Carbonyl Bonding on Oxophilic Metal Centers: Infrared Photodissociation Spectroscopy of Mononuclear and Dinuclear Titanium Carbonyl Cation Complexes

Mononuclear and dinuclear titanium carbonyl cation complexes including Ti(CO)6+, Ti(CO)7+, TiO(CO)5+, Ti2(CO)9+ and Ti2O(CO)9+ are produced via a laser vaporization supersonic cluster source. The ions are mass selected in a tandem time-of-flight mass spectrometer and studied with infrared photodissociation spectroscopy in the CO stretching frequency region. The structures are established by comparison of the experimental spectra with simulated spectra derived from density functional calculations. Only one IR band is observed for the 15-electron Ti(CO)6+ cation, which is characterized to have an octahedral Oh structure. The Ti(CO)7+ cation is determined to be a weakly bound complex involving a Ti(CO)6+ core ion instead of the seventh coordinated ion. The TiO(CO)5+ cation has a completed coordination sphere with a C4v structure. The Ti2(CO)9+ cation is determined to have a doublet Cs structure with two four-electron donor side-on bridging CO groups and one semibridging CO group. The Ti2O(CO)9+ cation has a ...