Trend-Analysis of Solid-State Structures: Low-Energy Conformational 'Reactions' Involving Directed and Coupled Movements in Half-Sandwich Compounds [CpFe(CO){C(=O)R}PPh3].

Trends in solid-state structures were used to identify preferred intramolecular movements in half-sandwich compounds [CpFe(CO){C(=O)R}PPh3]. Three weak interactions were analyzed: 1) the CH/π donor-acceptor interaction of phenyl rings in the PPh3 ligand, 2) the PhPPh3 face-on Cp stabilization, and 3) the hydrogen bond between the oxygen atom of the acyl group and an ortho-C-H bond of one of the PPh3 phenyl rings. Clockwise and counter-clockwise rotations established directed and coupled movements of the PPh3 ligand, the acyl group, and the phenyl rings within the PPh3 ligand.