6-Coordination of Arsenine to Titanium, Vanadium, and Chromium

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• 作者：Christoph Elschenbroich ; Jö ; rg Kroker ; Mathias Nowotny ; Andreas Behrendt ; Bernhard Metz ; and Klaus Harms
• 刊名：Organometallics
• 出版年：1999
• 出版时间：April 12, 1999
• 年：1999
• 卷：18
• 期：8
• 页码：1495 - 1503
• 全文大小：185K
• 年卷期：v.18,no.8(April 12, 1999)
• ISSN：1520-6041

文摘

By means of metal-ligand vapor co-condensation techniques the homoleptic arseninesandwich complexes (⁶-C₅H₅As)₂Ti (2), (⁶-C₅H₅As)₂V (3), and (⁶-C₅H₅As)₂Cr (4) have beenprepared. 2 is the first example of an unsubstituted group 15 heteroarene sandwich complexwhich yielded to full structural characterization by X-ray diffraction. The most remarkablefeature of the structure of 2 in the crystal is the synperiplanar conformation and the shortintramolecular interannular As···As distances which imply secondary bonding. The lattermay also contribute to the packing since interannular As···As distances, which fall short ofthe sum of the van der Waals radii, are detected. The result of a competition experiment, inwhich benzene and arsenine are offered as ligands to chromium, illustrate the pronouncedpreference of chromium for arsenine as an ⁶ ligand. The mixed-ligand complexes (⁶-C₅H₅As)(⁶-C₆H₆)Cr (6) and (⁶-C₅H₅As)Cr(CO)₃ (8) have also been prepared and studiedspectroscopically in order to underpin the notion that arsenine, compared to benzene, is thesuperior ⁶ ligand. The study is rounded off by an investigation of the redox behavior of 2,3, 4, and 6 (cyclic voltammetry) and by EPR measurements on 3 and 4⁺. The latter confirmthe pronounced -acceptor character of ⁶-arsenine. This conclusion is based on the increaseof the hyperfine coupling constant a(⁵¹V) upon going from bis(benzene)vanadium to thearsenine counterpart which is thought to reflect V(d_z²) orbital contraction in 3, caused by aslight increase of positive partial charge on vanadium.