Synthesis, structural characterization and reactivity of metallacarboranes of lanthanides and early transition metals

Several mono- and bisfunctional carboranes (DCH2CH2)RC 2B10H10 (R = H, DCH2CH2, D = MeO, Me2N) have been designed and successfully synthesized. They can be conveniently converted into the monoanions, the dianions and the tetraanions by treatment with suitable reagents. Their applications in organolanthanide and group 4 organometallic chemistry have been studied.;Reactions of alkali metal salt of these carboranes with LnCl3 in the presence of excess alkali metal afford a novel class of 13-vertex closo-metallacarboranes incorporating eta7-carboranyl ligands [{eta1:eta1:eta7-[(DCH 2CH2)RC2B10H10]Ln}{Na(solvent) x}]n. Structural studies show that the Lewis base functionalized sidearms have some effects on the coordination environments of the central metal atom, but do not change the gross structures of the 13-vertex closo-metallacarboranes. The reactivity patterns of these 13-vertex closo-metallacarboranes have been studied for the first time.;Reaction of [(Me2NCH2CH2)C2B 10H11]Na2 with YCl3 gives eta 1:eta6-[(Me2NCH2CH2)C 2B10H11]YCl(THF)3 containing an exopolyhedral Y-Cl bond, which offers an important intermediate for the preparation of lanthanacarboranes bearing the Ln-C or Ln-X (X = heteroatoms) bonds. On the other hand, it implies that Lewis base functionalized carboranes can stabilize half-sandwich metallacarboranes via the coordination of heteroatom from the sidearm. Silylamine elimination reactions of the neutral ligand 7-Me2NHCH2CH2-7,8-C 2B9H11 with Ln[N(SiHMe2)2] 3(THF)2 are effective method for the preparation of half-sandwich lanthanacarboranes.;High-valent group 4 half-sandwich metallacarboranes incorporating an eta 7-carboranyl ligand have been prepared and structurally characterized. The heteroatom-containing pendant sidearms on the carborane cage are both electronically and entropically necessary for the formation of such complexes.;Alkane elimination reaction of Hf(CH2SiMe3) 4 with a zwitterionic salt 1-Me2NHCH2CH2 -1,3-C2B10H12 has resulted in the isolation and structurally characterization of the first example of half-sandwich group 4 metallacarborane alkyls of the C2B10 system. This is also a new route to high-valent group 4 metallacarboranes.;Alkane or amine elimination reactions are also effective methods for the preparation of half-sandwich group 4 metal] acarboranes of the C 2B9 system. The Lewis base functionalized sidearm can effectively stabilize half-sandwich group 4 metallacarborane alkyls through intramolecular coordination. These novel metallacarborane alkyls undergo insertion reaction with alkyne and intramolecular hydrogen atom abstraction reactions.