Synthetic application of silicates/silanolates and their hydrolyzed polysilanol siloxanes for polyhedral oligomeric silsesquioxanes (POSSs)

Several types of silicate and their hydrolyzed polysilanols were applied to the synthesis of polyhedral oligomeric silsesquioxanes ( POSS s). Silicate cubic octasilicate [Si 8 O 20 ] 8− 5 was silylated with trimethylchlorosilane to yield the incompletely trimethylsilylated cubic octasilicate [Si 8 O 20 ](SiMe 3 ) 7 H 1b bearing one silanol in addition to the totally trimethylsilylated derivative [Si 8 O 20 ](SiMe 3 ) 8 1a . Further silylation of the monosilanol 1b with dimethylchlorosilane and α,ω‐hydridochlorooctamethyltetrasiloxane resulted in the formation of POSS s 1c , d , which have hydrosilyl groups as elongated siloxane side chain. Attempts to generate an amino‐substituted POSS via chloromethyldimethylsilylation of silicate 5 followed by reaction with amine as well as lithium amide failed. Amino‐substitution was accomplished via the use of amine as a catalyst for the capping reaction of incompletely condensed trisilanol 10b with γ‐aminopropyltrimethoxysilane affording mono amino‐functionalized POSS s 2b , c in moderate yields. Another group of silanolates 7 ‐ 9 was hydrolyzed with Ac OH or HC l to give the corresponding cyclic polysilanol siloxanes 11a‐c , respectively. Amine‐catalyzed condensation of several of these polysilanol siloxanes 11a‐c resulted in the formation of POSS s in high yields depending on the structure of substrates.