Theoretical Study of the Solvent Effect on the Electronic and Vibrational Properties of [CpFe(CO)2(NCS)] and [CpFe(CO)2(SCN)] Linkage Isomers

The present study illustrates the stability of [CpFe(CO)(2)(NCS)] and [CpFe(CO)(2)(SCN)] linkage isomers by the use of MPW1PW91 quantum method in the gas and solution phases. Our results reveal that the [CpFe(CO)(2)(NCS)] isomer is more stable than the [CpFe(CO)(2)(SCN)] isomer. Based on the polarizable continuum model, the effect of the solvent polarity on the stability, structural parameters, frontier orbital energies, and vibrational modes of carbonyl ligands ((CO)) of these linkage complexes is explored. The molecular orbital analysis suggests that the major contributions to HOMO and LUMO arise from the ambidentate ligand and Fe in two isomers, respectively. In addition, the bonding interaction between the CpFe(CO)(2) fragment and the ambidentate ligand is studied by means of the energy decomposition analysis. The back-bonding effect in Fe-CO bonds is revealed in the calculation of the quadrupole polarization of the carbon atom by the QTAIM analysis. The character of Fe-N and Fe-S bonds in these complexes is analyzed by the natural bond orbital analysis.