The synthesis, structure, and electrochemical properties of Fe(C≡CC≡N)(dppe)Cp and related compounds

The cyanoacetylide complex Fe(C≡CC≡N)(dppe)Cp (3) is readily obtained from sequential reaction of Fe(C≡CSiMe3)(dppe)Cp with methyllithium and phenyl cyanate. Complex 3 is a good metalloligand, and coordination to the metal fragments [RhCl(CO)2], [Ru(PPh3)2Cp]+, and [Ru(dppe)Cp*]+ affords the corresponding cyanoaceylide-bridged heterobimetallic complexes. In the case of the 36-electron complexes [Cp(dppe)Fe-C≡CC≡N-MLn]n+, spectroscopic and structural data are consistent with a degree of charge transfer from the iron centre to the rhodium or ruthenium centre via the C3N bridge, giving rise to a polarized ground state. Electrochemical and spectroelectrochemical methods reveal significant interactions between the metal centres in the oxidized (35 electron) derivatives, [Cp(dppe)Fe-C≡CC≡N-MLn](n+1)+. Key words: cyanide, cyanoacetylide, crystal structure.