroshi
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p. 2193 - 2200
(2007/10/03)
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- Electrochemical activation of nucleophilic substitution in aryl and vinyl halides with [CpFe(CO)2]- anion using homogeneous redox-catalysis
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The feasibility of indirect electrochemical activation of nucleophilic substitution in several non-active aryl and vinyl halides with [CpFe(CO)2]- by means of a specially introduced mediator (a reversible redox couple A/A·-) has been demonstrated. The efficiency of different mediators for several aryl and vinyl halides as well as the corresponding σ-aryl and σ-vinyl derivatives of (η5-cyclopentadienyl)irondicarbonyl has been examined. It was shown that by carefully selecting the mediator it becomes possible to perform the electrochemically induced substitution reaction even in those cases where the substitution products are reduced irreversibly and at less cathodic potentials than the initial substrates.
- Magdesieva,Kukhareva,Shaposhnikova,Artamkina,Beletskaya,Butin
-
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- Electrochemically induced aromatic nucleophilic substitution in p-diiodobenzene with 5-C5H5)Fe(CO)2>- and 5-C5H5)W(CO)3>--anions
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The reactions of p-diiodobenzene with 5-C5H5)Fe(CO)2>- and 5-C5H5)W(CO)3>- were studied using a complex of electrochemical techniques (cyclic voltammetry, rotating ring-disk electrode and preparative scale electrolysis).For 5-C5H5)Fe(CO)2>- it was shown that aromatic nucleophilic substitution of either one or two iodine atoms in p-diiodobenzene for η5-cyclopentadienylirondicarbonyl can be performed through electrochemical activation of the aryl halide.The ratio of (η5-C5H5)Fe(CO)2C6H4I and (η5-C5H5)Fe(CO)2C6H4Fe(CO)2(η5-C5H5) was shown to depend strongly on the electrolysis conditions: electrode potential, electrolysis duration, etc.The yield of (η5-C5H5)Fe(CO)2C6H4Fe(CO)2(η5-C5H5) can be considerably increased when (η5-C5H5)Fe(CO)2C6H4I is taken as a starting compound.For 5-C5H5)W(CO)3I- the main product of the reaction with p-diiodobenzene is (η5-C5H5)W(CO)3I. Keywords: Iron; Tungsten; Electrochemistry; Bond activation
- Magdesieva, T.V.,Kukhareva, I. I.,Artamkina, G. A.,Beletskaya, I. P.,Butin, K. P.
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p. 163 - 166
(2007/10/02)
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- Acyclic Cp(CO)2Fe disubstituted η1-vinylidene-η2-acetylene isomerizations
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Acyclic, disubstituted vinylidene complexes, [Cp(CO)2Fe=C=CR1R2]+TfO-, 3a-c (a, R1, R2 = Me; b, R1 = Ph, R2 = Me; c, R1, R2 = Ph), isomerize to nonterminal η2-acetylene complexes, [Cp(CO)2Fe(η2-R1-C≡C-R 2)]+TfO-, 5a-c, in CD2Cl2 above -50°C. Carbon-13 labeling and VT 13C NMR are used to track the formation of 3 and its conversion to 5. The isomerizations are intramolecular and apparently irreversible. That of 3b to 5b involves only phenyl migration. It is suggested that Cp(CO)2Fe η2-acetylenes are favored over Cp(CO)2Fe η1-vinylidenes under these conditions by the strongly electron withdrawing COs which, relative to less π-acidic ligands, destabilize the vinylidene and stabilize the π-acetylene.
- Bly, Robert S.,Zhong, Zhandong,Kane, Cathal,Bly, Ruta K.
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p. 899 - 905
(2008/10/08)
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- Electrochemically induced aromatic nucleophilic substitution with 5-C5H5)Fe(CO)2>- and 5-C5H5)Mo(CO)3>- anions
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The reaction of low SN(Ar)-active and non-active aryl halides p-XC6H4Hal (X=CH3, H, Cl, COCH3, CN or NO2; Hal=I or Br) with 5-C5H5)Fe(CO)2>- and 5-C5H5)Mo(CO)3>- is studied using a number of ele
- Magdesieva, T. V.,Kukhareva, I. I.,Artamkina, G. A.,Butin, K. P.,Beletskaya, I. P.
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p. 213 - 222
(2007/10/02)
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- Anionic, Four-co-ordinate, Ten-electron Bismuth Complexes: Aspects of Synthesis, Structure and Bonding
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The reaction between 2> 1 and 1 equivalent of Cl afforded the ionic complex 2> 2.The (1+) salt, 2> 3, was prepared similarly.An analogous bromide derivative, 2> 4, was prepared from the reaction between 2> 5 and Br.The reaction between 2> 7 and 1 equivalent of Cl afforded the complex 2> 8; that between Cl and 7 afforded 2> 9.In tetrahydrofuran (thf) solution some degree of dissociation of (1-) is observed for 8 and 9.The bromide complexes 2> 10 and n4>2> 11 were prepared from the reactions between 2> 12 and 1 equivalent of Br and n4>Br respectively.The tungsten complexes 2> 13 and 2> 14 were similarly prepared.Spectroscopic data for the complexes > 16 and > 17 are also presented.The structures of compounds 2, 8, 9 (as a thf solvate) and 13 were determined by X-ray crystallography.The structures of all of the compounds comprise a four-co-ordinate bismuth centre bonded to two chlorine atoms and two MLn fragments.The precise co-ordination geometries, however, vary from close to an idealised equatorially-vacant trigonal bipyramid (disphenoidal), 2 and 9, with axial chlorines and equatorial metal centres, to nearly tetrahedral, 8 and 13.These results are incorporated into a general discussion of the structures found for AB4E complexes, i.e. four-co-ordinate with ten valence electrons, and some ideas are advanced on possible electronic factors which determine the particular geometry adopted.
- Clegg, William,Compton, Neville A.,Errington, R. John,Fisher, George A.,Hockless, David C. R.,et al.
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p. 3515 - 3524
(2007/10/02)
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- Synthesis and crystal structures of the isoelectronic monocyclopentadienyliron complexes (η5-C5H5)Fe(P3)(CO)(I)> and 5-C5H5)Fe(P3)(NO)(I)>BF4
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Reaction of 5-C5H5)Fe(P3>(CO)(I)> (2) with nitrosonium tetrafluorobate gave the isoelectronic nitrosyl cation 5-C5H5)Fe(P3)(NO)(I)BF4 (3).Both compounds have been characterised crystallographically in order to compare the steric and electronic demands of carbonyl and nitrosonium groups in a common ligand environment.
- King, James E.,Simpson, Stephen J.
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- Reactivity of Main-Group-transition-metal bonds IX*. The kinetics of iodination of compounds containing two or more tin-transition-metal bonds
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Rate coefficients are reported for the cleavage by halogens of tin-transition-metal bonds in compounds containing two or more such bonds.Bond reactivity with iodine is in the order Sn-Co ca.Sn-Fe above Sn-Mo ca.Sn-W above Sn-Mn.Rates of halogenation of compounds containing three tin-transition-metal bonds show that a subtle balance between steric and electronic effects determines bond reactivity.
- Chipperfield, John R.,Clark, Stephen,Webster, David E.,Yusof, Halimahton
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p. 205 - 213
(2007/10/02)
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- Photochemical halide exchange in CpFe(CO)(L)X complexes (Cp = ν5-C5H5; L = CO, PPh3; X = Br, I). Tandem photosubstitution of X- and CO
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Upon irradiation with visible light in the presence of Bu4N+Y- (Y- is a halide lighter than X-) the title complexes undergo halide exchange.In the presence of PPh3 and Bu4N+Y- tandem photosubstitution of CO by PPh3 and X- by Y- takes place in high yield.
- Zakrzewski, Janusz
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p. C23 - C26
(2007/10/02)
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- Homo- and heterobimetallic μ(η1-O:η1-O′) formate complexes (M-OCHO-M′)+PF6- [M, M' = (η5-C5H5) (CO) (NO)Re, (η5-C5H5)(CO)3W, and (η5-C5H5)(CO) ...
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Full title: Homo- and heterobimetallic μ(η1-O:η1-O′) formate complexes (M-OCHO-M′)+PF6- [M, M' = (η5-C5H5) (CO) (NO)Re, (η5-C5H5)(CO)3W, and (η5-C5H5)(CO)2Fe]: Their synthesis, solution lability, and reactivity toward hydride donors. The rhenium and tungsten η1-O formates Cp(NO)(CO)Re-OC(O)H and Cp(CO)3W-OC(O)H are available through protonolysis (HBF4-HCO2H) of their methyl complexes. These formates, in turn, afford homobimetallic ReRe and WW μ(η1-O,O′) formates M-OCHO-M+ upon reacting with the requisite organometallic Lewis acid [M-H/Ph3C+]. Analogous heterobimetallic μ-formates FpRe and FpW [Fp = Cp(CO)2Fe] also are prepared by using similar reaction chemistry. The ReRe μ-formate salt is labile in solution; its dissociative equilibrium can be intercepted with FpOC(O)H to give the mixed FpRe μ-formate. Tungsten-containing bimetallic μ-formate salts, in contrast, do not reversibly dissociate in solution. Reactions of hydride donors, including Et3BDLi, with Cp(CO)3W-OCHO-W(CO)3Cp+ give only the W formate and Cp(CO)3W-H(D); no evidence was found for hydride (deutende) adding to the carboxylate carbon of the formate bridge.
- Tso, Chung C.,Cutler, Alan R.
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p. 471 - 475
(2008/10/08)
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- Carbene formation in the reactions of LFe{(CH2)3Br}(CO)2 (L = Cp, Cp*) with I-. X-ray crystal structures of CpFeI(CO){=C(CH2)3O} and CpFeI(CO){j=CCMe2(CH2)2O}. Analysis of the carbene orientations
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The reaction of LFe{(CH2)3Br}(CO)2 (L = Cp, Cp*) with LiI affords the new carbene complexes LFeI(CO){=C(CH2)3O}, both of which have been characterized spectroscopically; the Cp species has been characterized by X-ray crystallography as well. The unusual feature of the structure of CpFeI(CO)-{=C(CH2)3O} is the presence of two conformers within the unit cell. To a first approximation these are related by a rotation about the Fe=C axis. The reasons for the presence of the two conformers are examined by molecular mechanics and Fenske-Hall type calculations. Treatment of CpFeI(CO){=C(CH2)3O} with LDA followed by MeI results in CpFeI(CO){=CCMe2(CH2)2O}, whose crystal structure has just the single conformer in the unit cell.
- Adams, Harry,Bailey, Neil A.,Grayson, Martin,Ridgway, Christopher,Smith, Arnold J.,Taylor, Paul,Winter, Mark J.,Housecraft, Catherine E.
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p. 2621 - 2628
(2008/10/08)
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- Regio- and diastereoselectivity in the rearrangement of cationic iron(II) η1-1-(1-methylcycloalkyl)methylidenes
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A series of (CO)(η5-C5H5)(L)Fe-η 1-{[-(CH2)n-]C(CH3)CH(OCH 3)} complexes [7a-d (n = 2-5, L = CO) and 8a-d or 9a-d (n = 2-5, L = P(OMe)3)], when protonated in dichloromethane at -80 to -60°C, produce (CO)(η5-C5H5)(L)Fe-η 1,-{[-(CH2)n-]C(CH3)CH)} +'s [10a-d+ (n = 2-5, L = CO) or 11a-d+ (n = 2-5, L = P(OMe)3)] whose rearrangement to iron(II) η2-olefin complex(es) has been monitored at reduced temperature by NMR. The putative Fp [10a-d (n = 2-5, L = CO)] and Fp′ [11b (n = 3, L = P(OMe)3)] alkylidenes themselves are too reactive to detect at -80°C, but the P(OMe)3-ligated (Fp′) alkylidenes 11a,c,d (n = 2, 4, 5), being less reactive, can be observed by 13C, 1H, and/or 31P NMR at -80°C. The resulting Fp′(η2-olefin) complexes in all cases are appreciably less stable thermally than their Fp counterparts. The thermally unstable η2-olefin rearrangement products are identified by reduced temperature NMR of the reaction mixtures and by decomplexation with excess tetrabutylammonium iodide followed by capillary GLPC of the resulting olefin(s) 18a-d and 19d. These iron(II) η1-alkylidene rearrangements are highly regioselective: ring enlargement is exclusive in the Fp (10a-c) and Fp′ (11a-c) cases while methyl migration is prepoderant in the Fp and Fp′ cyclohexyls [10d and 11d (n = 5), respectively]. The rearrangements of the chiral Fp′ alkylidenes 11a-d are apparently also diastereoselective, producing substantially more of one diastereomeric η2-olefin complex than of its diastereotopic epimer . The less stable of the two diastereomeric Fp′ η2-1-methylcyclobutenes [14a or 15a (n = 2) (and possibly of the others as well)] isomerizes to the more stable under the reaction conditions, thus preventing an assessment of the true kinetic diastereoselectivity of this (and presumably of all these) Fp′ alkylidene rearrangment(s). The relative rates and regiospecificities of these η1-alkylidene to η2-olefin rearrangements apparently reflect the strain-energy differences between the starting Fp or Fp′ alkylidene and the rearranged β-Fp or Fp′ carbocation as estimated by molecular mechanics (PCMODEL) with ametallic cations as models for the starting alkylidenes and rearranged olefin complexes.
- Bly, Robert S.,Wu, Ruilian,Bly, Ruta K.
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p. 936 - 943
(2008/10/08)
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- Reactions of μ(α,ω)-alkanediyl complexes of iron(II) and tungsten(II) with tertiary phosphines and halogens; a mechanistic study
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Reactions of the μ(α,ω)alkanediyl complexes with neutral donor ligands initially give the monosubstituted monoacyl complexes , which then react further to give the disubstituted diacyl complexes (where Cp=η5-C5H5; n=3-7 and L=PPh3, PPh2Me or PMe3).Similar reactions of with the ligands L give the disubstituted diacyl complexes , although these latter reactions are considerably slower.In contrast to the reactions of the diiron compounds, the reactions of the dinuclear di-tungsten compounds also give the mono- and di-substituted alkanediyl compounds and .The reactions of the alkanediyl compounds of iron with halogens causes cleavage of both iron-carbon bonds and yield and X(CH2)nX.The mechanisms of these reactions are discussed.
- Moss, John R.,Scott, Louise G.
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p. 351 - 370
(2007/10/02)
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- Steric effects associated with monosubstituted cyclopentadienyl transition-metal complexes. Synthesis and NMR spectroscopic and molecular mechanics study of [(η5-C5H4But)Fe(CO)(L)I] complexes and crystal structure determination of [(η5-C5H4But)Fe(CO)(PPh 3)I]
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The influence of the bulky cyclopentadienyl substituent tert-butyl (But) on the conformational preferences of complexes of the type [(η5-C5H4But)Fe(CO)(L)I], where L = group 15 donor ligand, was investigated. 1H NMR spectra show that the four protons, H2-H5, on the cyclopentadienyl ligand give rise to four separate resonance groups. The distance between the two outer resonances, corresponding to the two ortho ring protons, increases with increasing size of L and ring substituent (Me, But). NMR coupling and nOe spectroscopy unambiguously indicate a conformational preference where H4 (the "meta" cyclopentadienyl ring proton) and the group 15 donor ligand are close to being eclipsed. Molecular mechanics methods were applied to [(η5-C5H4But)Fe(CO)P(OMe) 3I] to obtain a preferential conformation and energy profile for rotation about the iron-cyclopentadienyl bond axis. The lowest energy conformation obtained corresponded to that deduced from NMR spectroscopy. The crystal and molecular structure of [(η5-C5H4But)Fe(CO)(PPh 3)I] was obtained. (FeC28H28OIP: space group P1; Z = 2; a = 9.231 (2), b = 10.484 (2), c = 14.082 (2) A?; α = 111.47 (2), β = 79.02 (1), γ = 93.17 (2)°; R = 0.049.) The conformation of this compound when viewed along the iron-cyclopentadienyl axis corresponds to the most favorable conformer obtained from NMR and molecular mechanics studies, with H4 close to the PPh3 ligand.
- Du Plooy, Karen E.,Marais, Charles F.,Carlton, Laurence,Hunter, Roger,Boeyens, Jan C. A.,Coville, Neil J.
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p. 3855 - 3860
(2008/10/08)
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- Coordination chemistry of group 14 metalloles. 5. Use of dicarbonyl (η5-cyclopentadienyl) (1-methyl-2,5-diphenyl-silacyclopentadien-1-yl)iron as a four-electron ligand: Chemical properties and dynamic stereochemistry of the complexes
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Chlorine is displaced in 1-chloro-1-methyl-2,5-diphenylsilole by dicarbonyl(η5-cyclopentadienyl)ferrate(I) to give a silole with a Si-Fe σ bond. Attempts to displace the carbonyl ligands to give the corresponding silaferrocene were unsuccessful. This new silole behaves as an efficient η4-ligand with transition metals, giving a new series of complexes which present an interesting reactivity. Thus the Si-Fe bond can be cleaved without decoordination of the η4-ligand, and the Co-Co bond in (CO)6(η4-silole)Co2 can be cleaved without cleavage of the Fe-Si bond. These η4-complexes are fluxional as observed for other series. The interconversion, in solution, of the two enantiomers cis-Δuu and cis-Λuu has an activation energy of ~35 kJ mol-1 and a coalescence temperature of ~ 200 K. However, contrary to other cases, the presence of diastereoisomers cannot be detected.
- Colomer, Ernest,Corriu, Robert J. P.,Lheureux, Marc
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p. 2343 - 2348
(2008/10/08)
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- Destabilizing dπ-pπ orbital interactions and the alkylation reactions of iron(II)-thiolate complexes
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For CpFe(CO)2SR (1) (R = C6H4-p-Z; Z = OMe, H, Cl, CF3, NO2) the π-type interaction between formally occupied metal d orbitals and the sulfur lone pair that is principally 3p in character has been modeled with Fenske-Hall molecular orbital calculations and experimentally investigated by gas-phase photoelectron spectroscopy. A calculation for 1 (R = H) predicts that the highest occupied molecular orbital (HOMO) is metal-sulfur antibonding and largely sulfur in character. The observed HOMO ionization energies of 1 correlate with several chemical properties, including the rate of reaction of the thiolate ligand with alkyl halides. Solvent and substituent effects on the reaction rate favor a mechanism involving nucleophilic displacement of the halide by the coordinated thiolate ligand. The nucleophilicity of the coordinated thiolate ligand of 1 is related to the metal-sulfur dπ-pπ antibonding interactions.
- Ashby, Michael T.,Enemark, John H.,Lichtenberger, Dennis L.
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p. 191 - 197
(2008/10/08)
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- Reaction of diiron μ-alkylidyne complexes with diazo compounds
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The reaction of μ-methylidyne complex [(C5H5)(CO)Fe]2(μ-CO)(μ-CH) +PF6- (1) with ethyl diazoacetate gave the ester-substituted μ-alkenyl complex [(C5H5)(CO)Fe]2(μ-CO)(μ-η 1,η2-CH=CHCO2Et)+PF 6- (2) in 86% yield. 1 also reacted with diazomethane, diazoethane, methyl 2-diazopropionate, and (trimethylsilyl)diazomethane to give similar μ-alkenyl products. μ-Alkenyl complex 2 reacted with the nucleophiles NEt4+[HFe(CO)4]- and lithium diethyl malonate to give the carbene complexes [(C5H5)(CO)Fe]2(μ-CO)(μ-CHCH 2CO2Et) (17) and [(C5H5)(CO)Fe]2(μ-CO)(μ-CHCH(CO 2Et)CH(CO2Et)2) (16). Reductive dimerization of 2 gave the tetrairon carbene complex {[(C5H5)(CO)Fe]2(μ-CO)(μ-CHCHCO 2Et)}2. (25). The structure of 25 was determined by X-ray crystallography, monoclinic space group P21/c, with unit cell constants a = 12.318 (2) A?, b = 16.443 (2) A?, c = 17.679 (2) A?, β = 105.20 (1)°, and Z = 4.
- Casey, Charles P.,Austin, Edwin A.,Rheingold, Arnold L.
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p. 2157 - 2164
(2008/10/08)
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- Oxidative syntheses of cyclopentadienyl η2-acyl complexes and stereospecific conversion to an η2-ylide complex. X-ray crystal structures of Cp(NO)(I)Mo(η2-C(O)-p-tol) and Cp(NO)(I)Mo(η2-C(O)(PMe3)-p-tol)
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Reaction of either Cp(NO)(Mo)(η2)-C(O)-p-tol)-Fe(CO)2Cp (3) (p-tol = p-tolyl) or Cp(CO)(NO)Mo=C-(OLi)R (1) with I2 gives the η2-acyl complexes Cp(NO)-(I)Mo(η2-C(O)R (4) (R = p-tol, 4-t-BuC6H4, Me). Oxidation of 4 (R = aryl) gives carboxylato complex 5, while reaction of 4 (R = p-tol) with PMe3 gives at least a 95:5 ratio of diastereomers of the ylide complex Cp(NO)(I)Mo(η2-C-(O)(PMe3)-p-tol) (6).
- Bonnesen, Peter V.,Yau, Paul K. L.,Hersh, William H.
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p. 1587 - 1590
(2008/10/08)
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- Vinylation of cyclohexanone enolates using vinyl ether-iron complexes. Diastereoselectivity of carbon-carbon bond formation
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Cationic vinyl ether-iron complexes 1, isolated as stable BF4- salts, are readily available from α-halo acetals and ketals. The olefin ligand in these complexes is unsymmetrically bound to the metal, which accounts for the relatively low barrier for rotation about the formal double bond, which is observed in these substances (15-23 kcal/mol), and for the high regioselectivity with which nucleophiles add to the activated olefinic center. The salts 1 serve as vinylating, isopropenylating, and cis-propenylating reagents with cyclohexanone enolates. Reaction of 1a with cyclohexanone enolate gave a single diastereomeric product 5. This has been converted to the lactone 10, which establishes the relative configuration of the adjacent chiral centers in 5. The relative configuration of analogous chiral centers in the major diastereomer 16a, formed by the alkylation of 3-methylcyclohexanone enolate with 1a, has been established by a single-crystal X-ray diffraction study and shown to be identical with that in 5. Complex 1a also gives a single diastereoisomeric adduct with 6-methylcyclohexanone enolate, and this has been shown by 13C NMR studies to have the same relative configuration at the newly formed chiral centers as in 5 and 16a. Alkylation of 5-methylcyclohexanone enolate with 1b leads to a mixture of isopulegone and isoisopulegone, while alkylation of the kinetic enolate derived from 3-methyl-2-cyclohexenone with this complex yields isopiperitenone.
- Chang, Tony C. T.,Coolbaugh, Thomas S.,Foxman, Bruce M.,Rosenblum, Myron,Simms,Stockman
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p. 2394 - 2404
(2008/10/08)
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- Conversion of diiron bridging alkenyl complexes to monoiron alkenyl compounds and to alkenes
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The reaction of the diiron μ-pentenyl complex [(C5H5)2(CO)2Fe 2(μ-CO)(μ-η1,η2-(E)-CH= CHCH2CH2CH3)]+PF6 - (5) with CH3CN produces the monoiron pentenyl compound (C5H5)(CO)2Fe((E)-CH=CHCH2CH 2CH3) (10) in 67% yield. Similarly, the μ-vinyl complex [(C5H5)2(CO)2Fe 2(μ-CO)-(μ-η1,η2-CH=CH 2)]+PF6- (8b) reacts with CH3CN to produce (C5H5)(CO)2FeCH=CH2 (9) in 58% yield and (C5H5)(CO)Fe(CH3CN)2 +PF6- (11) in 54% yield. The kinetics of the reactions of 5 and of 8b with CH3CN are first order in both diiron complex and CH3CN. The 100-fold larger second-order rate constant for unsubstituted μ-vinyl complex 8b relative to μ-pentenyl complex 5 can best be explained by rate-determining attack of CH3CN on the μ-alkenyl complexes. μ-Alkenyl diiron complexes 5 and 8b were also converted to monoiron alkenyl compounds 10 (56% yield) and 9 (61% yield) by treatment with NaI and CO in acetone. Complete cleavage of the μ-alkenyl group from iron was achieved by treatment with LiI, CO, and HBF4; with these conditions, 1-pentene was obtained from 5 in 72% yield and CH2=CHCH(C6H4-p-CH3)2 (20) was obtained in 48% yield from [(C5H5)2(CO)2Fe 2(μ-CO)(μ-η1,η 2-(E)-CH=CHCH(C6H4-p-CH3) 2)]+PF6- (18).
- Casey, Charles P.,Marder, Seth R.,Colborn, Robert E.,Goodson, Patricia A.
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p. 199 - 203
(2008/10/08)
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- CHEMISCHE UND SPEKTROSKOPISCHE UNTERSUCHUNGEN AN KOMPLEX-KATIONEN DES TYPS (+). EIN BEITRAG ZUR DISKUSSION DER KOORDINATIONSEIGENSCHAFTEN VON PHOSPHANCHALKOGENIDEN UND DEREN HOEHEREN HOMOLOGEN
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The cations (+) are prepared from (+) and R3EX (R = CH3, i-C3H7, t-C4H9, C6H5, N(CH3)2; E = P, As, Sb; X = S, Se).NMR data indicate the ligands to be strong donors of the ylide type R3E(+)-X(-) in the coordinated state.On the other hand, the relative donor strength E = P>Sb>As may be interpreted as a result of (XE)Π bonding.
- Kuhn, Norbert,Schumann, Hans
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p. 181 - 194
(2007/10/02)
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- ALKENYLIRON COMPLEXES. CYCLOADDITION REACTIONS OF ORGANOIRON METALLOALKADIENES
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The metalloalkadienes, 2-Fp-1,3-butadiene (5), 1-Fp-1,3-butadiene (6), and 1-Fp-3-methyl-1,3-butadiene (7) (Fp = η-C5H5(CO)2Fe) form Diels-Alder adducts with a variety of electrophilic dienophiles.Kinetic experiments have demostrated that 5 is at least 100 times more reactive toward dimethyl acetylene dicarboxylate than 2-trimethylsiloxy-1,3-butadiene. 5 and toluene sulfonyl isocyanate from an imino lactone that is thought to arise via a stepwise process involving ionic species.The synthetic utility of 5 is limited by its low decomposition point (110 deg C) and the formation of nearly equimolar quantities of the 1,3- and 1,4-positional isomers of cycloadducts derived from several asymmetric dienophiles.
- Waterman, Paul S.,Belmonte, John E.,Bauch, Thomas E.,Belmonte, Patricia A.,Giering, Warren P.
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p. 235 - 250
(2007/10/02)
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- Preparative and reaction chemistry of the bimetallic μ-formate and μ-acetate complexes [(η-C5H5)(CO)2Fe]2O 2CR+PF6-
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Unidentate η1-O Fp-O2CR and bimetallic μ-(η1-O,O′) Fp2(O2CR)+PF6- carboxylate complexes (R = H. CH3) have been synthesized and characterized [Fp = (η5-C5H5)(CO)2Fe]. Even though only a formate or acetate ligand bridges the Fp centers, these Fp2 μ-carboxylate salts do not dissociate in even polar solvents. Nucleophilic hydride donors and other nucleophiles (I-, PPh3) cleave these bimetallic salts via direct displacement at an iron center. No evidence was found, using labeling studies, for hydride addition to the μ-(η1-O,O′)-formate bridge and transience of a μ-(η1-O,O′)-methylenedioxy ligand, Fp-OCH2O-Fp.
- Tso, Chung C.,Cutler, Alan R.
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p. 1242 - 1247
(2008/10/08)
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- Mono- and dinuclear thiocarbonyl complexes of iron, including [CpFe(CO)(CS)]2, CpFe(CO)(CS)I, and CpFe(CS)2I
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The thiocarbonyl dimers, cis- and trans-[CpFe(CO)(μ-CS)]2, are prepared by reduction of CpFe(CO)2(CS)+ with NaH. The S atom of a bridging thiocarbonyl group can be alkylated with MeOSO2F or MeI to give Cp2Fe2(CO)2(CS)(CSMe)+. With HgCl2 the Cp2Fe2(CO)2(CS)(CSHgCl2) adduct is formed. The [CpFe(CO)(CS)]2 dimer is cleaved by Br2 to yield CpFe(CO)(CS)Br. Ultraviolet photolysis of [CpFe(CO)2(CS)]CF3SO3 in CH2Cl2 yields an unstable but useful intermediate, CpFe(CO)(CS)(CF3SO3), that reacts with KX (X = I, Br, Cl) to give CpFe(CO)(CS)X. With various neutral ligands L (PPh3, pyridine, MeCN), CpFe(CO)(CS)(CF3SO3) gives [CpFe(CO)(CS)(L)]CF3SO3. When photolyzed in the presence of MeCN or Me2S, [CpFe-(CO)2(CS)]PF6 is converted to [CpFe(CS)(L)2]PF6 (L = MeCN, Me2S). The CO group in CpFe(CO)(CS)I is substituted by L groups (PEt3, PPh3, AsPh3, SbPh3, P(OMe)3, P(OPh)3) to form the corresponding CpFe(CS)(L)I products. One or two MeCN groups in [CpFe(CS)(MeCN)2]PF6 are substituted by neutral ligands L to give [CpFe(CS)(L)(MeCN)]PF6 (L = P(OMe)3 P(OPh)3), [CpFe(CS)(PPh3)2]PF6, [CpFe(CS)(bpy)]PF6, and [CpFe(CS)(phen)]PF6. The reaction of [CpFe(CS)(MeCN)2]PF6 with KI gives CpFe(CS)2I, one of the few known dithiocarbonyl complexes. IR and 1H and 13C NMR spectra of the complexes are also reported.
- Angelici, Robert J.,Dunker, Jan W.
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p. 2209 - 2215
(2008/10/08)
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- Iron and molybdenum methylidene compounds (C5H5)(CO)2FeCH2+ and (C5H5)(CO)3MoCH2+PF 6- as alkylating agents toward vinyl, allyl, and acetyl ligands. Preparation and characterization of a molybdenum (methyleneoxy)ethylidene iron compound, (C ...
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Full title: Iron and molybdenum methylidene compounds (C5H5)(CO)2FeCH2+ and (C5H5)(CO)3MoCH2+PF 6- as alkylating agents toward vinyl, allyl, and acetyl ligands. Preparation and characterization of a molybdenum (methyleneoxy)ethylidene iron compound, (C5H5)(CO)(PPh3)FeC(CH3)OCH 2Mo(CO)3(C5H5)+PF 6-. The methylidene complexes Cp(CO)2Fe=CH2+ (1) and Cp(CO)3MoCH2+PF6- (2) are used as alkylating agents toward coordinated ligands. Thus, 1 adds to the uncoordinated double bonds of FpCH=CH2 and FpCH2CH=CH2 (Fp = Cp(CO)2Fe) to give the homologated Fp2 salts [FpCH2]2CH+ and Fp[CH2= CHCH2CH2Fp]+. The former salt arises from electrophilic attack of 1 on the vinylic β-carbon, followed by isomerization of the resulting alkylidene intermediate FpCH+CH2CH2Fp to the observed Fp2 β-carbonium ion salt. The acetyl complex Cp(CO)(PPh3)FeCOCH3 (4), but not FpCOCH3, also undergoes alkylation by 1. A partially characterized [(methyleneoxy)ethylidene]iron, Cp(CO)(PPh3)FeC(CH3)OCH2Fp+ (16), results that readily degrades to the μ-acetyl compound Cp(CO)(PPh3)FeC(CH3)OFp+PF6 - as the major product. Use of the more electrophilic 2 converts 4 to the fully characterized adduct Cp(CO)(PPh3)-FeC(CH3)OCH2Mp+PF 6- (5) (Mp = Cp(CO)3Mo). Reactions of nucleophiles (I-, Cl-, various hydride donors) with 5 displace the starting acetyl complex 4 and leave the corresponding molybdenum methyl complex.
- Bodnar,Cutler
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p. 1558 - 1565
(2008/10/08)
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- Transition-metal complexes of small-ring allenes: Synthesis of (η5-C5H5)Fe(CO) 2(1,2-cycloheptadiene)OSO2CF3 and -BF4-
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(η5-C5H5)Fe(CO) 2(1,2-cycloheptadiene)OSO2CF3, the first example of a M(II) complex of a seven-membered-ring allene, has been synthesized by reaction of trimethylsilyl triflate with (η5-C5H5) (CO)2Fe-(7-methoxycycloheptene) in methylene chloride at -78°C. The complex is fluxional (Ea = 13.9 kcal/ mol) and reacts with Na2CO3/ethanol to give the ethyl ether 23 of expected regiochemistry. The triflate salt of the allene complex decomposes at room temperature in the presence of triphenylmethane to give π-complexes of 1,3-cycloheptadiene and cycloheptene. The corresponding fluoroborate salt (prepared from (η5-C5H5)Fe(CO) 2(7-methoxycycloheptene) and trimethyloxonium fluoroborate) is stable to these conditions, thus implicating the triflate ion in these reactions.
- Manganiello, Frank J.,Oon, Su Min,Radcliffe, Marc D.,Jones
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p. 1069 - 1072
(2008/10/08)
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- Generation and reactions of allylidene complexes of the (η5-cyclopentadienyl)dicarbonyliron and (η5-cyclopentadienyl)(trimethyl phosphite)carbonyliron systems
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A series of four dienyliron complexes, Cp-(CO)(L)FeCH=CHC(R1)=CHR2 [L = CO or P(OCH3)3; R1 = H, R2 = CH3 or R1 = CH3, R2 = H], is prepared by acylation of [Cp(CO)2Fe]Na with the appropriate dienoyl chlorides followed by photochemical decarbonylation and, when desired, ligand exchange of carbon monoxide by trimethyl phosphite. Treatment of these complexes with strong acid at low temperature produces the corresponding cationic allylidene complexes [Cp(CO)(L)Fe= CHCH=C(R1)CH2R2]+, which have been characterized by NMR and by their reaction behavior. Included among their reactions are rearrangement to an η2-diene complex, nucleophilic addition of triphenylphosphine and of sodium methylmercaptide, and alkene cyclopropanation.
- Kuo, Gee-Hong,Helquist, Paul,Kerber, Robert C.
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p. 806 - 808
(2008/10/08)
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- Reactivity of the monodentate dithiocarbamate ligand in CpFe(CO)2(η1-SC(S)NR2)
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The most convenient route to CpFe(CO)2(η1-SC(S)NR2) (1) is the reaction between CpFe(CO)3+PF6- (2) and Na+dtc- in acetone. Chelation of 1, which proceeds in very low yield thermally, is induced by PPh3 + CS2, Mo(CO)6, or Cp2TiCl2. Reaction of 1 with NO+PF6- leads to replacement of both carbonyls in 1 by NO+ together with chelation of the dtc ligand, giving [CpFe(NO)(η2-dtc)]+PF6- (3). Transmetalation of the dtc ligand in 1 is obtained upon heating with Fe2(CO)9 or [CpMo(CO)3]2, giving the known complexes Fe(CO)2(η2-dtc)2 (4) and CpMo(CO)2(η2-dtc) (5), respectively. Reaction of 1 with KCN in methanol gives the new anionic metallacycle K+[CpFe(CO)(SC(NR2)(SCN))]- (6), which can be acylated by PhCOCl to give CpFe(CO)(SC(NR2)SCNCOPh) (7). The reaction of 1 with electrophiles gives different products depending on whether the counteranion of the electrophilic reagent is a potential ligand: the action of CH3I leads to CpFe(CO)2I and MeSC(S)NMe2 whereas that of Me3O+BF4- gives [CpFe(CO)2(η1-SC(SMe)(NMe2))] +BF4- (8). This reaction also demonstrates the nucleophilic properties of the uncoordinated sulfur atom in a monodentate dtc complex.
- Catheline, Daniel,Román E., Enrique,Astruc, Didier
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p. 4508 - 4514
(2008/10/08)
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