Synthesis, Crystal Structure, and Magnetic Properties of Two Manganese(II) Polymers Bearing Ferrocenecarboxylato Ligands

Reactions of Mn(ClO 4 ) 2 · 6H 2 O with FcCO 2 Na [Fc = (η 5 ‐C 5 H 4 )Fe(η 5 ‐C 5 H 5 )] in methanol solution gave [Mn 3 (FcCO 2 ) 6 (CH 3 OH) 4 ] n ( 1 ), and, in the presence of 4,4′‐bipyridine (4,4′‐bpy), [Mn 3 (FcCO 2 ) 6 (H 2 O) 2 (4,4′‐bpy)] n ( 2 ). Both complexes have the similar chains with a sequence of –Mn–(μ 2 ‐COO) n –Mn–(μ 2 ‐COO)–Mn–(μ 2 ‐COO)–Mn–(μ 2 ‐COO) n –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 μ 2 ‐ferrocenecarboxylato‐ O , O′ bridging. The two Mn II ions in the dinuclear [Mn 2 (FcCO 2 ) 4 ] units of complex 1 are connected by four ferrocenecarboxylato ligands to form a swastika‐like shaped skeleton, which is rare in metallocenecarboxylato complexes. However, the two Mn II 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 antiferromagnetic 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. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)