Structurally diverse manganese(III) complexes of tetradentate N2O2 Schiff-base ligands with ancillary carboxylate donors

Abstract

A number of manganese(III) complexes of tetradentate N 2 O 2 Schiff-base ligands have been prepared with various additional carboxylate anions. Five of these compounds have been crystallographically characterised revealing that a remarkable array of structural chemistry is available. A polymeric species is observed for [{Mn(saltn)(O 2 CEt)} n ] 1, whereas a monomeric species is found in [Mn(saltn)(O 2 CBu t )] 2 [H 2 saltn = N,N′-bis (salicylidene)trimethylenediamine]. The anti-anti bridging of the manganese centres in 1 is in contrast to that in [{Mn(bsaltn)(O 2 CCH 2 Ph)} 2n ] 3 (H 2 bsaltn = 5-bromo derivative of H 2 saltn), which exhibits rare syn-anti bridging; 3 also contains a dimeric repeat unit due to an alternate 180° twist in the polymeric chain necessitated by steric constraints. In contrast, the complexes containing the dianion of N,N′-bis(3-methoxysalicylidene)ethane-1,2- diamine (H 2 msalen) appear to be isostructural, [{Mn(msalen)(O 2 CEt)} 2 ]·EtOH 4 and [{Mn(msalen)(O 2 CBu n )} 2 ] 5 being structurally characterised as essentially identical phenoxy-bridged dimers. An insoluble material of stoichiometry Mn 4 (O 2 CR) 3 (saltn) 3 (H 2 O) n (n = 0–3) was isolated from all reactions involving the saltn ligand; attempts to characterise these compounds by X-ray diffraction have been unsuccessful. However, the previously characterised manganese(IV) dimer [{Mn(saltn)O} 2 ]·2dmf 6 (dmf = dimethylformamide) and the monomeric species [Mn(saltn)(O 2 CEt)] 7 were isolated in attempts to crystallise these materials.