Pnictogen-Based Vanadacyclobutadiene Complexes.

Abstract

The reactivity of the V≡CtBu multiple bonds in the complex (dBDI)V≡CtBu(OEt2) (C) (dBDI2− = ArNC(CH3)CHC(CH2)NAr, Ar = 2,6-iPr2C6H3) 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 α-aza-vanadacyclobutadiene, (dBDI)V(kappa2-C,N-tBuCC(R)N) (R = Ad, 1; R = Ph, 2) and β-phospha-vanadacyclobutadiene moieties, (dBDI)V(kappa2-C,C-tBuCPCAd) (3). Complexes 1-3 are characterized using multinuclear and multidimensional NMR spectroscopy, including the preparation of the 50% 15N-enriched isotopologue (dBDI)V(kappa2-C,N-tBuCC(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(kappa2-C,C-tBuCC(H)CtBu) (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.