Synthesis and characterization of acetamidine rhodium(III) cationic methyl complex, trans-[Rh(Acac)(PPh3)2(CH3){NH[dbnd]C(NH2)CH3}][BPh4], produced by ammination of acetonitrile ligand in trans-[Rh(Acac)(PPh3)2(CH3)(CH3CN)][BPh4

Abstract

The rhodium(III) cationic methyl acetamidine complex, trans-[Rh(Acac)(PPh3)2(CH3){NHC(NH2)CH3}][BPh4], (1) is formed upon the reaction of trans-[Rh(Acac)(PPh3)2(CH3)(CH3CN)][BPh4] with ammonia gas in CH2Cl2 solution at temperatures between −15 °C and −20 °C. Complex 1 was characterized by elemental analysis, 31P{1H} and 1H NMR spectra, and single crystal X-ray diffraction study. The cation of 1 has a slightly distorted octahedral structure. The equatorial plane contains the acetylacetonate, methyl, and acetamidine ligands; two PPh3 ligands occupy the axial positions . The acetamidine ligand adopts the Z-configuration stabilized by hydrogen bonding with the oxygen atom of the acetylacetonate ligand, HN–H⋯O (1.90 Å). Complex 1 reacts with ammonia gas at temperatures between 0 °C and 20 °C to form cationic monophosphine complex [Rh(Acac)(PPh3)(CH3){NHC(NH2)CH3}(NH3)][BPh4] (2). Complex 2 was characterized by 31P{1H} and 1H NMR spectra without isolation.