Phosphane effects on formation and reactivity of [Ru(L)(PR3) ('N2Me2S2')] complexes with L = N2, N2H4, NH3, and CO

Metal-sulfur complex fragments, to which small molecules like N-2, N2H2, N2H4, NH3, or CO can bind, are desirable model compounds concerning enzymatic N-2 fixation. This paper reports on the effects of the phosphane co-ligand on formation and reactivity of [Ru(L)(PR3)('N2Me2S2')] ['N2Me2S2'(2-) = 1,2-ethanediamine-N,N'-dimethyl-N,N'-bis(2-benzenethiolate)(2-)] complexes with nitrogenase relevant ligands, especially N-2, N2H4, NH3, and CO. Treatment of [Ru(NCCH3)(4)Cl-2] with Li-2'N2Me2S2', excessive LiOMe, bulky PPh3 or PCy3, respectively, led to the formation of two series of [Ru(L)(PR3)('N2Me2S2')1 complexes [for R = Ph: 1b, 1c (L = NCCH3 6b (L = N2H4), 7b (L = N-2) 8b(1-3) (L = CO), 9b (L = NH3); for R = Cy: 1a (L = NCCH3), 6a (L = N2H4), 7a(L = N-2), 8a (L = CO), 9a (L = NH3)]. While the use of PPh3 (theta = 145degrees) yielded cis,trans and cis,cis isomers of [Ru(NCCH3)(PPh3)('N2Me2S2')] (1b, 1c), no isomer formation was observed with the bulkier phosphane PCy3 (theta = 170degrees). Sterically less demanding phosphanes (theta = 118-132degrees) afforded bisphosphane complexes [Ru(PR3)(2)('N2Me2S2')] [2d (R = Me), 2e (R = Et), 2f (R = nPr), and 2g (R = nBu)], which were practically inert and could only be converted in two cases and under drastic reaction conditions into the CO complexes [Ru(CO)(PR3)('N2Me2S2')] [4e (R=Et), 4f (R = nPr)]. The chelating bidentate phosphane dppe (bisdiphenylphosphanoethane) yielded exclusively the mononuclear complex [Ru(dppe)('N2Me2S2')] (3). (C) 2004 Elsevier B.V. All rights reserved.