STABILITY OF VANADIUM(II) ARYLOXIDES - SYNTHESIS AND CHARACTERIZATIONOF STERICALLY PROTECTED, NEUTRAL AND MONOMERIC VANADIUM(II) ARYLOXIDES - REACTIVITY WITH THE N-N BOND OF (ME3SI)CH=N=N

The preparation of neutral V(II) aryloxides has been achieved via liga nd-replacement reactions on three V(II) complexes (Mz2V(py))2(mu-N2), Mz2V(py)2, and VCl2(TMEDA)2 (Mz = o-Me2NCH2C6H4, TMEDA = N,N,N'N',-tet ramethylethylenediamine) with several phenols, or their corresponding alkali salts. In the case of sterically demanding phenols [2,6-(t-Bu)2 -4-MeC6H2OH, 2,6-Ph2PhOH, 2-(MeO)C6H4OH] it was possible to isolate an d characterize monomeric and neutral V(II) aryloxides with a variety o f coordination geometries. When similar reactions were carried out on the same complexes with less bulky alcohols (2,6-Me2PhOH, PhOH, t-BuOH ), monomeric V(III) and dimeric V(III)/V(IV) mixed-valence species wer e isolated. The crystal structures of the square-planar [2,6-(t-Bu)2-4 -MeC6H2O]2V(py)2 (4), saddle-shape (2,6-Ph2PhO)2V(TMEDA) (5), square-p yramidal (2,6-Ph2PhO)2V(py)3 (6), and octahedral [2-(MeO)C6H4O]2V(TMED A) (7) were demonstrated by X-ray diffraction analysis. Crystal data a re as follows. 4: C40H56VN2O2.(C7H8)2, M(r) = 833.12, triclinic, P1BAR , a = 9.701(2) angstrom, b = 15.303(3) angstrom, c = 9.000(2) angstrom , alpha = 101.99(2)degrees, beta = 112.59(2)degrees, gamma = 74.20(2)d egrees, V = 1179.0(4) angstrom3, Z = 1, lambda = 0.710 69 angstrom, R = 0.053, R(w) = 0.068, and GoF = 2.89 for 365 parameters and 3475 out of 4134 unique reflections. 5: C42H42N2O2V, M(r) = 657.74, monoclinic, P2(1)/a, a = 16.373(1) angstrom, b = 11.1624(9) angstrom, c = 19.536( 3) angstrom, beta = 97.35(1)degrees, V = 3541.3(7) angstrom3, Z = 4, l ambda = 0.709 30 angstrom, R = 0.044, R(w) = 0.017, and GoF = 1.63 for 589 parameters and 2714 out of 4603 unique reflections. 6: C51H41N3O2 V, M(r) = 778.85, monoclinic, C2/c, a = 20.65(2) angstrom, b = 14.28(1 ) angstrom, c = 16.08(1) angstrom, beta = 119.89(7)degrees, V = 4113(7 ) angstrom3, Z = 4, R = 0.053, R(w) = 0.049, and GoF = 1.34 for 259 pa rameters and 1505 out of 3182 unique reflections. 7: C20H30VN2O4, M(r) = 413.41, orthorhombic, Pna2(1), a = 13.519(5) angstrom, b = 13.846(4 ) angstrom, c = 11.196(2) angstrom, V = 2096(1) angstrom3, Z = 4, R = 0.037, R(w) = 0.047, and GoF = 1.96 for 244 parameters and 1669 out of 2116 unique reflections. Reaction of 7 with (Me3Si)CHN2 gave the new diamagnetic and dinuclear complex {[2-(MeO)C6H4O]2V}2[mu-NNCH-(SiMe3)] 2 (13). Complex 13 was co-crystallized in a 1/1 ratio with {[2-(MeO)C6 H4O]2V}2[mu-OC6H4(2-OCH3)]2, which was formed from the thermal degrada tion of 13 through a complicated reaction. Crystal data for the co-cry stallite NCH(SiMe3)]2/{[2-MeO)C6H4O]2V}2[mu-OC6H4(2-OCH3)]2 (14) are a s follows. 14: C39H45V2N2O10Si, M(r) = 831.76, triclinic, P1BAR, a = 1 4.443(6) angstrom, b = 15.039(6) angstrom, c = 10.679(3) angstrom, alp ha = 100.66(3)degrees, beta = 97.46(3)degrees, gamma = 113.84(3)degree s, V = 2030(1) angstrom3, Z = 2, R = 0.045, R(w) = 0.060, and GoF = 2. 45 for 488 parameters and 5530 out of 6946 unique reflections.