ZUR BILDUNG METALLACYCLISCHER FUENFRINGVERBINDUNGEN: REGIOSELEKTIVITAET DER ADDITION VON ALKINEN AN ZIRCONOCENKOMPLEXE

Article abstract of DOI:10.1016/0022-328X(83)80021-7

Metallacycles are formed upon thermolysis of (s-trans-η⁴-butadiene)zirconocene and binuclear (η²-aldehyde)zirconocene complexes or photolysis of diphenylzirconocene in the presence of t-butyl-, trimethylsilyl-, and phenyl-acetylene.From a surprising equally high preference for α-t-butyl- and -trimethylsilyl-substituted products as well as the statistically favoured 2,4-disubstituted metallacyclopentadienes formed from t-butyl- or trimethylsilyl-acetylene it is suggested, that the position of the substituents in the final product is predominantly determined by the coordination of the alkyne preceding the ring-closure reaction.In contrast to the thermally induced reactions the expected major product (2,5-disubstituted zirconacyclopentadiene) of the kinetically controlled cyclization reaction is formed upon photolysis of diphenylzirconocene in the presence of phenylacetylene.