The synthesis, characterization, and alkylation of nacnac chromium triflate derivatives

A Cr(III) triflate coordinated by the bulky β-diketiminate MeLiPr (MeLiPr = 2,4-pentane N,N′-bis(2,6-diisopropylphenyl)diketiminate) was synthesized from the corresponding bridging iodide complex [MeLiPrCr(μ-I)]2 by ligand substitution and subsequent oxidation with silver triflate (AgOTf). MeLiPr CrIII(OTf)2 exhibits rare trigonal bipyramidal geometry about Cr(III). Attempts to alkylate this triflate synthon with 1,4-dilithiobutane (Li(CH2)4Li) led to reduction, while reaction with dimethylzinc (ZnMe2) led to a mono-alkylated product; only the reaction with methyl lithium (MeLi) was successful in generating a dialkyl.

Graphical abstractSeveral chromium triflates have been prepared to serve as precursors for alkylation reactions. While 1,4-dilithiobutane proved too reducing, alkylation of a Cr(III) triflate with methyl lithium produced the first example of a neutral Cr(III) dialkyl supported by the bulky MeLiPr ligand.Figure optionsDownload full-size imageDownload as PowerPoint slide