Mixed halide/phosphine complexes of the dirhenium core. Part 7. Reactions of [Re_2I_8]~(2-) with monodentate phosphines

摘要

Reactions of the octaiododirhenate anion [Re_2I_8]_2 -with monodentate phosphines (PR_3 = PMe_3 (I), PMe_2Ph (2), PEt_3 (3), and PEt_2Ph (4 have been studied in two different solvents, ethanol and benzene, at room temperature. The reactions in ethanol resulted in two-electron reduction products having the Re_24 + core, Re_214(PR_3)_4 (R, = Me_3 (la) and Me_2Ph (2a), for which X-ray diffraction study revealed a 1,3.6,8 isomer type. The reaction of [Re_2I_8f- with PMe3 in benzene led to an intermediate edge-sharing bioctahedral dirhenium(l11) complex, Rel(~-1)214(PMe_3)_4 (Ib), with no metal-metal bond. The interaction of PEt3 with [Re_8]_2- in benzene again yielded a kinetic product with a different stoichiometry and a Rei + core. [Bu_4N][Re_216(PEt_3)_2] (3c). The analogous reactions of [ReJ8]2- with PMe_2Ph and PEt2Ph in benzene involved two-electron reductions and gave complex 2a and ReJ_4(PEt_2Ph)_4 (4a), as products. Reduction of Ib with KC8 gave laas the main product along with a few crystals of 1,3,6-ReJs(PMe_3)_3 (Id). Mixed iodide/phosphine complexes of the dirhenium core Re2" + , where n = 4 (la, 2a, 4a), 5 (Id, 3c), and 6 (Ib) have for the first time been characterized by X-ray crystallography. In addition, these products have been further identified by a combination of mass spectrometry and cyclic voltammetric measurements.