NEW FERROUS COMPLEXES BASED ON THE 2,2'-BIIMIDAZOLE LIGAND - STRUCTURAL, MOSSBAUER, AND MAGNETIC-PROPERTIES OF [FE-II(BIIMH(2))(3)(CH3OH)(2)]OAC(2), [FE-II(BIMH(2))3,]CO3[FE-II(BIMH)(2)](N), AND (FE-II(BIM))(N)

Four complexes, [Fe-II(bimH(2))(2)(CH3OH)(2)](OAc)(2) (1), [Fe-II(bimH (2))(3)]CO3 (2), [Fe-II(bimH)(2)](n) (3) and {Fe-II(bim)}(n) (4), wher ein bimH(2) = 2,2'-biimidazole, bimH(-) = biimidazolate monoanion, and bim2(-) = biimidazolate dianion, have been synthesized and studied. 1 crystallizes in the monoclinic system, space group P2(1)/n, Z = 2, a 9.021(1) Angstrom, b = 7.413(1) Angstrom, c = 17.700(2) Angstrom, beta = 97.23(1)degrees; 2 crystallizes in the tetragonal system, space gro up I4(1), Z = 4, a = b = 12.219(1) Angstrom, 14.334(2) Angstrom; 3 cry stallizes in the tetragonal system, space group P4(3), Z = 4, a = b = 8.5144(7) Angstrom, c = 18.273(3) Angstrom. The structures were solved by direct methods and refined to conventional agreement indices R = 0 .024 (1), 0.022 (2), and 0.032 (3) and R(W) = 0.024 (1), 0.023 (2), an d 0.039 (3) with 1725 (1), 2292 (2), and 2592 (3) unique reflections f or which I > 3 sigma(I). The molecular structure of 1 consists of [Fe- II(bimH(2))(2)(CH3OH)(2)](2+) complex cations and acetate anions assoc iated into infinite chains along a through hydrogen bonds involving th e amine nitrogen atoms of all bimH(2) ligands, all coordinated methano l molecules and noncoordinated acetate anions. The four nitrogen and t wo oxygen atoms constituting the distorted coordination octahedron aro und each Fe(II) originate from two chelating bimH(2) ligands and two m ethanol molecules. The structure of 2 consists of [Fe-II(bimH(2))(3)]( 2+) complex cations hydrogen bonded to carbonate dianions. The coordin ation geometry of the iron(II) center can be described as a distorted octahedron includind six nitrogen atoms originating from three chelati ng bimH(2) ligands. The ferrous center of each [Fe-II(bimH)(2)] neutra l unit of 3 is chelated to two biimidazolate monoanions cis to each ot her. Two deprotonated amine nitrogen donors arising from biimidazolate ligands of adjacent complex molecules supplement the iron(II) coordin ation octahedron. All iron atoms situated at the same z value are brid ged through the imidazolate rings affording a sheet spanning along a,b . These sheets are associated together into a 3D network in which each [Fe-II(bimH)(2)] molecule is linked to four nearest neighbors through N-C-N bridges. The synthesis, molecular crystal structure, IR, Mossba uer, and magnetic susceptibility studies of 1-4 evidence the variety o f structural types and properties obtained for iron(II) complexes of 2 ,2'-biimidazole and derived biimidazolate anions. Complex 1 is the fir st example of structurally characterized mononuclear ferrous compound including two bidentate bimH(2) and two monodentate oxygenated ligands affording a N4O2 coordination sphere to high-spin iron(II). Synthesis of 2 from Fe-II(bimH(2))(2)(HCOO)(2) and CO3HNa shows that formate an ions ate readily displaced from the iron(II) coordination sphere as sh own for the non-heme iron(II) of photosystem 2. 3 affords the first ex ample of bridging biimidazolate monoanion. 4 is the first inorganic po lymeric material including the bim(2-) dianion as tetradentate bridgin g ligand. The Mossbauer and magnetic properties of 4 indicate the pres ence of a weak ferromagnetic ground state resulting from the 3D orderi ng of this homometallic lattice. 3 and 4 are the first examples of iro n compounds including the biimidazolate monoanion (bimH(-)) and the bi imidazolate dianion (bim(2-)), respectively.