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

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 [CrCl3(thf)3] led selectively to the monomeric complex [Ap*CrCl2(thf)2]. Methylation of [Ap*CrCl2(thf)2] by methyllithium gave rise to a mixture of a dichromium methylidene and a dichromium methyl complex. Alkylation of [Ap′CrCl2(thf)2] (Ap′-H = (2,6-diisopropylphenyl)-[6-(2,6-dimethylphenyl)­pyridin-2-yl]­amine) afforded selectively the dimethyl complex [Ap′2CrCr­(CH3)2]. In addition to reductive alkylation, oxidative addition can be used to synthesize chromium methyl complexes. Selective oxidative addition was observed when CH3I was reacted with the quintuply bonded CrI dimer [Ap′CrCrAp′]. Here, the Grignard-like Cr2 compound [Ap′2CrCr­(μ-I)­(μ-CH3)] was formed. DFT calculations were performed to investigate the electronic structure of the organometallic complexes.