Metal Complexes of Biologically Important Ligands, CLXXV [1]. Pentamethylcyclopentadienyl Halfsandwich Complexes of Rhodium(III) and Iridium(III) with Schiff Bases from 2-(Diphenylphosphino)- benzaldehyde and α-Amino Acid Esters

The reactions of the chlorido-bridged complexes [Cp*M(Cl)(μ-Cl)]2 (M = Rh, Ir) with Schiff bases (P-N-O) from 2-(diphenylphosphino)benzaldehyde and α-amino acid esters afford the complexes Cp*M(Cl)2(P-N-O) in which the ligands function as monodentate P donors (M = Ir) or as bidentate P-N donors (M = Rh). These complexes can be converted into cationic complexes [Cp*M(Cl)(P-NO)]+ with bidentate P-N ligands by treatment with NH4PF6. The cationic complexes [Cp*M(Cl)(PN- O)]+Cl− have been detected also in solutions of Cp*M(Cl)2(P-N-O). The P-N-coordinated complex [Cp*Rh(Cl)(Ph2P-C6H4-C(H)=N-C(H)(CH2Ph)CO2Me)]+PF6 − was characterized by X-ray diffraction. From Cp*M(Cl)2(P-N-O) and AgBF4 or AgPF6 (molar ratio 1 : 2) the dicationic complexes [Cp*M(P-N-O)]2+ are formed in which the ester group is also coordinated to the metal atom. The Schiff base from 2-(diphenylphosphino)benzaldehyde and allylglycine ester acts as a tridentate ligand, however with coordination of the C=C allyl group instead of the ester function.