An Elongated Dihydrogen Complex of Iridium

Vincent Pons and D. Michael Heinekey*
Department of Chemistry, Box 351700, University of Washington, Seattle, Washington 98195-1700
J. Am. Chem. Soc., 2003, 125 (28), pp 8428–8429
DOI: 10.1021/ja035555j
Publication Date (Web): June 19, 2003
Copyright © 2003 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.

, heinekey@chem.washington.edu

Abstract

Abstract Image

Reaction of [Cp*Ir(dmpm)Cl]Cl with [Et3Si]B(ArF)4 (dmpm = bisdimethyl-phosphinomethane; ArF = C6F5) under hydrogen gas affords the dicationic complex [Cp*Ir(dmpm)H2]2+ (1), which is readily deprotonated by weak bases to give [Cp*Ir(dmpm)H]+. Complex 1 exists as a mixture of two isomers (97:3). On the basis of the magnitude of 2JH-P couplings and T1 measurements, a cis-dihydride or dihydrogen complex structure is suggested for the predominant isomer 1-cis (2JH-P = 6 Hz), with the minor isomer assigned a transoid structure 1-trans (2JH-P = 20 Hz). When the preparative reaction is carried out with HD gas, the resonance in the 1H NMR spectrum assigned to 1-cis-d1 exhibits1JH-D = 9.0 Hz. The observed values of 1JH-D vary significantly with temperature, increasing from 7.0 Hz at 223K to 9.0 Hz at 300 K. The observed chemical shift of 1-cis-d1 also varies significantly with temperature. These observations are interpreted in terms of a dynamic equilibrium between a cis-dihydride and a dihydrogen complex.

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History

  • Published In Issue July 16, 2003
  • Received April 9, 2003

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