Ruthenium Hydride and Dihydrogen Complexes with Dendrimeric Multidentate Ligands

Abstract

The reaction of the ruthenium polyhydrides RuH2(PPh3)4 and RuH2(H2)2(PCy3)2 with the previously reported dendrimers Gx-N(CH2PPh2)2 (first, second, and third generations; G1, G2, and G3) cleanly leads to the new complexes [Gx-N(CH2PPh2)2]RuH2(PPh3)2 (1-Gx) and [Gx-N(CH2PPh2)2]RuH2(H2)(PCy3), which exist as a mixture of isomers (3‘-Gx, 3‘‘-Gx, 4‘-Gx, and 4‘‘-Gx). Complexes 3-Gx/4-Gx were shown to accommodate a stretched dihydrogen ligand and to display a high temperature for the minimum of the T1 relaxation time, in agreement with their binding to the dendrimer in solution. The reactivity of these complexes with CO, leading to new dihydrido carbonyl ruthenium complexes (2-Gx, 5-Gx), is described.