Factors Influencing Coordination versus Oxidative Addition of C−H Bonds to Molybdenum and Tungsten: Structural and Spectroscopic Evidence That the Calixarene Framework Promotes C−H Bond Activation

Mo(PMe3)6 and W(PMe3)4(η2-CH2PMe2)H react with the diphenol CH2(ArMe2OH)2 (ArMe2 = C6H2Me2) to yield [κ2,η2-CH2(ArMe2O)2]M(PMe3)3H2 (M = Mo, W), which possess agostic M−H−C interactions. NMR spectroscopic studies provide evidence that the tungsten compound is in facile equilibrium with the metalated trihydride [κ3-CH(ArMe2O)2]W(PMe3)3H3.