Zirconocene imide

An exchange reaction occurs on treatment of the [2+2] cycloadduct obtained from a zirconocene imide and bis(trimethylsilyl)carbodiimide 260 and diphenylacetylene to form a new metalacycle 261. The latter reacts with diisopropylcarbodiimide to form the [2+2+2] cycloadduct 262.2 ... 

Zirconocene-imide complex (91) reacted smoothly with stilbene oxide to produce the corresponding cycloadduct (93) (Equation 41) [46]. The stereochemistry of the... 

In contrast, the reaction of zirconocene imide (91) with propylene oxide produced acyclic compound (95) exclusively (Equation 42) [47]. In this case, hydrogen transfer from the methyl group to the imide nitrogen proceeded in the intermediate (94) along with the ring opening of the epoxide. The complex (91) is reactive enough not only toward epoxides but also the other three-membered heterocycles such as aziridines and thiiranes. 

Imido zirconocenes see Imide Complexes) are synthesized from thermolysis of Cp2Zr(Me)NHR. They react with a wide variety of organic substrates (alkynes, imines, azides, carbodiimides, ketones) to yield [2 + 2] cycloaddition products (Scheme 4) see Metallacycle) ... 

Fig. 29. Diastereomeric complexes formed between zirconocene 60 and imide 4a...

The metallacycle undergoes a carbodiimide exchange reaction with a different carbodi-imide . Also, imino zirconocene complexes 103 undergo the [2-1-2] cycloaddition reaction... 

---