41830-14-2Relevant academic research and scientific papers
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.
Donor properties of diphosphine ligands in tungsten carbonyl complexes: Synchrotron radiation XPS measurements and DFT calculations
Crotti, Corrado,Farnetti, Erica,Celestino, Teresa,Stener, Mauro,Fontana, Stefano
, p. 5219 - 5225 (2008/10/09)
Synchrotron radiation XPS measurements of W 4f and P 2p core level binding energies in the series W(CO)4(P-P) (P-P = dppm (1), dppe (2), dppp (3), dppb (4), dmpe (5), F-dppe (6); dppm = bis(diphenylphosphino)methane, dppe = 1,2-bis(diphenylphos
Organometallic chemistry in a conventional microwave oven: The facile synthesis of group 6 carbonyl complexes
Ardon, Michael,Hogarth, Graeme,Oscroft, Daniel T.W.
, p. 2429 - 2435 (2007/10/03)
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.
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.
On the synthesis and 31P NMR spectrum of (CO)5W(μ-PPh2CH2PPh2)W(CO)5
Benson, J. W.,Keiter, E. A.,Keiter, R. L.
, p. 77 - 82 (2007/10/02)
The dimetallic complex, (CO)5W(μ-PPh2CH2PPh2)W(CO)5, is synthesized from either a 2:1 mixture of (CO)5W(NCMe) and (CO)5W(η1-PPh2CH2PPh2) or a 3:1 mixture of (CO)5W(NCMe) and PPh2CH2PPh2 in toluene at 60 deg C.The coupling constants, 2JPP' = 22.9 Hz, 1JWP = 246.9 Hz and 3JWP' = 4.5 Hz are consistent with those reported in the literature for similar complexes.The complex (CO)5W(η1-PPh2CH2PPh2) is stable with respect to chelation at room temperature. Keywords: Tungsten; Bis(diphneylphosphino)methane; P-31 NMR; Ditertiary phosphines; Coupling constants; Carbonyl
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
Lindner, Ekkehard,Fawzi, Riad,Mayer, Hermann August,Eichele, Klaus,Hiller, Wolfgang
, p. 1033 - 1043 (2008/10/08)
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.
Synthesis, reactivity, and X-ray structure of fac-W(CO)3(dppm) (CH3CN). Stereoselective preparation of fac-W(CO)3(13CO) (dppm) and subsequent intramolecular rearrangement processes
Darensbourg, Donald J.,Zalewski, David J.,Plepys, Christine,Campana, Charles
, p. 3727 - 3732 (2008/10/08)
The reaction of fac-W(CO)3(CH3CN)3 with an equimolar quantity of bis(diphenylphosphino)methane (dppm) results in the quantitative formation of fac-W(CO)3(dppm)(CH3CN). The solid-state structure of fac-W(CO)3(dppm)(CH3CN) was established by X-ray diffraction [P21/c (monoclinic), a = 10.937 (2) ?, b = 18.399 (4) ?, c = 15.194 (3) ?, β = 108.33 (1)°, Z = 4]. This compound reacts with 13CO to afford stereoselective fac-W(CO)3(13CO)(dppm). The reaction proceeds by a dissociative pathway, with activation parameters for loss of CH3CN being ΔH? = 23.5 kcal/mol and ΔS? = -6.0 eu. In a subsequent, intramolecular ligand rearrangement facial ? meridional isomerization occurs. Reaction of fac-W(CO)3(dppm)(CH3CN) with an additional 1 mol of dppm leads initially to formation of fac-W(CO)3(dppm)2, which contains both bidentate and monodentate dppm ligands. Isomerization and oxidation of the unattached phosphine eventually provided mer-W(CO)3(dppm)(Ph2PCH2P(O)Ph2). The structure of the latter species was determined by X-ray diffraction [P41 (tetragonal), a = 11.186 (4) ?, c = 40.498 (9) ?, Z = 4].
