Synthesis of enol esters and dimerization of terminal alkynes catalyzed by neutral and cationic vinylidene ruthenium complexes

In the current study Ru(II) vinylidene complexes of the general type: Cl2Ru {=C=C(H)R} (PR'(3))L (R = Ph, SiMe3, R' = Ph, Cyclohexyl (Cy) and L = phosphine or N-heterocyclic carbene) are synthesized and tested for the addition of carboxylic acids to terminal alkynes. A careful choice of the catalytic system, substrate and carboxylic acid gives access to alk-1-en-2-yl esters, alk-1-en-1-yl esters or enyne dimerization products. Furthermore, an extension was made to synthesize an analogous 14-electron species by treating one of the complexes with AgBF4 and its influence on the catalytic activity and selectivity are investigated.