Investigating Metal-Metal Bond Polarization in a Heteroleptic Tris-Ylide Diiron System.

This article describes the synthesis, characterization, and S-atom transfer reactivity of a series of -symmetric diiron complexes. The iron centers in each complex are coordinated in distinct ligand environments, with one (Fe) bound in a pseudo-trigonal bipyramidal geometry by three phosphinimine nitrogens in the equatorial plane, a tertiary amine, and the second metal center (Fe). Fe is coordinated, in turn, by Fe, three ylidic carbons in a trigonal plane, and, in certain cases, by an axial oxygen donor.

Mapping the Reactivity of Dicobalt Bridging Nitrides in Constrained Geometries.

Low-nuclearity nitrides of the late transition metals are rare and reactive molecular species, with little experimental precedent. The first putative examples of dicobalt bridging nitrides, [(PDI)Co(μ-N)(PMe)][OTf] (; PDI = pyridyldiimine; = 2 or 3, representing the length of the aliphatic chain linking PDI imino groups), were reported recently and shown to undergo a range of intramolecular reaction pathways, including N-H bond formation, C-H bond insertion, and P═N bond formation at the bridging nitride. The specific mode of reactivity changed with the phase of the reaction and the size of the macrocycle used to support the transient species.

Unusual cyanide and methyl binding modes at a dicobalt macrocycle following acetonitrile C-C bond activation.

This communication describes the C-C bond activation of acetonitrile and the trapping of the methyl and cyanide fragments by macrocyclic, dicobalt complexes. Both products display unique structural features as a result of the constraints imposed by the macrocycle. The bridged species [(PDI)Co(μ-CN)(PMe)][OTf] ([CoCN]) exhibits atypical Co-CN-Co binding, and upon either phosphine dissociation or oxidation, the flexible ligand framework is able to switch between different binding modes of μ-cyanide.

Effective Pincer Cobalt Precatalysts for Lewis Acid Assisted CO2 Hydrogenation.

The pincer ligand MeN[CH2CH2(P(i)Pr2)]2 ((iPr)PNP) was employed to support a series of cobalt(I) complexes, which were crystallographically characterized. A cobalt monochloride species, ((iPr)PNP)CoCl, served as a precursor for the preparation of several cobalt precatalysts for CO2 hydrogenation, including a cationic dicarbonyl cobalt complex, [((iPr)PNP)Co(CO)2](+). When paired with the Lewis acid lithium triflate, [((iPr)PNP)Co(CO)2](+) affords turnover numbers near 30 000 (at 1000 psi, 45 °C) for CO2-to-formate hydrogenation, which is a notable increase in activity from previously reported homogeneous cobalt catalysts.