Synthesis, Chemistry, and Structures of Neopentyl and (Trimethylsilyl)methyl Antimony and Bismuth Oligomers

Dehalogenation of RSbBr 2 (R = Me 3 CCH 2 ) with Mg gives cyclo-(RSb) n ( n = 4 ( 1a ), 5 ( 1b )). The compounds cyclo-(RBi) n (R = Me 3 CCH 2; n = 3 ( 2a ), 5 ( 2b )) form by reaction of RBiCl 2 with LiAlH 4 . Equilibria between 1a and 1b or between 2a and 2b favor the smaller rings at higher temperatures and dilution. Thermal reactions of 2a, b lead to R 4 Bi 2 ( 3; R = Me 3 CCH 2 ) and elemental bismuth. Reaction of 2a, b with W(CO) 5 (thf) (thf = tetrahydrofuran) gives [{ μ - η 2 - cis -(RBi) 2 }{W(CO) 5 } 2 ] ( 4; R = Me 3 CCH 2 ). Decomposition of [{ μ - η 2 - cis -(R‘Bi) 2 }{W(CO) 5 } 2 ] ( 5; R‘ = Me 3 SiCH 2 ) leads to [ η 2 - trans- (R‘Bi) 2 W(CO) 5 ] ( 6 ). The crystal structures of 1b, 4, and 6 are reported.