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.

Graphical abstractDimeric Rh(III) and Ir(III) Cp∗ complexes with pendant primary amine tether were synthesized from a Cp∗^NH2 tautomer and the respective metal(III) chlorides. The electrophilic metal center and the nucleophilic side chain functionality may be addressed separately under the appropriate reaction conditions.Figure optionsDownload full-size imageDownload as PowerPoint slide