Abstract
The reaction of Os 3 (CO) 12 with an excess of 1-hydroxypyridine-2-thione and Me 3 NO gives three mononuclear osmium complexes Os(CO) 2 (η 2 -SC 5 H 4 N(O)) 2 (1), Os(CO) 2 (η 2 -SC 5 H 4 N(O))(η 2 -SC 5 H 4 N) (2), and Os(CO) 2 (η 2 -SC 5 H 4 N) 2 (3). The results of single-crystal X-ray analyses reveal that complex 1 contains two O,S-chelate pyridine-2-thione N-oxide (PyOS) ligands, whereas complex 2 contains one O,S-chelate PyOS and one N,S-chelate pyridine-2-thiolate group. The unique structure of 2 provides evidence of the pathway for this transformation. When this reaction was monitored by 1 H NMR spectroscopy the triosmium complexes Os 3 (CO) 10 (μ-H)(μ-η 1 -S-C 5 H 4 N(O)) (4) and Os 3 (CO) 9 (μ-H)(μ-η 1 : η 2 -SC 5 H 4 N(O)) (5) were identified as intermediates in the formation of the mononuclear final products 1-3. The proposed pathway is further supported by the observation of several dinuclear osmium intermediates by electrospray ionization mass spectrometry. In addition, the reaction of Os 3 (CO) 12 with 1-hydroxypyridine-2-thione in the absence of Me 3 NO at 90°C generated mononuclear complex 2 as the major product along with smaller amounts of complexes 1 and 3. These results suggest that the N-oxide facilitates the decarbonylation reaction. Crystal data for 1: monoclinic, space group C2/c, a = 26.9990(5) Å, b = 7.6230(7) Å, c = 14.2980(13) Å, β = 101.620(2)°, V = 2882.4(4) Å 3 , Z = 8. Crystal data for 2: monoclinic, space group C2/c, a = 5.7884(3) Å, b = 13.9667(7) Å, c = 17.2575(9) Å, β = 96.686(1)°, V = 1385.69(12) Å 3 , Z = 4. © 2004 Elsevier B.V. All rights reserved.