Comparison of Decamethyldizincocene [(η5‑Cp*)2Zn2] versus Decamethylzincocene [Cp*2Zn] and Diethylzinc Et2Zn As Precatalysts for the Intermolecular Hydroamination Reaction

A comparison of the Zn–Zn bonded species [(η5-Cp*)2Zn2] versus the related organometallic zinc compound [Cp*2Zn] and ZnEt2 for the intermolecular hydroamination reaction in the presence of equimolar amounts of [PhNMe2H]­[B­(C6F5)4] is reported. All compounds show high reaction rates under mild conditions and a good functional group tolerance for the addition of aniline derivatives to primary alkynes. Within this series the metallocene [Cp*2Zn] is the most active one, whereas the zinc–zinc bonded species [(η5-Cp*)2Zn2] shows the best selectivity. Most remarkable is the unexpected excellent catalytic performance of the zinc–zinc bonded species [(η5-Cp*)2Zn2].