EPR spectra of CODH ICh (A) oxidized with benzyl viologen; (B) oxidized with benzyl viologen and in the presence of 1 mM potassium cyanate; (C) oxidized with benzyl viologen and in the presence of 20 mM potassium cyanate; (D) reduced with CO; (E) upon CO reduction, in the presence of 1 mM potassium cyanate; (F) reduced with dithionite; (G) reduced with dithionite and then in the presence of 20 mM potassium cyanate. EPR conditions: modulation amplitude 10 G for all spectra and (temperature, microwave power, frequency) (A) 12 K, 41.2 mW, 9.38 GHz; (B) 12 K, 41.18 mW, 9.38 GHz; (C) 12 K, 41.2 mW, 9.383 GHz; (D) 10 K, 41.22 mW, 9.382 GHz; (E) 12 K, 41.21 mW, 9.379 GHz; (F) 12 K, 41.21 mW, 9.38 GHz; (G) 11 K, 41.21 mW, 9.381 GHz.