Application of the Redox-Transmetalation Procedure to Access Divalent Lanthanide and Alkaline-Earth NHC Complexes** |
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| Authors: | Noah Schwarz Xiaofei Sun Dr Ravi Yadav Dr Ralf Köppe Dr Thomas Simler Prof?Dr Peter W Roesky |
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| Institution: | Institute of Inorganic Chemistry, Karlsruhe Institute of Technology (KIT), Engesserstraße 15, 76131 Karlsruhe, Germany |
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| Abstract: | Divalent lanthanide and alkaline-earth complexes supported by N-heterocyclic carbene (NHC) ligands have been accessed by redox-transmetalation between air-stable NHC-AgI complexes and the corresponding metals. By using the small ligand 1,3-dimethylimidazol-2-ylidene (IMe), two series of isostructural complexes were obtained: the tetra-NHC complexes LnI2(IMe)4] (Ln=Eu and Sm) and the bis-NHC complexes MI2(IMe)2(THF)2] (M=Yb, Ca and Sr). In the former, distortions in the NHC coordination were found to originate from intermolecular repulsions in the solid state. Application of the redox-transmetalation strategy with the bulkier 1,3-dimesitylimidazol-2-ylidene (IMes) ligand yielded SrI2(IMes)(THF)3], while using a similar procedure with Ca metal led to CaI2(THF)4] and uncoordinated IMes. DFT calculations were performed to rationalise the selective formation of the bis-NHC adduct in SrI2(IMe)2(THF)2] and the tetra-NHC adduct in SmI2(IMe)4]. Since the results in the gas phase point towards preferential formation of the tetra-NHC complexes for both metal centres, the differences between both arrangements are a result of solid-state effects such as slightly different packing forces. |
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| Keywords: | alkaline earth metals carbene ligands divalent lanthanides metal-ligand interactions redox-transmetalation |
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