Cages on a plane: a structural matrix for molecular 'sheets'.

A family of heterometallic Anderson-type 'wheels' of general formula [MM(hmp)12 ]4+ (MIII = Cr or Al and MII = Ni or Zn, Hhmp = 2-pyridinemethanol) has been extended to include MIII = Cr or Al and MII = Co, Fe, Mn or Cu, affording five new species of formulae [Cr2 Co5 (hmp)12 ](ClO4 )4 (1), [Cr2 Fe5 (hmp)12 ](ClO4 )4 (2), [Cr2 Mn5 (hmp)12 ](ClO4 )4 (3), [Cr2 Cu5 (hmp)12 ](ClO4 )2 (NO3 )2 (4) and [Al2 Co5 (hmp)12 ](ClO4 )4 (5). As per previous family members, the metallic skeleton common to the cations of 1-5 describes a centred hexagon with the two MIII sites disordered around the outer wheel, with the exception of compound 4 where the CuII sites are localised. A structurally related, but enlarged planar disc possessing a [MMII ] hexagon capped on each edge by a CuII ion can be formed, but only when MIII = Al and MII = Cu. In [AlCu(OH)12 (hmp)12 ](ClO4 )6 (NO3 )2 (6) the Anderson moiety contains a central, symmetry-imposed octahedral CuII ion surrounded by a wheel of AlIII ions. Solid-state dc susceptibility and magnetisation measurements reveal the presence of competing exchange interactions in 1-5, and very weak antiferromagnetic exchange between the CuII ions in 6 which may be intra- and/or intermolecular in nature.