Reactions of (polypyrazolylborato)(benzonitrile)rutheniums with terminal alkynes: Reactivity changeover by triethylamine toward arylalkyne polymerization or formation of (arylmethyl)(carbonyl) complexes

Reactions of (κ3-polypyrazolylborato)(benzonitrile)rutheniums [RuCl{B(4-Ypz)4}(PhCN)2] {4-Ypz; 4-bromo-1-pyrazolyl (Y = Br) and 1-pyrazolyl (Y = H) groups} with terminal alkynes were studied. For the reactions with arylalkynes HCtriple bond; length of mdashC(aryl) in the presence of NEt3, (arylmethyl)(carbonyl)rutheniums [Ru{CH2(aryl)}{B(4-Ypz)4}(CO)(PhCN)] were yielded, indicating alkyne Ctriple bond; length of mdashC bond cleavage, whereas in the absence of NEt3, arylalkyne polymerization proceeded instead of the (arylmethyl)ruthenium formation. Reasonably attributed reaction mechanism shows significant role of the vinylidene intermediates “Rudouble bond; length as m-dashCdouble bond; length as m-dashCH(aryl)”.