Model Investigations for Vanadium-Protein Interactions. Synthetic, Structural, and Physical Studies of Vanadium(III) and Oxovanadium(IV/V) Complexes with Amidate Ligands

Reaction of the amide ligand N-[2-((2-pyridylmethylene)amino)phenyl]pyridine-2-carboxamide (Hcapca) with VCl3 affords the compound trans-[VCl2(capca)] (1), the first example of a vanadium(III) complex containing a vanadium-deprotonated amide nitrogen bond, while reaction of bis(pentane-2,4-dionato)oxovanadium(IV) with the related ligands N-[2-((2-phenolylmethylene)amino)phenyl] pyridine-2-carboxamide (H(2)phepca), 1-(2-hydroxybenzamido)-2-(2-pyridinecarboxamido)benz (H(3)hypyb), and 1,2-bis(2-hydroxybenzamido)benzene (H(4)hybeb) yields the complexes [VO(phepca)] (2), Na[VO(hypyb)]. 2CH(3)OH (4 . 2CH(3)OH), and Na-2[VO(hybeb)]. 3CH(3)OH (5 . 3CH(3)OH) respectively. The preparation of the complex {N-[2-((2-thiophenoylmethylene)amino)phenyl]pyridine 2-carboxamido}oxovanadium(IV) (3) has been achieved by reaction of N-(2-aminophenyl)pyridine-2-carboxamide and 2-mercaptobenzaldehyde with [VO(CH3COO)(2)](x). Oxidation of complex 5 . 3CH(3)OH with silver nitrate gives its vanadium(V) analogue (8 . CH3OH), which is readily converted to its corresponding tetraethylammonium salt. (10 . CH2Cl2) by a reaction with Et(4)NCl. The crystal structures of the octahedral 1 . CH3CN, and the square-pyramidal complexes 3, 4 . CH3CN, 5 . 2CH(3)OH, and 10 were demonstrated by X-ray diffraction analysis. Crystal data are as follows: 1 . CH3CN, C18H13Cl2N4OV . CH3CN M(r) = 464.23, monoclinic, P2(1)/n, a = 10.5991(7) Angstrom, b = 13.9981(7) Angstrom, c = 14.4021(7) Angstrom, beta = 98.649(2)degrees, V = 2112.5(3) Angstrom(3), Z = 4, R = 0.0323, and R(w) = 0.0335; 3, C19H13N3O2SV, M(r) = 398.34, monoclinic, P2(1)/n, a = 12.1108(10) Angstrom, b = 19.4439(18) Angstrom, c = 7.2351(7) Angstrom; beta = 103.012(3)degrees, V = 1660.0(4) Angstrom(3), Z = 4, R = 0.0355, and R(w) = 0.0376; 4 . CH3CN, C19H12N3O4VNa . CH3CN, M(r) = 461.31, monoclinic, P2(1)/c, a = 11.528(1) Angstrom, b = 11.209(1) Angstrom, c = 16.512(2) Angstrom, beta = 103.928(4)degrees, V = 2071.0(5) Angstrom(3), Z = 4, R = 0.0649, and R(w) = 0.0806; 5 . 2CH(3)OH, C20H10N2O5VNa2 . 2CH(3)OH, M(r) = 519.31, triclinic, P1, a = 12.839(1) Angstrom, b = 8.334(1) Angstrom, 12.201(1) Angstrom, alpha = 106.492(2)degrees, beta = 105.408(2)degrees, gamma = 73.465(2)degrees, V = 1175.6(3) Angstrom(3), Z = 2, R = 0.0894, and R(w) = 0.1043; 10, C28H32N3O5V M(r) = 541.52, monoclinic, P2(1)/c, a = 11.711(3) Angstrom, b = 18.554(5) Angstrom, c = 12.335(3) Angstrom, beta = 95.947(9)degrees, V = 2666(2) Angstrom(3), Z = 4, R = 0.0904, and R(w) = 0.0879. In addition to the synthesis and crystallographic studies, we report the optical, infrared, magnetic, and electrochemical properties of these complexes. Electron paramagnetic resonance [of oxovanadium(IV) species] and H-1, C-13{H-1}, and V-51 nuclear magnetic resonance [of oxovanadium(V) complex] properties are reported as well. This study represents the firsr systematic study of vanadium(III), (VO2+)-O-IV, and (VO3+)-O-V species containing a vanadium-deprotonated amide nitrogen bond. Inorg Chem