Absolute configurations and crystal structures of the diastereoisomeric complexes of cis-dichloro(1,5-hexadiene)platinum(II) with ( S)-α-methylbenzylamine

Abstract

The crystal structures of the two diastereoisomeric complexes of cis-dichloro(1,5-hexadiene)platinum(II) with ( S)-α-methylbenzylamine and the absolute configurations of the three asymmetric centers present in each molecule have been determined. Both complexes crystallize in the orthorombic system, space group P2 12 12 1 with a=16.21 », b=12.23 », c=8.01 » [complex (I)] and a=23.53 », b=7.49 », c=8.69 » [complex (II)]. The structures have been solved by Patterson and Fourier methods and refined to R factors of 0.062 and 0.074 for complexes (I) and (II), using 1454 and 1132 independent reflections measured with counter techniques (Mo- K α), respectively. The two complexes present the usual square-planar arrangement of the ligands around the platinum atom, showing different conformations. The diastereoisomers undergo an antiracemization process in dichloromethane, but it is difficult to rationalize the differing stabilities of the two forms in terms of the conformations available to the isolated molecule.