Pincer ligands with an all-phosphorus donor set: subtle differences between rhodium and palladium
作者:Richard C. Bauer、Yann Gloaguen、Martin Lutz、Joost N. H. Reek、Bas de Bruin、Jarl Ivar van der Vlugt
DOI:10.1039/c1dt10360a
日期:——
The synthesis of a new, all-phosphorus pincer PPNEt2P ligand L3NEt2, which is derived from 2-indolylphosphine and features a central N2P(NEt2) core, is described. This ‘PPP’ species shows coordination toward Rh as a neutral trisphosphine ligand. Tridentate diphenylphosphine-derived PPHP ligands L1H and L2H, featuring a secondary phosphine core, show ‘ambivalent’ coordination, acting as persistent neutral triphosphine ligands with Rh, and as easily-formed monoanionic phosphido(bisphosphine) pincer ligands toward Pd. These subtle differences, which might be more general for group 9 and 10 metal complexes with this ligand set, are explained by comparative DFT calculations (BP86; def2-TZVP level of theory) for the Rh and Pd species involved, including those with the structurally related PNHP ligands. The optimized structure for complex PdCl(L2) indicates minimal overlap of available Pd d-orbitals with the lone pair of the central, deprotonated phosphorus atom (formally a phosphido fragment), suggesting that it behaves predominantly like a bulky phosphine instead of a phosphido fragment.
本文描述了一种新型全磷钳形 PPNEt2P 配体 L3NEt2 的合成过程,这种配体来自 2-吲哚基膦,具有一个中心 N2P(NEt2) 核心。这种 "PPP "物种作为中性三膦配体显示出与 Rh 的配位关系。三叉二苯基膦衍生的 PPHP 配体 L1H 和 L2H 具有二级膦核心,显示出 "矛盾 "配位,对 Rh 起着持久的中性三膦配体的作用,而对 Pd 则是易形成的单阴离子磷酰(双膦)钳配体。这些微妙的差异可能是具有该配体组的第 9 族和第 10 族金属配合物的普遍现象,通过对相关的 Rh 和 Pd 物种(包括具有结构上相关的 PNHP 配体)进行比较 DFT 计算(BP86;def2-TZVP 理论水平)可以得到解释。PdCl(L2) 复合物的优化结构表明,钯的可用 d 轨道与中央去质子化磷原子(形式上为磷酰片段)的孤对电子的重叠极少,这表明它的行为主要类似于大块膦,而不是磷酰片段。