Solid-State Structure and Solution Reactivity of [(Ph3P)4Ru(H)2] and Related Ru(II) Complexes Used in Catalysis: A Reinvestigation

X-ray analysis of [(Ph3P)(4)Ru(H)(2)] (1) prepared by a literature procedure [Young, R.; Wilkinson, G. Inorg. Synth. 1990, 28, 337] shows that 1 is cocrystallized with PPh3, explaining the previously reported observations of free phosphine in solutions of 1. Lattice PPh3-free forms of 1 have also been obtained, structurally characterized, and found to generate small quantities of uncoordinated PPh3 and another species (A) in solution. Against previous beliefs, however, A is not [(Ph3P)(3)Ru(H)(2)] (2), but [(Ph3P)(3)Ru(H-2)(H)(2)] (3) that forms in the reaction of 1 with adventitious water. This reaction apparently occurs via PPh3 loss from 1 to give 2, followed by H2O coordination, Ru(H)(OH2)/Ru(H-2)(OH) rearrangement, H2 loss, and dimerization to give [(Ph3P)(4)Ru-2(H)(2)(mu-OH)(2)] (4). The H-2 thus produced is trapped with 2 to give 3. Complexes 3 0.5C6H6, 3 2THF, 4 2H(2)O, [(Ph3P)(3)Ru(N-2)(H)(2)] (5), and [(Ph3P)(2)(H)Ru(mu-H)(3)Ru(PPh3)(3)] 0.5THF (6 0.5THF) have been structurally characterized for the first time. Also for the first time, a single-crystal X-ray diffraction study of the long-known [(Ph3P)(4)RuCl2] (7) has been performed to finally demonstrate that 7 is, in fact, [(Ph3P)(3)RuCl2] PPh3, precisely as proposed by Hoffman and Caulton as early as 1975 [Hoffman, P.R.; Caulton, K.G. J. Am. Chem. Soc. 1975, 97, 4221].