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

Tetra-kis(µ-acetato-κ2 O:O')bis-{[1,3-bis-(2,6-diiso-propyl-phen-yl)imidazol-2-yl-idene-κC 2]chromium(II)} tetra-hydro-furan disolvate, [Cr2(C2H3O2)4(C27H36N4)2]·2C4H8O or [Cr2(OAc)4(IDipp)2]·2C4H8O (1), and tetra-kis-(µ-acetato-κ2 O:O')bis-{[1,3-bis-(2,4,6-tri-methyl-phen-yl)imidazol-2-yl-idene-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. The mol-ecular 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.

Tetra-kis(µ-acetato-κ2O:O')bis-[(tetra-hydro-furan-κO)chromium(II)].

The title compound, [Cr2(C2H3O2)4(C4H8O)2] or [Cr2(OAc)4(THF)2] (OAc is acetate, THF is tetra-hydro-furan), was obtained by recrystallization of anhydrous chromium(II) acetate [Cr2(OAc)4] from hot tetra-hydro-furan. The centrosymmetric complex forms monoclinic crystals, space group C2/c, and consists of two CrII atoms bridged by four acetate ligands. Additionally, each CrII atom is coordinated by a terminal THF ligand, which leads to a square-pyramidal coordination.

Syntheses and crystal structures of three [M(acac)2(TMEDA)] complexes (M = Mn, Fe and Zn).

The complexes bis-(acetyl-acetonato-κ2 O,O')(N,N,N',N'-tetra-methyl-ethylenedi-amine-κ2 N,N')manganese(II), [Mn(C5H7O2)2(C6H16N2)], bis-(acetyl-acetonato-κ2 O,O')(N,N,N',N'-tetra-methyl-ethylenedi-amine-κ2 N,N')iron(II), [Fe(C5H7O2)2(C6H16N2)], and bis-(acetyl-acetonato-κ2 O,O')(N,N,N',N'-tetra-methyl-ethylenedi-amine-κ2 N,N')zinc(II), [Zn(C5H7O2)2(C6H16N2)], were synthesized from the reaction of the corresponding metal acetyl-acetonates [M(acac)2(H2O)2] with N,N,N',N'-tetra-methyl-ethylenedi-amine (TMEDA) in toluene. Each of the complexes displays a central metal atom which is nearly octa-hedrally surrounded by two chelating acac and one chelating TMEDA ligand, resulting in an N2O4 coordination set. Despite the chemical similarity of the complex units, the packing patterns for compounds 1-3 are different and thus the crystal structures are not isotypic.