Low-Valent Aminopyridinato Chromium Methyl Complexes via Reductive Alkylation and via Oxidative Addition of Iodomethane by a Cr-Cr Quintuple Bond

Abstract

The reaction of 1 equiv of the deprotonated (sterically demanding) aminopyridine Ap∗-H (Ap∗-H = (2,6-diisopropylphenyl)-[6-(2,4,6-triisopropylphenyl)pyridin-2-yl]amine) with [CrCl 3 (thf) 3 ] led selectively to the monomeric complex [Ap∗CrCl 2 (thf) 2 ]. Methylation of [Ap∗CrCl 2 (thf) 2 ] by methyllithium gave rise to a mixture of a dichromium methylidene and a dichromium methyl complex. Alkylation of [Ap′CrCl 2 (thf) 2 ] (Ap′-H = (2,6-diisopropylphenyl)-[6-(2,6-dimethylphenyl)pyridin-2-yl]amine) afforded selectively the dimethyl complex [Ap′ 2 CrCr(CH 3) 2 ]. In addition to reductive alkylation, oxidative addition can be used to synthesize chromium methyl complexes. Selective oxidative addition was observed when CH 3 I was reacted with the quintuply bonded Cr I dimer [Ap′CrCrAp′]. Here, the Grignard-like Cr 2 compound [Ap′ 2 CrCr(μ-I)(μ-CH 3)] was formed. DFT calculations were performed to investigate the electronic structure of the organometallic complexes (Chemical Equation).