Trigonal-bipyramidal, divalent Group 10 metal complexes supported by a tris(phosphino)silyl ligand

The mono-anionic, tetradentate tris(phosphino)silyl ligand, [SiP_R^3]- = [(2-R_2PC_6H_4)_3Si]-, provides access to electrophilic, trigonal bipyramidal Group 10 cations {[SiP_R^3]M(L)}+ that feature weakly coordinated ligands including toluene, dihydrogen, and dinitrogen. The toluene adduct {[SiP^(Ph)_3]Pt(tol)}+ shows a close contact between the metal center and an aryl C-H bond in the solid state. For the more electron-rich isopropylsubstituted ligand, it is possible to exclude the fifth, axial ligand to afford the four-coordinate, trigonal pyramidal complexes {[SiP^(iPr)_3]Pt}+ and {[SiP^(iPr)_3]Pd}+, in contrast to prototypical d^8 square-planar Pt and Pd geometries. The corresponding cationic Ni complexes reversibly coordinate dinitrogen and dihydrogen