New Highly Water-Soluble Rhodium Complexes Bearing 1,3,5-Triaza-7-phosphaadamantane (PTA) and/or Tris(hydroxymethyl) phosphine (THP)

A family of cationic and neutral highly water-soluble rhodium complexes [Cp*Rh(PTA)3]Cl2 (1), [Cp*RhCl2(THP)] (2), [Cp*RhCl(THP)2]Cl (3), and [Cp*RhCl(PTA)(THP)]Cl (4) have been synthesised and fully characterised [PTA = 1,3,5-triaza-7-phosphaadamantane; THP = tris(hydroxymethyl)phosphine]. Their water-solubility increases as the number of the phosphines coordinated to the metal centre is increased. The X-ray crystal structure of compound 2 was obtained and shows the presence of intermolecular hydrogen bonding. NMR speciation studies of [Cp*RhCl2(PTA)] in deuterated water show the existence of several equilibria involving substitution processes in which the water molecules can substitute both chloride and PTA ligands.