ALKYNE ADDUCTS OF [CP(ASTERISK)RU(SR)](2) AND INTERMEDIATES OF THE RUTHENIUM-CATALYZED FORMATION OF VINYL THIOETHERS (Z E)-RSCR'=CHR'' FROMRSH AND R'C-CR''/

Binuclear Ru complexes CpRu(mu-SR)(2)RuCp* (2; R = Et, Pr-i, (t)Bu) a nd the related complex CpRU(eta(1)-C6F5)(mu-S)(mu-SC6F5)RUCP* (3) are active catalysts for the addition of thiols to polar alkynes at room temperature. The addition of alkynes to one Ru of 2 and 3, respectivel y, is shown by NMR as the first step in the catalytic cycle. Four addi tional complexes, 7-10, all characterized by single-crystal X-ray stru ctures (Table 2), were isolated from the catalytic mixture. These are the insertion product of HC drop CCOOMe into the Ru-S bond of 2, CpRu (mu-SR)(mu(2)-eta(4)-MeOOC drop CCHSR)RuCp (7a), the double-vinyliden e complex u-S(t)Bu)(2)RuCp{eta(1)-=C=C(COOMe).CH=CH(COOMe)} (8), the double-insertion product of alkyne into 2c, )Bu){mu-eta(4)-(S(t)Bu)C=C (COOMe)CH=CHCOOMe}-RuCp (9), and a complex formed from linkage of fiv e HC drop CCOOMe molecules with two RuCp and one S(t)Bu unit, (CpRu)( 2) U)-B-t-2,3,5-(COOMe)(3)-6-(C=C(COOMe)-CH=CHCOOMe)} (10). 7 and 8 ar e active catalysts; 9 and 10 are stop complexes of the catalytic cycle . On the basis of these isolated and characterized intermediates a mec hanism for the catalytic cycle is suggested.