FACILE TRANSFORMATION OF A METAL-CARBONYL TO A METAL-CARBONYL SULFIDEBY REACTION WITH ELEMENTAL SULFUR

Elemental sulfur (S8) enters into a remarkably facile and unprecedente d addition reaction with (MeCp)2Nb(CO)CH2Si(CH3)3 (1) at room temperat ure, converting it to the carbonyl sulfide complex (MeCp)2Nb(eta2-COS) CH2Si(CH3)3 (2). The following key spectroscopic features of 2 indicat e the presence of coordinated COS: (1) mass spectral peaks at m/e 398 (M+), 370 (M+ - CO), and 338 (M+ - COS) (2) a C-13 NMR resonance at 24 9.1 ppm assigned to coordinated COS, and (3) an isotopically shifted n u(C=O) IR band of 2 at 1639 cm-1 (THF) when prepared from (MeCp)2Nb(C O)-C-13CH2Si(CH3)3 and S8, consistent with an eta2(C,S) mode. The pres ence of the C,S-coordinated COS molecule has been established by an X- ray diffraction study. Complex 2 is also produced (25 % yield) by Na/H g reduction of (MeCp)2Nb(Cl)CH2-Si(CH3)3 (THF/20-degrees-C/1 h) under an atmosphere of COS.