Reactions of 1-Hydroxypyridine-2-thione with Triosmium Clusters. Preparation and Transformation of <i>N</i>-Oxide-Containing Osmium Complexes

Abstract

The reaction of 1-hydroxypyridine-2-thione with Os 3 (CO) 11 (NCMe) has yielded three new complexes Os 3 (CO) 10 (μ-H)(μ-η 1 -S-C 5 H 4 N(O)) ( 1, 11% yield), Os 3 (CO) 10 (μ-H)(η 2 -S-C 5 H 4 N(O)) ( 2, 16% yield), and Os 3 (CO) 9 (μ-H)(μ-η 2:η 1 -SC 5 H 4 N(O)) ( 3, 3% yield). Similarly, treatment of complex Os 3 (CO) 10 (NCMe) 2 with this ligand has produced the major complexes 1 and trace of 3 . Prolonging the above two reactions increased the yield of 3 . Treatment of 1-hydroxypyridine-2-thione with triosmium isocyanide complexes Os 3 (CO) 10 (CNR)(NCMe) ( a, R = CH 2 Ph; b, R = Pr) has led to the formation of Os 3 (CO) 9 (μ-H)(CNR)(η 2 -SC 5 H 4 N(O)) ( 4 ), Os 3 (CO) 10 (μ-η 1 -C NHCH 2 Ph)(μ-η 1 -S-C 5 H 4 N(O)) ( 5 ), and Os 3 (CO) 9 (μ-H)(CNR)(μ-η 1 -S-C 5 H 4 N(O)) ( 6 ). The 4: 5 ratio depended upon the nature of the alkyl groups of the coordinated isocyanide. Reaction of either 1 or 2 with Me 3 NO resulted in CO loss and formation of complex 3 . Thermolysis of 1 at 80 °C generated Os 3 (CO) 9 (μ-H)(μ 3 -pyS) ( 7 ), Os 3 (CO) 9 (μ-OH)(μ 3 -pyS) ( 8 ), and byproduct CO 2 . Upon being heated at 80 °C, 3 was converted to 7 and 8 in a ratio of 1:4 as indicated by an in-situ NMR study. These observations show that 3 is an intermediate for the formation of 8 from 1 . Crystal structures of 1, 4b, 5a, and 8 were determined by X-ray diffraction analyses. The overall results indicate that the N -oxide group in these complexes exhibits versatile bonding modes on triosmium clusters.