Zirconium and Hafnium Permethylpentalene Compounds

A selection of new η8-permethylpentalene zirconium and hafnium complexes are reported. The first d-block metal bis­(permethylpentalene) sandwich complexes, (Pn*2M ; Pn* = C8Me6 ; M = Zr, Hf) have been synthesized and structurally characterized. The bis-allyl species Pn*M­(C3H5)2 (M = Zr, Hf) have been synthesized; these complexes are fluxional in solution and react with CO2 to give the double-insertion product Pn*M­(κ2-O2CCH2CHCH2)2 (M = Zr, Hf). We also report monometallic, bimetallic, and polymeric σ-bonded alkyl derivatives such as (Pn*Zr)2(μ-CH2)­(μ-Me)2, [Pn*Hf­(CH2Ph)3]­[Li­(1,4-dioxane)4], and [Pn*ZrPh­(μ-Ph)2­Li­(μ-1,4-dioxane)]n.