Bonding to titanium

The recent synthesis of a crystalline compound containing Ti bonded to cycl opentadienyl and a substituted dienyl fragment prompted the question of whe ther Ti-C contacts that were found to be shorter than other such bonded con tacts in the same molecule should be considered as short nonbonded contacts or "nonclassical metal-to-saturated-carbon atom interactions", fitting the description of agostic interactions. This question has a unique answer wit hin the framework of the quantum theory of atoms in molecules (QTAIM). QTAI M uses the measurable electron density to assign a molecular structure and the physics of an open system to determine the nature of the bonded interac tions. All of the classical bonding descriptors, when recast in terms of th e topologies of the electron density and the pair density, are faithfully r ecovered when QTAIM is applied to the hydrocarbon framework of the Ti compl ex, thereby justifying its application to the analysis of the Ti-C interact ions. No bond paths are found to link the Ti to the carbons exhibiting the "short contacts", and the topology of the density gives no indication of an incipient change in structure that would result in their formation.