STRUCTURALLY DIVERSE MANGANESE(III) COMPLEXES OF TETRADENTATE N2O2 SCHIFF-BASE LIGANDS WITH ANCILLARY CARBOXYLATE DONORS

A number of manganese(III) complexes of tetradentate N2O2 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)(O2CEt)}(n)] 1, where as a monomeric species is found in [Mn(saltn)(O2CBu')] 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)(O2C CH2Ph)}(2n)] 3 (H(2)bsaltn = 5-bromo derivative of H(2)saltn), which e xhibits rare syn-anti bridging; 3 also contains a dimeric repeat unit due to an alternate 180 degrees twist in the polymeric chain necessita ted by steric constraints. In contrast, the complexes containing the d ianion of N,N'-bis(3-methoxysalicylidene)ethane-1,2-diamine (H(2)msale n) appear to be isostructural, [{Mn(msalen)(O2CEt)}(2)] . EtOH 4 and [ {Mn(msalen)(O2CBun)}(2)] 5 being structurally characterised as essenti ally identical phenoxy-bridged dimers. An insoluble material of stoich iometry Mn-4(O2CR)(3)(saltn)(3)(H2O)(n) (n = 0-3) was isolated from al l reactions involving the saltn ligand; attempts to characterise these compounds by X-ray diffraction have been unsuccessful. However, the p reviously characterised manganese(IV) dimer [{Mn(saltn)O}(2)] . 2dmf 6 (dmf = dimethylformamide) and the monomeric species [Mn(saltn)(O2CEt) ] 7 were isolated in attempts to crystallise these materials.