Synthesis of the water-soluble [Rh(Tpms)(CO)(PTA)] compound, the first transition metal complex bearing the 1,3,5-triaza-7-phosphaadamantane (PTA) and the tris(1-pyrazolyl)methanesulfonate (Tpms) ligands

The water-soluble RhI compound [Rh(Tpms)(CO)(PTA)] (1) (Tpms = O3SC(pz)3−, PTA = 1,3,5-triaza-7-phosphaadamantane) has been easily prepared in high yield by a single-pot reaction of [{Rh(CO)2(μ-Cl)}2] with PTA and the tris(1-pyrazolyl)methanesulfonate lithium salt Li(Tpms), in a CH2Cl2/MeOH solution at room temperature. This synthetic strategy can be easily applied to the preparation of general [Rh(Tpms)(CO)(L)] (L = phosphine) complexes and constitutes a substantial improvement over the previously described procedures. Compound 1 is air stable in the solid state and water-soluble, affording stable solutions under an inert atmosphere. It has been characterized by IR, 1H, 31P{1H} and 13C{1H} NMR spectroscopies, elemental and single crystal X-ray diffraction structural analyses. The solid state structure of 1 has a square-planar geometry with the Tpms ligand coordinating the metal centre in a (κ2: N,N) bipodal mode. The title compound has also been investigated by cyclic voltammetry in CH3CN, and values of the EL Lever and PL Pickett electrochemical parameters (which measure the ligand net electron-donor character) are proposed for the PTA ligand. Complex 1 represents the first example of a transition metal complex bearing both PTA and Tpms (or any other tris(1-pyrazolyl)methane or derivative) ligands.