Reactions of the Zirconocene Complexes of Bis(trimethylsilyl)acetylene with Formaldehyde, Benzaldehyde, and Benzophenone

In reactions of the zirconocene derivative Cp 2 ZrC(SiMe 3 ) C(SiMe 3 )(THF) with ketones and aldehydes the influence of the various substituents of the carbonyl compounds upon the formation of different products was investigated. Formaldehyde reacts by an insertion of the carbonyl unit into a Zr−C bond to give a metallacycle which is additionally stabilized by the formation of a coordination dimer [Cp 2 ZrOCH 2 C(SiMe 3 ) C(SiMe 3 )] 2 ( 1 ). Benzaldehyde yields a monomeric metallacycle Cp 2 ZrOCHPhC(SiMe 3 ) C(SiMe 3 ) ( 2 ). Complex 2 is less stable than 1, and at higher temperatures it loses half of its moiety Me 3 SiC 2 SiMe 3, leaving {[Cp 2 ZrOCHPhC(SiMe 3 ) C(SiMe 3 )][Cp 2 Zr(η 2 -O CHPh)]} ( 3 ). Benzophenone gives no insertion, and the monomeric η 2 -ketone complex Cp 2 Zr(THF)(η 2 -O CPh 2 ) ( 4 ) was obtained.