Synthesis and characterization of organo-scandium and yttrium complexes stabilized by phosphinoamide ligands

Addition of three equivalents of phosphinoamine, ((ArNHPPr2)-Pr-i) [Ar = 3,5-dimethylphenyl] to M(CH2SiMe3)(3)(THF)(2) [M = Sc, Y] precursors gives complexes of the form ((ArNPPr2)-Pr-i)(3)M(THF) [M = Sc, Y]. In the case of scandium, addition of Sc(CH2SiMe3)(3)(THF)(2) to (ArNPiPr(2))(3)Sc(THF) affords ((ArNPPr2)-Pr-i)(2)Sc(CH2SiMe3)(THF), which has been isolated and structurally characterized. In contrast, addition of Y(CH2SiMe3)(3)(THF)(2) to ((ArNPPr2)-Pr-i)(3)Y(THF) generates a distribution of phosphinoamide-containing products consistent with the formulations ((ArNPPr2)-Pr-i)(2)Y(CH2SiMe3)(THF) and ((ArNPPr2)-Pr-i)Y(CH2SiMe3)(2)(THF), as ascertained using NMR spectroscopy. Attempts to react the alkyl-containing phosphinoamide complexes with small molecules such as H-2 led to disproportionation type processes.