A Mn-4(II) cubane and a novel (Mn10Mn4III)-Mn-II cluster from the use of di-2-pyridyl ketone in manganese acetate chemistry

The employment of di-2-pyridyl ketone, (py)(2)CO, in manganese(II) acetate chemistry is reported. The syntheses, crystal structures and magnetochemical characterisation are described for [Mn-4(II)(O2CMe)(4){(py)(2)C(OH)O}(4)] (1) and [(Mn10Mn4O4)-Mn-II-O-III(O2CMe)(20){(py)(2)C(OH) O}(4)] (2), where (py)(2)C(OH)O- is the monoanion of the gem-diol form of the ligand. The reaction of Mn(O2CMe)(2)center dot 4H(2)O with one equivalent of (py)(2)CO in Me2CO gives 1. Complex 2 was obtained from the 1 : 1 reaction, in EtOH, between Mn(O2CMe)(2)center dot 4H(2)O and (py)(2)CO in the presence of NEt3. The tetranuclear molecule 1 has a cubane topology with the Mn-II and the deprotonated oxygen atoms from the eta(1):eta(3):eta(1):mu(3) ligands occupying alternate vertices of the cube. The core of 2 consists of two mixed valence cubane {(Mn2Mn2III)-Mn-II(mu(3)-O)(2)(mu(3)-OR '')(2)}(4+) subunits that are linked through an unusual {Mn-6(II)(eta(1):eta(2):mu-O2CMe)(6)(eta(2):eta(2):mu(3)-O2CMe)(2)}(4+) moiety via twelve eta(1):eta(1):mu 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)(2)CO with carboxylate ligands.