Zwitterionic Cobalt Complexes with Bis(diphenylphosphino)(N-thioether)amine Assembling Ligands: Structural, EPR, Magnetic, and Computational Studies
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- 作者：Christophe Fliedel ; Vitor Rosa ; Bertrand Vileno ; Nathalie Parizel ; Sylvie Choua ; Christophe Gourlaouen ; Patrick Rosa ; Philippe Turek ; Pierre Braunstein
- 刊名：Inorganic Chemistry
- 出版年：2016
- 出版时间：May 2, 2016
- 年：2016
- 卷：55
- 期：9
- 页码：4183-4198
- 全文大小：846K
- 年卷期：0
- ISSN：1520-510X
文摘
The coordination of two heterofunctional P,P,S ligands of the N-functionalized DPPA-type bearing an alkylthioether or arylthioether N-substituent, (Ph2P)2N(CH2)3SMe (1) and (Ph2P)2N(p-C6H4)SMe (2), respectively, toward cobalt dichloride was investigated to examine the influence of the linker between the PNP nitrogen and the S atoms. The complexes [CoCl2(1)]2 (3) and [CoCl2(2)]2 (4) have been isolated, and 3 was shown by X-ray diffraction to be a unique dinuclear, zwitterion containing one CoCl moiety bis-chelated by two ligands 1 and one CoCl3 fragment coordinated by the S atom of a thioether function. The FT-IR, UV–vis, and EPR spectroscopic features of 3 were analyzed as the superposition of those of constitutive fragments identified by a retrosynthetic-type analysis. A similar approach provided insight into the nature of 4 for which no X-ray diffraction data could be obtained. A comparison between the spectroscopic features of 4 and of its constitutive fragments, [CoCl(2)2]PF6 (7) and [H2′]2[CoCl4] (8) (2′ = NH2(p-C6H4)SMe), and between those of 4 and 3 suggested that 4 could either have a zwitterionic structure, similar to that of 3, or contain a tetrahedral dicationic bis-chelated Co center associated with a CoCl4 dianion. Magnetic and EPR studies and theoretical calculations were performed. Doublet spin states were found for the pentacoordinated complexes [CoCl(1)2]PF6 (5) and 7 and anisotropic quadruplet spin states for the tetrahedral complexes [CoCl3(H1′)] (6) (1′ = NH2(CH2)3SMe) and 8. A very similar behavior was observed for 3 and 4, consisting in the juxtaposition of noninteracting doublet and quadruplet spin states. Antiferromagnetic interactions explain the formation of dimers for 6 and of layers for 8. The EPR signatures of 3 and 4 correspond to the superposition of low-spin nuclei in 5 and 7 and high-spin nuclei in 6 and 8, respectively. From DFT calculations, the solid-state structure of 4 appears best described as zwitterionic, with a low-spin state for the Co1 atom.