PNP-Ligated Heterometallic Rare-Earth/Ruthenium Hydride Complexes Bearing Phosphinophenyl and Phosphinomethyl Bridging Ligands

The reaction of rare-earth bis(alkyl) complexes containing a bis(phosphinophenyl)amido pincer (PNP), LnPNP(iPr),(CH2SiMe3)(2) (1-Ln, Ln = Y, Ho, Dy), with ruthenium trihydride phosphine complexes, Ru(C5Me5)H3PPh3 and Ru(C5Me5)H3PPh2Me, gave the corresponding bimetallic Ln/Ru complexes bearing two hydride ligands and a bridging phosphinophenyl (mu-C6H4PPh2-kappa P:kappa C-1, 2a-Ln) or a bridging phosphinomethyl ligand (mu-C6H4PPh2-kappa P:kappa C, 2b-Ln), respectively. Reaction of 2a-Y with CO gas at 1 atm and at 20 degrees C in toluened-d(8) afforded the complex 3a-Y, which bears a bridging pseudo-oxymethylene ligand (mu-OCH(sigma-C6H4)PPh2-kappa P:kappa O) and a bridging hydride ligand on the Y/Ru centers. Computational studies by the DFT method suggested that 3a-Y was formed in two steps: first the coordination of CO (Delta G(B3PW91) = 22.9; Delta G(M06) = 14.9 kcal/mol) and migratory insertion of the Y C6H4 group (Delta G(double dagger)(B3PW91) = 13.3; Delta G(double dagger)(M06) = 16.7 kcal/mol), followed by a rapid intramolecular hydride migration to the resulting acyl group. Complex 2b-Y reacted with organic nitriles (tBuCN, CH3CN, PhCN), an aldimine (PhNCHPh), an isonitrile (tBuNC), and group IX transition-metal carbonyls (M(C3Me3)(CO)(2), M = Rh, Ir) via insertion of the reactive Y-CH2 group into the unsaturated bond. These reactions afforded complexes with new ligand scaffolds, including a bridging alky-lidenearnidophosphine (4b-Y), an amidophosphine (7b-Y), an eta(2)-iminoacylphosphine (8b-Y), and oxycarbenephosphine (9b-Y and 10b-Y) ligands at the binuclear Y/Ru core. All of these reaction products were structurally characterized by X-ray crystallography, NMR spectroscopy, and elemental analyses.