Rhodium(I) and Iridium(I) Complexes of Ferrocenyl-Functionalized Amidinates and Bis(amidinates): κ2N-Coordination Versus Ferrocenyl Ortho-Metalation

The synthesis and characterization of two bulky ferrocenyl-functionalized amidinates and their lithium, potassium, rhodium(I), and iridium(I) complexes are reported. The ferrocenyl mono(amidine) [Fc{C-(NDipp)(NHDipp)}] (1) (Fc = ferrocenyl; Dipp = 2,6-diisopropylphenyl) and its potassium complex [Fc{C(NDipp)(2)K}center dot 3THF] (2) as well as the 1,1'-ferrocendiyl-bridged bis(amidinate) [fc{C(NMes)(2)Li}(2)center dot 3THF] (3) (fc = ferrocene-1,1'-diyl; Mes = mesityl) were synthesized. Salt metathesis reactions with the metal precursors [Rh(cod)Cl](2) (cod = 1,5-cyclooctadiene) and [Ir(cod)Cl](2) gave the rhodium(I) and iridium(I) complexes [Fc{C-(NDipp)(2)Rh(cod)}] (4), [fc{C(NMes)(2)Rh(cod)}(2)] (5), and [fc{C(NMes)(2)Ir(cod)}(2)] (6), as well as the ortho-metalated compound [(CP)Fe(C5H3)(C(NHDipp)(NDipp)Ir(cod)}] (7). As complex 7 showed an ortho-metalation on the ferrocene backbone, we investigated this reaction in more detail. It was found that the rhodium(I) complexes 4 and 5 also undergo ortho-metalation upon treatment with carbon monoxide (CO). After the carbonylation, the first known ortho-metalation of rhodium(I) on ferrocene complexes was observed for [(Cp)Fe{(C5H3)C(NHDipp)(NDipp)Rh(CO)(2)}] (8) and [Fe(C5H3)(2){C(NHMes)(NMes)Rh(CO)(2)}(2).] (9). A combined electrochemical and quantum chemical study revealed that depending on both the metal-bound ligand (CO vs cod) and the bonding mode (kappa N-2 vs ortho-metalated), the highest occupied molecular orbital is located more on iron or on rhodium/iridium.