Solid state conformational study of complexes containing the (o-P–C6H4–CN-κ2N,P) palladium six-membered chelated ring

The Cambridge Structural Database (CSD) V. 5.23 has been searched for all the structures containing the fragment Pd{o-P–C6H4–CN-κ2N,P}. Bond lengths, bond angles and the conformations adopted by the PdPCCCN chelated ring have been studied statistically. It has been found Pd–P and Pd–N distances in the mentioned compounds are, respectively, shorter and longer than the mean value found for these parameters when the CSD was searched irrespective of the ligands. The conformation of the chelated ring has been characterized by means of two torsion angles, and can be described in most cases as a plane containing the P and carbon atoms with Pd and N atoms situated at the same side out of this plane. Molecular mechanics calculations have been employed to justify the conformational preferences found. The calculated strain energy suggests a path for the movement of Pd and N atoms from one side of the PCCC plane to the other through a planar conformation. MM calculations in complex (η3-allyl)-(N-(2-(diphenylphosphino)benzylidene)-4-methoxyphenylamine)-palladium(II) indicate that planar conformation is energetically accessible, and the extent of preorganization for the free ligand in this compound has been evaluated of 74%.