2:2 Fe(III):ligand and "adamantane core" 4:2 Fe(III):ligand (hydr)oxo complexes of an acyclic ditopic ligand.

A bis-hydroxo-bridged diiron(III) complex and a bis-mu-oxo-bis-mu-hydroxo-bridged tetrairon(III) complex are isolated from the reaction of 2,6-bis((N,N'-bis-(2-picolyl)amino)methyl)-4-tert-butylphenol (Hbpbp) with iron perchlorate in acidic and neutral solutions respectively. The X-ray structure of the dinuclear complex [{(Hbpbp)Fe([mu-OH)}(2)](ClO(4))(4).2C(3)H(6)O (1.2C3H6O) shows that only one of the metal-binding cavities of each ligand is occupied by an iron(III) atom and two [Fe(Hbpbp)]3+ units are linked together by two hydroxo bridging groups to form a [Fe(III)-(mu-OH)](2) rhomb structure with Fe...Fe = 3.109(1)A. The non-coordinated tertiary amine of Hbpbp is protonated. Magnetic susceptibility measurements show a well-behaved weak antiferromagnetic coupling between the two Fe(III) atoms, J= -8 cm(-1). The tetranuclear complex [(bpbp)(2)Fe(4)(mu-O)(2)(mu-OH)(2)](ClO(4))(4)(2) was isolated as two different solvates .4CH(3)OH and .6H(2)O with markedly different crystal morphologies at pH ca. 6. Complex .4CH(3)OH forms red cubic crystals and .6H(2)O forms green crystalline platelets. The Fe(4)O(6) core of shows an adamantane-like structure: The six bridging oxygen atoms are provided by the two phenolato groups of the two bpbp(-) ligands, two bridging oxo groups and two bridging hydroxo groups. The hydroxo and oxo ligands could be distinguished on the basis of Fe-O bond lengths of the two different octahedral iron sites: Fe-mu-OH, 1.953(5), 2.013(5)A and Fe-mu-O, 1.803(5), 1.802(5)A. The difference in ligand environment is too small for allowing Mossbauer spectroscopy to distinguish between the two crystallographically independent Fe sites. The best fit to the magnetic susceptibility of .4CH(3)OH was achieved by using three coupling constants J(Fe-OPh-Fe)= 2.6 cm(-1), J(Fe-OH-Fe)=-0.9 cm(-1), J(Fe-O-Fe)=-101 cm(-1) and iron(III) single ion ZFS (|D|= 0.15 cm(-1)).

Fe(II) and Fe(III) mononuclear complexes with a pentadentate ligand built on the 1,3-diaminopropane unit. Structures and spectroscopic and electrochemical properties. Reaction with H2O2.

Two new iron complexes, [L(5)(3)Fe(II)Cl]PF(6) (1.PF(6)) and [(L(5)(3)H(+))Fe(III)Cl(3)]PF(6) (2.PF(6)), were synthesized (L(5)(3) = N-methyl-N,N',N'-tris(2-pyridylmethyl)propane-1,3-diamine), and their molecular structures were determined by X-ray crystallography. Their behavior in solution was studied by UV-vis spectroscopy and electrochemistry. Upon addition of a base to an acetonitrile solution of 2, the new unsymmetrical dinuclear complex [L(5)(3)Fe(III)OFe(III)Cl(3)](+) was detected. Treating 1 with hydrogen peroxide has allowed us to detect the low spin [L(5)(3)Fe(III)OOH](2+). Its spectroscopic properties (UV-vis, EPR and resonance Raman) are similar to those reported for related FeOOH complexes obtained with amine/pyridine ligands. Using stopped-flow absorption spectroscopy, the formation and degradation of [L(5)(3)Fe(III)OOH](2+) has been monitored, and a mechanism is proposed to reproduce the kinetic data.