Preparation, crystal structure determination and properties of adducts of indium methylene compounds with Group 15 donors

The reaction of InBr with CH2Br2 in 1,4-dioxane or acetonitrile yields the corresponding solvate of Br2InCH2Br, which on reaction with E(C6H5)3 (E=P, As, Sb) gives the indium(III)-Group 15 dimetallo-methane derivatives, Br3InCH2E(C6H5)3. The crystal structures of the two related compounds (E=As, Sb) have been determined by X-ray crystallography. For Br3InCH2As(C6H5)3, cell constants a=15.553(7), b=21.646(8), c=12.920 (10) Å; space group Pbca, Z=8, R=0.064, Rw=0.054, and for Br3InCH2Sb(C6H5)3, a=15.439(6) Å, b=22.016(4) c=13.138(5) Å; space group Pbca, Z=8, R=0.062, Rw=0.049. Results are also reported for I3InCH2As(C6H5)3 (cell constants a=12.0122(2), b=15.8526(3), c=13.4180(3) Å, β=109.933(1)°; space group P21/n, Z=4, R=0.0481, Rw=0.0431) and Br3InCH2N(C2H5)3 (a=7.362(2), b=14.700(2), c=13.049(1) Å, β=98.90(1)°; space group P21/n, Z=4, R=0.0418, Rw=0.0368). The structural results are compared with those for other organoindium ylids with the same general structure Br3InCH2L (L=P(C6H5)3; 1,1,3,3,-tetramethyl-2-thiourea; N,N,N′,N′-tetramethylethanediamine). Semi-empirical quantum mechanical calculations, using the PM3 method, were carried out on the series Br3InCH2E(C6H5)3 (E=P, As, Sb), and the calculated structural parameters are compared with the values determined by X-ray crystallography. The presence of an ylid ligand H2Cδ−δ+E(C6H5)3 in the organoindium compounds is confirmed. Mass spectra and thermogravimetric analysis strongly suggest that the thermal decomposition of the compounds occurs via fission of the indiumcarbon bond, leading to the corresponding ylid, which can be trapped by reacting the X3InCH2E(C6H5)3 compounds with HBr to produce the onium derivative [CH3E(C6H5)3]+ [InX4]− (E=P, As; X=Br, I).