M•••H-C interaction - Agostic or not: A comparison of phenyl- versus pyridyl-bridged transition metal dimers

Two transition metal complexes of 2,6-bis[N-(8-quinolyl)carbamoyl]pyridine (L1) and one of 2,6-bis[N-(8-quinolyl) carbamoyl] benzene (L2) were synthesized and structurally characterized. Nickel(II) and copper(II) complexes with L1 gave bifurcated-pyridine dimeric complexes (1 and 2). A copper(II) complex of L2 gave the dimeric complex, 3, in which the isophthaloyl C-H moieties of both ligands have short contacts with the pair of copper centers. Density functional theory calculations at the B3LYP/6-31G* and B97-D/6-31G* levels of theory offer strong supporting evidence that the Cu(II)center dot center dot center dot H-C interactions in 3 are best described as weak hydrogen bonds rather than agostic interactions. (C) 2014 Elsevier B. V. All rights reserved.