A new class of coordinatively unsaturated, monomeric organoscandium compounds, Cp*2Sc-R (Cp* = (rj5-C5Me5); R = halide, hydride, alkyl, alkenyl, alkynyl, aryl), has been prepared. Cp*2Sc-Cl is obtained from reaction of ScCl3(THF)3 (THF = tetrahydrofuran) with LiCp*, and Cp*2Sc-R (R = CH3, C6H5, C6H4CH3, CH2C6H5) from treatment of Cp*2Sc-Cl with the appropriate organoalkali reagent. These organoscandium compounds react with dihydrogen rapidly to yield R-H and Cp*2Sc-H. The tetrahydrofuran adducts Cp*2ScX(THF) (X = Cl, H, CH3) are obtained upon treatment of Cp*2Sc-X with tetrahydrofuran. Rapid exchange of dihydrogen with the hydride ligands of Cp*2Sc-H and Cp*2ScH(THF) occurs even at low temperatures. Other alkyl derivatives may be conveniently prepared by treatment of Cp*2Sc-H (or Cp*2ScH(THF)) with -olefins, e.g., Cp*2ScCH2CH3 from Cp*2Sc-H and ethylene. Aliene and Cp*2Sc-H afford Cp*2Sc(7j3-C3H5). Cp*2Sc-R (R = H, CH3, aryl) reacts with pyridine to yield Cp*2Sc(C, N-j;2-C5H4N), which crystallizes in the orthorhombic space group

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224ChemInform Abstract A new class of coordinatively unsaturated, monomeric organoscandium compounds has been prepared. (I), obtained from ScCl3(THF)3 and pentamethylcyclopentadienyllithium (xylenes, 140 rc C, 3 d), undergoes metathetical reactions with rganolithium reagents to give the derivatives (IIa)-(IIc) which react rapidly with H2 in hexane to yield the unstable complex (III) and in THF to yield the stable adduct (IV). Rapid exchange of dihydrogen with the hydride ligands of (III) and (IV) occurs even at low temperatures. eactions of (III), generated in situ, with olefins or allene at -80 rc C yield the derivatives (IId), (IIe) and (V). (III), (IIa), (IIb) (R: -Ph), (IIc) and (IV) react with Py to afford the orthometallated complex (VI), which crystallizes in the space group Pna21 with Z=4. Spectroscopic nd crystallographic data for (IIa) and (IId) indicate that the methyl ligand is bonded in an undistorted manner, while the ethyl ligand participates in a β-C-H to Sc "agostic" interaction. (IIa) crystallizes in the space group P212121 with Z=4. The H/D exchange between H2, renes and C-H bonds of alkanes, catalyzed by (III) and (IV) is investigated thermodynamically. (IIa) reacts with a range of hydrocarbons, activating their C-H bonds to afford CH4 and complexes such as (IIf). Kinetics for these reactions are studied. Very small differences n the rates of vinylic C-H bond activation for p-substituted styrenes (X: -CF3, -OMe) and aryl C-H bonds of PhY (Y: -CF3, -H, -Me, -NMe2) as well as the positional nonselectivity for activation of the meta and para C-H bonds of toluene indicate that the Sc center does not nteract substantially in the π-system of these substrates in the transition states for these reactions. Thus for sterically encumbered organoscandium compounds, sp2-hybridized C-H bonds are activated without formation of a π-complex;

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