Charge-Delocalized 魏2C,N-NHC-Amine Complexes of Rhodium, Iridium, and Ruthenium

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• 作者：Eveline Jansen ; Martin Lutz ; Bas de Bruin ; Cornelis J. Elsevier
• 刊名：Organometallics
• 出版年：2014
• 出版时间：June 9, 2014
• 年：2014
• 卷：33
• 期：11
• 页码：2853-2861
• 全文大小：389K
• 年卷期：v.33,no.11(June 9, 2014)
• ISSN：1520-6041

文摘

The development of a novel set of complexes bearing an NHC-amine ligand (C^NHC-NH₂) is described. M(cod) complexes (M = Ir, Rh) and a Ru complex have been synthesized in which three different coordination modes of the ligand were established: monodentate, neutral bidentate, and anionic bidentate. The anionic bidentate coordination mode of the anionic C^NHC-NH^{鈥?/sup> ligand arises from deprotonation of the amine moiety of the neutral CNHC-NH₂ ligand. Ligand deprotonation proved to be reversible for the Rh and Ir complexes, as was shown by subsequent treatment of the complexes with base and acid. The structural parameters of these differently coordinated ligands were examined, and it was shown that the conjugation of the aniline ring plays a major role in determining the ligand properties. Structural parameters derived from DFT calculations confirm delocalization of the anionic charge over the ligand framework, as is clear from a comparison of the (hypothetical) neutral bidentate complexes [M(cod)(魏2C,N-{CNHC-NH₂})]+ with those of the (synthesized) monoanionic complexes [M(cod)(魏2C,N-{CNHC-NH})] (M = Rh, Ir). A similar trend in the structure and bond lengths of the aniline rings was found in the solid-state structure of the novel dimeric complex [(Ru(魏2C,N-{CNHC-NH})(魏2C,N-{CNHC-NH₂})Cl)₂(渭-Cl)](PF₆). The octahedral d5 ruthenium(III) centers in this complex both contain a neutral bidentate CNHC-NH₂ ligand as well as an anionic bidentate CNHC-NH鈥?/sup> ligand. Quite remarkably, the complex is diamagnetic, arising from antiferromagnetic coupling of the two low-spin ruthenium(III) centers over the chloride linker. DFT calculations indeed confirm that the open-shell singlet electronic structure is most stable.}