Carbonylchromium derivatives of bismuth: New syntheses and relevance to C-O activation

We have discovered a series of novel pentacarbonylchromium derivatives of bismuth from the reactions of NaBiO₃ with [Cr(CO)₆] in KOH/MeOH solutions. When the reaction was carried out at room temperature, the highly charged [Bi{Cr(CO)₅}₄]^3- (1) was obtained, whose structure was shown by X-ray analysis to possess a central bismuth atom tetrahedrally coordinated to four [Cr(CO)₅] groups. As the reaction was heated at 80°C, the methyl-substituted complex [MeBi{Cr(CO)₅}₃]^2-(2) was obtained, presumably via the C-O activation of MeOH. Further reactions of 1 with CH₂Cl₂ or CH≡CCH₂Br form the halo-substituted complexes [XBi{Cr(CO)₅}₃]^2-(X = Cl, 3; Br, 4), respectively. On the other hand, the reactions of 1 with RI (R = Me, Et) led to the formation of the alkyl-substituted complexes [RBi{Cr(CO)₅}₃]^2-(R = Me, 2; Et). The formation of complexes 1-4 is discussed, presumably via the intermediate bismuthinidene [Bi{Cr(CO)₅}₃]^- or the trianion [Bi{Cr(CO)₅}₃]^3-.