Chart I.

Abbreviations and Designation of Ligands and Complexes

ACS = acetyl coenzyme A synthase; Ch = carboxydothermus hydrogenoformans; CODH = carbon monoxide dehydrogenase; dien = diethylenetriamine; dme = 1,2-dimethoxyethane; Mb = Methanosarcina barkeri; Me₆tren = tris(N,N'-dimethyl-2-aminoethyl)amine; Mt = Moorella thermoacetica; pyN₂ = N,N'-bis(phenyl)-2,6-pyridinedicarboxamidate(2-); pdtc = pyridine-2,6-dithiocarboxylate(2-); pyN₂^iPr2 = N,N'-bis(2,6-diisopropylphenyl)-2,6-pyridinedicarboxamidate(2-); pyN₂^Me2 = bis(2,6-dimethylphenyl)-2,6-pyridinedicarboxamidate(2-); pyN₂dien^Me3 = bis(phenyl-3,3'-(2,5,8-tri-N-methylamino-1,9-nonyl))-2,6-pyridinedicarboxamidate(2-); tdt = toluene-3,4-dithiolate(2-); TfO⁻ = triflate