Molecular dynamics of (η6-arene)tricarbonylchromium complexes in the solid state: carbon-13 nuclear magnetic resonance and crystal structure of [Cr(η6-C6HMe5)(CO)3]

Abstract

Variable-temperature solid-state ¹³ C NMR spectra have been recorded for a series of [Cr(η ⁶ -arene)(CO) ₃ ] complexes. In all cases there is evidence for carbonyl exchange in the solid state at elevated temperatures. Both the isotropic chemical shifts and the chemical shift anisotropies of the ¹³ CO groups were obtained. The relative ease of the carbonyl exchange depended on the extent of methyl substitution of the arene ring. It was more facile in those complexes with less symmetric arene rings. The single-crystal structure of [Cr(η ⁶ -C ₆ HMe ₅ )(CO) ₃ ] was determined at 150 K. X-Ray data recorded at room temperature led to a misleading structural refinement due to molecular motion.