title: Pentanuclear complexes with unusual structural topologies from the initial use of two aliphatic amino-alcohol ligands in Fe chemistry.
abstract: Five novel pentanuclear Fe(3+) clusters with the aliphatic amino-alcohol ligands 3-amino-1-propanol (Hap) and 2-(hydroxymethyl)piperidine (Hhmpip) [Fe(5)(μ(3)-Ο)(2)(L)(4)(O(2)CR)(7)] [L = ap(-), R = Ph (1); L = ap(-), R = C(CH(3))(3) (2); L = hmpip(-), R = Ph (3); L = hmpip(-), R = C(CH(3))(3) (4)] and [Fe(5)(μ(4)-Ο)(μ(3)-Ο)(O(2)CC(CH(3))(3))(8)(ap)(2)Cl(HO(2)CC(CH(3))(3))] (5) are reported. Compounds 1-4 were prepared from reactions of preformed trinuclear Fe(3+) clusters with the ligands in a molar ratio 1 : 5 in MeCN (1, 3, 4) or DMF (2), whereas compound 5 was prepared from the reaction of FeCl(3) with Hap in the presence of HO(2)CC(CH(3))(3) in a molar ratio 1 : 3 : 2 in MeCN. To the best of our knowledge, 1-5 are the first examples of Fe(3+) complexes with the ligands Hap and Hhmpip. The structures of 1-4 are composed of a quasi-planar [Fe(5)(μ(3)-O)(2)](11+) core which consists of two vertex-sharing [Fe(3)(μ(3)-O)](7+) triangles. The structure of 5 is based on the [Fe(5)(μ(4)-O)(μ(3)-O)](11+) core, in which the five Fe(3+) ions adopt a monocapped trigonal pyramidal topology. Variable-temperature magnetic susceptibility measurements on powdered microcrystalline samples of 1 and 5 revealed the existence of antiferromagnetic interactions which led to an S = 5/2 ground state. Mössbauer spectroscopy studies on powdered microcrystalline samples of 1 and 5 confirmed that all iron ions of both complexes are in the Fe(3+) (S = 5/2) state. The variation of the ligand environment in the various iron sites was reflected in their different quadruple splitting parameters. At T < 50 K the Mössbauer spectra indicated the onset of spin relaxation effects in the time scale of the technique (10(-7)-10(-8) s).
authors.affiliation: Department of Chemistry, University of Cyprus, 1678, Nicosia, Cyprus.
authors.forename: Christos M
authors.initials: CM
authors.lastname: Kizas
authors.forename: Manolis J
authors.initials: MJ
authors.lastname: Manos
authors.forename: Vassilios
authors.initials: V
authors.lastname: Nastopoulos
authors.forename: Athanassios K
authors.initials: AK
authors.lastname: Boudalis
authors.forename: Yiannis
authors.initials: Y
authors.lastname: Sanakis
authors.forename: Anastasios J
authors.initials: AJ
authors.lastname: Tasiopoulos
mesh_terms: D000605:Amino Alcohols / Q000138:chemical synthesis / Q000737:chemistry*; D018360:Crystallography, X-Ray; D005290:Ferric Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D008024:Ligands; D060328:Magnetic Phenomena; D008958:Models, Molecular; D015204:Spectroscopy, Mossbauer
chemical_list: D000605:Amino Alcohols; D005290:Ferric Compounds; D008024:Ligands