Cationic zirconocene complexes are active species in Ziegler-Natta catalysis for olefin polymerization. structure and metal-ligand bond strength strongly influence their activity. In the present work, the multiphoton dissociation (IRMPD) spectrum of mass selected Zr(C5H5)(2)(OH)(CH3CN)(+) cations was in the 300-1500 cm(-1) fingerprint range by coupling a Fourier-transform ion cyclotron resonance mass spectrometer equipped with an electrospray ionization (ESI) Source and the infrared free electron (IR-FEL) at the Centre Laser Infrarouge d'Orsay (CLIO). The experimental efforts are complemented quantum chemical Calculations at the MP2 and B3LYP levels using the 6-311G* basis set. assignments of transitions observed in the IRMPD spectra to modes of the Zr-O-H, C5H5, and CH3CN moieties are based oil comparison to calculated linear absorption spectra. Both the experimental data and Calculations provide unprecedented information about structure, metal-ligand bonding, charge and binding energy of the complex.