Synthesis, crystal structure, and magnetic properties of two manganese(II) polymers bearing ferrocenecarboxylato ligands
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Reactions of Mn(ClO4)(2)center dot 6H(2)O with FcCO(2)Na [Fc = (eta(5)-C5H4)Fe(eta(5)-C5H5)] in methanol solution gave [Mn-3(FcCO(2))(6)-(CH3OH)(4)](n) (1), and, in the presence of 4,4'-bipyridine (4,4'-bpy), [Mn-3(FcCO(2))(6)(H2O)(2)(4,4'-bpy)](n) (2). Both complexes have the similar chains with a sequence of -Mn-(mu(2)-COO)(n)-Mn-(mu(2)-COO)-Mn-(mu xi 2-COO)-Mn-(mu 2-COO),-Mn- (n = 4 and 2 for complex 1 and 2, respectively), which are constructed alternatively from mononuclear [Mn-II] units and dinuclear [Mn-2(FcCO(2))(4)] units by mu(2)-ferrocenecarboxylato-O,O' bridging. The two Mn-II ions in the dinuclear [Mn-2(FcCO(2))(4)] units of complex I are connected by four ferrocenecarboxylato ligands to form a swastika-like shaped skeleton, which is rare in metallocenecarboxylato complexes. However, the two Mull ions in the dinuclear [Mn-2(FcCO(2))(4)] units of complex 2 are bridged only by two carboxylato ligands, and the other two ferrocenecarboxylato ligands in this unit bind in a chelating mode. The chains in complex 2 are further interconnected by the coordinated 4,4'-bipyridine molecules to form two-dimensional coordination sheets. Magnetic susceptibility measurements revealed a weak anti-ferromagnetic coupling for both complexes. A model Heisenberg chain comprising classical spins coupled through alternating exchange interactions J(1)-J(1)-J(2) (AF1-AF1-AF2) is proposed to describe the magnetic behavior. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007).