Diorganoantimony trihalides

Diorganobismuth trihalides have not been isolated because of their thermal instability. Although diorganoantimony trihalides can be prepared, they are also generally unstable and decompose at elevated temperatures. In the case of diorganoantimony triiodides, only 70 has been isolated. 

Hexaorganoantimony and -bismuth anions have been described in Section III.A. Monoorganoantimony tetrahalides and diorganoantimony trihalides react readily with halide anions to form the corresponding hexacoordinate anions. Several examples are shown in equations 288 289 ", 290 and 29P" ... 

Diorganoantimony compounds react readily with X2 to form the corresponding trihalides in high yields (equations 231 and 232 ). Other oxidants such as SO2CI2, XeF2 and PhlF, have also been quite useful for the preparation (equations 233 2342 and 235 ). 

Diorganoantimony(V) trihalides seem to prefer six-coordinate, octahedral geometry, and as a consequence will associate into dimers. Thus, dimethylantimony(V) trichloride, Me2SbCl3, was found to be a dimer fMe2SbCl2(A/-Cl)]2, 154, with bridging chlorines, Sb-Cl 2.35 A and Sb- -Cl 2.80 A. A second isomeric form of this compound exists as an ion pair, [SbMe4]+[SbCl6] this illustrates the coordination preferences of antimony [391]. 

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