Second-generation ruthenium olefin metathesis catalysts bearing aminophosphine ligands were investigated with systematic variation of the ligand structure. The rates of phosphine dissociation ( k1; initiation rate) and relative phosphine reassociation ( k-1) were determined for two series of catalysts bearing cyclohexyl(morpholino)phosphine and cyclohexyl(piperidino)phosphine ligands. In both cases, incorporating P-N bonds into the architecture of the dissociating phosphine accelerates catalyst initiation relative to the parent [Ru]-PCy3 complex; however, this effect is muted for the tris(amino)phosphine-ligated complexes, which exhibit higher ligand binding constants in comparison to those with phosphines containing one or two cyclohexyl substituents. These results, along with X-ray crystallographic data and DFT calculations, were used to understand the influence of ligand structure on catalyst activity. Especially noteworthy is the application of phosphines containing incongruent substituents (PR1R'2); detailed analyses of factors affecting ligand dissociation, including steric effects, inductive effects, and ligand conformation, are presented. Computational studies of the reaction coordinate for ligand dissociation reveal that ligand conformational changes contribute to the rapid dissociation for the fastest-initiating catalyst of these series, which bears a cyclohexyl-bis(morpholino)phosphine ligand. Furthermore, the effect of amine incorporation was examined in the context of ring-opening metathesis polymerization, and reaction rates were found to correlate well with catalyst initiation rates. The combined experimental and computational studies presented in this report reveal important considerations for designing efficient ruthenium olefin metathesis catalysts.

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解缠结配体对复分解催化剂活性的影响：钌-氨基膦配合物的实验和计算研究

研究了带有氨基膦配体的第二代钌烯烃复分解催化剂，配体结构发生了系统变化。测定了带有环己基（吗啉）膦和环己基（哌啶基）膦配体的两个系列催化剂的膦离解速率（k1；引发速率）和相对膦再结合速率（k-1）。在这两种情况下，相对于母体 [Ru]-PCy3 复合物，将 PN 键结合到离解膦的结构中会加速催化剂的引发；然而，对于三（氨基）膦连接的复合物，这种效应是减弱的，与含有一个或两个环己基取代基的膦相比，三（氨基）膦连接的复合物表现出更高的配体结合常数。这些结果，连同 X 射线晶体学数据和 DFT 计算，用于了解配体结构对催化剂活性的影响。尤其值得注意的是含有不一致取代基（PR1R'2）的膦的应用；详细分析了影响配体解离的因素，包括空间效应、诱导效应和配体构象。配体解离反应坐标的计算研究表明，配体构象变化有助于这些系列中最快引发催化剂的快速解离，该催化剂带有环己基-双（吗啉代）膦配体。此外，在开环复分解聚合的背景下检查了胺掺入的影响，发现反应速率与催化剂引发速率密切相关。