Mixed chloride/phosphine complexes of the dirhenium core. 6. Rare or unprecedented isomers of [Re2Cl6(PR3)(2)] stoichiometry

Several new paramagnetic dirhenium(II,III) anions of the formula [Re2Cl6P2] (-) (P-2 = (PPr3n)(2) (1), (PEt2Ph)(2) (2), dppp (3)) have been isolated in the form of their tetrabutylammonium salts as the kinetic products in reac tions of [Re2Cl8](2-) with an appropriate phosphine ligand. All three compl exes have been characterized in solution by cyclic voltammetry, ESR, and ma ss spectroscopy. Three different isomeric forms of the [Re2Cl6P2] core have been recognized in the solid state by X-ray crystallography. The known 1,7 -isomer (C-2h) With a centrosymmetric disposition of phosphine groups was f ound for PPr3n (1a) and PEt2Ph (2) ligands. The compound [(Bu4N)-N-n][Re2Cl 6(PPr3n)(2)] was also crystallized in the unprecedented form of a 1,6-isome r (C-2) (1b) which can be derived from 1a by a 90 degrees rotation of the l igands around the metal-metal bond. For the diphosphine, a C-s isomer of [R e2Cl6(dppp)](-) (3) was discovered having the dppp ligand chelating on one rhenium atom. Crystallographic data are as follows: for 1a, monoclinic spac e group P2(1)/n with a = 12.758(1) Angstrom, b = 15.755(5) Angstrom, c = 24 .160(3) Angstrom, beta = 104.22(1)degrees, and Z = 4; for 1b, monoclinic sp ace group P2(1)/c with a = 16.3355(8) Angstrom, b = 12.656(1) Angstrom, c = 22.892(2) Angstrom, beta = 94.735(6)degrees, and Z = 1; for 2, triclinic s pace group P (1) over bar with a = 11.868(1) Angstrom, b = 12.125(2) Angstr om, c = 15.375(3) Angstrom, alpha = 88.01(1)degrees, beta = 82.64(1)degrees , gamma = 88.47(1)degrees, and Z = 2; for 3, triclinic space group P (1) ov er bar with 11.8986(4) Angstrom, b = 11.913(1) Angstrom, c = 18.383(2) Angs trom, alpha = 102.23(2)degrees, beta = 108.003(5)degrees, gamma = 97.38(1)d egrees, and Z = 2.