A Model for the CO-Inhibited Form of [NiFe] Hydrogenase: Synthesis of $(CO)_3 Fe(\mu - S^t Bu)_3 Ni\{ SC_6 H_3 - 2,6 - (mesityl)_2 \}$ and Reversible CO Addition at the Ni Site

A [NiFe] hydrogenase model compound having a distorted trigonal-pyramidal nickel center, (CO)₃ $Fe(\mu - S_t Bu_3 )$ Ni(SDmp), 1 (Dmp= C₆ H₃ -2; 6-(mesityl)₂), was synthesized from the reaction of the tetranuclear Fe-Ni-Ni-Fe complex [(CO)₃ $Fe(\mu - S_t Bu_3 )$ Ni]₂ (µ-Br) 2# 2 with NaSDmp at -40 ° C. The nickel site of complex 1 was found to add CO or CN f Bu at -40 ° C to give (CO)₃ $Fe(\mu - S_t Bu)$$Fe(\mu - S_t Bu_2 )$ Ni(CO) (SDmp), 3, or (CO)₃ $Fe(\mu - S_t Bu)$(/