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Co-ordination Chemistry of Higher Oxidation States. Part 23. Synthesis and Properties of Tetrahalogenoiridium(IV) Complexes, . Crystal and Molecular Structure of trans-

DOI: 10.1039/DT9870001901

Source and publish data:

Journal of the Chemical Society, Dalton Transactions p. 1901 - 1910 (1987)

Update date:2022-07-29

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Authors:

Cipriano, Robert A.Cipriano, Robert A.

Levason, WilliamLevason, William

Pletcher, DerekPletcher, Derek

Powell, Nigel A.Powell, Nigel A.

Webster, MichaelWebster, Michael

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Article abstract of DOI:10.1039/DT9870001901

The iridium(III) anions trans-- have been prepared and oxidised with chlorine to purple iridium(IV) trans-.Dark green trans- (L = py, PEt3, PMe2Ph, AsEt3, AsMe2Ph, or SMe2) were obtained similarly from trans-- and Br2 or HNO3.The (L = PPh3, AsPh3, or SbPh3) are made directly from IrCl3.nH2O + 2L, followed by chlorination of the intermediate <(IrL2Cl3)n> produced; cis- (L = py or SbMe3) and trans-- (L = TeMe2, X = Cl; L = SeMe2,X = Br) are also described.The iridium (IV) complexes have been characterised by analysis, i.r., and u.v.-visible spectroscopy and for the complex by X-ray diffraction.Crystals of trans- are monoclinic, space group P21/n with a = 8.442(1), b = 13.933(2), c = 9.617(1) Angstroem, β = 103.85(1) deg, Z = 2, and R = 0.041 for 1 826 reflections 3?(F)>.Discrete centrosymmetric molecules with Ir-Br 2.455(1), 2.463(1) and Ir-As 2.489(1) Angstroem are present.Assignments are proposed for the u.v.-visible spectra of trans- in terms mainly of ?X, ?X, ?L -> Ir (t2g) ligand-to-metal charge-transfer transitions.For most couples, --, the electron-transfer reaction is close to reversible and formal potentials, estimated from the cyclic voltammograms, correlate well with spectroscopic data.The voltammograms for four anions (X = Cl, L = TeMe2 and X = Br, L = SbPh3, SeMe2, or dimethyl sulphoxide) show that the corresponding iridium(IV) complexes have half-lives of only a few seconds and this explains the failure to isolate them from chemical syntheses.Ciclic voltammograms for - (L PEt3, SMe2, SeMe2 or py) show that oxidation occurs at more positive potentials, but the rhodium(IV) complexes are unstable.Neutral iridium(III) complexes are not oxidised by X2 or HNO3, and possible reasons for this and the crucial role of the - intermediates in the preparation of are discussed.

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