NEW TRIPLY BRIDGED DIIRON(III) COMPLEXES WITH [FE-2(MU-O)-(MU-X)2]2+ CORES [X = MECO2, PHCO2 OR (PHO)2PO2]

A group of three diiron(III) complexes having [Fe2(mu-O)(mu-X)2]2, cores (X = benzoate, acetate or diphenyl phosphate) has been synthesised with the use of unsymmetrical facially capping tridentate ligands (L1 and L2), where L1 and L2 are [2-(2-pyridyl)ethyl](2-pyridylmethyl)amine and methyl[2-(2-pyridyl)ethyl](2-pyridylmethyl)amine respectively. The lability of the bridging acetate groups in [Fe(mu-O)(mu-MeCO2)2L22]2+ has been demonstrated by exchange with diphenyl phosphate and deuterioacetate as revealed by UV/VIS and H-1 NMR studies. These complexes exhibit infrared, electronic and Mossbauer spectral features very similar to those of mu-oxo-diiron(III) proteins as well as of mu-oxo-bis(mu-carboxylato) or p-oxo-bis(mu-phosphato)diiron(III) complexes. The inequivalence in the chelate rings around each iron(III) might have caused the asymmetry in these compounds which is reflected in their distinctively strong antiferromagnetic coupling (J = - 1 27, -1 25 and - 1 08 cm for the benzoate-, acetate- and phosphate-bridged complexes respectively).