Derivation of a new set of force field parameters for ammine complexes of chromium(III) containing halogenido ligands: modeling of the trans-influence of halogenido ligands

An approach to model the trans-influence using partial atomic charges derived from the molecular electrostatic potential by means of the restrained electrostatic potential (RESP) fitting method is exemplified on a series of halogenido-ammine octahedral chromium(III) complexes. RESP charges incorporated in the present vibrationally optimized consistent force field account for second-order phenomena, improve the modeling and assignment of skeletal vibrations, and reproduce the trends in frequency shifts along the F, Cl, Br, I series. In addition, a supplementary statistical analysis is given for the Cr-halogen bonds in the crystal structures from the CSD.