- Bis(pyrazolyl)methanetetracarbonyl-chromium(0), -molybdenum(0) and -tungsten(0)
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Bis(pyrazolyl)methanetetracarbonyl-chromium(0), -molybdenum(0) and -tungsten(0) were prepared from M(CO)6 and characterized by IR, 1H and 13C NMR spectroscopy.They are of only moderate stability as solid or in solution, being more stable in acetone than i
- Lobbia, Giancarlo Gioia,Bonati, Flavio
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- Synthesis, structure and bonding of new mono- and dinuclear molybdenum complexes containing pyridine-2-thiolate (pyS) and different P-donors
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Three new molybdenum complexes have been synthesized from one-pot reactions between Mo(CO)3(NCMe)3 and pyridine-2-thiol (pySH) in the presence of different P-donors. Reaction with P(OMe)3 in MeCN at ca. 55 °C gives Mo(CO)
- Haque, Mohd. Rezaul,Ghosh, Shishir,Hogarth, Graeme,Richmond, Michael G.,Kabir, Shariff E.
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- 2,3-benzo-7-phosphanorbornadiene complexes: Synthesis and chemistry
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The reaction of benzyne with 3,4-dimethylphosphole pentacarbonylmolybdenum complexes affords the corresponding 2,3-benzo-7-phosphanorbornadiene complexes through [4+2] cycloaddition. The condensation takes place on the less hindered side of the phosphole ring corresponding to the phosphorus substituent as shown by the X-ray crystal structure analysis of the phenyl derivative (2). The strain at the bridge of 2 (C-P-C angle ca. 80°) induces a variety of splitting reactions. Upon decomplexation by dppe at 110°C in toluene, phenylphosphinidene is generated and recovered as phenylphosphine. Upon sulfurization under the same conditions, [PhPS2] is formed and trapped as a [4+2] adduct with 2,3-dimethylbutadiene. Potassium tertbutylate attacks the bridge in THF at - 78°C and, after methylation and hydrolytic workup, yields [Ph(Me)P-(OH)Mo(CO)5].
- Compain, Carine,Donnadieu, Bruno,Mathey, Francois
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- Photochemical Unmasking of 1,3-Dithiol-2-ones: An Alternative Route to Heteroleptic Dithiolene Complexes from Low-Valent Molybdenum and Tungsten Precursors
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Mono-dithiolene complexes [Mo(CO)2(dt)(dppe)] and [W(CO)2(dt)(dppe)] {dt = cyclohex-1-ene-1,2-dithiol; 5,6-dihydro-2H-pyran-3,4-dithiol and dppe= 1,2-bis(diphenylphosphino)ethane} were synthesized by a photochemical procedure. The typical basic de-protection of the dithiolene ligand precursor was replaced by a light-induced opening of the 1,2-dithiole-2-one moiety. Advantages of this targeted approach comprise higher yields, cleaner transformations, and the possibility to continuously and precisely monitor the reaction progress. The light induced pericyclic reaction of the protection group releases carbon monoxide with formation of a 1,2-dithione, which is capable of oxidizing the electron rich metal precursor due to its non-innocence character. This procedure works well with molybdenum(0) and tungsten(0) precursors and particularly well with dithiolene ligands bearing aliphatic backbones, which are typically and notoriously difficult to handle when applying strictly chemical procedures.
- Elvers, Benedict J.,Schulzke, Carola,Fischer, Christian
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- Microwave-assisted synthesis of group 6 (Cr, Mo, W) zerovalent organometallic carbonyl compounds
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The microwave-assisted synthesis of a series of compounds of the form ML(CO)4 (M = Cr, Mo, W; L = en, bipy, dppm, dppe), results in the reduction of reaction times and an increase in yields over previously published syntheses. Reaction times are reduced by a factor of 5 to over 500.
- VanAtta, Sky L.,Duclos, Brian A.,Green, David B.
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- Rapid synthesis of Group VI carbonyl complexes by coupling borohydride catalysis and microwave heating
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Several Group VI tetracarbonyl phosphine and tertiary amine complexes [M(CO)4 L2, M = Cr, Mo, W, L2 = 2PPh 3, dppm, dppe, dppp, dppb, bpy, phen, dppf] were synthesized in minutes in the microwave at moderate temperature, atmospheric pressure, and utilizing NaBH4 as a catalyst. The reactions were optimized by careful solvent selection. The octahedral complexes were isolated in percent yields ranging from 17 to 95. The lower temperatures, shorter reaction times, benign solvents, and lower pressures as compared to the traditional thermal syntheses provide a rapid, eco-friendly synthetic route to these common Group VI complexes.
- Birdwhistell, Kurt R.,Schulz, Brian E.,Dizon, Paula M.
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- Ligand electronic effect on reductive elimination of biphenyl from ci s-[Pt(Ph)2(diphosphine)] complexes bearing electron-poor diphosphine: Correlation study between experimental and theoretical results
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The reductive elimination of biphenyl from cis-[Pt(Ph) 2(diphosphine)] (3) was studied to clarify the electronic effects of diphosphine ligands on the reaction. Reaction kinetic data were evaluated in d8-toluene within 80-110 °C usin
- Korenaga, Toshinobu,Abe, Kayoko,Ko, Aram,Maenishi, Ryota,Sakai, Takashi
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p. 4025 - 4035
(2010/11/19)
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- Carbamoylation of aryl halides by molybdenum or tungsten carbonyl amine complexes
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When aryl halide is treated with molybdenum carbonyl amine complex in the presence of base, carbamoylation proceeds to give amide in good yield. The proposed mechanism involves oxidative addition of aryl halide to molybdenum(0) complex, migratory insertio
- Ren, Wei,Yamane, Motoki
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supporting information; experimental part
p. 3017 - 3020
(2010/07/05)
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- Organometallic chemistry in a conventional microwave oven: The facile synthesis of group 6 carbonyl complexes
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Syntheses proceeding by reflux may be improved, accelerated and simplified, by carrying out the reaction in a modified conventional microwave oven. To demonstrate the potential of this method, the synthesis of over 20 group 6 organometallic compounds is reported. Hexacarbonyls, most notably Mo(CO)6, react with a range of mono, and bi, and tridentate ligands in a modified conventional microwave oven. They generally proceed without an inert atmosphere, yields are high and reaction times are short. For example, cis -[Mo(CO)4(dppe)] is prepared in >95% yield in 20 min. Reaction of Mo(CO)6 with dicyclopentadiene affords a simple one-step synthesis of [CpMo(CO)3]2 in >90% yield, which reacts further with alkynes in toluene to produce dimetallatetrahedrane derivatives, [Cp2Mo2(CO)4 (μ-RC2R)]; presumably via the in situ formation of air-sensitive [CpMo(CO)2]2. Dimolybdenum tetra-acetate is also prepared in 48% yield in 45 min, however, this reaction requires an inert atmosphere. While W(CO)6 reacts rapidly with amines to give cis diamine adducts in high yields, direct reactions with phosphines are not so clean. Bis(phosphine) complexes are, however, cleanly formed when a small amount of piperidine is added to the reaction mixture, presumably via the bis(piperidine) complex cis-[W(CO)4(pip)2]. Reactions with Cr(CO)6 generally require an inert atmosphere and proceed less cleanly, although the important synthon [Cr(CO)5 Cl][NEt4] was prepared in 30 min (74% yield), while [(η6-C6H5OMe)Cr(CO)3] can be prepared in 45% after 4 h.
- Ardon, Michael,Hogarth, Graeme,Oscroft, Daniel T.W.
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p. 2429 - 2435
(2007/10/03)
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- Ligand substitution kinetics in M(CO)4(η2:2-norbornadiene) complexes (M=Cr, Mo, W): Displacement of norbornadiene by bis(diphenylphosphino)alkanes
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The thermal substitution kinetics of norbornadiene (NBD) by bis(diphenylphosphino)alkanes (PP), (C6H5)2P(CH2)nP(C 6H5)2 (n=1, 2, 3) in M(CO)4(η2:2-NBD) complexes (M=Cr, Mo, W), were studied by quantitative FT-IR spectroscopy. The reaction rate exhibits first-order dependence on the concentration of the starting complex, and the observed rate constant depends on the concentration of the leaving NBD ligand and on the concentration and the nature of the entering PP ligand. In the proposed mechanism there are two competing initial steps: an associative reaction involving the attachment of the entering PP ligand to the transition metal center and a dissociative reaction involving the stepwise detachment of the diolefin ligand from the transition metal center. A rate law is derived from the proposed mechanism. The activation parameters are obtained from the evaluation of the kinetic data. It is found that at higher concentrations of the entering ligand, the associative path is dominant, while at lower concentrations the contribution of the dissociative path becomes significant. Both the observed rate constant and the activation parameters show noticeable variation with the chain length of the diphosphine ligand.
- Tekkaya, Aysin,Oezkar, Saim
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p. 208 - 216
(2007/10/03)
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- Formation of 1,2-bis (diphenylphosphino)ethane, dppe, from two coordinated diphenylvinylphosphine (DPVP) ligands; Crystal structures of cis- and trans- (DPVP)2 Mo (CO)4 and (dppe)M(CO)4 (M=Cr, Mo)
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Photolysis of a 1:2 mixture of M(CO)6 (M=Cr, Mo) and diphenylvinylphosphine (DPVP) in tetrahydrofuran produces (DPVP)M(CO)5, cis- and trans- (DPVP)2M(CO)4, (dppe)M(CO)4 (dppe=1,2-bis (diphenylphosphino)ethane, and fac- (dppe) (DPVP)Mo (CO)3. The complexes have been characterized by elemental analysis, infrared and 1H, 13C{ 1H} and 31P{ 1H} NMR spectroscopy and in four cases by X-ray crystallography. The Mo-P bond lengths for cis- (DPVP)2Mo (CO)4 (2.5509 (10) A, ave.) are longer than those for the trans-isomer (2.4713 (7) A) due to the greater trans influence of CO than of DPVP. The Mo-P bond lengths for (dppe)Mo (CO)4 (2.5020 (11) A, ave.) lie between these two values.
- Maitra, Kalyani,Nelson, John H.
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p. 203 - 210
(2008/10/08)
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- Synthesis and characterization of novel neutral σ-alkynylcarbonylnitrosyl molybdenum(0) and tungsten(0) complexes. Crystal structure of [Mo(C≡CnPR)(CO) 2(dppe)(NO)] [dppe = 1,2-bis(diphenylphosphino) ethane]
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σ-Alkynyl dicarbonyl complexes [M(C≡CR)(CO)2(dppe)(NO)] (M = Mo, R = H, tBu, nPr, iPr, Ph, CH2OCH3, SiMe3; M = W, R = H, tBu, nPr) have been prepared by reaction of mer-[M(CO)3(dppe)(NO)][BF4] with an equimolar amount of the acetylide salt M′C≡CR (M′ = Li, Na). The complexes [M(CO)2(NCMe)(dppe)(NO)] [BF4] (M = Mo, W) and [Mo(CO)(NCMe)2(dppe)(NO)][BF4] obtained by reaction of mer-[M(CO)3(dppe)(NO)][BF4] with acetonitrile are suitable precursors for the synthesis of the complexes [M(CO)2(dppe)(PR3)(NO)][BF4] (M = Mo, W, PR3 = PMe3, PMe2Ph) and [M(CO)(NCMe)(dppe)(PR3)(NO)][BF4] (PR3 = PMe2Ph, PPh3, P(OPh)3). The reaction of [Mo(CO)2(NCMe)(dppe)(NO)][BF4] with NaS(o--C6H4Me) yields the neutral complex [Mo{S(o-C6H4Me)}(CO)2(dppe)(NO)]. The crystal structure of [Mo(C≡CnPr)(CO)2(dppe)(NO)] has been determined by X-ray diffraction methods. The Mo atom displays a distorted octahedral coordination involving the N and C atoms of the nitrosyl and the alkynyl ligands in the apical positions and the P atoms from the dppe chelating ligand and two C atoms from terminal carbonyl groups in the equatorial positions.
- Gamasa, M. Pilar,Gimeno, Jose,Zhang, Lei,Lanfranchi, Maurizio,Tiripicchio, Antonio
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p. 287 - 297
(2007/10/03)
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- Preparation of α-Diazines and α-2-Pyridylazines containing (1R)-(+)-Camphor or (1R)-(-)-Fenchone Residues and their Complexes with Group 6 Metal Carbonyls
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New 2,3,6,7-tetraaza-1,3,5,7-octatetraene (α-diazine) derivatives camph=N-N=CH-CH=N-N=camph I, where camph is a (1R)-(+)-camphor residue, C10H16, and fench=N-N=CH-CH=N-N=fench II, where fench is a 1R-(-)-fenchone residue, C10H16, have been obtained together with the 2'-pyridyl derivatives camph=N-N=CHC5H4N III and fench=N-N=CHC5H4N IV.The configurations around the four C=N bonds of I or II are E,E,E,E whilst those around the two azine C=N bonds in III and IV are E,E.Complexes of the types (M = Cr, Mo or W; L = I-IV), (L = I, L' = NCMe, PPh3 or AsPh3; L = II-IV, L' = PPh3), (L = III or IV) and 3-CH2CH=CH2)L> (L = I, III or IV) containing these azines as ligands have also been obtained.Complexes of II are the most unstable and these together with tetracarbonyl complexes of IV appear to show restricted rotation around the N-N bond(s) caused by the steric requirements of the methyl groups on the fenchone residue(s).All the complexes have been characterised by multinuclear NMR (1H, 13C and 31P), IR and UV/VIS spectroscopies and mass spectrometry.The crystal structures of camph=N-N=CH-CH=N-N=camph I and fench=N-N=CHC5H4N IV have been determined.
- Shaw, Bernard L.,Thornton-Pett, Mark,Vessey, Jonathan D.
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p. 3597 - 3606
(2007/10/02)
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- Substituted metal carbonyls. XXIII. Syntheses of unicoordinated diphosphine complexes of Cr and Mo and their entry into heterobimetallics MM'(CO)10(μ-P-P) as metalloligands
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A series of pentacarbonyl complexes of chromium and molybdenum with unicoordinated-diphosphines, M(CO)5(η1-P-P) (P-P=dppe, dppp, dppb) has been prepared by amine oxide-induced phosphine substitution of the binary carbonyls.The basicity of the pendant phosphine groups was demonstrated by their ready conversion to the diphosphine-bridged heterobimetallic complexes (OC)5M(μ-P-P)M'(CO)5 (M,M'=Cr, Mo, W; M M') in the presence of M'(CO)5(CH3CN).The complexes were characterized by IR and NMR (1H and 31P-) spectroscopy.
- Gan, Kim-Suan,Lee, Hian Kee,Hor, T.S. Andy
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p. 197 - 202
(2007/10/02)
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- Reactions of (PPh3)3> with Group 6 Metal Carbonyls. Crystal Structure and Reactivity with Diphosphines of the Linear Heterotrinuclear Complex 2(CO)6(PPh3)2>
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The compound (PPh3)3> 1 reacts with the Group 6 metal carbonyls, , in hot aromatic solvents giving different reaction products according to the stability of the metal carbonyl: (CO)4(PPh3)2> 2 (M = Cr); and trans- (M = W) and the dark brown 2(CO)6(PPh3)2> 3 (M = Mo).The structure of 3 has been established from X-ray diffraction analysis.This compound reacts, in boiling toluene, with diphosphines (Ph2P)2X to form 2(CO)4 (diphosphine)2> (diphosphine = dppm 4 or dppb 5) and for X = C2H4 (dppe) or C3H6 (dppp) a mixture of and (CO)(diphosphine)> was obtained.The new trinuclear complexes have been characterised by elemental analysis and by spectroscopic (IR and NMR) methods.
- Anillo, Adela,Garcia-Granda, Santiago,Obeso-Rosete, Ricardo,Rubio-Gonzalez, Juan Manuel
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p. 3287 - 3292
(2007/10/02)
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- Effect of ring size on NMR parameters: Cyclic bisphosphine complexes of molybdenum, tungsten, and platinum. Bond angle dependence of metal shieldings, metal-phosphorus coupling constants, and the 31P chemical shift anisotropy in the solid state
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The 31P chemical shift tensors of bis(phosphine) complexes of the type [M] [Ph2P(CH2)nPPh2] ([M] = (OC)4Mo, (OC)4W, Cl2Pt; n = 1-5) and of fac-(OC)3Mo[PPh(CH2CH2PPh2) 2] were determined by solid-state NMR techniques and correlated with structural features of the compounds. δ(31P), 1JM-P, and δ(M) show a dependence on the ring size in the solution NMR spectra of the four- to six-membered chelates; for larger rings this dependence vanishes. A model for the orientation of the 31P shift tensor principal components within the molecular frame is proposed. Each tensor component displays a different dependence on the ring size; the isotropic shift is dominated by the component perpendicular to the ring plane. Changes in this component are explained in terms of variations of the M-P-C angles. Generally speaking, the behavior of each of the tensor components must be regarded as a complex interplay of all six bond angles at phosphorus. The crystal structure of (OC)4W[Ph2P(CH2)4PPh2] (2d) was determined by X-ray diffraction. Crystals of 2d are monoclinic, space group P21/n, a = 1202.8 (1) pm, b = 1531.8 (1) pm, c = 1654.1 (2) pm, β = 104.72 (1)°, and Z = 4.
- Lindner, Ekkehard,Fawzi, Riad,Mayer, Hermann August,Eichele, Klaus,Hiller, Wolfgang
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p. 1033 - 1043
(2008/10/08)
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- Heat of reaction of (norbornadiene)molybdenum tetracarbonyl with monodentate and bidentate ligands. Solution thermochemical study of ligand substitution in the complexes cis-L2Mo(CO)4
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The enthalpy of reaction of (NBD)Mo(CO)4 (NBD = norbornadiene) with a number of monodentate and bidentate ligands forming cis-L2Mo(CO)4 has been measured at 30°C in THF solution. The heats of reaction span a range of 33 kcal/mol. The order of stability for monodentate ligands is PCl3 6H5)3 6H5)3 3 6H5)3 6H5)2(CH3) 6H5)(CH3)2 3)3 3 6H11)NC 3 3. The series of chelating bidentate phosphines R2P-(CH2)nPR2 (n = 1-4, R = C6H5; n = 1, 2, R = CH3) and several related ligands were investigated. The chelating ring systems in the metallacycles show strain energies of about 8 kcal/mol for four-membered rings. The mixed ligand (C6H5)2PCH2CH2-As(C 6H5)2 shows a heat of binding midway between the heats of binding of (C6H5)2PCH2CH2P(C 6H5)2 and (C6H5)2AsCH2C-H2As(C 6H5)2, implying group additivity in this system. The complex (phen)Mo(CO)4 is some 5 kcal/mol more stable than (bpy)Mo(CO)4, presumably due to conformational effects in the free ligand. The ligand 1,5-cyclooctadiene forms a complex 2 kcal/mol less stable than that of norbornadiene. The influences of steric and electronic factors in determining the Mo-L bond strength are discussed.
- Mukerjee, Shakti L.,Nolan, Steven P.,Hoff, Carl D.,Lopez De La Vega, Ramon
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