Hexacoordinate Mono- and Diorganoantimony Compounds

Some new mono- and diorganoantimony chloride derivatives were obtained according to the following reactions.2 

2 Compounds (p-YC6H4)2SbBr2(acac) (Y = N02, Cl, H, CI[3, CHsO) were prepared from p-YC6H4SbO(OH)2 11, 18h) and p-YC6H4SbCl3(acac) (Y = N()2, H, CH3) were obtained from corresponding stibonic acid (18a, b). HMPA = hexamethylphosphoric triamide DMSO = dimethyl sulfoxide PyO = pyridine iV-oxide 4-CHjPyO = y-picoline JV-oxide TPPO = triphenylphosphine oxide. 

These compounds are stable at room temperature in the solid state, but in solution some monomethylantimony tetrachloride adducts, ChbiSbChL (L = HMPA, at room temperature L = PyO or 4-CH3PyO above 70°), decompose into CH3C1 and Sb( l3L. 

All these compounds mentioned contain a hexacoordinate antimony atom. From the PMR spectrum of C3H5SbCl3(acac) in CHC13, we have suggested a structure I in which the phenyl and the acetylacetonatc groups are in the same plane (18a). Recently, a similar structure has been established for the methyl analog, CHjSbCl3(acac) (19), by X-ray crystallography. 

SbCl2(acac), wo proposed that isomerization of the frans-phenyl (II) (peak A) to a s-phcnyl (III) (peak B) isomer takes place and that the two isomers are in equilibrium in solution.3 In the solid state, this compound gave two crystal forms. Both forms show the same PMR spectral properties on solution as described in the foregoing. The X-ray struc- 

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