Sulfur chelated ruthenium compounds represented by the following formula: wherein M indicates the ruthenium metal bound to a benzylidene carbon; R represents C1-C7 alkyl group or optionally substituted aryl; X1 and X2 each independently represent halogen; Y1 and Y2 each independently denote unsubstituted or alkyl-substituted phenyl; and Z independently represents hydrogen, electron withdrawing or electron donating substituent, with m being an integer from 1 to 4, and processes and compositions related thereto.