Reactions of the dicarbonyl complex Re2Cl4(dppm)2(CO)2 with nitriles and isocyanides. Synthesis of [Re2Cl3(dppm)2(CO)2L]n+ (n = 0, 1; L = RCN, RNC) and the structural characterization of [Re2Cl3(dppm)2(CO)2(NCC2H5)]PF6
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The dicarbonyl complex Cl2Re(μ-Cl)(μ-CO)(μ-dppm)2ReCl(CO) (dppm = bis(diphenylphosphino)methane) reacts with nitriles (RCN) and isocyanides (RNC) in the presence of T1PF6 to generate cations of stoichiometry [Re2Cl3(dppm)2(CO)2L]PF6 (L = CH3CN, C2H5CN, C6H5CN, Me2CHNC, Me3CNC). These complexes exhibit a well-defined electrochemistry including a chemically accessible reduction (E1/2 ≃ -0,1 V vs. Ag/AgCl). The reactions of cobaltocene with these salts produce the paramagnetic neutral complexes Re2Cl3(dppm)2(CO)2L, the first examples of multiply bonded dirhenium complexes that possess the Re23+ core. The nitrile compound [Re2Cl3(dppm)2(CO)2(NCC2h5)]PF6-Ch2Cl2-1/2(C2H5)20 has been characterized by X-ray crystallography. It forms crystals in space group P1 with Z = 2 and the following unit cell dimensions: a = 16.574 (5) Å, b = 17.617 (6) Å, c = 12.238 (3) Å, α = 101.94 (2)°, β = 107.64 (2)°, γ = 65.54 (2)°, V= 3086 (2) Å3. The cation is an edge-sharing bioctahedron with one bridging CO and one bridging C1. The central plane containing the shared edge has the EtCN, μ-CO, and CO ligands along one side and three CI atoms along the other. The bridging bidentate dppm ligands occupy the positions above and below this plane. The Re-Re distance is 2.586 (1) Å, the average Re-P distance is 2.472  Å, the Re-CO(terminal) distance is 1.92 (2) Å, and the two Re-CO(bridge) distances are 2.00 (2) and 2.13 (2) Å. The Re-Cl(bridge) distances, 2.473 (5) and 2.448 (4) Å, are longer than the Re-Cl(terminal) distances, 2.407 (5) and 2.419 (5) Å, as expected. This structure provides further insight into the structure of the Re2Cl4(dppm)2(CO)2 molecule, which forms systematically disordered crystals. © 1985, American Chemical Society. All rights reserved.
author list (cited authors)
Cotton, F. A., Dunbar, K. R., Falvello, L. R., & Walton, R. A.