cyclo-Stannasiloxanes Containing both Oxygen Atoms and Methylene Moieties within the Ring and Formation of Related Organotin Oxo Clusters

The syntheses of the 8-membered stannasiloxanes cyclo-[RR′SnOSi­(Me2)­CH2]2 (5, R = R′ = Ph; 6, R = R′ = t-Bu; 7, R = Me2N­(CH2)3, R′ = Ph) is reported. These react with organoelement oxides, providing the novel metallasiloxanes cyclo-[Me2SiCH2(RR′)­SnOMO] (8, R = R′ = Ph, M = t-Bu2Sn; 9, R = R′ = t-Bu, M = t-Bu2Sn; 10, R = Me2N­(CH2)3, R′ = Ph, M = t-Bu2Sn; 11, R = Me2N­(CH2)3, R′ = Ph, M = Ph2Ge). Among these, compound 11 is the first example of such species being composed of four different group 14 elements in the 6-membered-ring skeleton. On contact with moist air compound 8 surprisingly undergoes Sn–Ph bond cleavage, giving the diorganotinoxo cluster [PhSn­(CH2Me2SiO)­Sn­(μ3-O)­(μ-OH)t-Bu2]2 (12), which shows a ladder-type structure. The latter reacts with 2 molar equiv of t-Bu2SnO, affording the Sn6-diorganotin oxo cluster [t-Bu2(μ-OH)­Sn­(μ3-O)­SnPh­(CH2Me2SiO)­Sn-t-Bu2(μ3-O)]2 (13). The compounds have been characterized by NMR spectroscopy, electrospray mass spectrometry, and in the case of compounds 5–7, 12, and 13 also by single-crystal X-ray diffraction analysis.