MIXED CARBONYL-ISOCYANIDE AND CARBONYL-NITRILE COMPLEXES DERIVED FROM THE REACTIONS OF THE MULTIPLY BONDED DIRHENIUM(II) COMPLEXES RE2X4(DPPM)2(CO) (X = CL OR BR - DPPM = PH2PCH2PPH2) - THE STRUCTURAL CHARACTERIZATION OF CL2RE(MU-CL)(MU-DPPM)2RECL(CO) AND CL2RE(MU-CL)(MU-CO)(MU-DPPM)2RECL(CNXYLYL)
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Reactions of the triply bonded dirhenium(II) complexes Re2X4(dppm)2(X = Cl or Br; dppm = bis(diphenylphosphino)methane) with carbon monoxide yield the monocarbonyls X2Re(-X)(-dppm)2ReX(CO). The chloride derivative Re2Cl4(dppm)2(CO) (1), which has been characterized by X-ray diffraction, cocrystallizes with three independent benzene molecules in the hexagonal space group P63/m (No. 176). The cell dimensions are = 28.469 (4) , c = 14.301 (2) , V = 10037 (4) 3, and Z = 6. The ReRe bond distance is 2.338 (1) and the molecule has a novel A-frame-like structure. The crystal structure was refined to R = 0.048 (unit weights). Reactions of this molecule with 1 equiv of an isocyanide (RNC) generate complexes of stoichiometry Re2Cl4(dppm)2(CO)(CNR) (R = i-Pr, t-Bu, xylyl, or mesityl) in which the CO ligand is in either a terminal or bridging position, depending on the isocyanide used. The xylylNC derivative Cl2Re(-Cl)(-CO)(-dppm)2ReCl(CNxylyl) (2) has been characterized by X-ray crystallography. Compound 2 crystallizes in the monoclinic system, space group P21/n, with a = 18.211 (4) , b = 15.907 (2) , c = 20.887 (6) , = 93.63 (3), V = 6048 (1) 3, and Z = 4. The crystal structure was refined to residuals of R = 0.0650, Rw= 0.0691. The ReRe bond distance is 2.581 (2) , and the molecule comprises a pair of distorted, edge-sharing octahedra. The monocarbonyl reacts readily with an excess of nitrile RCN in the presence of T1PF6to yield the PF6- salts of stoichiometry [Re2Cl3(dppm)2(CO)(NCR)2]PF6(R = CH3, C2H5, or C6H5). The IR and NMR (1H and 31 P{1H}) spectral properties of these particular complexes suggest that there is an all-cis arrangement of chloride ligands on one side of the molecule. 1986, American Chemical Society. All rights reserved.
