319909-49-4Relevant academic research and scientific papers
Compounds with unbridged dative metal-metal bonds of formula (R3P)2(OC)3OsW(CO)5 and related complexes
Jiang, Faming,Jenkins, Hilary A.,Biradha, Kumar,Davis, Harry B.,Pomeroy, Roland K.,Zaworotko, Michael J.
, p. 5049 - 5062 (2000)
Complexes of formula (R3P)2(OC)3OsW(CO)5 and similar complexes have been prepared from W(CO)5(THF) and Os(CO)3(PR3)2 in CH2Cl2/hexane at room temperature. The analogous Cr complexes could not be synthesized except for [MeC(CH2O)3P]2(OC)3OsCr(CO)5 and (Me2PCH2CH2PMe2)(OC)3OsCr(CO)5, that is, with sterically undemanding P substituents. Tungsten compounds with P ligands with cone angles greater than approx. 125° could also not be prepared. The crystal structures of (Me2PCH2CH2PMe2)(OC)3OsM(CO)5 (M = Cr, W), [MeC-(CH2O)3P]2(OC)3OsW(CO)5 (2), (OC)3(Me3P)2OsW(CO)5, (3), [MeC(CH2O)3P](OC)3(Me3P)OsW(CO)5, (4), and [(MeO)3P](OC)3(Me3P)OsW(CO)5 (5) reveal that all have unbridged OsM bonds that are considerably longer than the corresponding OsM bond in (Me3P)(OC)4OsM(CO)5. The P ligands have an axial, radial arrangement except in 3, where the PMe3 ligands have a trans, diradial orientation. In 4 and 5 the phosphite ligands are in the site trans to the OsW bond even though they have smaller cone angles than the PMe3 ligand. Solution NMR data indicates that for 2 and 3 both the ax,rad and dirad isomers are present; for 4 both ax,rad forms are present, whereas for 5 only the solid state form is found. There was no evidence in solution for the dirad forms of 4 and 5. (The 13C NMR spectra of the compounds also indicated that 2JPC becomes zero for PMC angles of about 103°). The unusual site preference of the P ligands in these molecules is interpreted in terms of steric effects and an electronic preference for a good π-acceptor ligand to adopt the position trans to the dative metal-metal bond. Complexes 2, 3, and 5 react with PPh3 in CH2Cl2 at room temperature over 2 days to give W(CO)5(PPh3) and Os(CO)3(PR3)(PR′3) in the order 3 > 5 > 2.
