Reactions of dicobalt octacarbonyl with dinucleating and mononucleating bis(imino)pyridine ligands.

This work focuses on the application of dicobalt octacarbonyl (Co(CO)) as a metal precursor in the chemistry of formally low-valent cobalt with redox-active bis(imino)pyridine [NNN] ligands. The reactions of both mononucleating mesityl-substituted bis(aldimino)pyridine (L) and dinucleating macrocyclic xanthene-bridged di(bis(aldimino)pyridine) (L) with Co(CO) were investigated. Independent of the metal-to-ligand ratio (1 : 1 or 1 : 2 ligand to Co(CO)), the reaction of the dinucleating ligand L with Co(CO) produces a tetranuclear complex [Co(L)(CO)] featuring two discrete [Co[NNN](CO)] units.

Cooperative bimetallic reactivity of a heterodinuclear molybdenum-copper model of Mo-Cu CODH.

The synthesis of a heterodinucleating ligand LH2 (LH2 = (E)-3-(((2,7-di-tert-butyl-9,9-dimethyl-5-((pyridin-2-ylmethylene)amino)-9H-xanthen-4-yl)amino)methyl)benzene-1,2-diol) was undertaken toward a functional model of the bimetallic active site found in Mo-Cu carbon monoxide dehydrogenase (Mo-Cu CODH), and to understand the origins of heterobimetallic cooperativity exhibited by the enzyme. LH2 features a hard potentially dianionic catechol chelate for binding Mo(vi) and a soft iminopyridine chelate for binding Cu(i). Treatment of LH2 with either Cu(i) or M(vi) (M = Mo, W) sources leads to the anticipated site-selective incorporation of the respective metals.

Divergent reactivity of a new dinuclear xanthene-bridged bis(iminopyridine) di-nickel complex with alkynes.

The reaction of a dinucleating bis(iminopyridine) ligand L bearing a xanthene linker (L = N,N'-(2,7-di-tert-butyl-9,9-dimethyl-9H-xanthene-4,5-diyl)bis(1-(pyridin-2-yl)methanimine)) with Ni(COD)(DPA) (COD = cyclooctadiene, DPA = diphenylacetylene) leads to the formation of a new dinuclear complex Ni(L)(DPA). Ni(L)(DPA) can also be obtained in a one-pot reaction involving Ni(COD), DPA and L. The X-ray structure of Ni(L)(DPA) reveals two square-planar Ni centers bridged by a DPA ligand.