AMn II4 cubane and a novel MnII10MnIII4 cluster from the use of di-2-pyridyl ketone in manganese acetate chemistry

The employment of di-2-pyridyl ketone, (py) 2CO, in manganese(II) acetate chemistry is reported. The syntheses, crystal structures and magnetochemical characterisation are described for [MnII4(O2CMe)4{(py)2C(OH)O}4] (1) and [MnII10MnIII4O4(O2CMe)20{ (py)2C (OH)O}4] (2), where (py)2C(OH)O- is the monoanion of the gem-diol form of the ligand. The reaction of Mn(O2CMe)2·4H2O with one equivalent of (py)2CO in Me2CO gives 1. Complex 2 was obtained from the 1 : 1 reaction, in EtOH, between Mn(O2CMe)2·4H2O and (py)2CO in the presence of NEt3. The tetranuclear molecule 1 has a cubane topology with the MnII and the deprotonated oxygen atoms from the η1:η3:η1:μ3 ligands occupying alternate vertices of the cube. The core of 2 consists of two mixed valence cubane {MnII2MnIII2(μ3-O)2(μ3-OR'')2}4+ subunits that are linked through an unusual {MnII6(η1:η2:μ-O2CMe)6(η2:η2:μ3-O2CMe)2}4+ moiety via twelve η1:η1:μ MeCO2- groups. Some suggestions have been made concerning the possible assembly of 2 from 1. The magnetic properties of 1 in the 300–5 K range have been modelled with two J values, which reveal weak antiferromagnetic interactions within the molecule. Complex 2 has a low spin ground state. This work demonstrates the flexibility, versatility and synthetic potential of combining (py)2CO with carboxylate ligands.