37823-96-4Relevant articles and documents
Formation and reactions of tetracarbonyl intermediates of the Fischer carbene complex (CO)5WqqC(OMe)Ph. A laser flash photolysis study using time-resolved infrared and UV/vis spectroscopy
Gut, Hans-Peter,Welte, Nicolas,Link, Uwe,Fischer, Helmut,Steiner, Ulrich E.
, p. 2354 - 2364 (2000)
The results of nanosecond laser flash photolysis (XeCl excimer irradiation at 308 nm) of the Fischer carbene complex [(CO)5WqqC(OMe)Ph] (CZ) in di-n-butyl ether and n-hexane are reported. Spectrokinetical detection of the intermediates was based on transient absorptions simultaneously recorded in the UV/vis and the IR spectral regions. The primary photoproducts are the unstable isomer CE produced with a quantum yield of about 30% and a tetracarbonyl complex I-S, probably of structure [(CO)4(S)WqqC(OMe)Ph], where S is a solvent molecule. The quantum yield of CO photoelimination was estimated as 1.7%. The CE isomer was found to return to the stable CZ isomer within a few microseconds, confirming previous results of McGarvey and co-workers. The tetracarbonyl species reacts with cosolutes present in the solution such as N2, H2O, acetonitrile, and methyl trans-crotonate to form secondary complexes of cis-tetracarbonyl complex structure [(CO)4(L)WqqC(OMe)Ph] (I-L). The tetracarbonyl complexes react readily with CO. For I-N2 in n-hexane the rate constant is 3.5 × 108 M-1 s-1. The rate constants of the corresponding reactions with acetonitrile (MeCN) and the olefin are larger by a factor of 2. In the presence of CO the complexes I-MeCN and I-olefin revert to CZ in a dissociative reaction mechanism. The rate constants for the elimination of MeCN or olefin are 5 and 105 s-1, respectively. The I-olefin complex irreversibly decomposes with a rate constant of 8 × 103 s-1.
Abstraction of methyl from neutral Fischer-type carbene complexes: A new site for nucleophilic attack
Toomey, Laurence M.,Atwood, Jim D.
, p. 490 - 493 (2008/10/08)
Reactions of Fischer-type carbene complexes, M(CO)5(C(OMe)Ph) (M = Cr, W), with metal carbonyl anions (M′- = CpFe(CO)2-, Re(CO)5-, Mn(CO)4PPh3-, Co(CO)3PPh3-, Cp*Cr(CO)3-, CpMo(CO)3-) result in demethylation of the carbene complexes. The products are M(CO)5C(O)Ph- and M′-Me, characterized by infrared and NMR spectroscopy. A slower rate for reaction with W(CO)5(C(OEt)Ph) in comparison to the methyl analogue is consistent with nucleophilic attack of the metal carbonyl anion on the methyl of the methoxy group of the carbene. This is a new type of nucleophilic attack on a Fischer-type carbene.
Synthesis of carbyne complexes of chromium, molybdenum, and tungsten by formal oxide abstraction from acyl ligands
McDermott, Gregory A.,Dorries, Alison M.,Mayr, Andreas
, p. 925 - 931 (2008/10/08)
Reaction of the acyl metal complexes [NMe4][M(C(O)R)(CO)5] (R = C6H5, M = Cr, Mo, W; R = CH3, M = W) with the Lewis acids COCl2, C2O2Cl2, C2O2Br2, and ClC(O)OCCl3 in CH2Cl2 at low temperatures (≤-78°C) and subsequent warming of the solutions (≤0°C) lead to clean formation of trans-halo(carbyne)tetracarbonylmetal complexes, [M(CR)(X)(CO)4] (X = Cl, Br). The carbyne complexes [M(CR)X(CO)4] are transformed into stabilized derivatives [M(CR)X(CO)2L2] by the addition of donor ligands (L2 = (pyridine)2 (py), tetramethylethylenediamine (tmeda), bipyridine (bpy)). The complex [W-(CPh)(O2CCF3)(CO)2(tmeda)] is prepared in a similar reaction sequence from [NMe4][W(C(O)Ph)(CO)5], (CF3CO)2O, and tmeda. Reaction of [NMe4][W(C(O)Ph)(CO)5] with C2O2Br2 and 1 equiv of PPh3 gives [W(CPh)Br(CO)3(PPh3)]. The bis(pyridine)-substituted complexes [W(CPh)Cl(CO)2(py)2] undergo further substitution reactions with PMe3 and Ph2PCH2CH2PPh2 (dppe) to give [W(CPh)Cl(CO)2(PMe3)2] and [W(CPh)Cl(CO)2(dppe)].
