MOLYBDENUM(III) CHLORIDE TETRAHYDROTHIOPHENE (THT) COMPLEXES IN THE CATALYTIC POLYMERIZATION AND CYCLOTRIMERIZATION OF ALKYNES - STRUCTURESAND REACTIVITIES OF THE POSSIBLE INTERMEDIATES [MOCL3(THT)(2)(PHC-CR)] (R=ME OR ET)

The binuclear complexes [Mo2Cl6(tht)(3)] (both the C-2. and C-s isomer s, tht = tetrahydrothiophene) have been found to be active catalysts f or the selective polymerization and cyclotrimerization of a variety of alkynes. The mononuclear complex [MoCl3(tht)(3)] shows similar behavi our, leading to the postulate that the active species in all cases is mononuclear. Two unique molybdenum(III) alkyne complexes, [MoCl3(tht)( 2)L] (L = PhC=CMe or PhC=CEt) have been isolated and structurally char acterized. The structural parameters for these complexes suggest that the alkynes behave as four-electron donors. These complexes are also c atalytically active, and the alkyne L is incorporated into the product cyclotrimers and polymers suggesting they are the first intermediates in the formation of active catalysts from the original thioether comp lexes.