Sulfur chelated ruthenium compounds useful as olefin metathesis catalysts

1) A sulfur chelated ruthenium compound 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.