SYNTHESIS AND DERIVATIVES OF PENTAKIS[(TRIMETHYLSILYL)OXY]ANTIMONY

Pentakis[(trimethylsilyl)oxy]antimony(V) [Sb(OSiMe3)5; 1] is prepared from SbCl5 and 5 equiv of NaOSiMe3 in benzene or hexane solution. Acco rding to mass spectrometric and NMR spectroscopic data, 1 appears to b e a monomer. It forms a pyridine adduct pyr-Sb(OSiMes)5 (2), the cryst al structure of which has been determined. The mononuclear complex has octahedrally coordinated antimony atoms. With an additional equivalen t of NaOSiMe3, the antimonate complex Na[Sb(OSiMe3)6] (3) is formed, w hich crystallizes as a monoglyme adduct [Na(MeOCH2CH2OMe)] [Sb(OSiMe3) 6] (3a). Partial hydrolysis of 3, or a direct synthesis using NaOSiMe3 and NaOH as reagents for SbCl5, leads to the crystalline dinuclear co mplex Na2-[Sb2(OH)2(OSiMe3)10], the structure of which has also been d etermined. It features two cubes with a common Na2O2 face and tetracoo rdinated sodium and hexacoordinated antimony atoms. The hydroxy groups are in bridgehead positions. NMR data suggest that the dimers dissoci ate in solution to give octahedral mononuclear complexes with the sily loxy groups in fixed cis and trans positions (4:1) relative to the OH groups.