Metal-metal versus metal-ligand bonding in dimetal compounds with tridentate ligands

Reaction of a 'VCl2. nTHF' solution, prepared by the reduction of VCl2(THF) (3) with NaBEt3H in THF, and Lidpa (dpa = the anion of 2,2'-dipyridylamine) in a mixture of THF/toluene at reflux temperature yields the bioctahedral V-2(dpa)(4). THF (1) compound. A similar reaction performed in THF at 0 deg rees C gave [V-2(dpa)(3)(mu-Cl)(2)Li-2(THF)(6)][BEt3H] (2), in which a dpa ligand adopts a novel 'doubly-chelating/bridging' coordination mode. Compou nd 2 reacts with CH2Cl2 giving V-2(dpa)(3)Cl-2. 2CH(2)Cl(2) (3), a valence delocalized V(II)...V(III) bioctahedral complex. In all three complexes, th e formation of four additional metal-ligand bonds is favored over the forma tion of a V-V bond. The V V separations are 3.038(2), 3.024(2) and 3.091(2) Angstrom for 1-3, respectively. Crystal data are: compound 1, space group P2/n, a=13.102(2), b=9.294(2), c=16.510(4) Angstrom, beta=98.98(2)", V= 198 5.7(6) Angstrom(3) and Z = 2; compound 2, space group I2/a, a = 19.4674(8), b = 14.390(1), c = 24.219(2) Angstrom, P = 92.954(7)", V=6775.4(7) Angstro m(3) and 2=2; compound 3, space group P2(1)/c, a=12.0853(8), b=18.679(2), c =16.709(2), beta=109.98(1)degrees, V= 3544.9(6) Angstrom(3) and Z = 4. (C) 2000 Elsevier Science S.A. All rights reserved.