Modulation of Metal Carbonyl Stretching Frequencies in the Second Coordination Sphere through the Internal Stark Effect

Spectroscopic and computational examination of a homologous series of rhodium(I) pybox carbonyl complexes has revealed a correlation between the conformation of the flanking aryl-substituted oxazoline donors and the carbonyl stretching frequency. This relationship is also observed experimentally for octahedral rhodium(III) and ruthenium(II) variants and cannot be explained through the classical, Dewar-Chatt-Duncanson, interpretation of metal-carbonyl bonding. Instead, these findings are reconciled by local changes in the magnitude of the electric field that is projected along the metal-carbonyl vector: the internal Stark effect.

Automated summary

A spectroscopic and computational examination of a series of rhodium(I) pybox carbonyl complexes reveals a correlation between the conformation of the aryl-substituted oxazoline donors and the carbonyl stretching frequency. This correlation is observed in both octahedral rhodium(III) and ruthenium(II) variants and cannot be explained by the classical interpretation of metal-carbonyl bonding. Instead, it is explained by local changes in the electric field projected along the metal-carbonyl vector.