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A Triiron Complex Containing the Carboxylate‐Free {Fe 3 (μ 3 ‐O)} 7+ Core and Distorted Pentagonal‐Bipyramidal Metal Centres
Author(s) -
Sreerama Subramanya Gupta,
Pal Samudranil
Publication year - 2004
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200400427
Subject(s) - pentagonal bipyramidal molecular geometry , chemistry , crystallography , carboxylate , crystal structure , metal , molecule , coordination sphere , bipyramid , trigonal bipyramidal molecular geometry , hydrogen bond , perchlorate , stereochemistry , ion , organic chemistry
The reaction of Fe(ClO 4 ) 3 ·6H 2 O, 1,2‐bis(biacetylmonoximeimino)ethane (H 2 bamen) and triethylamine (1:1:2 mol ratio) in methanol affords a trinuclear complex with the formula [Fe 3 (μ 3 ‐O)(μ 3 ‐bamen) 3 ]ClO 4 ·2H 2 O. The structure of the complex cation in this species shows a symmetric planar central {Fe 3 (μ 3 ‐O)} 7+ unit coordinated to three N 4 O 2 donor bridging (via oximate groups) ligands (bamen 2− ). The N 4 O 3 coordination sphere around each metal centre is very close to pentagonal‐bipyramidal. Four N atoms of one bamen 2− and the oxo group satisfy five coordination sites and form a pentagonal plane around the metal ion. The axial sites are occupied by two oximato O atoms from the other two bamen 2− ligands. Thus, in addition to the μ 3 ‐oxo group, two oximate groups provide two additional bridges between each pair of metal centres. In the crystal lattice, the water molecules exist as hydrogen‐bonded dimers and these water dimers together with the perchlorate ions form a hydrogen‐bond‐supported helix. The complex cations form a chain via C−H ··· O interactions involving a methyl group and a metal‐coordinated oximato O atom. The helix of {(H 2 O) 2 ClO 4 − } units and the chain of [Fe 3 O(bamen) 3 ] + cations are connected by O−H ··· O interactions which involve a water molecule and a second oximato O atom. In its cyclic voltammogram, the complex displays metal‐centred oxidation as well as reduction responses. Variable‐temperature magnetic susceptibility measurements revealed the presence of an antiferromagnetic interaction [ J = −41.0(2) cm −1 ] between the Fe III centres in this complex. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)