Alkyl cyanoferrates, cyanocobaltates, and cyanonickelates as new reagents for cross-coupling with organic halides

Article abstract of DOI:10.1055/s-1995-3872

Cyano ate-complexes of unknown structure (the following formulae are based only on the stoichiometry of the educts) are produced in situ by the action of 1-4 equivalents of methyllithium on M(CN)₂ (where M = Fe, Co, Ni) at -78°C. Some of these new reagents are very favorable to cross-coupling with organic halides: coupling with 1-bromononane can be achieved by Me₃Ni(CN)₂Li₃, Me₄Ni(CN)₂Li₄, or Me₄Fe(CN)₂Li₄ in 83-90% yield, and with 1-chlorononane by Me₄Ni(CN)₂Li₄ in 80% yield. Me₂Fe(CN)₂Li₂ and Me₃Fe(CN)₂Li₃ couple with α-bromostyrene with similar yields (89 and 84%, respectively) as the homoleptic complexes Me₄FeLi₂ and Me₄CoLi₂, whereas Me₂Co(CN)₂Li₂ and Me₃Co(CN)₂Li₃ are clearly superior to these complexes in their coupling with 1-bromonaphthalene (giving 89 and 95% yield, respectively). Me₃Co(CN)₂Li₃ and Me₄Co(CN)₂Li₄ gave coupling products with 1-chloro- and 1-fluoronaphthalene in 77 and 67% yield, respectively. MeCo(CN)₂Li is by far superior to other stoichiometric reagents in the coupling (81%) with 1-bromo-2-phenylethyne. Butyl cyano ate-complexes cause the cross-coupling on 1-bromononane and 1-bromonaphthalene in unsatisfactory yields due to side reactions.