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 HCC(aryl) in the presence of NEt3, (arylmethyl)(carbonyl)rutheniums [Ru{CH2(aryl)}{B(4-Ypz)4}(CO)(PhCN)] were yielded, indicating alkyne CC 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 “RuCCH(aryl)”.

(Polypyrazolylborato)(benzonitrile)rutheniums [RuCl{B(4-Ypz)4}(PhCN)2] {4-Ypz; 4-bromo-1-pyrazolyl and 1-pyrazolyl groups} were allowed to react with arylalkynes HCC(aryl) in the presence of NEt3 to afford (arylmethyl)(carbonyl)rutheniums [Ru{CH2(aryl)}{B(4-Ypz)4}(CO)(PhCN)], whereas in the absence of NEt3, arylalkyne polymerization proceeded instead. Reasonably attributed reaction mechanism shows significant role of the vinylidene intermediates “RuCCH(aryl)”.Figure optionsDownload as PowerPoint slideHighlights
► Alkyne hydration.
► Arylalkyne polymerization.
► (Arylmethyl)(carbonyl) ruthenium.
► Role of NEt3.