The synthesis of the stannasiloxanes 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 singlecrystal 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(OSnt-Bu 2 ) 2 O] (11) and cyclo-{t-Bu 2 Sn[OSn(CH 2 SiMe 3 ) 2 ] 2 O} (12).

The synthesis is reported of the novel stannasiloxanes cyclo-M(OSiPh2)2O (1, M = Sn[(CH2)3NMe2]2; 2, M = Sn[(CH2)3N(Me)CH2]2; 4, M = Sn[Cp(CO)2Fe]2; 5, M = Sn[Cp(CO)3W]2; 6, M = Sn(t-Bu)[Cp(CO)3W]) and cyclo-(Ph2SiOSnR2O)2 (3, R = (CH2)3NMe2), and of the stannagermoxane cyclo-t-Bu2Sn(OGePh2)2O (7). The molecular structures are described of 1−4, 6, and 7. The compounds exhibit reduced ring strain as a result of either intramolecular Sn−N coordination (1, 2) or electronic influence of the transition-metal fragments (4−6), and consequently they are six-membered rings in solution as well as in the solid state, whereas compound 3 is an eight-membered ring.

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