Synthesis, catalytic activity, and photophysical properties of 5,6-membered Pd and PtSCS′-pincer complexes based on thiophosphorylated 3-amino(hydroxy)benzoic acid thioanilides

Abstract

Novel unsymmetrical SCS′-pincer ligands, 1-[PhNHC(S)]-3-[Ph₂P(S)NH]-C₆H₄ (3) and 1-[PhNHC(S)]-3-[Ph₂P(S)O]C₆H₄ (7), bearing a thiocarbamoyl moiety in combination with thiophosphorylamino- and thiophosphoryloxy-donating groups, respectively, were obtained via thiophosphorylation of 3-amino- and 3-hydroxy-benzoic acid (thio)anilides 1 and 6. Direct cyclometallation of the central benzene ring in the ligands 3 and 7 in reaction with (PhCN)₂MCl₂ (M = Pd, Pt) as a metal precursor afforded κ³-SCS′-hybrid pincer complexes 8, 9 with 5- and 6-membered fused metallacycles in good to high yields (67–95%). The complexes 8 and 9 were characterized by multinuclear NMR (³¹P, ¹H, ¹³C) and IR spectroscopy as well as single-crystal X-ray crystallography. Palladium complexes 8a and 9a were shown to be active catalysts for the Suzuki–Miyaura cross-coupling reaction. In the solid state the ligands 3 and 7 as well as their Pt(II) and Pd(II) complexes 8 and 9 are luminescent at 300 K. The emission of the complexes has the different origin depending on the metal nature.