Bonding in Transition Metal−Ether Complexes: The Spectroscopy and Reactivity of the Zr Atom−Dimethyl Ether System

The reactivity and bonding of neutral Zr metal atoms with dimethyl ether have been thoroughly characterized using flow tube reactor, PFI-ZEKE, and DFT techniques. Between 275 and 371 K, these species form an association complex with the Zr bound to the ether O atom. Using a flow tube reactor, the equilibrium constant for the association reaction has been found to be 6 ± 2 × 10 -14 cm 3 at 361 ± 10 K. From this measure the Zr−dimethyl ether bond energy is estimated to be 80 ± 2 kJ mol -1 . The ZEKE spectrum of the association complex is reproduced very well by DFT calculations. The calculations indicate that the Zr−dimethyl ether complex is bound by dative bonding involving donation of electron density from the highest occupied dimethyl ether orbital of a 1 symmetry to the Zr 4d orbital of σ symmetry directed along the Zr−dimethyl ether bond axis. Dative bonding interactions are much stronger than donor−acceptor bonding as the vacant dimethyl ether antibonding orbital lies too high in energy for back-donation of electron density from Zr to be efficient. This finding is likely a general characteristic of neutral transition metal−ether complexes. To our knowledge, these results constitute the most detailed investigation, to date, of neutral transition metal−ether bonding and reactivity.