Influence of solvents on the insertion of methacrolein into zirconacyclopropenes

Abstract

The reaction of Cp 2Zr(L)( η 2-Me 3SiC 2) (L = THF, py) with equimolar amounts of H 2C = CMe-CHO at room temperature depends strongly on the ligands L and the solvents that are used. With L = THF, in the THF solution the insertion product Cp 2 ZrOCH(CME=CH 2)C(SiMe 3)=C (SiMe 3) 1 was isolated, whereas by conducting the reaction in n-hexane solution an alkyne substitution with 1,4-coordination of the methacrolein takes place and the binuclear complex [ Cp 2 ZrOCH=CMeCH 2] 2 2 was obtained. In conttrast, with L = py (a stronger ligand) only a 1:1 ratio of 1 and 2 was observed in both THF and in n-hexane. At 50°C complex 1 was converted into 2 and the alkyne was eliminated quantitatively. Complexes 1 and 2 were characterized by IR and NMR spectroscopical measurements and 1 by an additional X-ray structure determination.