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Syntheses and Characterization of a Series of Binuclear Iridium Complexes


Smith, Terrance Patrick (1982) Syntheses and Characterization of a Series of Binuclear Iridium Complexes. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/xc18-n193.


A binuclear iridium(I) isocyanide complex has been synthesized and its photophysics and chemistry have been synthesized and its photophysics and chemistry have been investigated. The complex Ir2(TMB)2+4 (TMB = 2.5-dimethyl 2,5 diisocyanohexane), possesses an intense absorption band maximizing at 625 nm in the visible region. Excitation into this feature results in two long wavelength luminescence bands at 735 nm and 1080 nm. The longer wavelength feature has been assigned as phosphorescence (E(3A2) → A1(1A1)) from the lowest electronic excited state; the lifetime of this state is 200 ns and is independent of temperature between 77 K and 298 K. In contrast, the E(3A2) excited state of the analogous rhodium complex exhibits a dramatic temperature dependence. This difference is ascribed to the proximity of ligand field states to the lowest excited state; in the rhodium case the ligand field states are thermally accessible whereas for the iridium case they lie at much higher energy.

The d8 - d8 iridium complex oxidatively adds a variety of small molecules (e.g. I2, Br2, Cl2, CH3I, HCl). The reactivity is quite similar to that of the analogous rhodium system (Rh2(TMB)2+4). One interesting difference is the fact that the HC1 adduct of Rh2(TMB)2+4 is directly observable only at low temperature. Nonetheless, a similar hydride species is postulated as an important intermediate in the production of hydrogen in another binuclear rhodium system.

A number of spectroscopic methods have been employed to explore the bonding in symmetric oxidative addition adducts. A linear correlation between metal-metal-force constant and intermetallic distance has been uncovered. The structure of the iodine adduct, Ir2(TMB)4I2(BPh4)2, has been determined; the intermetallic distance 2.803(4) Å. Also dynamic 1H NMR reveals that binuclear complexes containing the TMB ligand are rapidly undergoing conformation changes at ambient temperatures; the activation barriers for this process range from 12 to 15 kcal/mole.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Chemistry
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Chemistry
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Bercaw, John E.
Thesis Committee:
  • Bercaw, John E. (chair)
  • Gray, Harry B.
  • Janda, Kenneth C.
  • Marsh, Richard Edward
Defense Date:8 March 1982
Record Number:CaltechETD:etd-02252009-153626
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:767
Deposited By: Imported from ETD-db
Deposited On:26 Feb 2009
Last Modified:16 Apr 2021 22:15

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