Inverse Sandwich Cyclopentadienyl Complexes of Sodium in the Gas Phase

Infrared multiple photon dissociation (IRMPD) experiments and electronic structure computations have been used to explore the structures and energetics of binding in gas phase sodium cyclopentadienyl complexes of the general form Na _nCp _n-1⁺. Computational work for the analogous anionic Na _nCp _n+1^- complexes reveals nearly identical energetics for the loss of neutral NaCp units from both cationic and anionic species leading to the conclusion that the binding in the gas phase species is largely electrostatic, arising primarily from ion-ion and ion-dipole interactions. This is supported by an examination of the molecular orbitals of these species, which show no orbital overlap between the Na and Cp moieties. Observation of peaks in the IRMPD spectra, which do not correspond to any of the computed linear absorption frequencies, strongly suggest the contribution of overtone and combination bands.