Halogeno, hydride, and alkyl carbonyl–monocyclopentadienyl niobium derivatives. Crystal and molecular structure of [Nb(η-C5H5)Cl(H)(CO)(PMe3)2]

Abstract

The reduction of [Nb(η-C₅H₅)Cl₂(CO)L₂][L = PMe₃, (1); L = PMe₂Ph, (2)] with two equivalents of sodium amalgam (10%) yields [{Nb(η-C₅H₅)(CO)L₃}_n][L = PMe₃, (3); L = PMe₂Ph, (4)]. Complexes (3) and (4) react with HCl and HBF₄ to give the hydrides [Nb(η-C₅H₅)Cl(H)(CO)L₂][L = PMe₃, (5); L = PMe₂Ph, (6)] and [Nb(η-C₅H₅)H(CO)L₃]BF ₄[L = PMe₃, (7), L = PMe₂Ph, (8)], with halogens to give the halides [Nb(η-C₅H₅)X₂(CO)L₂][X = Cl, L = PMe₃, (1); X = Cl, L = PMe₂Ph, (2); X = Br; L = PMe₃, (9); X = Br, L = PMe₂Ph, (10); X = I, L = PMe₃, (11); X = I, L = PMe₂Ph, (12)], and with Mel to give the alkyls [Nb(η-C₅H₅)Me(CO)(PMe₃)₃]I (13) and [Nb(η-C₅H₅)I(Me)(CO)(PMe₂Ph)₂](14). Spectroscopic (i.r. and n.m.r.) data are provided for all these compounds. The X-ray crystal and molecular structure of (5) has been determined [monoclinic, space group P2₁/a, with a= 12.662(6), b= 10.562(3), c= 13.168(6)Å, β= 92.84(1)°, and Z= 4]. The structure was solved by Patterson and Fourier methods and refined by full-matrix least-squares methods to R= 0.044 for 1 957 observed reflections. The structure was consistent with that expected from spectroscopic observations. The molecule shows a pseudo-octahedral arrangement with CO, Cl, and both PMe₃ ligands occupying equatorial positions. The spectroscopic data infer that the hydride ligand occupies an axial position trans to the η-C₅H₅, ring.