Synthesis\nand Structure of Silyl-Substituted Bis(cyclopentadienyl)\nScandium(III) Halide Complexes

Despite the importance of bis(cyclopentadienyl) scandium(III)\nhalide\ncomplexes as precursors in the development of scandium metallocene\nchemistry, relatively few examples of this class have been structurally\ncharacterized. Since the cyclopentadienyl ring substitution pattern\nand the halide identity can have a major influence on organoscandium\ncomplex synthesis and reactivity, it is critical to have a variety\nof well-characterized [(C<sub>5</sub>R<sub>5</sub>)<sub>2</sub>ScX]<sub>n</sub> starting materials (R = H, alkyl, silyl; X = halide) available\nfor exploration of this area. To remedy this deficiency, reactions\nbetween ScX<sub>3</sub> (X = Cl and I) and 2 equiv of a variety of\npotassium cyclopentadienide reagents have been examined. This has\nprovided, in good crystalline yield, the compounds [C<sub>5</sub>H<sub>3</sub>(SiMe<sub>3</sub>)<sub>2</sub>]<sub>2</sub>ScI, [C<sub>5</sub>Me<sub>4</sub>(SiMe<sub>3</sub>)]<sub>2</sub>ScI, [C<sub>5</sub>­Me<sub>4</sub>­(SiMe<sub>2</sub><i><sup>t</sup></i>Bu)]<sub>2</sub>ScI, {[C<sub>5</sub>H<sub>4</sub>­(SiMe<sub>3</sub>)]<sub>2</sub>­Sc(μ-I)}<sub>2</sub>, {[C<sub>5</sub>H<sub>4</sub>(Si<i><sup>i</sup></i>Pr<sub>3</sub>)]<sub>2</sub>Sc(μ-I)}<sub>2</sub>, and {[C<sub>5</sub>H<sub>3</sub>(SiMe<sub>3</sub>)<sub>2</sub>]<sub>2</sub>Sc(μ-Cl)}<sub>2</sub>, each of which has been\ncharacterized by X-ray crystallography, elemental analysis, NMR spectroscopy\n(<sup>1</sup>H, <sup>13</sup>C{<sup>1</sup>H}, <sup>29</sup>Si{<sup>1</sup>H}, and <sup>45</sup>Sc), and infrared spectroscopy. The study\nhas also revealed the facile cocrystallization of the oxide {[C<sub>5</sub>H<sub>3</sub>(SiMe<sub>3</sub>)<sub>2</sub>]<sub>2</sub>Sc}<sub>2</sub>(μ-O) and hydroxide {[C<sub>5</sub>H<sub>3</sub>(SiMe<sub>3</sub>)<sub>2</sub>]<sub>2</sub>Sc(μ-OH)}<sub>2</sub> impurities\nfrom preparations of [C<sub>5</sub>H<sub>3</sub>(SiMe<sub>3</sub>)<sub>2</sub>]<sub>2</sub>ScI using samples of ScI<sub>3</sub> that presumably\ncontain an oxide contaminant.