Heterometallic multiple bonding: delocalized three-center σ and π bonding in chains of 4d and 5d transition metals.

Abstract

Heterotrimetallic compounds Mo2Ru(dpa)4Cl2 (1) and W2Ru(dpa)4Cl2 (2) are prepared by reactions of M2(dpa)4 (M = Mo or W; dpa = 2,2'-dipyridylamide) with [Ru(CO)3Cl2]2. Crystallographic studies reveal short Mo-Ru and W-Ru distances, 2.38 Å (1) and 2.39 Å (2), suggestive of delocalized Mo-Mo-Ru and W-W-Ru bonding. In contrast to the σ bonding found in the corresponding iron compounds, density functional theory calculations reveal both a three-center/two-electron σ bond and two three-center/four-electron π bonds in the M-M-Ru compounds.