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.

Subtle changes to the bulk of 1 : 1 adducts of DMAP with magnesium(i) complexes leads to steric control over the products arising from their reductive oligomerisations of carbon monoxide.

The first examples of magnesium benzenehexolate complexes are prepared by reductive hexamerizations of CO, in reactions that are initiated (or catalyzed) by [Mo(CO) 6 ]. These reactions are closely related to Justus von Liebig's classical 1834 study on the reduction of CO gas with molten potassium, which yields K 6 C 6 O 6 (amongst other products), by an as yet unknown mechanism. File list (2) download file view on ChemRxiv C6O6 manuscript.pdf (428.67 KiB) download file view on ChemRxiv C6O6 SI.pdf (1.99 MiB)

A series of novel Cp*-based (Cp*=η(5)-C5Me5) agostic, bis(σ-borate), and boratrane complexes have been synthesized from diruthenium and dirhodium analogues of pentaborane(9). The synthesis and structural characterization of the first neutral ruthenadiborane(6) analogue are also reported. This new route offers a very efficient method for the isolation of bis(σ-borate) and agostic complexes from diruthenapentaborane(9).