Oligomerization of early transition metal {M(OH)(3)}(2)(mu-C-2) acetylidestoward 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)-substi tuted (M = Ti, V) cyclopolyenes as simple models of metal carbides. We stud ied 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 spec ies. Special emphasis was placed on the comparison of the main properties o f these metal substituted cyclopolyenes with those of the corresponding cyc lopolyenes 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 s tructures and molecular geometries found for the vanadium species suggest a metalla radialene nature for these compounds, with the endocyclic conjugat ion of carbon-carbon double bonds replaced by an exocyclic arrangement of c arbon-metal double bonds.