Normal to abnormal ItBu·AlH3 isomerization in solution and in the solid state†
A complex of an N-heterocyclic carbene ItBu (1,3-di-tert-butylimidazolin-2-ylidene) and aluminum hydride was observed to isomerize into an abnormal carbene complex aItBu·AlH3 (aItBu = 1,3-di-tert-butylimidazolin-4-ylidene) in a polar solvent, and, for the first time, in the solid state. ItBu·AlH3 and aItBu·AlH3 were structurally characterized by single crystal X-ray diffraction analysis. NMR studies and DFT computations indicate that the polarity of the solvent promotes the isomerization process. The possible pathways for the isomerization are discussed on the basis of the DFT computational studies.