Amination of Bridging Vinyliminium Ligands in Diiron Complexes: C-N Bond Forming Reactions for Amidine-Alkylidene Species

The vinyliminium complexes [Fe-2{mu-eta(1):eta(3)-C(CO2Me)C(H)CN(Me)-(R)}(mu-CO)(CO)(Cp)(2)][SO3CF3] [R = Me, 1a; R = 4-C6H4OMe, 1b; R = CH2Ph, 1c] react with primary amines (NH2R'; R'= Me, Et, Bun, (CH2)(2)NH2, CH2Ph) and ammonia to give the corresponding bridging amidine-alkylidene complexes [Fe-2{mu-kappa(1)(N):eta(1)(C):kappa(1)(C)-C(CO2Me)CH2C{N(Me)(R)}(NR')}(mu-CO)(CO)(Cp)(2)] (4aj) in 7090% yields. Likewise, the vinyliminium complex [Fe-2{mu-eta(1):eta(3)-C(CO2Me)C(CO2Me)CN(Me)(2)}(mu-CO)(CO)(Cp)(2)][SO3CF3] (1d) reacts with NH2R' (R'= Me, Et) to form the corresponding amidine-alkylidene [Fe-2{mu-eta(1)(N):kappa(1)(C):eta(1)(C)-C(CO2Me)CH(CO2Me)C(NMe2)(NR')}(mu-CO)(CO)(Cp)(2)] [R'= Me, 8a; R' = Et, 8b], generating selectively one of the two diastereoisomers associated with the presence of the methylidene unit -CH(COO2Me) within the bridging ligand. Amination of the vinyliminium complexes 1ac takes place also with hydrazine, resulting in the formation of [Fe-2{mu-kappa(1)(N):eta(1)(C)eta(1)(C)-C(CO2Me)CH2C{N(Me)(R)}(NNH2)}(mu-CO)(CO)(Cp)(2)] [R = Me, 5a; R = 4-C6H4OMe, 5b; R = CH2Ph, 5c]. Complexes 1b and 1d react with NHMe2, affording the en-(1,1)diamino-alkylidene complexes [Fe2{mu-eta(1):eta(3)-C(CO2Me)C(R')C(NMe2)N(Me)(R)}(mu-CO)(CO)(Cp)(2)] [R = 4-C6H4OMe, R' = H, 9b; R = Me, R' = CO2Me, 9d]. The reaction of 1c with piperidine results in formation of the amidine-alkylidene [Fe-2{mu-kappa(1)(N):eta(1)(C):eta(1)(C)-C(CO2Me)CH2C{N(Me)(CH2Ph)}(CH2CH2CH2CH-CH2)}(mu-CO)(CO)(Cp)(2)] (10), which implies piperidine ring-opening. All the products have been purified by alumina chromatography and characterized by analytical and spectroscopic methods; in addition, the molecular structures of 4f, 5b, and 8a have been ascertained by X-ray diffraction studies.