Reductive Trimerization of CO to the Deltate Dianion Using Activated Magnesium(I) Compounds

Abstract

This study details syntheses of unsymmetrical magnesium(I)−adduct complexes, [( Ar Nacnac)-(D)Mg−Mg( Ar Nacnac)] ( Ar Nacnac = [(ArNC-Me) 2 CH] − ), Ar = xylyl (Xyl), mesityl (Mes), 2,6diethylphenyl (Dep), or 2,6-diisopropylphenyl (Dip); D = N-heterocyclic carbene or 4-dimethylaminopyridine, DMAP), which X-ray crystallographic studies show to have markedly elongated Mg−Mg bonds. Two of these highly reactive species are shown to reductively trimerize CO to yield rare crystallographically characterized examples of the planar, aromatic deltate dianion, incorporated in the complexes [{( Dip Nacnac)(D)Mg(μ-C 3 O 3 )Mg( Dip Nacnac)} 2 ] (D = DMAP or :C{N(Me)C-(Me)} 2 ). DFT calculations suggest that these complexes form via stepwise two-electron reductions of three CO molecules, resulting in the formation of three C−C bonds within the cyclic deltate unit. This work highlights the utility of activated magnesium(I) adduct complexes as soluble organometallic models for the study of reductive C−C bond-forming events in, for example, the heterogeneously catalyzed Fischer−Tropsch process.

Chemistry of alkaline earth metals: It is not all ionic and definitely not boring!

“…While most of its coordination chemistry is dominated by Mg 2+ , these N-heterocyclic carbenes can be reduced at least once using KC 8 , leading to a complex in which the radical is then stabilized by a chelating N-donor ligand such as bipyridine (Fig. 4, bottom [24]. They can also lead to non-cyclic 1,2dimagnesioethane or -ethene compounds that can be useful as multipurpose reagents for organometallic synthesis [25].…”

Sterically controlled reductive oligomerisations of CO by activated magnesium(i) compounds: deltate vs. ethenediolate formation

“…7 In order to access well-dened s-block metal complexes of oxocarbon anions derived from CO, we have recently reported on reactions of this gas with reducing b-diketiminate coordinated magnesium(I) compounds. 8,9 Initially, it was found that three-coordinate examples of these Mg-Mg bonded species, viz.…”

Magnesium Cyanide or Isocyanide?

“…Surprisingly,insome reports on rare examples of terminally bound metal isocyanides,the cyanide/ isocyanide isomerism is not even subject of discussion. [23][24][25] Since there is ab road interest in metal-CN isomerism from at heoretical [26] or experimental [27] point of view,w eh ere report the synthesis and structure of aM gc omplex with at erminal CN À ligand and provide af irst comprehensive discussion on (iso)cyanide preference.…”