A Series of [Co(Mabiq)Cl_2–n] (n = 0, 1, 2) Compounds and Evidence for the Elusive Bimetallic Form

Abstract

. (2015) A series of [Co(Mabiq)Cl2-n] (n = 0, 1, 2) compounds and evidence for the elusive bimetallic form. Inorganic Chemistry.

Electrocatalytic H2 Evolution by the Co‐Mabiq Complex Requires Tempering of the Redox‐Active Ligand

“…The Co‐Mabiq complexes adopt formal metal oxidation states of 0→+3, encompassing the full range of oxidation states invoked in metal‐based HER pathways. We therefore reasoned that the compounds also might act as electrocatalysts for H 2 evolution.…”

“…The doubly reduced ‘Co 0 ’ form is in actuality a Co II containing, ligand biradical complex, in which the bipyrimidine moiety also is reduced. The electronic structures of both complexes were previously established by spectroscopic and DFT computational methods . We questioned how the unique electronic structures might impact their reactivity.…”

“…Mabiq is redox‐active, capable of storing electrons on each of its diketiminate and bipyrimidine units . An electron transfer series of Co‐Mabiq complexes was previously reported, which exemplify ligand‐centered reduction among the formally ‘low valent’ compounds . We have previously shown that the reaction of protons with [Co II (Mabiq ⋅⋅ )] − – containing the two electron reduced Mabiq ligand – leads to the formation of [Co(MabiqH 2 )], in which the macrocycle effectively stores H 2 on the bipyrimidine moiety .…”

A macrocyclic ‘Co0’ complex: the relevance of ligand non-innocence to reactivity

“…The molecular structure ( Figure S1) resembles that of the previously isolated Co(Mabiq)Cl, 26 The title Co 0 compound was obtained upon treatment of Co(Mabiq) with one equivalent of Na in THF, yielding the dark red 1. The compound is dimeric in the solid state ( Figure 2); the two bipyrimidine (bpm) units are within π-stacking distance (3.47 Å).…”

“…Compound 1 completes the electron transfer series of our Co-Mabiq complexes, which already included the formally monovalent Co(Mabiq) (2), 26 and now encompasses the full complement of formal oxidation states (0 → +3) invoked in the catalytic cycles of the HER and CO2 reduction. The characterization of 1 by crystallographic, spectroscopic and DFT computational methods is described herein.…”