Abstract
Bis(borane) adducts Acenap(PiPr2·BH3)(PRH·BH3) (Acenap = acenaphthene-5,6-diyl; 4a, R = Ph; 4b, R = ferrocenyl, Fc; 4c, R = H) were synthesised by the reaction of excess H3B·SMe2 with either phosphino-phosphonium salts [Acenap(PiPr2)(PR)](+)Cl(-) (1a, R = Ph; 1b, R = Fc), or bis(phosphine) Acenap(PiPr2)(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(PiPr2)(μ-BH2)(PR·BH3) (5a, R = Ph; 5b, R = Fc; 5c, R = H). Thermolysis of 5c results in loss of the terminal borane moiety to afford Acenap(PiPr2)(μ-BH2)(PH) (14). Single crystal X-ray structures of 3, 4b and 5a-c are reported.
Highlights
Dehydrocoupling reactions (E–H + E′–H → E–E′ + H2) are an interesting and effective way of generating bonds between main-group elements, with concomitant evolution of H2
Dehydrocoupling reactions that occur by thermal or autocatalytic routes are known,[7,8] the vast majority of recent work has focused on catalysis, with transition metals.[6,9,10,11]
The synthesis and characterisation of the bis(borane) adduct 4a were recently reported by our group.[26]
Summary
Dehydrocoupling reactions (E–H + E′–H → E–E′ + H2) are an interesting and effective way of generating bonds between main-group elements, with concomitant evolution of H2. 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(PiPr2)(μ-BH2)(PR·BH3) (5a, R = Ph; 5b, R = Fc; 5c, R = H). Scheme 1 Synthesis of bis(borane) adducts 4a–c and BH2 bridged compounds 5a–c.
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