Synthesis of metallasiloxanes of group 13-15 and their application in catalysis

Herein we report on the synthesis, characterization and catalytic application of metallasiloxanes of group 13-15. Reactions of R(Me)Si(OH)(2) (R = N(SiMe3)-2,6-iPr(2)C(6)H(3)) (A) with Bi(NEt2)(3), Sb(NEt2)(3), Ge[N(SiMe3)(2)](2) and AlMe3 afforded [R(Me)SiO2BiNEt2](2) (1), [R(Me)SiO2SbOSi(OH)(Me)R](2) (2), [R(Me)SiO2](3)(GeH)(2) (3), and [R(Me)SiO2AlMe(THF)](2) (4), respectively. Reactions of RSi(OH)(3) (B) with Bi(NEt2)(3) and AlMe3 produced complexes (RSiO3Bi)(4) (5) and (RSiO3)(2)[AlMe(THF)](3) (6). Compounds 1-6 have been characterized by IR and NMR spectroscopy, single crystal X-ray structure and elemental analysis. Each of the compounds 1, 2 and 4 features an eight-membered ring of composition Si2O4Bi2, Si2O4Sb2 and Si2O4Al2, while 3 and 6 exhibit a bicyclic structure with the respective skeletons of Si3O6Ge2 and Si2O6Al3. Compound 5 has a cubic core of Si4O12Bi4. Compounds 1-6 exhibit very good catalytic activity in the addition reaction of trimethylsilyl cyanide (TMSCN) with benzaldehyde. Compound 5 was found to be the best catalyst and its activity was probed in the reactions of TMSCN with a number of aldehydes and ketones.