VOLATILE TRIS-TERTIARY-ALKOXIDES OF YTTRIUM AND LANTHANUM - THE X-RAY CRYSTAL-STRUCTURE OF [LA3(OBU-TERT)9(BU-TERTOH)2]

Tertiary alkoxides of yttrium and lanthanum have been prepared by addition of excess tertiary alcohol to the metal tris-(bis-trimethylsilylamides), M{N(SiMe3)2}3 (M = Y, La), and characterized by elemental analyses, NMR, IR and mass spectroscopy. With t-butanol and t-amyl alcohol the alcoholates [Y3(OBu(t))9(Bu(t)OH)2] (1), [Y3(OAm(t))9 (Am(t)OH)2] (2) and [La3(OBu(t))9(Bu(t)OH)2] (3) were isolated. With higher tertiary alcohols the tris-t-alkoxides [M(OR)3] were obtained [M = Y, R = CMe2Pr(i)(4), CMeEtPr(i)(5), CEt3 (6); M = La, R = CMe2Pr(i) (7), CMeEtPr(i) (8)] as dimers. The coordinated Bu(t)OH in 1 could be replaced by THF or pyridine but not by trimethylamine. The X-ray crystal structure of 3 showed that the La3 triangle is capped by two mu-3-OBu(t) groups with three mu-2-OBu(t) bridges as in [La3(mu-3-OBu(t))2(mu-OBu(t))3(OBu(t))4(Bu(t)OH)2]. The variable temperature NMR data suggest that compounds 1 and 2 have the same structure in solution as compound 3.