Cohydrolysis of Organotin Chlorides with Trimethylchlorosilane. Okawara's Pioneering Work Revisited and Extended

The synthesis of the stannasiloxanes {[R 2 (Me 3 SiO)Sn] 2 O} 2 ( 1, R = Me; 2, R = Et), [R 2 (Me 3 SiO)Sn] 2 O ( 8, R = Me 3 SiCH 2; 9, R = t -Bu), R 2 Sn(OSiMe 3 ) 2 ( 3, R = i -Pr; 4, R = Me 3 SiCH 2; 5, R = t -Bu; 6, R = Cp(CO) 3 W; 7, R = Cp(CO) 2 Fe), and [Cp(CO) 2 Fe] 2 Sn(OSiPh 3 ) 2 ( 7a ), the monoorganotin trichloride Me 3 SiCH 2 SnCl 3 ( 13 ), and the organotin oxocluster (Me 3 SiCH 2 Sn) 12 O 14 (OH) 6 Cl 2 ( 14 ) is reported. Their identity was confirmed by both solution and solid state multinuclear NMR spectroscopy and in the case of 1, 2, 6, 7a, and 14 also by single-crystal X-ray analyses. A spinning sideband analysis of the 119 Sn MAS spectra reveals the coordination geometries of the tin atoms in the stannasiloxanes 1 and 2 to be different from those of related diorganotin oxides (R 2 SnO) n (R = Me, Et). In solution, 1 and 2 exhibit an intramolecular exchange process as well as monomer−dimer equilibria. The reaction of 4 with cyclo -( t -Bu 2 SnO) 3 and of cyclo -[(Me 3 SiCH 2 ) 2 SnO] 3 with cyclo -( t -Bu 2 SnO) 3 provided evidence for the formation in situ of the mixed tetraorganodistannoxane t -Bu 2 (Me 3 SiO)SnOSn(OSiMe 3 )(CH 2 SiMe 3 ) 2 ( 10 ) and of the hexaorganotristannoxanes cyclo -[(Me 3 SiCH 2 ) 2 Sn(OSn t -Bu 2 ) 2 O] ( 11 ) and cyclo -{ t -Bu 2 Sn[OSn(CH 2 SiMe 3 ) 2 ] 2 O} ( 12 ).