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

Abstract

The reaction of rare-earth bis(alkyl) complexes containing a bis(phosphinophenyl)amido pincer (PNP), LnPNPiPr(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 (μ-C6H4PPh2-κP:κC1, 2a-Ln) or a bridging phosphinomethyl ligand (μ-CH2PPh2-κP:κC, 2b-Ln), respectively. Reaction of 2a-Y with CO gas at 1 atm and at 20 °C in toluene-d8 afforded the complex 3a-Y, which bears a bridging pseudooxymethylene ligand (μ-OCH(o-C6H4)PPh2-κP:κO) 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 (ΔG(B3PW91) = 22.9; ΔG(M06) = 14.9 kcal/mol) and migratory insertion of the Y–C6H4 group (ΔG⧧(B3PW91) = 13.3; ΔG⧧(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(C5Me5)(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 alkylideneamidophosphine (4b-Y), an amidophosphine (7b-Y), an η2-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.