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

Reaction of a ‘VCl2·nTHF’ solution, prepared by the reduction of VCl3(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 V2(dpa)4·THF (1) compound. A similar reaction performed in THF at 0°C gave [V2(dpa)3(μ-Cl)2Li2(THF)6][BEt3H] (2), in which a dpa ligand adopts a novel ‘doubly-chelating/bridging’ coordination mode. Compound 2 reacts with CH2Cl2 giving V2(dpa)3Cl2·2CH2Cl2 (3), a valence delocalized V(II)⋯V(III) bioctahedral complex. In all three complexes, the formation of four additional metalligand bonds is favored over the formation of a VV bond. The V⋯V separations are 3.038(2), 3.024(2) and 3.091(2) Å 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) Å, β=98.98(2)°, V=1985.7(6) Å3 and Z=2; compound 2, space group I2/a, a=19.4674(8), b=14.390(1), c=24.219(2) Å, β=92.954(7)°, V=6775.4(7) Å3 and Z=2; compound 3, space group P21/c, a=12.0853(8), b=18.679(2), c=16.709(2), β=109.98(1)°, V=3544.9(6) Å3 and Z=4.