Substitution of {eta}{sup 2}-dihydrogen by toluene and alkanes in IrXH{sub 2}(H{sub 2})(PPr{sup i}{sub 3}){sub 2} complexes
- Univ. of Hawaii, Honolulu, HA (United States)
We have found that the equilibrium position is highly solvent dependent. It has also been observed that hydrogen is liberated with vigorous effervescence when solid samples of IrXH{sub 2}(H{sub 2})(PPr{sup i}{sub 3}){sub 2}, X = Cl (1), Br (2), I (3), are dissolved in hydrocarbons. These observations suggest that the five-coordinate complexes establish a rapid equilibrium with solvent coordinated complexes in conjunction with the relatively slow equilibrium with the dihydrogen complex. In order to explore this possibility, we have carried out variable temperature {sup 1}H NMR spectroscopic studies of equilibrated solutions of 1, 2, and 3 and the corresponding five-coordinate complexes, IrXH{sub 2}(PPr{sup i}{sub 3}){sub 2}, X = Cl (4), Br (5), I (6), in toluene-d{sub 8}, methylcyclohexane-d{sub 14}, and n-hexane-d{sub 14}. Our studies demonstrate that the energetics of the reversible loss of H{sub 2} from IrXH{sub 2}(H{sub 2})(PR{sub 3}){sub 2} complexes are highly solvent dependent. Apparently toluene and, in the case of the iodo complex, alkanes can compete with H{sub 2} for binding to the five-coordinate IrXH{sub 2}(PR{sub 3}){sub 2} complexes. The competitive interaction of hydrocarbon solvents has been overlooked in earlier analyses of the factors which influence the stabilization of dihydrogen IrXH{sub 2}(H{sub 2})(PR{sub 3}){sub 2} complexes. This work illustrates that toluene and alkane complexes can be of major thermodynamic significance. 10 refs., 1 fig., 1 tab.
- OSTI ID:
- 380880
- Journal Information:
- Journal of the American Chemical Society, Vol. 118, Issue 36; Other Information: PBD: 11 Sep 1996
- Country of Publication:
- United States
- Language:
- English
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