LIGANDS FOR OXOVANADIUM(IV) - BIS(CATECHOLAMIDE) COORDINATION AND INTERMOLECULAR HYDROGEN-BONDING TO THE OXO ATOM

As a first step in the design of ligands which will bind selectively the vanadyl (VO2+) ion, the syntheses of two 1,3-bis(2,2'-diethyl)benzene-linked bis(catecholamide) ligands and their corresponding oxovanadium(IV) complexes are described. The ligands form 1:1 ligand:VO2+ complexes which exhibit similar spectroscopic properties; vis/UV spectra and EPR parameters are characteristic of bis(catecholato) coordination. The complexes also show similar quasi-reversible electrochemical behavior for the V(V)/V(IV) redox couple. The structures of the VO2+ complexes of both 3,5-bis[2-(2,3-dihydroxybenzamido)ethyl]phenol (1) (designed to be capable of hydrogen bonding to VO2+) and the comparison of 1,3-bis[2-(2,3-dihydroxybenzamido)ethyl]benzene (2) (with no hydrogen bond capability) have been determined. The solid-state structure of K2[VO(1)].3C3H7NO reveals an intermolecular hydrogen bond to the vanadyl oxo atom between symmetry-related complexes. This hydrogen bond weakens the V=O bond and results in a change in the coordination sphere for the solid-state structure relative to the [VO(2)]2- complex. The complex K2[VO(1)].3C3H7NO crystallizes in the space group P2(1)/n (No. 14) with unit cell parameters a = 13.644-(3) angstrom, b = 16.643(5) angstrom, c = 16.753(2) angstrom, beta = 99.13(1)-degrees, V = 3756(2) angstrom3, and Z = 4; R (R(w)) = 3.6 (4.3)% for 478 parameters and 3995 reflections with F(o)2 > 3sigma(F(o)2). The complex K2[VO(2)].3(C3H7NO) also crystallizes in P2(1)/n with unit cell parameters a = 13.844(4) angstrom, b = 17.633(7) angstrom, c = 16.410(4) angstrom, beta = 108.07(2)-degrees, V = 3808(2) angstrom3, and Z = 4; R (R(w)) = 5.1 (6.6)% for 482 parameters and 3572 reflections with F(o)2 > 3sigma(F(o)2).