Reactions of alkynes with mononulear benzylidene complexes and with binuclear $um-benzylidene complexes of tungsten

Article abstract of DOI:10.1016/0304-5102(88)85100-9

Benzylidene(pentacarbonyl)tungsten complexes react with (a) diethylaminopropyne via the insertion of one C=C bond into the W=C bond to give (CO)₅W=C(NEt₂)-C(Me)=C(C₆H₄R-p)H and with (b) an excess of 2-butyne to give (CO)₅W-[MeC≡CMe] and different C(C₆H₄R-p)H/MeC≡CMe coupling products. With both alkynes no polymerization occurs. In contrast, when t-BuC≡CH is employed in large excess, rapid polymerization is observed. A mechanism for the polymerization is proposed which involves the intial formation of a vinylidene complex. On thermolysis of the terminal benzylidene complexes in inert solvents benzylidene-bridged bis(pentacarbonyltungsten) complexes are formed which slowly lose one CO ligand.