Abstract
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-iPr2C6H3) (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.
Highlights
Metallasiloxanes derived from organic silanols have attracted considerable interest because they act as structural models for the naturally occurring metallasilicates, synthetic metal-containing zeolites,1 and for the heterogeneous silica-supported transition metal catalysts
Some of the transition metal-containing siloxanes have been proved to act as catalysts for reactions such as alkene polymerization,3 metathesis,4 epoxidation,5 hydroformylation,6 and specified Diels–Alder reactions7 with both homogeneous and heterogeneous applicability
A reacted with Sb(NEt2)3 in a molar ratio of Scheme 1 Synthesis of compounds 1–4
Summary
Metallasiloxanes derived from organic silanols have attracted considerable interest because they act as structural models for the naturally occurring metallasilicates, synthetic metal-containing zeolites,1 and for the heterogeneous silica-supported transition metal catalysts.2 Interestingly, some of the transition metal-containing siloxanes have been proved to act as catalysts for reactions such as alkene polymerization,3 metathesis,4 epoxidation,5 hydroformylation,6 and specified Diels–Alder reactions7 with both homogeneous and heterogeneous applicability. Compounds 1–6 have been characterized by IR and NMR spectroscopy, single crystal X-ray structure and elemental analysis. Compounds 1–6 exhibit very good catalytic activity in the addition reaction of trimethylsilyl cyanide (TMSCN) with benzaldehyde.
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