The flexibility of the cycloheptatrienyl ring in cycloheptatrienylvanadium carbonyl derivatives

In the lowest energy singlet (C7H7)2V2(CO)n (n = 5, 4, 3) structures the hapticity of the C7H7 ring is adjusted to give a VV triple bond of ∼2.5 Å length. Still higher order V-V bonds are found in the (C7H7)2V2(CO)n (n = 2, 1) structures. Low-energy (C7H7)2V2 structures include a bent singlet structure with a formal V-V sextuple bond and a linear D7d triplet structure with a VV triple bond.