Carbonyl rhodium(I) complexes containing (H)PNX (X = O or N) ligands deriving from natural aminoacid–amides. Synthesis, X-ray structure and spectroscopic characterization

The polyfunctional (H)PNX (X = O or N) ligands 1 and 2 react with Rh(CO)₂Cl]₂ to give the corresponding chloro carbonyl complexes {Rhκ²-(H)PN](CO)Cl} (1a and 2a), where the neutral ligands coordinate in a κ²-PN bidentate fashion, the square planar coordination being completed by the CO trans to N and the chloride trans to P. In chloroform solution 1a maintains its original structure, while 2a partially transforms into the cationic species {Rhκ³-(H)PNO](CO)}Cl. The chloroform solutions of 1a and 2a react with AgPF₆ to give the purely cationic species {Rhκ³-(H)PNO](CO)}PF₆ (1a]⁺ and 2a]⁺), while addition of Et₃N originates the neutral species {Rhκ³-PNN′](CO)} (1b and 2b). All the complexes have been characterized by microanalysis, IR, ¹H NMR as well as ³¹P{¹H} NMR spectroscopy. The X-ray structures of ligand 1 and complex 1b are also reported.