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

Abstract

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), [Mn3(FcCO 2 )6(H20)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-0,0' 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.