Hybridization vs. Bond Stretching Isomerism in Ru(II) Cyclometalated Complexes of 2-Phenylpyridine

Abstract

The phenomenon of formation of two isomers, yellow and orange, of the cyclometalated Ru(II) complex, [Ru(o-C6H4-py)(MeCN)4]+, was investigated by EELS spectroscopy and theoretical calculations. Both forms show very similar structures and spectroscopic properties, but slight differences in X-ray data and absorption between them were noted. No double minimum on the potential energy surface was found and thus these two forms cannot be considered as bond stretching isomers. However, the DFT study revealed the change in the hybridization of the carbon in trans-position of one of acetonitrile ligands. This effect can be responsible for the difference in colour. The results of the theoretical modelling coincide well with the experimental EELS data.

Bond-bending isomerism and metallophilicity in metal–halogen anions (Cu,Ag,Au)2X3−, X = F, Cl, Br, I, At

“…9 Although a number of systems have been suspected to be BSI and investigated, 10 the number of compounds, which demonstrate this isomerism, is very limited but undoubtedly observed. 11,12 As some systems differs in their magnetic states, Hoffmann and Parkin distinguished "bond-stretch" isomerism, where both isomers, lie on the same energy surface, from "spinstate" isomerism where a change of multiplicity occurs. 13 More recently, giving up controversies, Li et al 14 investigated the possible relationship between bond-isomerism and the competition between covalent bonding and aurophilic interactions in the gaseous complex (Au 2 I 3 ) − .…”

“…9 Although a number of systems have been suspected to be BSI and investigated, 10 the number of compounds, which demonstrate this isomerism, is very limited but undoubtedly observed. 11,12 As some systems differs in their magnetic states, Hoffmann and Parkin distinguished “bond-stretch” isomerism, where both isomers, lie on the same energy surface, from “spin-state” isomerism where a change of multiplicity occurs. 13…”