Completing the series of Group VI heterotrimetallic M2Cr(dpa)(4)Cl-2 (M-2 = Cr-2, Mo-2, MoW and W-2) compounds and investigating their metal-metal interactions using density functional theory

摘要

Metalation of the quadruply bonded Mo-2(dpa)(4) and W-2(dpa)(4) (dpa = 2,2'-dipyridylamido) compounds with CrCl2 results in the formation of the new heterotrimetallic complexes Mo2Cr(dpa)(4)Cl-2 (1) and W2Cr(dpa)(4)Cl-2 (2). X-ray crystal structures of 1 and 2 reveal short Mo-2 center dot center dot center dot Cr and W-2 center dot center dot center dot Cr distances of 2.69 and 2.65 angstrom, respectively. Electronic absorption spectra and electrochemical data for 1 and 2 are presented. Variable temperature magnetic susceptibility measurements establish the electronic spin states of 1 and 2, which are S = 2. Molecular orbital analysis by density functional theory (DFT) calculations reveals a 3-center/3-electron sigma bonding configuration leading to a partial sigma type interaction between the M-2 quadruply bonded unit and Cr in 1 and 2. Time-dependent DFT provides support for the assignment of the lowest energy feature in the electronic absorption spectra of 1 and 2 as a delta -> delta(+) transition with M-2-to-Cr charge transfer character. (C) 2014 Elsevier B.V. All rights reserved.