Synthesis and Structure of Silyl-Substituted Bis(cyclopentadienyl) Scandium(III) Halide Complexes

Despite the importance of bis(cyclopentadienyl) scandium(III) halide complexes as precursors in the development of scandium metallocene chemistry, relatively few examples of this class have been structurally characterized. Since the cyclopentadienyl ring substitution pattern and the halide identity can have a major influence on organoscandium complex synthesis and reactivity, it is critical to have a variety of well-characterized [(C5R5)2ScX]n starting materials (R = H, alkyl, silyl; X = halide) available for exploration of this area. To remedy this deficiency, reactions between ScX3 (X = Cl and I) and 2 equiv of a variety of potassium cyclopentadienide reagents have been examined. This has provided, in good crystalline yield, the compounds [C5H3(SiMe3)2]2ScI, [C5Me4(SiMe3)]2ScI, [C5Me4(SiMe2tBu)]2ScI, {[C5H4(SiMe3)]2Sc(μ-I)}2, {[C5H4(SiiPr3)]2Sc(μ-I)}2, and {[C5H3(SiMe3)2]2Sc(μ-Cl)}2, each of which has been characterized by X-ray crystallography, elemental analysis, NMR spectroscopy (1H, 13C{1H}, 29Si{1H}, and 45Sc), and infrared spectroscopy. The study has also revealed the facile cocrystallization of the oxide {[C5H3(SiMe3)2]2Sc}2(μ-O) and hydroxide {[C5H3(SiMe3)2]2Sc(μ-OH)}2 impurities from preparations of [C5H3(SiMe3)2]2ScI using samples of ScI3 that presumably contain an oxide contaminant.