- Phosphido-bridged heterodinuclear complexes of CrPd, MoPd, WPd, and MnPd. X-ray crystal structures of and
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A series of phosphido-bridged heterodinuclear complexes has been prepared by the low temperature reaction of the labile chain complexes trans-2(PhCN)2> (m = Cr, Mo, W(CO)2Cp; Mn(CO)4) with 3 molar equivalents of PCy2H or PPh2H.The crystal struc
- Braunstein, Pierre,Jesus, Ernesto de,Tiripicchio, Antonio,Camellini, Marisa Tiripicchio
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- The enthalpy of insertion of sulfur into the metal-hydrogen bond. Synthetic, structural, and calorimetric study of the complexes HS-M(CO)3C5R5 [M = Cr, Mo, W; R = H, Me]
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Synthetic and calorimetric studies of the sulfhydryl complexes HS-M(CO)3C5R5 (M = Cr, R = Me; M = Mo, W, R = H, Me) are reported. The Mo and W complexes can be obtained in high yield by reaction of the hydrido complexes H-M(CO)3C5R5 with Ph3Sb=S, which readily undergoes single S atom transfer to the metal-hydrogen bond yielding the metal-sulfhydryl complex. Direct reaction between the metal hydrides and a limited amount of sulfur also yields the sulfhydryl complexes as the dominant organometallic product. At sulfur atom/metal hydride ratios higher than 1/1, additional products formulated as HSn-M(CO)3C5R5 are detected. The enthalpies of insertion of sulfur from Ph3Sb=S and S8 into the metal-hydrogen bond have been determined by solution calorimetry. The HS-M(CO)3C5R5 complexes (M= Mo, W) are readily desulfurized by PCy3 for R = H, but not for R = Me. The M-SH bond strength estimates for the complexes HS-M(CO)3C5Me5 increases in the order Cr (46) 3C5Me5 group has a pKa value at least 4 pKa units less acidic than that of H-Mo(CO)3C5Me5. The crystal structure of HS-Mo(CO)3C5Me5 is reported.
- Bauer, Andreas,Capps, Kenneth B.,Wixmerten, Bodo,Abboud, Khalil A.,Hoff, Carl D.
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- A structural study of [CpM(CO)3H] (M = Cr, Mo and W) by single-crystal X-ray diffraction and DFT calculations: Sterically crowded yet surprisingly flexible molecules
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The single-crystal X-ray structures of the complexes [CpCr(CO) 3H] 1, [CpMo(CO)3H] 2 and [CpW(CO)3H] 3 are reported. The results indicate that 1 adopts a structure close to a distorted three-legged piano stool geometry, wh
- Burchell, Richard P. L.,Sirsch, Peter,Decken, Andreas,McGrady, G. Sean
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- PHOTOINDUZIERTE UND THERMISCHE REAKTIONEN DER UEBERGANGSMETALLETHYLVERBINDUNGEN CpM(CO)3Et (Cp = η5-CYCLOPENTADIENYL; Et = ETHYL; M = Mo, W)
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In the compounds CpM(CO)3Et (M = Mo, W) the metal-ethyl ?-bond is photolabile.Upon irradiation of a solution of CpM(CO)3Et with UV light mainly 2, CpM(CO)3H, ethane, and ethylene are produced.Formation of CpM(CO)3H is indicative of a β-elimination pathway for the photoinduced degradation.In the presence of trimethylphosphane (L) UV-irradiation of a solution of CpM(CO)3Et leads to the products Cp(CO)(L)2M-M(CO)3Cp, CpM(CO)2(L)Et and CpM(CO)2(L)H, while the thermal reaction produces the propionyl complexes CpM(CO)2(L)(COEt).
- Alt, H. G.,Eichner, M. E.
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- Dimetallagermanes of molybdenum and tungsten: Synthesis, structure and reactions
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Reaction of the trichlorogermyl complexes CpM(CO)3GeCl3 3a or 3b with Li[CpM(CO)3] 2a or 2b, which were obtained from CpM(CO)3H 1a or 1b and LiBun, afforded the dimetalladichlorogermanes [CpM(CO)3]2GeCl2 4a or 4b (Cp = C5H5; a M = Mo; b M = W). Similarly, treatment of Cp*Mo(CO)3GeCl3 3c with K[Cp*Mo(CO)3] 2c yielded selectively [Cp*Mo(CO)3]2GeCl2 4c (Cp* = C5Me5). Complex 3c was obtained from Cp*Mo(CO)3H 1c in two steps. The first step involved an insertion of GeCl2 into the molybdenum-hydrogen bond of 1c to give the dichlorogermyl complex Cp*Mo(CO)3GeCl2H 5c followed by chlorination of 5c with CCl4. The dimetalladichlorogermanes 4a-4c contain two reactive sites for further functionalization, the transition-metal centers and the germanium atom. This has been demonstrated by the CO/PMe3 ligand exchange reaction of 4a to give [Cp(CO)3Mo(μ-GeCl2){trans-Mo(CO)2(PMe 3)Cp}] 6a and the substitution reaction of 4a with LiAlH4 to afford the dimetallagermane [CpMo(CO)3]2GeH2 7a. The crystal structures of 4a, 4b and 6a have been reported.
- Filippou, Alexander C.,Winter, Johannes G.,Kociok-Koehn, Gabriele,Hinz, Isolde
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- Haloalkyl complexes of the transition metals. VIII. The synthesis and properties of (X = OCH3, Cl, Br, I) and their reactivity with neutral donor ligands
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The complexes (Cp = η5-C5H5, X = Cl, Br, I) have been prepared.Their reactions with a series of tertiary phosphines, amines, SMe2 and AsPh3 in THF, CH3CN, CH2Cl2 and MeOH have been investigated.Two types of cationic products, namely the ylide complexes + and the disubstituted complexes +, were obtained, the outcome depending on the halide (X), the pKa, cone angle and concentration of the ligand (L), and the solvent used.These variables were also found to have significant influence on the reaction rates.The reactions of with L were found to be significantly slower than those of the analogous complexes with the same ligands.
- Friedrich, Holger B.,Moss, John R.
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- Reactivity of 17-electron organometallic tungsten and molybdenum radicals: A laser flash photolysis study
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Visible (460-490 nm) laser flash photolysis of [CpW(CO)3]2 or [CpMo(CO)3]2 induces homolysis of the metal-metal bond with formation of 17-electron radicals, CpM(CO)3. Radical dimerization results in quantitative recovery of the parent dimer and can be followed by the time-resolved increase in dimer absorbance. The reaction follows clean second-order kinetics, -d[CpM(CO)3]/dt = 2kc[CpM(CO)3]2; kc(W) = 6.2 × 109 and kc(Mo) = 3.9 × 109 L mol-1 s-1 in CH3CN at 23°C. The CpM(CO)3 radicals react with organic and inorganic halides and pseudohalides by an atom-transfer mechanism. In the presence of a large excess of the halide-containing substrate, the rate of loss of the radical, -d[CpM(CO)3]/dt, proceeds according to a mixed first- and second-order rate law. The pseudo-first-order rate constants for reactions with organic halides vary linearly with the concentration of the organic halide; bimolecular rate constants for CpW(CO)3 range from 3.9 × 102 L mol-1 s-1 with CH2Br2 to 1.34 × 109 L mol-1 s-1 for CBr4. The reactivity trends (RI > RBr > RCl) and (benzyl > allyl > 3° > 2° > 1° > CH3) are observed. The 7 orders of magnitude variation in bimolecular rate constants is attributed to a highly selective atom abstraction process. The range of rate constants for atom abstraction from halo- and pseudohalopentaamminecobalt(III) and halobis(dimethylglyoximato)cobalt(III) complexes is smaller (2 orders of magnitude, from 1.6 × 107 L mol-1 s-1 for NCCo(NH3)52+ to > 2 × 10- L mol-1 s-1 for BrCo(dmgH)2py), because of the upper limit imposed by diffusion. Transfer of the halogen atom from both organic and metal substrates to CpW(CO)3 was confirmed by the IR spectrum of the organometallic product, CpW(CO)3X (X = Cl, Br, or I). Dioxygen traps CpW(CO)3 with a rate constant k = 3.3 × 109 L mol-1 s-1. Light-initiated chain reactions were observed at high concentrations of RX, XCoL5nt, or O2. Hydroperoxides react with CpW(CO)3 by a radical mechanism. The reaction observed between CpW(CO)3 and (n-Bu)3SnH is not consistent with either outer-sphere electron transfer or a hydrogen atom abstraction mechanism; oxidative addition to the 17-electron radical is believed to occur in this case. The dimer [(C5H4COOCH3)W(CO)3]2 shows photoreactivity in organic solvents which is very similar to that of [CpW(CO)3]2.
- Scott, Susannah L.,Espenson, James H.,Zhu, Zuolin
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- Homogeneous pressure hydrogenation of quinolines effected by a bench-stable tungsten-based pre-catalyst
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We report on an operationally simple catalytic method for the tungsten-catalyzed hydrogenation of quinolines through the use of the easily handled and self-contained precursor [WCl(η5-Cp)(CO)3]. This half sandwich complex is indefinitely storable on the bench in simple screw-capped bottles or stoppered flasks and can, if required, be prepared on a multi-gram scale while the actual catalytic transformations were performed in the presence of a Lewis acid in order to achieve both decent substrate conversions and product yields. The described method represents a facile and atom-efficient access to a variety of 1,2,3,4-tetrahydroquinolines that circumvents the use of cost-intensive and oxygen-sensitive phosphine ligands as well as auxiliary hydride reagents.
- Heizinger, Christian,Topf, Christoph,Vielhaber, Thomas
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p. 451 - 461
(2021/11/11)
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- Acid-base interaction between transition-metal hydrides: Dihydrogen bonding and dihydrogen evolution
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Reaction of the acidic tungsten(II) hydride 2 with the nickel(II) pincer complex 1 in either THF or toluene after an initial dihydrogen bonding (DHB) interaction led to the formation of the Ni-W bimetallic species 3 (see picture). The first example of DHB between two metal hydrides with opposite polarity was analyzed by NMR and IR spectroscopy, X-ray crystallography, and DFT calculations.
- Levina, Vladislava A.,Rossin, Andrea,Belkova, Natalia V.,Chierotti, Michele R.,Epstein, Lina M.,Filippov, Oleg A.,Gobetto, Roberto,Gonsalvi, Luca,Lledos, Agusti,Shubina, Elena S.,Zanobini, Fabrizio,Peruzzini, Maurizio
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p. 1367 - 1370
(2011/04/18)
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- Reactivity of the unsaturated hydride [Mo2(η5- C5H5)2(μ-H)(μ-PCy2)(CO) 2] toward 17- and 16-electron metal carbonyl fragments: Rational synthesis of electron-deficient heterometallic clusters
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Reactions of the 30-electron hydride [Mo2Cp2(μ-H) (μ-PCy2)(CO)2] (Cp = η5-C 5H5) with the 17-electron-fragment precursors [M 2Cp2(CO)n] (M = Mo, W, n = 6; M = Ru, n = 4) or [Mn2(CO)10] lead to the 46-electron clusters [Mo 2MCp3(μ-PCy2)(μ3-CO)(CO) 4] (M = Mo, W), [Mo2RuCp3(μ-PCy 2)(μ-CO)(CO)3], and [MnMo2Cp 2(μ-PCy2)(μ-CO)2(CO)5]. The structure of the trimolybdenum cluster was confirmed by an X-ray diffraction study and displays two long (ca. 3.1 A) and one short Mo-Mo distance (2.743(1) A). The title unsaturated hydride also proved to be highly reactive toward the appropriate precursors of 16-electron fragments such as M(CO) 5 (M = Cr, Mo, W) and MnCp′(CO)2 (Cp′ = η5-C5H4CH3), then leading to the 46-electron hydride clusters [MMo2Cp2(μ3-H) (μ-PCy2)(CO)7] (M = Cr, Mo, W) and [MnMo 2Cp2Cp′(μ3-H)(μ-PCy 2)(CO)4]. The structures of the compounds having Mo 2W and Mo2Mn skeletons were also determined by X-ray diffraction methods, both of them displaying Mo-Mo distances (ca. 2.6 A) somewhat shorter than expected for double Mo=Mo bonds and Mo - M distances longer than the corresponding single-bond lengths. A similar reaction takes place with the 12-electron compound CuCl, to give the hydride [CuMo 2ClCp2(μ3-H)(μ-PCy2)(CO) 2]. In contrast, the reaction of the title hydride with [Fe 2(CO)9], a precursor of the 16-electron fragment Fe(CO)4, gives the heterodinuclear complex [FeMo(μ-PCy 2)(CO)6] (Fe - Mo = 2.931(1) A).
- Alvarez, Celedonio M.,Alvarez, M. Angeles,Garcia, M. Esther,Ramos, Alberto,Ruiz, Miguel A.,Graiff, Claudia,Tiripicchio, Antonio
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p. 321 - 331
(2008/10/09)
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- Unbridged homo and hetero dinuclear complexes of Group 6 and 8 metals: Synthesis, characterization and comparison of X-ray crystallographic data
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Several novel compounds of the type Cp/Cp*(CO)3M-M′(CO)nCp/Cp* (M = Cr, Mo, W; M′ = Ru, n = 2; M′ = Mo, n = 3; Cp = C5H5, Cp* = C5Me5) were synthesized, characterized, their structures compared and preliminary reactivity studies were carried out. The main investigations were focused on the molybdenum and ruthenium containing heterobimetallic compounds Cp(CO)3Mo-Ru(CO)2Cp (1) as well as Cp(CO)3Mo-Ru(CO)2Cp* (2) and Cp*(CO)3Mo-Ru(CO)2Cp (3), the latter two representing a 'mixed-metal mixed-ligand' type of complexes with the former (1) having identical ligands on both metal cores. For the first time comparison of properties of unbridged bimetallic complexes with molybdenum and ruthenium metal cores was elaborated. The novel Cp(CO)3Mo-Mo(CO)3Cp* (4) consists of two identical metal cores and of 'mixed' ligands. 4 was prepared by treating NaMo(CO)3Cp with Cp*Mo(CO)3Br (5) after a route for the synthesis of the latter was established. 1 reacted with halides or AlCl3, respectively, under cleavage of the metal-metal bond to form Cp(CO)nMHal (M = Mo, n = 3; M = Ru, n = 2; Hal = Br, I, Cl) but was shown to be inert towards substrates such as CO2 CO, PPh3 or CS2 under the chosen conditions. The corresponding anionic species Cp(CO)nM- were obtained when 1 was reacted with alkali metal benzophenyl ketyl.
- Straub, Thomas,Haukka, Matti,Pakkanen, Tapani A.
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p. 106 - 116
(2007/10/03)
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- Synthesis of hydridoplatinum-molybdenum (or tungsten) heterodinuclear complexes by β-hydrogen elimination of (dppe)EtPt-MCp(CO)3. Selective hydride transfer from Pt to Mo (or W)
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Hydridoplatinum-molybdenum (or tungsten) heterodinuclear complexes (dppe)HPt-MCp(CO)3 [M = Mo (1), W (2); dppe = 1,2-bis(diphenylphosphino)ethane] have been prepared by selective β-hydrogen elimination of corresponding ethylplatinum-molybdenum
- Komiya, Sanshiro,Yasuda, Toshiyuki,Fukuoka, Atsushi,Hirano, Masafumi
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- Oxidation of magnesium by tricarbonylcyclopentadienylmolybdenum(II) and tricarbonylcyclopentadienyltungsten(II) chlorides
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The main products of manesium oxidation by tricarbonylcyclopentadienylmolybdenum(II) and tricarhonylcyclopentadienyltungsten(II) chlorides in THF are the corresponding analogs of Grignard reagents and their symmetrization products. Kinetic regularities of the reactions of these molybdenum and tungsten organohalides with magnesium in THF and DMF were established, and thermodynamic parameters of adsorption of the reagents on the magnesium surface were determined.
- Piskunov,Spirina,Artemov,Maslennikov
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p. 1321 - 1324
(2007/10/03)
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- Synthesis of chloro and methyl imido cyclopentadienyl molybdenum and tungsten complexes. X-ray molecular structures of [WCp*Clme2(NtBu) ] , [MoCp*ClMe2(NtBu)] and [WCp*ClMe2(NtBu)]
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Alternative methods to prepare [MCp′Cl4], [MCp′(NtBu)] and [MCp′Cl3(NtBu)] [M = Mo, Cp′ = η-C5Me5 (Cp*); M = W, Cp′ = η5-C5H5 (Cp), η5-C5Me5 (Cp*) ] in high yields are reported. Alkylation of [MCp′Cl3(N1Bu) ] with stoichiometric amounts of LiMe or MeMgCl under appropriate conditions leads to the dimethyl [MCp′ClMe2(N1Bu)] and trimethyl [MCp′Me3NtBu)], (M = Mo, Cp′ = Cp*; M = W, Cp′ = Cp, Cp*) complexes. The 18-electron trimethyltungsten complex [WCp*Me3(NtBu)] reacts very slowly with CN(2,6-Me2C6,H3) to give the insertion product [WCp*{C(Me) = N(2,6-Me2C6H3) }Me2(NtBu)]. All of the new compounds reported were characterized by elemental analyses, IR and NMR spectroscopy and the X-ray molecular structures of [WCp*Cl3(NtBu)], [MoCp*ClMe2(NtBu)] and [WCp*ClMe2(NtBu)] have been determined by diffraction methods.
- Gomez Sal,Jimenez, Ignacio,Martin, Avelino,Pedraz, Teresa,Royo, Pascual,Selles, Alberto,Vazquez De Miguel, Amelio
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p. 270 - 278
(2008/10/08)
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- Neutralization of palladium hydroxides, [L2Pd2(R)2(μ-OH)2], by M-H acids, [CpM(CO)3H] (M = W, Mo, Cr)
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The reaction of [L2Pd2(Ph)2(μ-OH)2] (L = Ph3P, Cy3P) with an equimolar amount of [CpM-(CO)3H] (M = W, Mo, Cr) afforded the organometallic hydroxo clusters [L2Pd2(Ph)2(μ-OH)-(μ-CO) 2(μ3-CO)MCp) (1-3) in high yield. These reactions can be regarded as the neutralization of an acidic transition-metal hydride by a basic transition-metal hydroxide. The structure of the Pd2Cr cluster 3 was established by a single-crystal X-ray diffraction study. The trinuclear hydroxo clusters are stable in the solid state but slowly decompose in solution, the decomposition path being strongly dependent on the nature of M. Facile and selective decomposition of 1 (M = W) resulted in the formation of [(Ph3P)2Pd2(Ph)2(μ-OH) 2], biphenyl, and the tetranuclear Pd2W2 cluster 4. Similar tetranuclear clusters 4-8 were obtained in high yield when the palladium hydroxo dimers were neutralized with excess [CpM(CO)3H] or [Cp*W(CO)3H]. However, these reactions proceed by a different pathway involving Ph/H exchange processes, and resulted in the formation of benzene and [CpM(CO)3Ph] or [Cp*W-(CO)3Ph], respectively. Labeling experiments suggested that H atoms of the hydrido and hydroxo ligands underwent an exchange which was faster than the neutralization and the concomitant formation of the metal-metal bond. Infrared and NMR studies show that the structures of the trinuclear hydroxo clusters were more rigid than those of the tetranuclear species. Tetranuclear systems containing three different metals, Pd2WMo (9) and Pd2WCr (10), were prepared and characterized.
- Kuznetsov, Vladimir F.,Bensimon, Corinne,Facey, Glenn A.,Grushin, Vladimir V.,Alper, Howard
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- Transition-metal hydrides and carbonyl anions as ligands toward a Pt centre in rhenium-platinum triangular clusters: A qualitative order of 'thermodynamic nucleophilicity'
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Six novel mixed-metal spiked-triangle complexes [Re2Pt(μ-H)2(CO)9{X}] have been obtained. The metallo-ligands X bound to the Pt vertex are either transition-metal hydrides, such as HMn(CO)5, HRe(CO)4(PPh3), HRe(CO)3(PPh3)2, or carbonyl anions, such as [Mn(CO)5]-, [WCp(CO)3]- and [Co(CO)4]-. Two main synthetic routes have been used to prepare these complexes: (i) replacement of the labile ligand 1,5-cyclooctadiene (COD) of [Re2Pt(μ-H)2(CO)8(COD)] with CO and X; (ii) substitution of the labile 'ligand' HRe(CO)5 in [Re2Pt(μ-H)2(CO)9{HRe(CO)5}] by the ligands X. The neutral species [Re2PtMn(μ-H)3(CO)14] has been obtained by protonation of [Re2Pt(μ-H)2(CO)9{Mn(CO)5}] -. Variable temperature 1H NMR investigations showed that it exists in solution as two isomers a and b, likely differing in the location of one hydride, a having the structure [Re2Pt(μ-H)2(CO)9{HMn(CO)5}], and b the structure [Re2Pt(μ-H)3(CO)9{Mn(CO)5}]. The ligand HMn(CO)5 of a shows a high lability, being in fast exchange with free [HMn(CO)5] even at 193 K. At higher temperature interconversion between the two isomers and exchange between the hydrides bound to Pt in b is observed. The treatment of [Re2Pt(μ-H)2(CO)9{WCp(CO)3}] - with strong acids failed to give the protonated derivative. The strong nucleophile [FeCp(CO)2]- reacted with [Re2Pt(μ-H)2(CO)9{HRe(CO)5}] as a Broensted base rather than as a nucleophile, giving deprotonation instead of substitution of the labile HRe(CO)5 ligand bound to Pt. The complex [Re2Pt(μ-H)2(CO)9{HRe(CO) 4(PPh3)}] has been characterised by X-ray single crystal analysis. It crystallises in the monoclinic space group P21/c (No. 14) with a=9.229(3), b=30.700(8), c=12.915(3) A, β=98.05(2)°, V=3623(2) A3 and Z=4. A series of displacement reactions of the type [Re2Pt(μ-H)2(CO)9{X}]+X′ ? [Re2Pt(μ-H)2(CO)9(X′)] + X allowed the following qualitative order of affinity of the metallo-ligands X for the Pt atom (a scale of 'thermodynamic nucleophilicity') to be established: [Re(CO)5]- > [HRe2(CO)9]-≈[Mn(CO)5] ->[WCp(CO)3]->[Co(CO)4] -> [HRe(CO)4(PPh3)]>[HRe(CO)3(PPh 3)2]>[HRe(CO)5]>[HMn(CO) 5]>[HWCp(CO)3].
- Bergamo, Mirka,Beringhelli, Tiziana,Ciani, Gianfranco,D'Alfonso, Giuseppe,Moret, Massimo,Sironi, Angelo
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p. 291 - 303
(2008/10/08)
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- C-H cleavages in the photoreactions of [M2(η5 -C5H5)2(CO)6](M=Mo,W):Isolation and characterization of the V-shaped trinuclear clusters [M2M′ (μ-η1,η5-C5H4)(η 5-C5H5)2(CO)6](M,M′=Mo or W)
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Irradiation of toluene solutions of the complexes [M2Cp2(CO)6] (M = Mo, W; Cp = η5-C5H5) with UV-visible light at -35°C gives the new trinuclear compounds [M3(μ-η1,η5-C5H 4)Cp2(CO)6] in moderate (M = Mo) or medium (M = W) yields, along with the known complexes [MH(CO)3Cp], [W2(μ-H)2(CO)4Cp2], and [M2Cp2(CO)4]. Similar treatment of equimolar mixtures of [W2Cp2(CO)6] and [Mo2Cp2(CO)4] gives a complex mixture containing (in order of decreasing yield) the mixed-metal compounds [Mo2W(μ-η1,η5-C5H 4)Cp2(CO)6], [MoW2(μ-η1,η5-C5H 4)-Cp2(CO)6] (two isomers), and [W3(μ-η1,η5-C5H 4)Cp2(CO)6], along with [WH(CO)3Cp] as dominant hydrido species. The structure of the new trinuclear compounds has been determined by single crystal X-ray diffraction studies on those species with W3, Mo2W, and W2Mo metal cores. Crystals of the W2Mo compound were found to be an equimolar mixture of both isomers detected in solution, so that two of the three metal positions are best described as 0.5 Mo + 0.5 W. Otherwise, the three crystal structures are virtually identical. These 46 electron molecules exhibit a V-shaped metal core (angle ca. 105°) with a short (ca. 2.52 A?) and a long (ca. 3.12 A?) intermetallic separation the central position being always occupied by a tungsten atom. Each of the metal atoms involved in the short bond carries out a cyclopentadienyl group and a carbonyl ligand which bridges that bond in a linear semibridging fashion. The outer metal atom has also a terminal carbonyl group. Finally, the third metal atom bears a μ-η1,η5-cyclopentadienylidene ligand, σ-bonded to the central tungsten atom, and three terminal carbonyl groups. Variable-temperature 1H NMR spectroscopy reveals that all trinuclear compounds exhibit fluxional behavior in solution, which is thought to result from two independent rearrangements. In addition, the trimolybdenum complex undergoes a slower dynamic process which implies a proton exchange between cyclopentadienylidene and cyclopentadienyl ligands in the molecule, as suggested by 2D EXSY experiments.
- Alvarez, M. Angeles,García, M. Esther,Riera, Víctor,Ruiz, Miguel A.,Bois, Claudette,Jeannin
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p. 1324 - 1335
(2007/10/02)
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- Ionic hydrogenations of hindered olefins at low temperature. Hydride transfer reactions of transition metal hydrides
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Sterically hindered olefins can be hydrogenated at -50 °C in dichloromethane using triflic acid (CF3SO3H) and a hydride donor. Mechanistic studies indicate that these reactions proceed by hydride transfer to the carbenium ion that is formed by protonation of the olefin. Olefins that form tertiary carbenium ions upon protonation are hydrogenated in high yields (90-100%). Styrenes generally produce lower yields of hydrogenated products (50-60%). Suitable hydride donors include HSiEt3 and several transition metal carbonyl hydrides (HW(CO)3Cp, HW(CO)3Cp*, HMo-(CO)3Cp, HMn(CO)5, HRe(CO)5, and HOs(CO)2Cp*; Cp = η-C5H5, Cp* = η5-C5Me5). A characteristic that is required for transition metal hydrides to be effective is that the cationic dihydrides (or dihydrogen complexes) that result from their protonation must have sufficient acidity to transfer a proton to the olefin, as well as sufficient thermal stability to avoid significant decomposition on the time scale of the hydrogenation reaction. Metal hydrides that fail due to insufficient stability of their protonated forms include HMo(CO)2(PPh3)Cp, HMo(CO)3Cp*, and HFe(CO)2Cp*. Other hydrides that fail are those that are protonated to give dihydrides or dihydrogen complexes that are not sufficiently acidic to protonate olefins, as found for HW(CO)2(PMe3)Cp and HRu(CO)(PMe3)Cp.
- Bullock, R. Morris,Song, Jeong-Sup
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p. 8602 - 8612
(2007/10/02)
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- Chemistry of dinuclear fulvalene complexes. Dihydrides, Zwitterions, and ring-slippage complexes, derived from FvM2(CO)6 (M = Mo, W)
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Reduction of the metal - metal-bonded complex FvW2(CO)6 generated the dianion FvW2(CO)62-. An X-ray crystallographic analysis of [Et4N+]2[FvW2(CO)62- (monoclinic space group P21/c, a = 7.687(2) A, b = 13.752(4) A, c = 16.297(5) A, β = 94.80(2)°, V = 1716.8(8) A3, Z = 4) showed the dianion to contain a planar Fv ring system bonded to the two metal centers in an anti fashion. The diuanion reacted with a number of electrophiles to yield the neutral species FvW2(CO)6E2 (E = H, Me, Et, σ-C3H6. CH2Ph). The pKa values for the two consecutive deprotonations of FvW2(CO)6H2 were determined as 14.0 and 16.6 by equilibrium measurements in acetonitrile. Thermolysis and photolysis of FvW2(CO)6H2 yielded FvW2-(CO)6 and H2. Unlike Cp2W2(CO)6, FvW2(CO)6 underwent protonation at the W-W bond by HBF4·Et2O in acetonitrile. Reactions of FvW2(CO)6 and FvMo2(CO)6 with PMe3 and Me2-PCH2PMe2 (dmpm) resulted in generation of the dinuclear zwitterions FvM2(CO)5(PMe3)2 and FvM2(CO)5)(dmpm), respectively. An X-ray crystallographic analysis of FvMo2(CO)5 (orthorhombic space group P212121, a = 9.1049(8) A, b = 12.2598(14) A, c = 20.1606(18) A, V = 2250.4(7) A3, Z = 4) showed an anti coordination of the Mo(CO)3- and Mo(CO)2(dmpm)+ moieties at a planar Fv ligand. Electrophiles added at the anionic part of the zwitterions, whereas LiAlH4 effected reduction of coordinated CO to CH3 at the cationic center of FvMo2-(CO)5(PMe3)2. Excess PMe3 caused the conversion of FvMo2(CO)5(PMe3)2 and FvMo2(CO)5)-(dmpm) to Mo(CO)3(PMe3)3 along with FvMo(CO)2(PMe3)2 and FvMo(CO)2(dmpm), respectively. These reactions constitute the first ring-slippage reactions that have been observed in fulvalene metal complexes. When treated with Mo(CO)3(NCMe)3, FvMo(CO)2(PMe3)2 cleanly regenerated FvMo2(CO)5(PMe3)2.
- Tilset,Peter,Vollhardt,Boese
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p. 3146 - 3169
(2008/10/08)
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- Reactivity and structure of (η6-C6(CH3)6)Mn(CO) 2H: Stable alkylrhenium analogues
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The reactivity of Mr′H (2; Mr′ = (η6-C6(CH3)6)Mn(CO)2) with protic acids, Lewis bases, and transition-metal organometallics is reported. Reaction of 2 with triflic acid or HBF4·Et2O generates H2 and [Mr′(S)]+ (S = CH2Cl2, OEt2, CF3SO3-). Treatment of 2 with CpW(CO)3X (X = Cl, I), CpFe(CO)2X (X = Cl, I), and Mn(CO)6Br results in metathesis to give Mr′X and CpW(CO)3H, CpFe(CO)2H, and Mn(CO)5H, respectively. Reaction of 2 with [CpFe(CO)2]2 produces CpFe(CO)2H and the new complex Mr′Fe(CO)2Cp. The reaction of [Rr′CO]PF6 (Rr??? = (η6-C6(CH3)6)Re(CO)2) with (CH3)3NO and (n-Bu)4NCl results in the formation of Rr′Cl (5a). Reaction of 5a with t-BuLi produces Rr′(C(CH3)3), while reaction with K(C2H5)3BH yields Rr′C2H5. The structures of 2 and 5a, determined by single-crystal X-ray diffraction studies, are reported here. Compound 2 crystallizes in the space group Pna21 with unit cell dimensions α = 11.918(1) A?, b = 10.826(2) A?, c = 10.465(1) A?, Z = 4, V = 1350.2 A?3, R1 = 0.042, and R2 = 0.043. Compound 5a crystallizes in the space group Pbca with unit cell dimensions a = 13.689(0) A?, b = 13.573(0) A?, c = 15.298(0) A?, Z = 8, V = 2842.4 A?3, R1 = 0.085, and R2 = 0.18.
- Schlom, Peter J.,Morken, Ann M.,Eyman, Darrell P.,Baenziger, Norman C.,Schauer, Steven J.
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p. 3461 - 3467
(2008/10/08)
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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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- Rotation of coordinated acetylide ligands on the triangular surface of trinuclear heterometallic clusters
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Convenient and widely applicable synthetic routes to the trinuclear heterometallic acetylide complexes LMM′2(CO)8(C≡CR) have been developed. These routes involve the reaction of metal acetylides LM(CO)3(C≡CR) (L = Cp and Cp*; M = W and Mo; R = Ph, C5H4F, C5H4OMe, tBu, and nPr) with Os3(CO)10(NCMe)2 and with Ru3(CO)12. For the WOs2 derivatives prepared (1-3), the acetylide ligand adopts an asymmetric arrangement in which the acetylide C-C vector is coordinated to one of the W-Os bonds. For all the WRu2 derivatives (4-9), the acetylide ligand adopts both the asymmetric (with its C-C bond orthogonal to one of the W-Ru bonds) and the symmetric arrangement (with its C-C bond orthogonal to the unique Ru-Ru bond) and undergoes rapid interconversion in solution. For the MoRu2 derivatives (10, 11), the acetylide favors the asymmetric form in both solution and the solid state; however, when the substituent R and the ligand L are replaced by a bulky tert-butyl group and Cp* ligand, respectively (13), the symmetric form becomes the dominant species. The dynamic 13C NMR studies suggest that the acetylide ligand of the WOs2 derivatives is static but, in the asymmetric MoRu2 derivatives (10, 11), the acetylide is fluxional and undergoes migration from one Mo-Ru edge to the other. The preference of the site selectivity for the acetylide ligand has also been studied by variation of the transition-metal atoms (M and M′), the accessory ligand (L), and the substituent (R). The structures of the complexes CpWOs2(CO)8(C≡CPh) (1), CpWRu2(CO)8(C≡CPh) (4), and CpMoRu2(CO)8(C≡CPh) (10) have been determined by single-crystal X-ray diffraction studies. Crystal data for 1: space group P21/c; a = 8.332 (3) ?, b = 14.543 (4) ?, c = 17.819 (5) ?, β = 94.46 (3)°, Z = 4; final R = 0.068, Rw = 0.090, and GOF = 1.768. Crystal data for 4: space group P21/n; a = 12.476 (1) ?, b = 13.216 (4) ?, c = 13.395 (4) ?, β = 97.99 (2)°, Z = 4; final R = 0.029, Rw = 0.027, and GOF = 1.583. Crystal data for 10: space group P21/c; a = 12.770 (4) ?, b = 8.188 (4) ?, c = 21.313 (4) ?, β = 91.26 (2)°, Z = 4; final R = 0.030, Rw = 0.031, and GOF = 2.34.
- Hwang, Der-Kweng,Chi, Yun,Peng, Shie-Ming,Lee, Gene-Hsiang
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p. 2709 - 2718
(2008/10/08)
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- Synthesis and thermolysis of neutral metal formyl complexes of molybdenum, tungsten, manganese, and rhenium
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The possible intermediacy of catalyst-bound formyls in syngas transformations has prompted efforts to prepare and study the chemistry of transition-metal formyl complexes over more than a decade. We have used a mild borohydride in our reactions with metal carbonyl cations and have introduced some variations into the syntheses which allow, in almost all cases, for the pure formyl complex to be precipitated from solution as it is formed. The formyl complexes and their cationic precursors are shown. Seven of the formyls are new; improved procedures have been established for the other four. All but one of the compounds have been isolated.
- Gibson,Owens,Mandal,Sattich,Franco
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p. 498 - 505
(2008/10/08)
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- Tungsten iron heterobimetallic complexes: Preparation and reactions
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Organometallic cyclopentadienyl-substituted phosphines (η5-C5H4PPh2)Fe(CO) 2CH3 (3) and (η5-C5H4PPh2)W(CO) 3CH3 (4) were prepared from (η5-C5H5)M(CO)nCH3 (M = Fe, n = 2; M = W, n = 3) by lithiation of the cyclopentadienyl ring followed by reaction with chlorodiphenylphosphine. Complexes 3 and 4 were used to synthesize heterobimetallic compounds CH3(CO)2Fe(η5-C5H 4PPh2-μ) WCH3(CO)2Cp (5) and CH3(CO)3W(η5-C5H 4PPh2-μ)Fe(COCH3)(CO)Cp (8), whose X-ray structures were determined. CH3(CO)2Fe(η5-C5H 4PPh2-μ)WCl(CO)Cp (6) was also prepared by the substitution of a carbonyl ligand on Cp(CO)3WCl by 3. The reaction of 3 with [Cp(CO)3W]+BF4- gave the heterobimetallic cation [CH3-(CO)2Fe(η5-C5H 4PPh2-μ)W(CO)3Cp]+BF 4- (7). The reduction of 6 with sodium amalgam gave the heterobimetallic anion, and although this anion could be alkylated with methyl iodide to yield 5, protonation of the anion did not produce the hydride. The reaction of the heterobimetallic cation 7 with methyllithium produced CH3(CO)2Fe(η5-C5H 4PPh2-μ)W(COCH3)(CO)Cp (12). Reaction of 7 with excess sodium borohydride gave low yields of the tungsten hydride heterobimetallic complex CH3(CO)2Fe(η5-C5H 4PPh2-μ)W(H)(CO)2Cp (10).
- Stille,Smith, Charlene,Anderson,Miller
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p. 1040 - 1047
(2008/10/08)
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- Mehrfacchbindungen zwischen Hauptgruppenelementen und Uebergangsmetallen XLV. Eigenschaften und Reaktionsverhalten von Hydrogenchalkogenid-Komplexen der Metalle Chrom, Molybdaan und Wolfram
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Hydrogensulfido and hydrogenselenido complexes of general composition (η5-C5R50(CO)3M(EH) (R = H, CH3; M = Cr, Mo, W; E = S, Se) react at the EH functions by deprotonation, bimolecular elimination of H2E or by loss of the chalcogen atoms E.Reac
- Fischer, Roland A.,Herrmann, Wolfgang A.
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p. 377 - 388
(2007/10/02)
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- Stepwise synthesis of heteronuclear Pt2M and PdPtM clusters (M = Cr, Mo, W)
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The dinuclear complex (μ-C5H5)(μ-2-MeC3H4)Pt 2(P-i-Pr3)2 (1), which is prepared from (η5-C5H5)Pt-(η3-2-MeC 3H4) and Pt(P-i-Pr3)2, reacts with Me3SiBr to produce the structurally related compound (μ-2-MeC3H4)(μ-Br)Pt2(P-i-Pr 3)2 (4). Reaction of 4 with [(C5H5)M(CO)3]Na (M = Mo, W) leads to displacement of the bridging bromide by the tricarbonyl(cyclopentadienyl)metal anion and formation of the trinuclear clusters (C5H5)(2-MeC3H4)(CO) 3(P-i-Pr3)2Pt2M (5, 6). The analogous mixed-metal PdPtM complexes 9-11 are similarly prepared, starting from (μ-C5H5)(μ-2-MeC3H 4)PdPt(P-i-Pr3)2 (7) via (μ-2-MeC3H4)(μ-Br)-PdPt(P-i-Pr3) 2 (8) as the intermediate that subsequently reacts with [(C5H5)M(CO)3]Na (M = Cr, Mo, W) to form (C5H5)(2-MeC3H4)(CO) 3(P-i-Pr3)2PdPtM (9-11). The IR and 1H, 13C, and 31P NMR spectroscopic data of 5, 6, and 9-11 confirm that the new heteronuclear clusters contain a tetrahedral Pt2MC or PdPtMC framework, the carbon atom of which belongs to a triply bridging CO group.
- Thometzek, Peter,Werner, Helmut
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p. 1169 - 1172
(2008/10/08)
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- Photochemical Reduction of CpW(CO)3CH3 (Cp = η5-C5H5) to CpW(CO)3(1-); An Isolobal Analogy to the Disproportionation of Cp2Mo2(CO)6
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Irradiation (λ > 380 nm) of CpW(CO)3Me in inert solvents in the presence of PPh3 gives as well as the substitution product CpW(CO)2(PPh3)Me (Φ disappearance CpW(CO)3Me = 0.45 +/- 0.005, Φ apparance CpW(CO)3(1-) = 0.04 +/- 0.01).The mechanism of CpW(CO)3(1-) formation was studied.Experiments suggest that CpW(CO)2(PPh3)Me may be an intermediate in the reaction but direct reductive elimination of PPh3Me(1+) from this species or from CpW(CO)(PPh3)2Me was ruled out.Experiments using PTol3 demonstrated that PAr3Me(1+) (Ar = aryl) is formed from exogenous, not coordinated, phosphine.The mechanism proposed for the reduction of CpW(CO)3Me involves the intermediate formation of phosphoranyl radicals, .PPh3Me, formed by addition of Me radicals (from W-CH3 homolysis) to PPh3.Phosphoranyl reduction of a variety of metal species which are present in solution is shown to lead to CpW(CO)3(1-).The proposed mechanism is isolobal with a mechanism we proposed for the photochemical disproportionation of metal-metal bonded dimers (e.g., Cp2Mo2(CO)6) involving 19-valence-electron intermediates.
- Goldman, Alan S.,Tyler, David R.
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- Formation of tungsten-triosmium clusters. Crystal structure and reactivity of (η5-C5H5)WOs3(CO) 12(μ3-CC6H4CH 3)(μ-H)2
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Previous studies have identified three mixed-metal clusters (1-3) as the major products from the reaction of CpW(CO)2(CTol) (Cp = η5-C5H5; Tol = p-C6H4CH3) and H2Os3(CO)10. A fourth, minor, product has been isolated and identified spectroscopically as CpWOs3(CO)12(μ3-CTol)(μ-H)2 (4). Complex 4 crystallizes in the centrosymmetric monoclinic space group P21/n with a = 12.531 (3) A?, b = 11.007 (2) A?, c = 21.733 (4) A?, β = 105.78(2)°, V = 2884.6 (11) A?3, and Z = 4. Diffraction data (Mo Kα, 2θ = 4-45°) were collected on a Syntex P21 automated diffractometer, and the structure was refined to RF = 6.2% for 3014 data with |Fo| > 3.0σ(|Fo|). The molecule contains a triangular triosmium core (Os(1)-Os(2) = 2.912 (1) A?, Os(2)-Os(3) = 2.875 (1) A?, Os(3)-Os(1) = 2.835 (1) A?) in which the two longer distances are believed to be associated with bridging hydride ligands; in addition, the triosmium system is capped by an asymmetrically triply bridging μ3-CTol ligand (Os(1)-C(06) = 2.184 (20) A?, Os(2)-C(06) = 2.051 (19) A?, Os(3)-C(06) = 2.025 (20) A?) and Os(1) is linked to a pendant CpW(CO)3 fragment (Os(1)-W = 3.097 (1) A?). In refluxing toluene complex 4 eliminates CpW(CO)3H and reacts with H2 or CO to form H3Os3(CO)9(μ3-CTol) (5) or HOs3(CO)10(μ3-CTol) (6), respectively. The related reaction of 4 with CpW(CO)2(CTol) provides CpWOs3(CO)10(μ3-CTol)2H (3), which implicates 4 as an intermediate in the previous synthesis of 3. The reaction of CpW(CO)2(CTol) with D2Os3(CO)10 leads to a partially modified product distribution that strongly favors the acyl complex (1-d2) at the expense of deuterated 3 + 4. This is interpreted in terms of linked pathways for forming 1 and 4 but a separate pathway for forming 2.
- Chi, Yun,Shapley, John R.,Churchill, Melvyn Rowen,Li, Yong-Ji
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p. 4165 - 4170
(2008/10/08)
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- DARSTELLUNG UND CHARAKTERISIERUNG VON METALLACYCLISCHEN ALKENYLKETONKOMPLEXEN DES CHROMS, MOLYBDAENS UND WOLFRAMS. MOLEKUELSTRUKTUR VON
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The photoinduced reaction of η5-ArM(CO)3R complexes (η5-Ar = C5H5, C5H4Me,C5Me5, C9H7; M = Cr, Mo, W; R = Me, Et, nPr, nBu) with symmetrical and asymmetrical alkynes, R1CCR2 (R1/su
- Alt, Helmut G.,Engelhardt, Heidi E.,Thewalt, Ulf,Riede, Juergen
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p. 165 - 178
(2007/10/02)
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- DARSTELLUNG UND CHARAKTERISIERUNG DER WOLFRAM-ACETYLENKOMPLEXE η5-ArW(CO)(R1C2R2)R UND η5-ArW(CO)(R1C2R2)COR (Ar = C5H5, C5H4Me, C5Me5; R1, R2 = H, Me, Ph; R = Me, Et, nPr, nBu, Ph)
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The photoinduced reaction of the complexes η-ArW(CO)3R (I) (Ar = C5H5, C5H4Me, C5Me5; R = Me, Et nPr, nBu, Ph) with symmetrical or asymmetrical acetylenes R1C2R2 (R1, R2 = H, Me, Ph) in pentane solution at -30 deg C yields primarily the acetylene acyl complexes η5-ArW(CO)(R1C2R2)COR (II).Upon warming, complexes II undergo dismutation to form the acetylene alkyl complexes η5-ArW(CO)(R1C2R2)R (III) and the metallacyclic alkenylketone complexes (IV).The alkyl complexes III add two-electron ligands, such as carbon monoxide, phosphanes and phosphites, even at -100 deg C to give acyl derivatives of the type II.The alkyne complexes II and III represent 18-electron species with the acetylene acting as a four-electron ligand; therefore the alkyl ligands containing hydrogen in the β-position with respect to the metal are surprisingly stable towards photoinduced β-hydrogen elimination.The acyl ligands in II show carbene-like properties giving rise to a zwitterionic character in these compounds.
- Alt, Helmut G.
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p. 149 - 164
(2007/10/02)
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- Photochemistry of Alkyltricarbonyl(η5-cyclopentadienyl)tungsten (alkyl = Et, Prn, Pri, Bun, or CH2Ph), Tricarbonyl(η5-cyclopentadienyl)(phenyl)tungsten, Tricarbonyl(η5-pentamethylcyclopentadienyl)(n-propyl)tungsten, and Tricarbonyl(η5-cyclopentadienyl)(ethyl)-...
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The photoreaction of 5-C5R'5)> complexes (M = Mo,or W; R = Et, Prn, Pri, Bun, Ph, or CH2Ph; R'= H or Me) have been studied in solution (-30 to 20 deg C) and in gas matrices (12-30 K).In alkane solutions in the absence of ligands the alkyl complexes that contain β-hydrogens initially undergo β-photoelimination at -30 deg C to give 5-C5R'5)> complexes of which only the trans isomers colud be detected, isolated, and characterised (i.r., n.m.r., and mass spectra).Intramolecular rotation of the olefin ligands about the tungsten-olefin bond axis was observed by low-temperature (-80 deg C) n.m.r. spectroscopy; asymetric olefins gave rotamers in different proportions.Prolonged photolysis of 5-C5R'5)> complexes in alkane solutions gave 5-C5R'5)> complexes and ultimately 5-C5R'5)>2>.The dimer 5-C5H5)>2> was the only metal-containing photoproduct when 5-C5H5)> was photolysed alone in pentane at -30 deg C, while for 5-C5H5)> the major photoproduct was 3-CH2Ph)(η5-C5H5)>.In the presence of C2H4, the phenyl and benzyl complexes gave the new monosubstitution products 5-C5H5)> (R = Ph or CH2Ph) whereas the alkyl complexes all gave 5-C5R'5)> as the main metal-containing product.In CH4 and CO gas matrices at 12 K the primary photolysis step was shown to be photo-ejection of a CO ligand and the formation of the 16-electron species 5-C5R'5)> (R = alkyl or aryl).The identity of the co-ordinatively unsaturated species was confirmed by (13)CO-labelling in 5-C5H5)> and fitting the terminal CO stretching bands using an energy-factored force-field program.For the alkyl complexes with β-hydrogens, thermal and photochemical reactions led to the conversion of 5-C5R'5)> species into the olefin-hydride complexes 5-C5R'5)>.Gas matrix studies for the W complexes at 12 K showed the presence of both cis and trans isomers together with intramolecular cis trans isomerisation whereas in a previous paraffin-wax disc study of 5-C5R'5)> complexes (M = Mo or W; R = Et or n-C5H11; R'= H or Me) at 77 K only trans isomers were observed.Photolysis of the benzyl complex, 5-C5H5)>, led to the formation of the η3-bonded benzyl complex, 3-CH2Ph)(η5-C5H5)> in CH4, Ar, and CO matrices.The olefin-hydride species with asymmetric olefins, 5-C5H5)>, were found to be formed and to exist as rotamers in gas matrices at 12 K.Prolonged photolysis of the alkyl complexes resulted in the formation of 5-C5R'5)> complexes.In the presence of ligands L (L = C2H4 or N2) the 16-electron intermediate 5-C5H5)> gave addition products 5-C5H5)> at 12 k but no such products were observed for 5-C5H5)>.The combination of solution and matrix isolation studies established that the primary photolysis ...
- Mahmoud, Khalil A.,Rest, Anthony J.,Alt, Helmut G.,Eichner, Manfred E.,Jansen, Brigitte M.
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p. 175 - 186
(2007/10/02)
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- Comparative Photochemistry of Tricarbonyl(η5-cyclopentadienyl)methyl- and -ethyl-molybdenum and -tungsten in Poly(vinyl chloride) Film Matrices at 12-298 K
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The photoreactions of 5-C5H5)(CO)3(CH3)> and 5-C5H5)(CO)3(C2H5)> complexes (M = Mo or W) in poly(vinyl chloride) (pvc) film matrices over a wide temperature range have been monitored using i.r. spectroscopy.At 298 K the methyl complexes dealkylate on irradiation (λ > 300 nm) to form 5-C5H5)(CO)3Cl>, 5-C5H5)(CO)3H>, and 5-C5H5)2(CO)6>.Photolysis at 12 K leads primarily to the formation of 5-C5H5)(CO)2(CH3)>.In the case of molybdenum, M-CH3 bond cleavage also occurs at 12 K and the complexes 5-C5H5)(CO)3Cl> and 5-C5H5)(CO)3H> are generated on warming the matrices.Photolysis of 5-C5H5)(CO)3(C2H5)> at 12 K proceeds with the formation of 5-C5H5)(CO)2(C2H5)> which rearranges photochemically or thermally to form trans-5-C5H5)(CO)2(C2H4)H>.The cis-ethylene-hydride complex is also observed for tungsten at temperatures below ca. 50 K.At 298 K, photolysis of 5-C5H5)(CO)3(C2H5)> leads directly to trans-5-C5H5)(CO)2(C2H4)H> which reacts further to form 5-C5H5)(CO)3H>, 5-C5H5)(C0)2(C2H4)Cl>, 5-C5H5)(CO)3Cl>, and 5-C5H5)2(CO)6>.However, on photolysis of 5-C5H5)(CO)3(C2H5)> at 298 K the main product observed is with trace amounts of 5-C5H5)(CO)3H>, 5-C5H5)(CO)3Cl>, and 5-C5H5)2(CO)6>.
- Hooker, Richard H.,Rest, Antony J.
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p. 761 - 770
(2007/10/02)
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- Stereochemical studies on thermal and photochemical reactions of η5-C5H5W(CO)3(phenethyl) containing deuterium-labeled phenethyl ligands
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Reaction of erythro-C6H5CHDCHDOS(O)2C6H 4CH3-p with Na[η5-C5H5W(CO)3] proceeds with inversion of configuration at α-carbon to yield η5-C5H5W(CO)3CHDCHDC 6H5-threo in ≥95% diastereomeric purity. This product reacts with liquid SO2 at room temperature to give η5-C5H5W(CO)3S(O) 2CHDCHDC6H5-erythro and with 2 equiv of I2 in CHCl3 to afford threo-C6H5CHDCHDI and η5-C5H5W(CO)2I3. Iodine cleavage of η5-C5H5W(CO)3CD 2CH2C6H5 yields isomerically pure C6H5CH2CD2I. These cleavage results are rationalized by electrophilic addition of I+ to tungsten, reductive elimination of phenethyl iodide, and coordination of I-, followed by oxidation of the resultant η5-C5H5W(CO)3I to η5-C5H5W(CO)2I3 with a second equivalent of I2. Photolysis of η5-C5H5W(CO)3CH 2CH2C6H5 in cyclohexane under argon or CO with 350-nm lamps affords η5-C5H5W(CO)2(η 3-CH(CH3)C6H5), which was isolated and characterized by 1H and 13C NMR and IR spectroscopy and mass spectrometry. It appears to be nonfluxional at temperatures up to 117°C in toluene-d8 by 1H NMR spectroscopy. The same product obtains on irradiation of η5-C5H5W(CO)3H and excess styrene and of η5-C5H5W(CO)3CH(CH 3)C6H5. Photolysis of η5-C5H5W(CO)3CHDCHDC 6H5-threo in cyclohexane solution does not change its diastereomeric purity. This result is interpreted by the absence of any significant photochemically induced W-C σ bond homolysis. Irradiation of η5-C5H5W-(CO)3CD 2CH2C6H5 leads to no observable H-D scrambling in unreacted tungsten-phenethyl complex. The η3-methylbenzyl complex η5-C5H5W(CO)2(η 3-CH1-yDy(CH3-xDx)C 6H5), isolated from photolysis of each of η5-C5H5W(CO)3CHDCHDC 6H5 and η5-C5H5W(CO)3CD 2CH2C6H5 in cyclohexane, shows essentially statistical distribution of 1H between the (CH3-xD1-y) (CH1-yDy) positions. These results are rationalized by rapid isomerization via hydrogen (or deuterium) shifts of photogenerated 16-electron η5-C5H5W-(CO)2CH 2-xDxCH2-yC6H5 to η5-C5H5W(CO)2CH 1-yDy(CH3-xDx)C6H 5, followed by collapse of the latter to η5-C5H5W(CO)2(η 3-CH1-yDy(CH3-xDx)C 6H5). β-Hydrogen (or -deuterium) transfer in η5-C5H5W(CO)2-(phenethyl) to give η5-C5H5W(CO)2(H or D) (styrene) appears to be much faster than CO capture to yield η5-C5H5W(CO)3(phenethyl), even under 1 atm of CO.
- Su, Shiu-Chin H.,Wojcicki, Andrew
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p. 1296 - 1301
(2008/10/08)
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- GEZIELTE SYNTHESE DREIKERNIGER HETEROMETALL-CLUSTER MIT VIER VERSCHIEDENEN GERUESTATOMEN
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The trinuclear heterometallic cluster Va-Vc possessing a tetrahedral framework of four different atoms (MPdPtC) have been prepared from (μ-2-MeC3H4)(μ-Br)PdPt(PPr3i)2 (IV) and Na (M = Cr, M, W).Complex IV is obtained from (μ-2-MeC3H4)(μ-C5H5)PdPt(PPr3i)2 and Me3SiBr by bridge-ligand exchange.Following the same concept, the synthesis of the Pt2Mo and Pt2W heterometallic clusters VIIIa, VIIIb has also been achieved.
- Thometzek, P.,Werner, H.
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p. C29 - C34
(2007/10/02)
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- THE REACTION OF FORMYL FLUORIDE WITH TRANSITION METAL COMPLEXES
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Formyl fluoride reacts with metal carbonyl anions in a manner similar to acetic formic anhydride.Although formyl complexes may have been formed as unstable intermediates, no neutral formyl complexes could be isolated but rather the expected decomposition products, the metal carbonyl hydrides or dimers, were produced.The attempted oxidative addition of formyl fluoride to various coordinately unsaturated metal complexes also did not result in the formation of formyl derivatives.HF adducts were obtained from the reaction of Ir(CO)Cl(PR3)2 or M(PPh3)4 (M=Pt or Pd) with formyl fluoride whereas Ru(NO)Cl(PPh3)2 and Rh(PPh3)3Cl give the CO complexes Ru(NO)(CO)Cl(PPh3)2 and Rh(CO)Cl(PPh3)2, respectively.
- Doyle, Gerald
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p. 355 - 362
(2007/10/02)
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- Transition Metal Substituted Phosphanes, Arsanes, and Stibanes, XXIII. Stable Transition Metal Dimethylarsanes Bearing a Tricarbonyl(cyclopentadienyl)chromium, -molybdenum or -tungsten Substituent
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By the interaction of (CH3)2AsCl with Na or C5H5(CO)3M-Si(CH3)3 stable carbonyl(cyclopentadienyl)metal dimethylarsanes of the formula C5H5(CO)3M-As(CH3)2 (M=Cr, Mo, W) (1-3) are obtained for the first time.Their thermal treatment in the solid state yields 2 and 2, in solution with loss of CO the cyclic species 2 4a (Mo), 4b (W) are formed.Under photolytic conditions in addition to 4a, b the aggregation products trans-C5H5(CO)2M-As(CH3)2 (5a, b) and x (6a, b) are isolated.Alkyl halides and (CH3)3SiI readily convert 1-3 into the cationic complexes X (R=CH3, CH2C(O)C6H5, CH2Si(CH3)3, Si(CH3)3; X=Br, I) (7a-f).With chlorine or bromine the extremely labile dihalogen adducts C5H5(CO)3M-AS(CH3)2Hal2 (8a-c) are formed, which rapidly decompose to (CH3)2AsHal and C5H5(CO)3MoHal or C5H5(CO)3WH.HCl, CF3CO2H, (CH3)3SnH, Na/Hg, CH3MgI, and (CH3)3PCH2 cleave the transition metal-arsenic bond under very mild conditions.
- Malisch, Wolfgang,Kuhn, Max,Albert, Walter,Roessner, Helga
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p. 3318 - 3333
(2007/10/02)
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