DIRECT ELECTROCHEMICAL SYNTHESIS OF X2INCH2X COMPOUNDS (X = BR, I) AND A STUDY OF THEIR COORDINATION CHEMISTRY

The electrochemical oxidation of indium in CH2X2/CH3CN media (X = Cl, Br, I) gives InX. Indium(I) chloride disproportionates, but InBr or InI react with CH2X2 to give X2InCH2X (X = Br, I) derivatives. Treatment of the latter with Et4NX gives the 1:1 electrolytes Et4N[X3InCH2X]. With triphenylphosphine, Br2InCH2Br forms the phosphonium ylid derivative Br3InCH2P(C6H5)3, whose structure has been established by X-ray crystallography: cell constants a = 14.076 (4) angstrom, b = 7.610 (2) angstrom, c = 12.931 (2) angstrom; space group Pna2(1); R = 0.034, R(w) = 0.034. Reaction between N,N,N',N'-tetramethylethanediamine (tmen) and Br2InCH2Br also gives a cyclized nitrogen ylid Br3 activated InCH2NMe2CH2NMe2: cell constants a = 12.814 (3) angstrom, b = 15.721 (4) angstrom, c = 21.343 (5) angstrom; space group Pbca; R = 0.045, R(w) = 0.047. The iodo species I2InCH2I undergoes redistribution in solution, and two tmen derivatives were isolated, I3 activated InCH2NMe2CH2NMe2 and [I activated In(CH2NMe2CH2NMe2)2](I)2. The latter has two identical cyclized ylid ligands: a = 11.414 (4) angstrom, b = 14.592 (6) angstrom, c = 16.144 (7) angstrom, beta = 110.1 (4)-degrees; space group P2(1)/c; R = 0.051, R(w) = 0.051. The H-1 and C-13 NMR spectra show that the CH2 group in X2InCH2X is electron-poor, in keeping with the tendency for nucleophilic ligands to react at this site as well as at the metal.