Bonding in transition metal-ether complexes : the spectroscopy and reactivity of the Zr atom-dimethyl ether system

摘要

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 cm3 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 a1 symmetry to the Zr 4d orbital of 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.