Functionalized borazines as precursors for new silica gels

Trialkynylborazines have been prepared in excellent yields by reacting alkynyl-bis(diisopropylamino) borane with powdered ammonium chloride in toluene. These were subsequently used in hydrosilylations with trichlorosilane and trialkoxysilanes using platinum on charcoal as heterogeneous catalyst. This reaction is stereoselective and gives the beta-isomers as major product. The tris(beta-tricholorsilylvinyl)-substituted derivative (Cl3SiCH=CH)(3)B3N3H3 was isolated in pure form and transformed into a highly functionalized silica gel by a sol-gel process. This gel has a specific surface of about 315 m(2) g(-1) and is the first containing intact borazine rings. The structures of (iPr(2)N)(2)B-C=CH, B, B', B"-(HC=CH)(3)B3N3H3, B,B', B"-(Me3SiC=CH)(3)B3N3H3 and B,B',B"-(Cl3Si-CH=CH)(3)B3N3H3 were determined by X-ray structure analyses and are reported.