Side chain functionalized η5-tetramethyl cyclopentadienyl complexes of Rh and Ir with a pendant primary amine group

Conversion of 2-(2,3,4,5-tetramethylcyclopentadien)ethylamine tautomere C5Me4H2(CHCH2)NH2 (1) with MCl3 · n H2O (M = Rh, Ir) under acidic conditions gives the respective μ-chloro-bridged chelates [(η5-Me4Cp(CH2)2NH3)RhCl2]2Cl2 (2) and [(η5-Me4Cp(CH2)2NH3)IrCl2]2Cl2 (3). The dimeric complexes are received as ammonium salts and thus display good solubility in strong donor solvents such as water and DMSO. Addition of triphenyl phosphine converts Rh-dimer 2 into the mononuclear phosphine complex 4. Under basic conditions, no intramolecular coordination of the pendant NH2 is observed and thus the primary amino group of 4 reacts selectively with succinic anhydride by formation of a peptide bond. Hence, the electrophilic metal center and the latent nucleophilic nitrogen, which represent complementary functionalities, can be addressed separately under the appropriate reaction conditions.