Yttrium Alkyl and Benzyl Complexes with Amino−Amidinate Monoanionic Ancillary Ligands

Abstract

The sequential reaction of YCl3(THF)3.5 with [t-BuC(Ni-Pr)2]Li (Li[A]) and 2 equiv of LiCH(SiMe3)2 gave the mono(amidinate) dialkyl yttrium complex [t-BuC(Ni-Pr)2]Y[CH(SiMe3)2]2(μ-Cl)Li(THF)3 (1), which was structurally characterized. Use of the potentially tridentate amidinate−amine ligands [PhC(NSiMe3)N(CH2)nNMe2]- (n = 2, B; 3, C) yielded the salt-free dialkyl complexes [PhC(NSiMe3)N(CH2)nNMe2]Y[CH(SiMe3)2]2 (n = 2, 2a; 3, 2b). A structure determination of 2a showed the tridentate ligand to adopt an approximately meridional geometry. Attempts to prepare analogous benzyl or trimethysilylmethyl complexes with ligand B yielded the ate-complexes Li[PhC(NSiMe3)N(CH2)2NMe2]2Y(R)2 (R = CH2Ph, 3a; CH2SiMe3, 3b). A crystal structure of 3a showed that the Li ion is encapsulated by two amidinate and two amine nitrogens. The increased spacer length between the amidinate and amine functionalities in ligand C prevented encapsulation of the Li ion, but still produced a bis(amidinate) yttrium benzyl complex, [PhC(NSiMe3)N(CH2)3NMe2]2YCH2Ph (4). In this compound only one of the two dimethylamino functionalities is coordinated to the metal center.