SYNTHESIS AND CHARACTERIZATION OF MONO-(PENTAMETHYLCYCLOPENTADIENYL)ALKOXYSCANDIUM ALKYL DERIVATIVES, (ETA-5-C5ME5)(OR)SCR'

Strategies for the syntheses of the title compounds are described. Cp*Sc(acac)2 (Cp* = (eta-5-C5Me5); acac = acetylacetonate) is prepared by treatment of Sc(acac)3 with Cp*MgCl.THF. Oligomeric [Cp*ScCl2]n is prepared by treatment of Cp*Sc(acac)2 with two equivalents of AlCl3. Cp*(OR)ScCl (R = 2,4,6-C6H2(CMe3)3, 3,5-C6H3(CMe3)2) are obtained as their THF adducts via treatment of [Cp*ScCl2]n with LiOR in THF or as their lithium chloride adducts via treatment of [Cp*ScCl2]n with LiOR in toluene in the presence of PMe3. Whereas the alkylation of Cp*{O-2,4,6-C6H2(CMe3)3}ScCl yields unstable products which appear to readily undergo metalation of an ortho tert-butyl group with loss of alkane, treatment of Cp*{O-3,5-C6H3(CMe3)2}ScCl with methyllithium yields an unreactive scandium methyl derivative, which is likely dimeric [Cp*(CH3)Sc{mu-O-3,5-C6H3(CMe3)2}]2. This methyl derivative proved to be unexpectedly inert toward olefins, 2-butyne and even Lewis bases such as pyridine and THF.