Approaches to Sigma Complexes via Displacement of Agostic Interactions: An Experimental and Theoretical Investigation

摘要

A series of coordinatively unsaturated, 16-electron, cationic ruthenium complexes bearing PNP pincer ligands of the type [RuH(L)((PNP)-P-R)](+) (L = PPh3, R = PhCH2 (3), Ph (4); L = CO, R = PhCH2 (5); (PNP)-P-R = RN(CH2CH2PPh2)(2)) has been prepared and characterized. These complexes exhibit agostic interaction in the sixth coordination site. The binding of various X-H (X = H, Si, B, and C) bonds in small molecules such as H-2, silanes, tetracoordinate boranes, and CH4 to the ruthenium center via displacement of the relatively weak agostic interaction in these complexes has been studied. Structures of [RuH(L)((PNP)-P-R)](+) (L = PPh3, R = PhCH2 (3), Ph (4); L = CO, R = PhCH2 (5); (PNP)-P-R = RN(CH2CH2PPh2)(2)) complexes and the sigma-borane complex trans-[RuH(CO)(eta(1)-H-BH2 center dot NMe3)((PNP)-P-R)](+) (R = PhCH2 (15)) have been established by X-ray crystallography. The relative binding strengths of the X-H bonds to ruthenium center in these complexes has been studied using computational methods.