Solid-State Structure and Solution Reactivity of [(Ph3P)4Ru(H)2] and Related Ru(II) Complexes Used in Catalysis: A Reinvestigation
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X-ray analysis of [(Ph3P)4Ru(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)3Ru(H)2] (2), but [(Ph3P)3Ru(H2)(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(H2)(OH) rearrangement, H2 loss, and dimerization to give [(Ph3P)4Ru2(H)2(μ-OH)2] (4). The H2 thus produced is trapped with 2 to give 3. Complexes 3·0.5C6H6, 3·2THF, 4·2H2O, [(Ph3P)3Ru(N2)(H)2] (5), and [(Ph3P)2(H)Ru(μ-H)3Ru(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)4RuCl2]” (7) has been performed to finally demonstrate that 7 is, in fact, [(Ph3P)3RuCl2]·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].
采用文献方法[Young, R.; Wilkinson, G. *Inorganic Syntheses* (Inorg. Synth.) 1990, 28, 337]制备的四(三苯基膦（triphenylphosphine, PPh₃）)二氢合钌(II)（化学式为[(PPh₃)₄Ru(H)₂]，记为1）的X射线衍射分析结果显示，该配合物与三苯基膦共结晶，这解释了此前报道的1的溶液中存在游离三苯基膦的实验现象。研究人员还获得了不含晶格三苯基膦的1的晶型，并对其进行了结构表征，发现该晶型在溶液中会生成少量游离三苯基膦与另一物种A。然而与此前认知相悖的是，物种A并非[(三苯基膦)₃合钌(II)二氢]（记为2），而是[(三苯基膦)₃合钌(II)二氢·分子氢]（记为3），该物种由1与痕量水反应生成。该反应的历程大致为：1先失去三苯基膦得到2，随后水分子配位，经历Ru(H)(OH₂)/Ru(H₂)(OH)重排、脱除氢气，再发生二聚反应，最终生成[(三苯基膦)₄合二钌(II)二氢·μ-二羟基桥]（记为4）。反应中脱除的氢气会被2捕获，进而生成3。配合物3·0.5苯（benzene, C₆H₆）、3·2四氢呋喃（tetrahydrofuran, THF）、4·2水、[(三苯基膦)₃合钌(II)二氢·氮气（dinitrogen, N₂）]（记为5）以及[(三苯基膦)₂氢合钌(II)·μ-三氢桥·(三苯基膦)₃合钌(II)]·0.5四氢呋喃（记为6·0.5THF）均为首次完成结构表征。此外，研究人员首次对长期被记作"[(三苯基膦)₄合钌(II)二氯]"（记为7）的物种开展了单晶X射线衍射分析，最终证实该物种实为[(三苯基膦)₃合钌(II)二氯]·三苯基膦，这与Hoffman和Caulton早在1975年提出的推断完全一致[Hoffman, P.R.; Caulton, K.G. *Journal of the American Chemical Society* (J. Am. Chem. Soc.) 1975, 97, 4221]。
