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

Tetrakis(μ-acetato-κ 2 O : O ′)bis{[1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene-κ C 2 ]chromium(II)} tetrahydrofuran disolvate, [Cr 2 (C 2 H 3 O 2 ) 4 (C 27 H 36 N 4 ) 2 ]·2C 4 H 8 O or [Cr 2 (OAc) 4 (IDipp) 2 ]·2C 4 H 8 O ( 1 ), and tetrakis(μ-acetato-κ 2 O : O ′)bis{[1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene-κ C 2 ]chromium(II)}, {Cr 2 (C 2 H 3 O 2 ) 4 (C 21 H 24 N 2 ) 2 ] or [Cr 2 (OAc) 4 (IMes) 2 ] ( 2 ), were synthesized from anhydrous chromium(II) acetate [Cr 2 (OAc) 4 ] and the corresponding NHC (NHC = N-heterocyclic carbene) in toluene as solvent. Both complexes crystallize in the triclinic system, space group P 1̄. The molecular structures consist of Cr 2 (OAc) 4 paddle-wheels that carry two terminal NHC ligands. This leads to a square-pyramidal coordination of the chromium atoms.