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Published on: July 27, 2022
Four-coordinate iridium(I) monohydrides: reversible dinitrogen binding, bond activations, and deprotonations
Matthew D Millard1, Curtis E Moore, Arnold L Rheingold
1Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, Mail Code 0358, La Jolla, California 92093-0358, USA.
Journal of the American Chemical Society
|June 17, 2010
Summary
This study successfully isolated and characterized elusive four-coordinate iridium(I) monohydride complexes using a sterically hindered phosphine ligand. These findings provide concrete evidence for previously postulated reactive species in chemical transformations.
Area of Science:
- Organometallic Chemistry
- Coordination Chemistry
- Catalysis Research
Background:
- Four-coordinate iridium(I) monohydride complexes are proposed reactive intermediates in various chemical reactions.
- Previous attempts to isolate these species have been hampered by their inherent instability.
- The development of robust ligands is crucial for stabilizing transient organometallic species.
Purpose of the Study:
- To synthesize and characterize isolable four-coordinate iridium(I) monohydride complexes.
- To provide definitive evidence for the existence of these elusive species.
- To explore the reactivity and stability of these complexes using a sterically hindered phosphine ligand.
Main Methods:
- Synthesis of iridium complexes using a methyleneadamantyl substituted phosphine ligand (L(mAd)).
- Reactions of dihydride-chloride precursors with organometallic reagents (PhMgBr, Li[HBEt(3)]).
- Spectroscopic characterization (NMR) and reactivity studies under various conditions (N(2), H(2), H(2)O, Li[12-c-4]).
Main Results:
- Isolation of a square planar iridium(I) monohydride complex, HIr(N(2))(L(mAd))(2), and a trihydride complex, H(3)Ir(L(mAd))(2).
- Observation of an equilibrium between HIr(N(2))(L(mAd))(2) and its cyclometalated form, H(2)Ir(kappa(2)-P,C-L(mAd))(L(mAd)).
- Generation of pentahydride and dihydride hydroxide complexes upon reaction with H(2) and H(2)O, respectively.
- Formation of a stable four-coordinate Ir(I) monohydride salt, [Li(12-c-4)(2)][HIr(kappa(2)-P,C-L(mAd))(L(mAd))].
Conclusions:
- The use of the sterically hindered L(mAd) ligand enabled the isolation of previously elusive four-coordinate iridium(I) monohydride complexes.
- These complexes exhibit unique reactivity, forming various hydrido species under different reaction conditions.
- The study provides a stable platform for investigating the fundamental chemistry of these important organometallic intermediates.
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