Electronic Structure of the [Tris(dithiolene)chromium]z (z = 0, 1−, 2−, 3−) Electron Transfer Series and Their Manganese(IV) Analogues. An X-ray Absorption S
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- 作者：Priyabrata Banerjee ; Stephen Sproules ; Thomas Weyhermller ; Serena DeBeer George ; Karl Wieghardt
- 刊名：Inorganic Chemistry
- 出版年：2009
- 出版时间：July 6, 2009
- 年：2009
- 卷：48
- 期：13
- 页码：5829-5847
- 全文大小：1535K
- 年卷期：v.48,no.13(July 6, 2009)
- ISSN：1520-510X
文摘
From the reaction mixture of 3,6-dichlorobenzene-1,2-dithiol, H2(Cl2-bdt), [CrCl3(thf)3], and NEt3 in tetrahydrofuran (thf) in the presence of air, dark green crystals of [N(n-Bu)4]2[Cr(Cl2-bdt)3] (S = 1) (1) were isolated upon addition of [N(n-Bu)4]Br. Oxidation of the AsPh4+ salt of 1 with [Fc]PF6 yielded microcrystals of [AsPh4][Cr(Cl2-bdt)3] (S = 1/2) (2) whereas the reduction of 1 with sodium amalgam produced light green crystals of [N-(n-Bu)4]3[Cr(Cl2-bdt)3]·thf (S = 3/2) (3). The corresponding maleonitriledithiolato complexes [PPh4]2[Cr(mnt)3] (S = 1) (4) and [PPh4]3[Cr(mnt)3] (S = 3/2) (5) have been synthesized. Isoelectronic manganese complexes of 3 and 5, namely, [NEt4]2[Mn(Cl2-bdt)3] (S = 3/2) (6) and [PPh4]2[Mn(mnt)3] (S = 3/2) (7), have also been prepared. Complexes 1, 6, and 7 have been characterized by single crystal X-ray crystallography. Complexes 1−7 have been electrochemically studied and their UV−vis and electron paramagnetic resonance spectra (EPR) have been recorded; magnetic properties have been elucidated by temperature-dependent susceptibility measurements. It is shown by chromium K-edge and sulfur K-edge X-ray absorption spectroscopy (XAS) that the oxidation state of the central Cr ion in each compound is the same (+III, d3) and that all one-electron redox processes are ligand-based, involving one, two, or three ligand π radical monoanions. Complexes 6 and 7 possess a MnIV ion with three dianionic ligands. The results have been corroborated by broken symmetry (BS) density functional theoretical (DFT) calculations by using the B3LYP functional. Time-dependent DFT calculations have been performed to calculate the metal and sulfur K-pre-edges. It is suggested that the neutral complexes [Cr(dithiolene)3]0 S = 0 possess octahedral rather than trigonal prismatic CrS6 polyhedra. Three ligand π radicals (Srad = 1/2) couple antiferromagnetically to the central Cr(III) ion (d3) yielding the observed diamagnetic ground state. It is established that the four members of the [Cr(dithiolene)3]z (z = 0, 1−, 2−, 3−) electron transfer series are related by ligand-based one-electron transfer processes; for each of the four members it is shown that they contain a central Cr(III) (d3) ion, and the CrS6 polyhedron is a (distorted) octahedron.