Generation and polymerization of silacyclopropanes in the reaction of bis(chloromethyl)diorganosilanes with magnesium

Abstract

The reaction of bis(chloromethyl)diorganosilanes (R2Si(CH2Cl)(2): 1a, R = Me; 1b, R = allyl; 1c, R = benzyl; 1d, R = Ph) with magnesium gives 2a-d (65-90%) of formula MeR2SiCH2(SiR2CH2CH2)(n)H (n = 1, 2, 3,...) and dimethyldiorganosilanes 3a-d (17-9%). The trapping reaction of the intermediates generated in the reaction of 1d with magnesium using CD3OD gives the corresponding CD3OD-trapped product of the 1,1-diphenylsilacyclopropane intermediate, Ph2Si(OCD3)(CH2CH2D) (6'), along with the deuterated products of Ph2Si(CH2D)(CH2Cl) (5'), Ph2Si(CH2D)(2) (3d'), and 2d'. The results are consistent with a reaction course in which silacyclopropane intermediates are generated in the reaction of 1a-d with magnesium and then polymerized to 2a-d.