Alkali Metallosilicates: Synthesis, Structure and Evaluation in the ROP of ϵ‐Caprolactone. Issue 32 (6th August 2021) - Pérez‐Pérez, Jovana
Abstract: A series of metallosilicate complexes ( t BuO)2 (RO)SiOM (R= t Bu, i Pr, Et, Me; M=Li, Na, K) were prepared from tailor‐made silanols. The complexes show different degree of association and feature heterocubane, double‐heterocubane or hexagonal prism framework in solid state while ESI‐MS shows fragmentation of the oligomers. The steric hindrance around the silicon atom has a direct influence over the association of the alkali derivatives, and the size of the alkali metal influences the shape of the Mx Ox core. These compounds were studied as initiators in the ROP of ϵ‐caprolactone, varying temperature, reaction‐time, monomer/initiator ratio, metal center variation and association degree. The best results were achieved with [{( t BuO)3 SiO}4 Li4 ] (1 ) producing an almost quantitive yield of polycaprolactone (97 %, Mn =35 kg mol −1, M w / M n =1.72). Abstract : We describe the syntheses and characterization of twelve [( t BuO)2 (RO)SiOM]n (n=4, 6; R= t Bu, i Pr, Et, Me; M=Li, Na, K) alkali metallosilicates. Depending on the metal and the steric bulk of the silanol, tetrameric or hexameric aggregates were obtained. These complexes are active in ROP of ϵ ‐CL producing polycaprolactone with moderate molecular weight distribution.