Synthesis of permethylyttrocene alkyl complexes

Reaction of Cp*2Y(μ-Cl)2 · 2OEt2 (1) with MeLi gives the new complexes Cp*2Y(μ-Me)(μ-Cl)Li · 2OEt2 (3), Cp*2Y(μ-Me)2Li · OEt2 (4) and Cp*2YNe · THF (5) depending on the reaction conditions and stoichiometry. Salt incorporation is also observed when Grignard reagents react with Cp*P2YCl · THF (2), e.g. Cp*2YMe · [MgCl2 · 2THF] (6), Cp*P2YCH2Ph · [MgCl2 · 2THF] (7) and Cp*2Y(η1-CH2C-Me7z.dbnd;CH2) · [MgCl2 · 2THF] (9) being formed. The reaction of 2 with (2,6-xylyl)MgBr gives Cp*2YCl · [MgBr2 · 2THF] (8) and not the expected yttrocene aryl. From the IR spectra of the complexes 6, 7, 8, and 9 it is concluded that the THF ligand is coordinated to magnesium. The dimeric [Cp*2Y(μ-Me)2AlMe2]2 is obtained from Cp*2YCl · THF and LiAlMe4. A 1H NMR study has yielded the thermodynamic parameters ΔH° (41.5 ± kJ mol−1) and ΔS° (30.2 ± 2.4 e.u.) for the dimer-monomer equilibrium of this complex. Above ca. 75°C the monomeric Cp*2Y(μ-Me2)AlMe2 appears to dissociate into an ion pair Cp*2Y+ and AlMe4−. The compounds Cp*2YMe · THF and [Cp*P2Y(μ-Me)2AlMe2]2 are active catalysts for polymerization of ethene but not of propene. The initial activities for ethene polymerization of these complexes are 229 and 125 g mmol−1 (Y) h−1 atm−1, respectively, at 30°C. Above 75°C [Cp*2Y(μ-Me)2AlMe2] loses its activity, but regains it when the temperature is lowere