Spontaneous dehydrocoupling in peri-substituted phosphine-borane adducts

摘要

Bis(borane) adducts Acenap(PiPr(2)center dot BH3)(PRH center dot BH3) (Acenap = acenaphthene-5,6-diyl; 4a, R = Ph; 4b, R = ferrocenyl, Fc; 4c, R = H) were synthesised by the reaction of excess H3B center dot SMe2 with either phosphino-phosphonium salts [Acenap(PiPr(2))(PR)]Cl-+(-) (1a, R = Ph; 1b, R = Fc), or bis(phosphine)Acenap(PiPr(2))(PH2) (3). Bis(borane) adducts 4a-c were found to undergo dihydrogen elimination at room temperature, this spontaneous catalyst-free phosphine-borane dehydrocoupling yields BH2 bridged species Acenap(PiPr(2))(mu-BH2)-(PR center dot BH3) (5a, R = Ph; 5b, R = Fc; 5c, R = H). Thermolysis of 5c results in loss of the terminal borane moiety to afford Acenap(PiPr(2))(mu-BH2)(PH) (14). Single crystal X-ray structures of 3, 4b and 5a-c are reported.