Highly basic alkyl-substituted bis(benzhydryl) CaII and YbII complexes with β-CH–M agostic interactions

The reaction between potassium derivative {[(4-Bu^tC₆H₄)₂CH]⁻K⁺}_n and alkyl iodides gives new 1,1-bis(4-tert-butylphenyl)alkanes which can be deprotonated with BuⁿNa to produce species [(4-Bu^tC₆H₄)₂CR]⁻Na⁺ (R=Me, Buⁱ). The salt metathesis of the latter with base-free CaI₂ or YbI₂ affords novel bis(hydrocarbyl) complexes [(4-Bu^tC₆H₄)₂CR]₂M(TMEDA) (M=Ca, R=Me; M=Yb, R=Buⁱ). The hyperconjugation of the central carbanion with alkyl groups pronouncedly enhances the basic properties of the compounds which would perform CH bond activation in toluene and thiophene, in distinction to the related ‘nonalkylated’ analogues with (4-Bu^tC₆H₄)₂CH⁻ ligand.