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Synthesis and characterization of nonclassical polyhydride complexes of iridium

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Title: Synthesis and characterization of nonclassical polyhydride complexes of iridium
Authors: Mediati, Mario
Issue Date: 1992
Abstract: The complexes, IrClH2(PR3)2(H2) (R = Pri, 1a; Cy, 1b) were generated through the reaction of the corresponding unsaturated dihydride complexes, IrClH2(PR3)2 (R = Pri, 2a; Cy, 2b) with Hz in solution or the solid state. The complexes were also prepared through treatment of THF solutions of IrCl3.3H2O and two equivalents of phosphine with two equivalents of sodium naphthalide under an atmosphere of hydrogen. The molecular structure of 1a.C10H8 was determined by a single crystal X-ray diffraction study. Under an atmosphere of argon, la and 1b eliminate Hz and convert back to the unsaturated complexes. Variable temperature 1H NMR studies of the complexes, la and 1b in toluene-d8 solution under 0.5 atm of H2 show that they establish rapid equilibria with 2a and 2b respectively which are sensitive to hydrogen pressure and temperature. Similar studies of the more sterically hindered IrClH2(PBut3)2, 2c, under 0.5 atm of H2 show only indirect evidence of a much slower equilibrium with 1c, while low concentrations of 1c can be directly observed under 1 atm of Hz. The presence of dihydrogen ligands in la and 1b are indicated by their extremely facile exchange with free Hz and by the minimum T1 values for the 1H NMR resonances due to the exchanging metal bound hydrogens at 300 MHz of 22 and 27 msec respectively. Variable temperature 31P{lH}NMR spectra of 13 dissolved in toluene-d8 also demonstrate the interconversion of 1a and 2a. The reversible uptake of hydrogen by 2a in the solid state was studied through monitoring of M-H absorptions by FTIR spectroscopy. Similar studies of the reaction of 2a with D2 establish that the intramolecular exchange between the dihydrogen and hydride ligands of 13 occurs in the solid state.
Description: Thesis (Ph. D.)--University of Hawaii at Manoa, 1992.
Includes bibliographical references (leaves 83-88)
Microfiche.
xi, 88 leaves, bound ill. 29 cm
URI/DOI: http://hdl.handle.net/10125/9505
Rights: All UHM dissertations and theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission from the copyright owner.
Appears in Collections:Ph.D. - Chemistry



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