Synthesis and Structural Characterization of Azatitanacyclobutane Derivatives

The titanocene vinylidene intermediate [Cp*2Ti=C=CH2] (9) reacted with the carbodiimides R−N=C=N−R [R = p-CH3C6H4 (19a), C6H11 (19b)] to give the N=C-cycloaddition products [Cp*2Ti{−NR−C(=NR)−(C=CH2)−}] [(R = p-CH3C6H4 (20a), C6H11 (20b)]. The X-ray structure of 20a in form of a surprisingly stable n-hexane clathrate is presented. The azatitanacyclobutane [Cp*2Ti{−NPh−C(Ph)(H)−(C=CH2)−}] (22) was formed from the reaction between 9 and benzylidene aniline [PhN=C(Ph)H (21)]. Reactivity studies showed that azatitanacyclobutanes are unreactive upon typical ring-enlargement reactions as observed for other four-membered titanacycles.