Mixed Chloride/Phosphine Complexes of the Dirhenium Core. 10. Redox Reactions of an Ede-Sharing Dirhenium(III) Non-metal-Metal-Bonded Complex, Re_2(#mu#-Cl)_2(PMe_3)_4

摘要

Reduction and oxidation reactions of the dirhenium(III) non-meal-metal-bonded dge-sharing complex, Re_2(#mu#-Cl)_2Cl_4(PMe_3)_4 (1), have been studied. Several new mono- and dinuclear rhenium compounds have been isolated and structurally characterized in the course of this study. Reductions of 1 with 1 and 2 equiv of KC_8 result in an unusual face-sharing complex having an Re_2~(5-) core, Re_2(#mu#-Cl)_3Cl_2(PMe_3)_4 (2), and a triply bonded Re~II compound, 1,2,7,8-Re_2Cl_4(PMe_3)_4 (3), respectively. Two-electron reduction of 1 in the presence of tetrabutylammonium chloride affords a new triply bonded complex of the Re_2~(4+) core, [Bu~n_4N][1,2,7-Re_2Cl_5(PMe_3)_3] (4). Oxidation of 1 with NOBF_4 yields a Re~IV mononuclear compound, trans-ReCl_4(PMe_3)_2 (5). Two isomers of the monomeric Re~III anion, [ReCl_4(PMe_3)_2]~- (6, 7), have been isolated as side products. The crystal structures of compounds 2 and 4-7 have been determined by X-ray crystallography. The Re-Re distance in the face-sharing complex 2 of 2.686(1) A is relatively short. The metal-metal bond length in anion 4 of 2.2354(7) A is consistent with the usual values for the triply bonded Re_2~(4+) core compounds. In addition, a cis arrangement of trimethylphosphineligands in the starting material 1 is retained upon reduction in the dinuclear products 2-4.