Ni(II) (dioxo[16]aneN5)-Induced Methane Formation from Methyl Coenzyme M

The nickel tetrapyrrole containing factor, F430, is implicated in the final methane evolution step in methanogenic ba~terial-~ and has attracted considerable a t t e n t i ~ n . ~T- ~he essential role of F430 in methane formation was demonstrated by Ankel-Fuchs and Thauer, who reported the in vitro catalysis of H3CSCH2CH2S03-, methyl coenzyme M (methyl-CoM), to methane and CoM by purified methyl-CoM reductase under reducing condit i o n ~ .S~in ce F,,o exists in both the Ni(1) (or Ni(II1)) and the Ni(I1) states in Methanobacterium thermoautotrophicum,loi,t ll is of interest to examine the role of the nickel ion oxidation stateI2.l3 in methyl-CoM catalysis. We have found both the mono- and the divalent oxidation states of the water-soluble Ni(dioxo[ 161- aneNS), NiL, complexI4 catalyze methyl-CoM to methane and CoM