Oxovanadium(IV)-Amide Binding. Synthetic, Structural, and Physical Studies of {N-[2-(4-Oxopent-2-En-2-Ylamino)Phenyl]Pyridine-2-Carboxamido}Oxovanadium(IV) and {N-[2-(4-Phenyl-4-Oxobut-2-en-2-Ylamino)Phenyl]Pyridine-2-Carboxamido}Oxovanadium(IV)

Abstract

The complexes [VO(pycac)] and [VO(pycbac)] were prepared by the reaction of bis(pentane-2, 4-dionato)oxovanadium(IV) with either N-[2-(4-oxopent-2-en-2-ylamino)phenyl]pyridine-2-carboxamide (H2pycac) or 7V-[2-(4-phenyloxobut-2-en-2-ylamino)-phenyl]pyridine-2-carboxamide (H2pycbac) in a methanolic solution. Crystals of [VO(pycac)] crystallized from nitromethane were monoclinic, space group P21n with a = 7.5938 (1) Å, b = 30.161 (1) Å, c = 13.6982 (2) Å, β = 86.468 (1)°, Z=8, and Rw = 5.39%. Crystallization of [VO(pycac)] from chlorobenzene yielded triclinic crystals with a space group PI and a = 7.8558 (5) Å, b = 12.934 (1) Å, c = 15.675 (1) Å, α = 78.594 (2)°, β = 89.938 (2)°, γ = 88.097 (2)°, Z = 4, and Rw = 6.45%. [VO(pycbac)] crystals were monoclinic, space group P21/c with a = 6.5422 (4) k, b= 14.4786 (8) Å, c = 19.963 (1) Å, β = 93.461 (2)°, Z = 4, and Rw = 3.80%. The geometry about vanadium in each structure approximates a square pyramid with an average V=0 bond length of 1.595 Å with the metal ion 0.669 A above the basal plane. The average V-N(pyridine), V-N(amine), V-N(amide), and V-O bond lengths are 2.100, 2.045, 1.981, and 1.916 Å, respectively. The V-N(amide) and V-0 bond lengths constitute rare examples of such short V-N and V-0 distances that have been reported for oxovanadium(IV) complexes to date. In addition to the synthesis and crystallographic studies, we report the optical, infrared, magnetic, electron paramagnetic resonance, and electrochemical properties of these complexes. This study represents the first systematic study of oxovanadium containing a vanadium-amide bond. © 1992, American Chemical Society. All rights reserved.