119850-65-6Relevant articles and documents
Complexes with unbridged dative bonds between osmium and a group 6 element. Structures of (Me3P)(OC)4OsM(CO)5 (M = Cr, W)
Davis, Harry B.,Einstein, Frederick W. B.,Glavina, Paul G.,Jones, Terry,Pomeroy, Roland K.,Rushman, Paul
, p. 1030 - 1039 (2008/10/08)
Complexes of the type (R3P)(OC)4OsM(CO)5 (R = Me, OMe, Ph, etc.; M = Cr, Mo, W) have been prepared from the reaction of Os(CO)4(PR3) and M(CO)5(THF) in hexane. The structures of (Me3P)(OC)4OsCr(CO)5 (1) and (Me3P)(OC)4OsW(CO)5 (2) have been determined by X-ray crystallography: Compound 1 crystallizes in the space group P21/n, with a = 9.231 (1) ?, b = 18.153 (1) A, c = 10.865 (1) ?, β = 91.08 (1)°, and Z = 4; R = 0.023, Rw = 0.028 for 1748 observed reflections. Compound 2 crystallizes in the space group P21/n, with a = 8.832 (1) ?, b = 16.241 (2) ?, β = 12.988 (2) ?, β = 101.99 (1)°, and Z = 4; R = 0.019, Rw = 0.023 for 2189 observed reflections. In both 1 and 2 the Os(CO)4(PMe3) molecule acts as a ligand to the M(CO)5 fragment via an unbridged donor-acceptor metal-metal bond (Os-Cr = 2.9787 (14) ?; Os-W = 3.0756 (5) ?); the phosphine ligand is trans to the metal-metal bond. The major spectroscopic features of the (R3P)(OC)4OsM(CO)5 complexes indicate these compounds adopt the same structure in solution. There are, however, weak signals in the 13C (and 1H and 31P) NMR spectra that are consistent with small amounts of the isomer with the phosphorus ligand cis to the metal-metal bond. For 2, the isomers were shown to be in rapid equilibrium by the spin saturation transfer technique. The well-known mechanism that involves pairwise carbonyl exchange between metal atoms accounts for the observations regarding the isomerization. The homoleptic derivative (OC)5OsCr(CO)5 has also been prepared. Although unstable in solution at room temperature, the 13C NMR spectrum in CD2Cl2 at -40°C indicates it also has a structure with an unbridged, Os-Cr dative bond.
