16743-46-7Relevant articles and documents
Rapid synthesis of Group VI carbonyl complexes by coupling borohydride catalysis and microwave heating
Birdwhistell, Kurt R.,Schulz, Brian E.,Dizon, Paula M.
, p. 69 - 71 (2013/01/15)
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.
Electrochemistry of group VI metal carbonyl compounds containing 1,1′-bis(diphenylphosphino)ferrocene
Ohs, Amanda C.,Rheingold, Arnold L.,Shaw, Michael J.,Nataro, Chip
, p. 4655 - 4660 (2008/10/09)
The oxidative electrochemistry of a variety of homo- and bimetallic group VI metal carbonyl compounds containing 1,1′-bis(diphenylphosphino) ferrocene (dppf) with the general formulas M(CO)5(dppf) (1a-c), M(CO)4(dppf) (2a-c), and (CO)5M(dppf)M'(CO)5 (3a-f) (M, M' = Cr, Mo, W) was investigated. The effect of the group VI metal and the coordination mode of the dppf ligand on the potential at which the oxidation of the group VI metals and the ferrocene backbone of dppf occurred was examined.
Microwave-assisted synthesis of group 6 (Cr, Mo, W) zerovalent organometallic carbonyl compounds
VanAtta, Sky L.,Duclos, Brian A.,Green, David B.
, p. 2397 - 2399 (2008/10/08)
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.
Ligand substitution kinetics in M(CO)4(η2:2-norbornadiene) complexes (M=Cr, Mo, W): Displacement of norbornadiene by bis(diphenylphosphino)alkanes
Tekkaya, Aysin,Oezkar, Saim
, p. 208 - 216 (2007/10/03)
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.
Ligand substitution kinetics in M(CO)4 (η2:2-1,5-cyclooctadiene) complexes (M=Cr, Mo, W) - Substitution of 1,5-cyclooctadiene by bis(diphenylphosphino)alkanes
Kayran, Ceyhan,Kozanoglu, Ferda,Oezkar, Saim,Saldamli, Saltuk,Tekkaya, Aysin,Kreiter, Cornelius G.
, p. 229 - 236 (2008/10/08)
The thermal substitution kinetics of 1,5-cyclooctadiene (COD) by bis(diphenylphosphino)alkanes (PP), (C6H5)2P(CH2)nP(C 6H5)2 (n = 1, 2, 3) in M(CO)4(η2:2-COD) 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 COD ligand and on the concentration and the nature of the entering PP ligand. In the proposed mechanism, the rate determining step is the cleavage of one metal-olefin bond of the COD ligand. A rate-law is derived from the proposed mechanism. The evaluation of the kinetic data gives the activation parameters which support an associative mechanism in the transition states. Both the observed rate constant and the activation parameters show little variation with the chain length of the diphosphine ligand.
Substitution and addition reactions of the (CO)3(η7-tropylium)M cations (M = Cr, Mo, W) with tertiary diphosphines
Brown, David A.,Burns, John,Glass, William K.,Cunningham, Desmond,Higgins, Tim,McArdle, Patrick,Salama, Mabrouk M.
, p. 2662 - 2667 (2008/10/08)
The reactions of the title compounds I-III, [(η7-C7H7)M(CO)3]BF4 (M = Cr, Mo, and W, respectively), with the diphosphines PPh2(CH2)nPPh2 (n = 1-4) at low temperatures (-40 to -60°C) form two new series of complexes which are quite different from previous carbonyl substitution products. The first series (IV-VI) formed by the diphosphines (n = 1-3) comprise 7-exo ring adducts involving the bonding of only one phosphorus atom of the diphosphine to ring carbon atom 7 of I. The second series (VII and VIII) are diphosphine ring linked dimers, e.g. [(7,7′-exo-dppb){η6-C7H7)Cr(CO) 3}2] [BF4]2, for which X-ray crystallography confirms a diphosphine linked ring-ring structure with the Cr(CO)3 moieties situated on opposite sides of the ring systems. The ring C-phosphorus bond length of 1.852 A? indicates a relatively weak bond, consistent with facile cleavage of these adducts on reaction with nucleophiles such as hydride.
Reaction pathways of geometrically constrained 17-electron cis-[M(CO)4(L-L)]+ cations (M = Cr, Mo, W; L-L = bidentate ligand)
Bond,Colton,Kevekordes,Panagiotidou
, p. 1430 - 1435 (2008/10/08)
Oxidation of cis-M(CO)4(L-L) (where M = Cr, Mo, W and L-L is a bidentate ligand with P, As, or Se donor atoms) leads to generation of geometrically constrained 17-electron cations cis-[M(CO)4(L-L)]+, which cannot lower their energy by isomerization to the trans+ configuration, as is the case with [M(CO)4L2]+ and related complexes (L = monodentate P or As ligand). In this work, a marked contrast in reaction pathways between geometrically constrained compounds and other classes of compounds is shown to exist. The relative stability of cis-[Cr(CO)4(dpm)]+ in dichloromethane allows complete characterization of its chemical and electrochemical behavior; it undergoes photocatalytic reduction, substitution, redox, and disproportionation reactions, all of which regenerate Cr(CO)4(dpm). Other cis-[Cr(CO)4(L-L)]+ species are much less stable. The voltammetric oxidations (scan rates 50-500 mV s-1) of Mo(CO)4(L-L) (L-L = dpe, dpmSe) are very unusual. While these species approach chemical reversibility at ambient temperatures in dichloromethane, anomalous temperature dependence leads to the observation of complete chemical irreversibility at -78°C and the concomitant appearance of a new reduction response, well removed from the potential of the reversible process. In the presence of Cl-, PPh3, or L-L the one-electron voltammetric response is converted into an irreversible two-electron process (L-L = dpe) or an irreversible one-electron process (L-L = dpmSe). Other molybdenum and tungsten complexes give chemically irreversible one-electron oxidative voltammetric responses in both dichloromethane and acetonitrile. In acetonitrile, a second one-electron-oxidation process may be observed at very positive potentials. Reaction of cis-M(CO)4(L-L) with NOPF6 produces [M(CO)3NO(L-L)]+ rather than cis-[M(CO)4(L-L)]+. Mechanisms for the chemical and electrochemical oxidation processes are presented in terms of pathways that allow a lowering of energy associated with the formation of 17-electron geometrically constrained cis-[M(CO)4(L-L)]+ cations.
REACTIVITY OF ANIONIC METAL CARBONYL HIDRIDES TOWARD BIS(DIPHENYLPHOSPHINO)METHANE COMPLEXES OF PALLADIUM AND PLATINUM
Braunstein, Pierre,Oswald, Benoit
, p. 229 - 238 (2007/10/02)
The reactions between or and (3) in THF have been shown to give the trimetallic cluster ; because of the residual acidity of the H ligand in the starting anions, they behave as pre
