Blazina Damir, Duckett Simon B, Dyson Paul J, Lohman Joost A B
Department of Chemistry, University of York Heslington, York YO10 5DD, UK.
Chemistry. 2003 Mar 3;9(5):1045-61. doi: 10.1002/chem.200390098.
The reactivity of the cluster family [Ru(3)(CO)(12-x)(L)(x)] (in which L=PMe(3), PMe(2)Ph, PPh(3) and PCy(3), x=1-3) towards hydrogen is described. When x=2, three isomers of [Ru(3)(H)(mu-H)(CO)(9)(L)(2)] are formed, which differ in the arrangement of their equatorial phosphines. Kinetic studies reveal the presence of intra- and inter-isomer exchange processes with activation parameters and solvent effects indicating the involvement of ruthenium-ruthenium bond heterolysis and CO loss, respectively. When x=3, reaction with H(2) proceeds to form identical products to those found with x=2, while when x=1 a single isomer of [Ru(3)(H)(mu-H)(CO)(10)(L)] is formed. Species [Ru(3)(H)(mu-H)(CO)(9)(L)(2)] have been shown to play a kinetically significant role in the hydrogenation of an alkyne substrate through initial CO loss, with rates of H(2) transfer being explicitly determined for each isomer. A less significant secondary reaction involving loss of L yields a detectable product that contains both a pendant vinyl unit and a bridging hydride ligand. Competing pathways that involve fragmentation to form [Ru(H)(2)(CO)(2)(L)(alkyne)] are also observed and shown to be favoured by nonpolar solvents. Kinetic data reveal that catalysis based on [Ru(3)(CO)(10)(PPh(3))(2)] is the most efficient although [Ru(3)(H)(mu-H)(CO)(9)(PMe(3))(2)] corresponds to the most active of the detected intermediates.
描述了簇合物家族[Ru₃(CO)₁₂₋ₓ(L)ₓ]（其中L = PMe₃、PMe₂Ph、PPh₃和PCy₃，x = 1 - 3）与氢气的反应活性。当x = 2时，形成了[Ru₃(H)(μ-H)(CO)₉(L)₂]的三种异构体，它们赤道面膦的排列方式不同。动力学研究表明存在异构体内部和异构体之间的交换过程，其活化参数和溶剂效应分别表明涉及钌-钌键的异裂和CO的损失。当x = 3时，与H₂反应生成的产物与x = 2时相同，而当x = 1时，形成[Ru₃(H)(μ-H)(CO)₁₀(L)]的单一异构体。已证明[Ru₃(H)(μ-H)(CO)₉(L)₂]物种通过最初的CO损失在炔烃底物的氢化反应中起动力学上重要的作用，已明确测定了每种异构体的H₂转移速率。涉及L损失的不太重要的二级反应产生了一种可检测的产物，该产物同时含有一个侧链乙烯基单元和一个桥连氢化物配体。还观察到了涉及碎片化形成[Ru(H)₂(CO)₂(L)(炔烃)]的竞争途径，并表明非极性溶剂有利于该途径。动力学数据表明，基于[Ru₃(CO)₁₀(PPh₃)₂]的催化是最有效的，尽管[Ru₃(H)(μ-H)(CO)₉(PMe₃)₂]是检测到的最具活性的中间体。
