Synthesis and characterization of Pd(0) and Pt(0) metallocryptands encapsulating Tl+ ion

Pt(0)/Pd(0) metallocryptates encapsulating TI(I) have been constructed utilizing mixed phosphine-imine ligands 2,9-bis(diphenylphosphino)-1,10-phenathroline, P(2)phen, and 6,6'-bis(diphenylphosphino)-2,2'-bipyridine, P(2)bpy. The red compounds [M2Tl(P(2)phen)(NO3) (M = Pt, 1; M = Pd, 3) and [M2Tl(P(2)bpy)(3)](NO3) (M = Pt, 2; M = Pd, 4) have been isolated as air-stable crystalline solids. Complexes 1-4 exhibit single signals in their Tl-205 NMR spectra that are well deshielded compared to the TiNO3(aq) reference signal. Additionally, Pt-195 NMR spectra of complexes 1 and 2 exhibit a doublet of quartets pattern resulting from large one-bond couplings to both P-31 and Tl-205. Characterization of 1-4 by single-crystal X-ray diffraction studies confirms the metallocryptand structure consisting of three phosphine-imine ligands in a D-3-symmetric cage with the TI(I) ion in its center and the zero-valent Pt or Pd atoms on each end. Each Pd or Pt atom is coordinated to three phosphorus centers, forming approximately trigonal geometry. The Tl(I) ion is positioned away from the imine nitrogen atoms of the phosphine ligands by similar to3.5 Angstrom. Further, the outer capping metals are distorted toward the central TI(I) ion, indicating a strong interaction. The Pt-Tl and Pd-TI separations are at similar to2.8 Angstrom each, further manifesting the strength of the metallophilic attraction in these assemblies.