Straightforward synthesis of novel cyclic metallasiloxanes supported by an N,C,N-chelating ligand

Abstract

The reaction of an N,C,N-intramolecularly coordinated tin(IV) carbonate LSn(Ph)(CO₃) (1) and antimony(III) and bismuth(III) oxides (LMO)₂ (where M = Sb (2), Bi (3) and L = C₆H₃-2,6-(CH₂NMe₂)₂) with (HO)SiPh₂(O)SiPh₂(OH) in 1 : 1 (in the case of 1) or 1 : 2 molar ratio (in the cases of 2 and 3) gave the metallasiloxanes cyclo-LSn(Ph)(OSiPh₂)₂O (4) and cyclo-LM(OSiPh₂)₂O (where M = Sb (6) and Bi (7)) containing six-membered MSi₂O₃ rings. Alternatively, the compounds 4, 6 and 7 can be also prepared reacting Ph₂Si(OH)₂ and compounds 1, 2 and 3, respectively, in the molar ratio of either 2 : 1 (for 4) or 4 : 1 (for 6 and 7). The reaction of Ph₂Si(OH)₂ with 1 in 1 : 1 molar ratio gave cyclo-Ph₂Si(OSnL(Ph)O)₂SiPh₂ (5) containing an eight-membered Sn₂Si₂O₄ stannasiloxane ring. The analogous eight-membered stibasiloxane derivative cyclo-Ph₂Si(OSbLO)₂SiPh₂ (8) was obtained as well, while attempts to synthesize the bismuth analogue failed. Compounds 1–3 react with the siloxane cyclo-(Me₂SiO)₃ providing either eight-membered metallasiloxanes cyclo-LSn(Ph)(OSiMe₂O)₂SiMe₂ (9) and cyclo-LSb(OSiMe₂O)₂SiMe₂ (10) or the six-membered bismutasiloxane cyclo-LBi(OSiMe₂)₂O (11). All compounds were characterized with the help of elemental analysis, ¹H, ¹³C, ²⁹Si and ¹¹⁹Sn NMR spectroscopy, and single crystal X-ray diffraction analyses (except 9 and 10).