Oligomerization of early transition metal M(OH)(3)(2)(mu-C-2) acetylides toward the formation of [(OH)(3)MC](n) (n=4,6) metalla carbides: A theoretical study by density functional theory

Density functional calculations were performed on a series of M(OH3)-substituted (M = Ti, V) cyclopolyenes as simple models of metal carbides. We studied the oligomerization of the metal acetylide complexes {MLn}(2) (mu-C-2) as a possible precursor of these [(OH)(3)MC](n) (n = 4,6) hypothetical species. Special emphasis was placed on the comparison of the main properties of these metal substituted cyclopolyenes with those of the corresponding cyclopolyenes in an attempt to study the effects of the metal substituents on the organic C-4 and C-6 cyclic moieties. Whereas for the titanium species, the pi system of the polyene moiety is slightly perturbed, the electronic structures and molecular geometries found for the vanadium species suggest a metalla radialene nature for these compounds, with the endocyclic conjugation of carbon-carbon double bonds replaced by an exocyclic arrangement of carbon-metal double bonds.