ALKYLIRON AND ALKYLCOBALT REGENTS .10. ALKYL CYANOFERRATES, CYANOCOBALTATES, AND CYANONICKELATES AS NEW REAGENTS FOR CROSS-COUPLING WITH ORGANIC HALIDES

Cyano ate-complexes of unknown structure (the following formulae are b ased 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 degrees C. Some of these new reagents are very fav orable to cross-coupling with organic halides: coupling with 1-bromono nane can be achieved by Me(3)Ni(CN)(2)Li-3, Me(4)Ni(CN)(2)Li-4, or Me( 4)Fe(CN)(2)Li-4 in 83-90% yield, and with 1-chlorononane by Me(4)Ni(CN )(2)Li-4 in 80% yield (Table 1). Me(2)Fe(CN)(2)Li-2 and Me(3)Fe(CN)(2) Li-3 couple with alpha-bromostyrene with similar yields (89 and 84%, r espectively) as the homoleptic complexes Me(4)FeLi(2) and Me(4)CoLi(2) (Table 2), whereas Me(2)Co(CN)(2)Li-2 and Me(3)Co(CN)(2)Li-3 are clea rly superior to these complexes in their coupling with 1-bromonaphthal ene (giving 89 and 95% yield, respectively). Me(3)Co(CN)(2)Li-3 and Me (4)Co(CN)(2)Li-4 gave coupling products with 1-chloro- and 1-fluoronap hthalene in 77 and 67% yield, respectively. MeCo(CN)(2)Li is by far su perior to other stoichiometric reagents (Table 4) in the coupling (81% ) with 1-bromo-2-phenylethyne (postulated mechanism: Scheme 4). Butyl cyano ate-complexes cause the cross-coupling on 1-bromononane and 1-br omonaphthalene in unsatisfactory yields due to side reactions (Table 1 and 3).