The crystal structure and reactivity of [(η-C5H5)NiOs3(µ-H)3(CO)8(PPh2H)]; 1H and 31P nuclear magnetic resonance spectroscopic characterization of [(η-C5H5)NiOs3(µ-H)2(µ-HgBr)(CO)8(PPh2H)] and related complexes

Abstract

By reacting [(η-C₅H₅)NiOs₃(µ-H)₃(CO)₉](1a) with PPh₂H in the presence of Me₃NO, [(η-C₅H₅)NiOs₃(µ-H)₃(CO)₈(PPh₂H)](3a) has been obtained. The crystal structure of (3a) has been determined by X-ray methods. Crystals are monoclinic, space group P2₁/n with Z= 4 in a unit cell of dimensions a= 14.110(6), b= 23.962(9), c= 8.479(6)Å, and β= 95.73(2)°. The structure has been solved from diffractometer data by direct and Fourier methods and refined by full-matrix least squares to R= 0.033 for 3187 observed reflections. The structure consists of a tetrahedral arrangement of metal atoms with the three hydrides bridging the Os–Os edges; the phosphine ligand replaces an axial carbonyl of the starting complex. Both complexes (1a) and (3a) react with NaH in tetrahydrofuran to give the corresponding monoanions; these react with HgBr₂ affording µ-HgBr derivatives which have been characterized by i.r. and n.m.r. spectroscopy. Deuteriation experiments have shown that the faster rate of formation of the anion derived from (3a), with respect to that from (1a), is due to the presence of the P–H group, which is probably the site of attack by NaH.