Protolysis of five-membered metallacyclocumulene complexes of zirconocene and hafnocene.

[Display omitted] The reactions of the five-membered metallacyclocumulene complexes Cp 2 M[η4ButC 4 But] (M = Zr, Hf) with an equimolar amount of HCl in dioxane at 20 °C result in linear complexes Cp 2 M(Cl)–C(But)=CH–C CBut, whereas the reaction with an excess of HCl affords Cp 2 MCl 2 and trans -ButCH=CH–C CBut. The reaction of the latter hydrocarbon with an equivalent amount of the bis(trimethylsilyl)acetylene complex of zirconocene Cp 2 Zr(Me 3 SiC 2 SiMe 3)(Py) leads to bis(trimethylsilyl)acetylene and a five-membered zircona-cycloallene complex. This complex can also be obtained in 'one-pot' via the reactions of five-membered zircona-cyclocumulene with two equivalents of HCl and subsequent treatment with magnesium in THF. [ABSTRACT FROM AUTHOR]