Spectroelectrochemical Characterization of the Two-Step Redox System {(-pz)[Os(CN)5]2}n-<
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- 作者：Fridmann M. Hornung ; Frank Baumann ; Wolfgang Kaim ; José ; A. Olabe ; Leonardo D. Slep ; and Jan Fiedler
- 刊名：Inorganic Chemistry
- 出版年：1998
- 出版时间：January 26, 1998
- 年：1998
- 卷：37
- 期：2
- 页码：311 - 316
- 全文大小：106K
- 年卷期：v.37,no.2(January 26, 1998)
- ISSN：1520-510X
文摘
The pyrazine-bridged diosmium(II) complex{(
-C4H4N2)[Os(CN)5]2}6-has been synthesized as the hexapotassiumsalt and was converted to the hexakis(tetrabutylammonium) compoundby ion exchange. Its stepwise oxidationto the Os2IIIOsII andOs2IIIOsIII states wasmonitored spectroelectrochemically in acetonitrile/0.1 MBu4NPF6 inthe UV-vis-NIR and IR regions and by EPR. TheOsII2 species exhibits long-wavelengthsolvatochromic MLCTbands at 14 800 and 18 480 cm-1. Thepentaanionic mixed-valent ion has a comproportionation constantKc of105.8 and is distinguished by several electronicabsorptions in the IR region. The bands at 1972, 2480,4000,5000, 7170, and 11 900 cm-1 are similar butappreciably lower in energy than those reported for theanalogouscomplex{(-C4H4N2)[Os(NH3)5]2}5+.In addition to CN vibrational stretching features shifted onelectron transferthere is an additional sharp band only for the 5- ion at1582 cm-1 which is attributed to a pyrazinering vibration.The intensity of this band suggests an unsymmetrical situation andthus valence localization on the vibrationaltime scale. The EPR signals at g
=2.0563 and g
= 1.761 point toward excitedstates lying close to the doubletground state and to significant metal/cyanide interaction.Compared to the Creutz-Taube ion{(-C4H4N2)[Ru(NH3)5]2}5+ and itsosmium homologue, the 5- ion described here exhibits a lower degreeof metal-metal coupling.
-C4H4N2)[Os(CN)5]2}6-has been synthesized as the hexapotassiumsalt and was converted to the hexakis(tetrabutylammonium) compoundby ion exchange. Its stepwise oxidationto the Os2IIIOsII andOs2IIIOsIII states wasmonitored spectroelectrochemically in acetonitrile/0.1 MBu4NPF6 inthe UV-vis-NIR and IR regions and by EPR. TheOsII2 species exhibits long-wavelengthsolvatochromic MLCTbands at 14 800 and 18 480 cm-1. Thepentaanionic mixed-valent ion has a comproportionation constantKc of105.8 and is distinguished by several electronicabsorptions in the IR region. The bands at 1972, 2480,4000,5000, 7170, and 11 900 cm-1 are similar butappreciably lower in energy than those reported for theanalogouscomplex{(-C4H4N2)[Os(NH3)5]2}5+.In addition to CN vibrational stretching features shifted onelectron transferthere is an additional sharp band only for the 5- ion at1582 cm-1 which is attributed to a pyrazinering vibration.The intensity of this band suggests an unsymmetrical situation andthus valence localization on the vibrationaltime scale. The EPR signals at g =2.0563 and g = 1.761 point toward excitedstates lying close to the doubletground state and to significant metal/cyanide interaction.Compared to the Creutz-Taube ion{(-C4H4N2)[Ru(NH3)5]2}5+ and itsosmium homologue, the 5- ion described here exhibits a lower degreeof metal-metal coupling.