Experimental and theoretical electron density of intermediates in palladium-phenanthroline catalyzed carbonylation of amines and reductive carbonylation of nitroarenes.

The accurate electron density distribution in Pd(Neoc)Cl2 (CO) (Neoc = 2,9-dimethyl-1,10-phenanthroline) was measured and calculated to investigate the chemical bonding features, the electrostatic forces and the polarizable bonds in this complex, which is a prototype of the proposed intermediate in the catalytic carbonylation of amines and nitroarenes. The quantum theory of atoms in molecules enables to investigate the nature of the elusive fifth coordination in the complex, which is approximately intermediate between a bypiramid penta-coordination and a square planar tetra-coordination. The analysis of the electrostatic potential and of the distributed atomic polarizabilities enables to address the sites that are more prompt to react, in particular in the context of the catalytic cycle. © 2017 Wiley Periodicals, Inc.