Macrocyclic Platinum(II) Complexes with a Bifunctional Diphosphine Ligand

The preparation and coordination chemistry of a ditopic ligand scaffold (1(H2)), containing both a phosphorus-donor (P) and a nitrogen-donor (N) binding pocket, is reported. The ligand was synthesized by reductive amination from 3-(di-phenylphosphino)benzaldehyde and N-(2-aminophenyl)-N-methylbenzene-1,2-diamine. Selective coordination in the P-pocket was achieved for PtII, with careful control over the reaction conditions and precursor materials providing access to either the thermodynamic cis isomer, cis-PtCl2(1(H2)) (2), or the kinetic trans isomer, trans-PtCl2(1(H2)) (3). Both species have been fully characterized both in the solid state and in solution. Thermodynamic parameters for isomerization processes of 2 and 3 have been determined. Halide abstraction from 2 and 3 led to formation of cis-[Pt(CH3CN)(Cl)(1(H2))]BF4 and trans-[Pt(CH3CN)(Cl)(1(H2))]BF4.