Application of the Redox-Transmetalation Procedure to Access Divalent Lanthanide and Alkaline-Earth NHC Complexes*.

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.

SUBMITTER: Schwarz N 

PROVIDER: S-EPMC8518399 | biostudies-literature | 2021 Sep

REPOSITORIES: biostudies-literature