Dimethylcalcium.

Abstract

The salt metathesis reaction between homoleptic calcium bis(trimethylsilyl)amide [Ca{N(SiMe3)2}2]2 and "halide-free" methyllithium allowed for the isolation of X-ray-amorphous dimethylcalcium [CaMe2]n in good yields and purities. The formation of [CaMe2]n was proven by microanalysis and NMR/FTIR spectroscopic methods as well as a series of derivatization reactions. Despite slowly decomposing thf, [CaMe2]n could be crystallized from chilled thf solutions as the heptametallic adduct [(thf)10Ca7Me14]. Reaction of [CaMe2]n with CaI2 in thf led to the dimeric complex [(thf)3Ca(Me)(I)]2, whereas in tetrahydropyran (thp) the trinuclear complex [(thp)5Ca3(Me)5(I)] was obtained, both representing the first crystallographically characterized heavy-Grignard compounds with methyl groups as the hydrocarbyl ligand. While protonolysis of [CaMe2]n with the superbulky proligand HTptBu,Me in nonpolar solvents gave homoleptic (TptBu,Me)2Ca, reaction in donor solvents (thf, thp) afforded the monomeric complexes [(TptBu,Me)Ca(Me)(thf)] and [(TptBu,Me)Ca(Me)(thp)], which are the first examples bearing terminal Ca-CH3 functionalities. Grignard-type nucleophilic methyl-group transfer to hexamethylacetone gave access to the dimeric alkoxide complexes [(thf)Ca(OCtBu2Me)2]2 and [(tBu2CO)Ca(μ2-OCtBu2Me)3Ca(OCtBu2Me)]. Finally, addition of the Lewis acid GaMe3 to [CaMe2]n led to the corresponding tetramethylgallate compound [Ca(GaMe4)2]n.