Abnormal cyclopalladation of Schiff bases made of metallocenyl aldehydes and α-ferrocenylethylamine: Unexpected formation of the heteroannular 3-atomic bridge

Cyclopalladation of the Schiff bases of general formula McCHdouble bond; length as m-dashN–CH(Me)Fc (Mcdouble bond; length as m-dashFc, Ru) (1a,b) with a chiral centre leads to the mixtures of three products, two of which (2 and 3) are planar chiral diastereomers formed from homoannular substitution into the aldehyde fragment. The third product 4 is a result of the unusual heteroannular palladation of the amine fragment in starting aldimine. This ansa-structure 4 having 3-atomic C–N–Pd bridge is without precedent in metallocenes. The molecular structures of all organopalladium compounds obtained have been proved using X-ray analysis of single crystals.