Sulfur chelated ruthenium compounds useful as olefin metathesis catalysts

A process for preparing 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;
• wherein the process is illustrated by the following route of synthesis:
• said process comprises reacting a benzaldehyde derivative of formula (1), wherein L is a leaving group, with thiol RSH to give 2-thiobenzaldehyde derivative of formula (2), transforming said derivative of formula (2) into the corresponding alkene of formula (3) through a Wittig reaction, and reacting said compound of formula (3) with a ruthenium compound of formula (4) to form the sulfur chelated ruthenium product of formula (I), wherein Z, m, R, X1, X2, Y1, Y2 have the meanings defined above, L is a leaving group and PCy3 is a phosphine which contains three cyclic aliphatic moieties.