2018/01/12 by Benjamin M. Wolf, Christoph Stuhl, Cäcilia Maichle‐Mößmer +1 · 1 citation
Chemistry · #Coordination Chemistry and Organometallics #Organometallic Complex Synthesis and Catalysis #Synthetic Organic Chemistry Methods
paper · doi:10.1021/jacs.7b12984
openalex publication_date 2018/01/12 · openalex created_date 2022/05/12 · openalex updated_date 2026/06/15
The salt metathesis reaction between homoleptic calcium bis(trimethylsilyl)amide [CaN(SiMe 3 ) 2 2 ] 2 and “halide-free” methyllithium allowed for the isolation of X-ray-amorphous dimethylcalcium [CaMe 2 ] n in good yields and purities. The formation of [CaMe 2 ] n was proven by microanalysis and NMR/FTIR spectroscopic methods as well as a series of derivatization reactions. Despite slowly decomposing thf, [CaMe 2 ] n could be crystallized from chilled thf solutions as the heptametallic adduct [(thf) 10 Ca 7 Me 14 ]. Reaction of [CaMe 2 ] n with CaI 2 in thf led to the dimeric complex [(thf) 3 Ca(Me)(I)] 2, whereas in tetrahydropyran (thp) the trinuclear complex [(thp) 5 Ca 3 (Me) 5 (I)] was obtained, both representing the first crystallographically characterized heavy-Grignard compounds with methyl groups as the hydrocarbyl ligand. While protonolysis of [CaMe 2 ] n with the superbulky proligand HTp t Bu,Me in nonpolar solvents gave homoleptic (Tp t Bu,Me ) 2 Ca, reaction in donor solvents (thf, thp) afforded the monomeric complexes [(Tp t Bu,Me )Ca(Me)(thf)] and [(Tp t Bu,Me )Ca(Me)(thp)], which are the first examples bearing terminal Ca–CH 3 functionalities. Grignard-type nucleophilic methyl-group transfer to hexamethylacetone gave access to the dimeric alkoxide complexes [(thf)Ca(OC t Bu 2 Me) 2 ] 2 and [( t Bu 2 CO)Ca(μ 2 -OC t Bu 2 Me) 3 Ca(OC t Bu 2 Me)]. Finally, addition of the Lewis acid GaMe 3 to [CaMe 2 ] n led to the corresponding tetramethylgallate compound [Ca(GaMe 4 ) 2 ] n .