The diiron vinyliminium complexes [Fe 2 {μ-η 1 :η 3 -C(R′)C(H)CN(Me)(R)}(μ-CO)(CO)(Cp) 2 ][SO 3 CF 3 ] (R=Me, R′=SiMe 3 (1a); R=Me, R′=CH 2 OH (1b); R=CH 2 Ph, R′=Tol (1c), Tol=4-MeC 6 H 4 ; R=CH 2 Ph, R′=COOMe (1d); R=CH 2 Ph, R′=SiMe 3 (1e)) undergo regio- and stereo-selective addition by cyanide ion (from NBu4nCN), affording the corresponding bridging cyano-functionalized allylidene compounds [Fe 2 {μ-η 1 :η 3 -C(R′)C(H)C(CN)N(Me)(R)}(μ-CO)(CO)(Cp) 2 ] (3a–e), in good yields. Similarly, the diiron vinyliminium complexes [Fe 2 {μ-η 1 :η 3 -C(R′)C(R′)CN(Me)(R)}(μ-CO)(CO)(Cp) 2 ][SO 3 CF 3 ] (R=R′=Me (2a); R=Me, R′=Ph (2b); R=CH 2 Ph, R′=Me (2c); R=CH 2 Ph, R′=COOMe (2d)) react with cyanide and yield [Fe 2 {μ-η 1 :η 3 -C(R′)C(R′)C(CN)N(Me)(R)}(μ-CO)(CO)(Cp) 2 ] (9a–d). The reactions of the vinyliminium complex [Fe 2 {μ-η 1 :η 3 -C(Tol)CHCN(Me)(4-C 6 H 4 CF 3 )}(μ-CO)(CO)(Cp) 2 ][SO 3 CF 3 ] (4) with NaBH 4 and NBu4nCN afford the allylidene [Fe 2 {μ-C(Tol)C(H)C(H)N(Me)(C 6 H 4 CF 3 )}(μ-CO)(CO)(Cp) 2 ] (5) and the cyanoallylidene [Fe 2 {μ-C(Tol)C(H)C(CN)N(Me)(C 6 H 4 CF 3 )}(μ-CO)(CO)(Cp) 2 ] (6), respectively. Analogously, the diruthenium vinyliminium complex [Ru 2 {μ-η 1 :η 3 -C(SiMe 3 )CHCN(Me)(CH 2 Ph)}(μ-CO)(CO)(Cp) 2 ][SO 3 CF 3 ] (7) reacts with NBu4nCN to give [Ru 2 {μ-η 1 :η 3 -C(SiMe 3 )CHC(CN)N(Me)(CH 2 Ph)}(μ-CO)(CO)(Cp) 2 ] (8).Finally, cyanide addition to [Fe 2 {μ-η 1 :η 3 -C(COOMe)C(COOMe)CN(Me)(Xyl)}(μ-CO)(CO)(Cp) 2 ][SO 3 CF 3 ] (2e) (Xyl=2,6-Me 2 C 6 H 3 ), yields the cyano-functionalized bis-alkylidene complex [Fe 2 {μ-η 1 :η 2 -C(COOMe)C(COOMe)(CN)CN(Me)(Xyl)}(μ-CO)(CO)(Cp) 2 ] (10). The molecular structures of 3a and 9a have been elucidated by X-ray diffraction.