ACTIVATED CYANIDE

Addition of cis-Na[Fe-2(CN)Cp-2(mu-CO)(2)CO] (1) to a twenty-fold exce ss of phthaloyl dichloride (succinyl dichloride, glutaryldichloride) l eads to the mu-phthalimidocarbyne (3) (mu-succinimidocarbyne (9), mu-g lutarimidocarbyne (10)) [Fe2Cp2(mu-CO)(CO)(2)]A (A = Cl (a), PF6 (b), BPh4 (c)) complexes which are studied by IR, NMR (H-1, C-13), MS (pos- FAB) and X-ray (3b, 3c, 10b). The C-N bonds in the N,N-diacylated cyan o bridges are highly elongated (> 1.30 Angstrom) in comparison with th e CN triple bond in the cyanide precursor. Their facile cleavage in su bsequent 1:1 reactions with a second [Fe-2(CN)Cp-2(mu-CO)(2)CO](-) ani on to give the tetraferrioazaallenium system mu-CO)(CO)(2){mu(4)-C=N=C }Fe2Cp2(mu-CO)(CO)(2)](+) prove 3 to be the long sought after 'activat ed cyanide' - intermediate in the synthesis of this compound from 1 an d phthaloyl dichloride (2:1). In the reaction of 10b with 1, the tetra iron complex Cp2(CO)3{mu(4)-CNC(=O)(CH2)(3)(=O)NC}Fe2Cp2(CO)(3) (7) fo rms as a byproduct along with tetraferrioazaallenium, while the short- chain derivative Fe2Cp2(CO)(3){mu(4)-CNC(=O)-C(=O)NC}Fe2Cp2(CO)(3) (8) is obtained from stoichiometric reaction of 1 with oxalyl dichloride. (C) 1998 Elsevier Science S.A.