Gallium and gallium dichloride, new solid-state reductants in preparative transition metal chemistry. New, lower temperature syntheses and convenient isolation of hexatantalum tetradecachloride octahydrate, Ta(6)(mu-Cl)(12)Cl(2)(OH(2))(4).4H(2)O, and synthesis and solid-state structure of a tetraalkylammonium derivative, [N(CH(2)Ph)Bu(3)](4)[Ta(6)(mu-Cl)(12)Cl(6)], of the reduced [Ta(6)(mu-Cl)(12)](2+) cluster core(1)

Reduction of TaCl(5) with either Ga or Ga(2)Cl(4), in the presence of NaCl, in a sealed borosilicate glass ampule at 500 degrees C, followed by aqueous Soxhlet extraction and treatment with SnCl(2) and hydrochloric acid, yielded Ta(6)(mu-Cl)(12)Cl(2)(OH(2))(4).4H(2)O in 92% (Ga) or 96% (Ga(2)Cl(4)) yield. Ga(2)Cl(4), a probable intermediate in the Ga-based reduction, is a more convenient reductant than Ga because it is readily dispersed in the reaction mixture, and these mixtures do not require homogenizations in order to afford high yields. Ta(6)(mu-Cl)(12)Cl(2)(OH(2))(4).4H(2)O was converted by ligand exchange to the first tetraalkylammonium derivative, [N(CH(2)Ph)Bu(3)](4)[Ta(6)(mu-Cl)(12)Cl(6)], of the reduced cluster core Ta(6)(mu-Cl)(12)(2+), in 88% yield. [N(CH(2)Ph)Bu(3)](4)[Ta(6)(mu-Cl)(12)Cl(6)] crystallizes from 1,2-dichloroethane/toluene mixtures in two crystalline morphologies, a nonsolvated cubic form and a solvated needle form. The solid-state molecular structures of both crystalline morphologies of [N(CH(2)Ph)Bu(3)](4)[Ta(6)(mu-Cl)(12)Cl(6)] consist of octahedral, 16 VEC hexatantalum cluster anions with an average Ta-Ta distance of 2.900[2] A, a Ta-Cl(bridge) distance of 2.463[2] A, a Ta-Cl(terminal) distance of 2.567[5] A, and a Ta-Cl-Ta angle of 72.1[1] degrees for the cubic form, and for the solvated needle morphology, an average Ta-Ta distance of 2.900[1] A, a Ta-Cl(bridge) distance of 2.461[1]A, a Ta-Cl(terminal) distance of 2.567[3] A, and a Ta-Cl-Ta angle of 72.19[7] degrees.