Platinum(II) Complexes of Cyclic Triphosphenium Ions: a 31P NMR Spectroscopic and Computational Study

The first transition metal complexes of cyclic triphosphenium ions have been unequivocally identified in solution by P-31 NMR spectroscopy. The ligands coordinate to platinum(II) via the central phosphorus atom, but only when at least one of the outer phosphorus atoms has non-aromatic substituents. Depending on the system, either trans- (the kinetic reaction product) and/or cis- (the thermodynamic reaction product) complexes are formed. The (1)J coupling constants between Pt-195 and the central phosphorus atom of the CTI (P-A) are small for both cis- and trans-isomers, between 900 and 1300 Hz, whereas other phosphanes in these complexes derived from the platinum(II) starting material show normal (1)J(PtP) values. These results suggest a possible long P-Pt bond between the overall positively charged ligand and the platinum(II) cation. Calculations including predicted P-31 NMR shifts for the CTIs and their Pt(II) complexes largely support our experimental findings.