Rapid Reduction of Nitric Oxide to Dinitrogen by Zirconium(II):  Kinetic Studies on a Reaction Controlled by Gas−Liquid Transport

Kristopher McNeill*† and Robert G. Bergman
Contribution from the Department of Chemistry, University of California, Berkeley, California 94720
J. Am. Chem. Soc., 1999, 121 (36), pp 8260–8269
DOI: 10.1021/ja983011p
Publication Date (Web): August 31, 1999
Copyright © 1999 American Chemical Society
*

In papers with more than one author, the asterisk indicates the name of the author to whom inquiries about the paper should be addressed.

,
†

 Current address:  Department of Chemistry, University of Minnesota, 207 Pleasant St. SE, Minneapolis, MN 55455.

Abstract

Nitric oxide reacts with Cp2Zr(PMe3)2 (1; Cp = η5-C5H5) in THF or toluene to yield dinitrogen and an oligomeric oxozirconocene species, [CpxZrOy]n. The reduction of NO occurs in two distinct steps:  1 reduces 2 equiv of NO to 1 equiv of N2O, and then 1 reduces N2O to N2. In each step, 1 is converted to a monomeric oxozirconocene species [Cp2ZrO], which may be trapped by the addition of Me3SiCl or Cp2ZrMe2, to form Cp2Zr(OSiMe3)(Cl) and [Cp2ZrMe]2O, respectively. Kinetics for the reduction of NO by 1 were followed at low temperature (160 < T < 195 K) by monitoring the change in pressure of the system. Complete reaction was observed in less than 15 s, even at the lowest temperatures. The typical kinetic trace displayed two decay regimes, zero- and first-order, which were interpreted as the result of competing mass-transfer and chemical reaction processes. The kinetic results support a rate-limiting bimolecular reaction between NO and 1. The subsequent intermediates and mechanistic possibilities are discussed.

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History

  • Published In Issue September 15, 1999
  • Received August 21, 1998

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