Pnictogen-based vanadacyclobutadiene complexes

Abstract

The reactivity of the V^Ct Bu multiple bonds in the complex (dBDI)V^Ct Bu(OEt2) (C) (dBDI2− = ArNC(CH3)CHC(CH2)NAr, Ar = 2,6-i Pr2C6H3) with unsaturated substrates such as N^CR (R = Ad or Ph) and P^CAd leads to the formation of rare 3d transition metal compounds featuring a-azavanadacyclobutadiene, (dBDI)V(k2 -C,N-t BuCC(R)N) (R = Ad, 1; R = Ph, 2) and b-phosphavanadacyclobutadiene moieties, (dBDI)V(k2 -C,C-t BuCPCAd) (3). Complexes 1–3 are characterized using multinuclear and multidimensional NMR spectroscopy, including the preparation of the 50% 15N-enriched isotopologue (dBDI)V(k2 -C,N-t BuCC(Ad)15N) (1-15N). Solid-state structural analysis is used to determine the dominant resonance structures of these unique pnictogen-based vanadacyclobutadienes. A systematic comparison with the known vanadacyclobutadiene (dBDI)V(k2 - C,C-t BuCC(H)Ct Bu) (4) is also presented. Theoretical investigations into the electronic structure of 2– 4 highlight the crucial role of unique V–heteroatom interactions in stabilizing the vanadacyclobutadienes and identify the most dominant resonance structures.