Synthesis, Crystal Structures and NMR Spectroscopic Studies on Ruthenium Complexes with Phosphanylacetal and Phosphanylthioacetal Ligands

The chemistry of the mixed PS-donor ligands [2-(1,3-dioxolan-2-yl)phenyl]diphenylphosphane (PhPOO, 1), and [2-(1,3-dithiolan-2-yl)phenyl]diphenylphosphane (PhPSS, 2) with the Ru-II precursors [RuCl2(PPh3)(3)] and [RuCl2(4-cymene)](2) has been investigated. The structures of the resulting complexes were analysed by X-ray crystallography and H-1, C-13 and P-31 NMR spectroscopy, and their activity as catalysts for hydrosilylation was examined. Reaction of 1 with [RuCl2(PPh3)(3)] in methanol solution produced [RuCl2(PhP(OMe)(2))(2)] (3) (with [RuCl2(MeOH)(PhP(OMe)(2))(PPh3)] (3a) as a side product), whereas the same reaction with [RuCl2(4-cymene)](2) produced [RuCl2(PhPOO)(2)] (4). The dioxolane complex 4 showed fluxional behaviour by NMR spectroscopy, whereas 3 did not. Reaction of PhPSS with [RuCl2(PPh3)(3)] in methanol solution produced [RuCl2(PhPSS)(2)] (5), and reaction with [RuCl2(4-cymene)](2) produced the cationic complex [RuCl(4-cymene)(PhPSS)](+) (6) by precipitation with NaBPh4. In solution both 5 and 6 exist in two isomeric forms, and neither shows evidence of fluxionality at room temperature. Of the complexes tested only the acetal species 3 showed any significant hydrosilylation activity. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim., Germany, 2009)