Two chromium(II) acetate complexes with N-heterocyclic carbene (NHC) coligands

Abstract

Tetrakis(μ-acetato-κ2 O:O′)bis{[1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene-κC 2]chromium(II)} tetrahydrofuran disolvate, [Cr2(C2H3O2)4(C27H36N4)2]·2C4H8O or [Cr2(OAc)4(IDipp)2]·2C4H8O (1), and tetrakis(μ-acetato-κ2 O:O′)bis{[1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene-κC 2]chromium(II)}, {Cr2(C2H3O2)4(C21H24N2)2] or [Cr2(OAc)4(IMes)2] (2), were synthesized from anhydrous chromium(II) acetate [Cr2(OAc)4] and the corresponding NHC (NHC = N-heterocyclic carbene) in toluene as solvent. Both complexes crystallize in the triclinic system, space group P\overline{1}. The molecular structures consist of Cr2(OAc)4 paddle-wheels that carry two terminal NHC ligands. This leads to a square-pyramidal coordination of the chromium atoms.