CLUSTERS AS LIGANDS .3. GENERATION OF TRICOBALT CLUSTER CARBOXYLATE-BRIDGED IRON-COBALT AND MANGANESE-COBALT MIXED-METAL ALKOXIDE CUBES FROM IRON AND MANGANESE TRICOBALT CLUSTER METAL CARBOXYLATES

The reaction of the cluster-substituted carboxylic acid, (CO)(9)Co3CCO OH, with M(CH3CO2)(2) permits the isolation of M-2{(CO)(9)Co3CCo2}(4)( THF)(2), M = Mn (1), Fe (2), Co (3) respectively. Single crystals coul d not be obtained directly from any of these compounds; however, the s low redox degradation of Hg{(CO)(9)Co3CCO2}(2) in THF leads to crystal line [Co-2((CO)(9)Co3CCO2)(4)(THF)(2)], which has been characterized b y single crystal X-ray structure analysis. Both compounds 1 and 2 reac t with methanol and the products Co-III(MeO)(6)(MeOH)(2){(CO)(9)Co3CCO 2}(4)].2MeOH, M = Mn (4), Fe (5) respectively, have been isolated as c rystalline solids. The formulation of these new mixed-metal cubane clu sters is based on analytical data, single crystal X-ray structure anal ysis, and the Mossbauer spectrum of 5. The inner Co-II centers are der ived from sacrificial decomposition of the tricobalt clusters during p recipitation of the product. For both 4 and 5 the magnetic susceptibil ity data show high room temperature magnetic moments which decrease wi th decreasing temperature consistent with weak antiferromagnetic coupl ing between the core metal centers and with S=0 ground states. The for mation of these unusual carboxylate coordinated mixed-metal alkoxide c ubes derives from the properties of a transition metal cluster as a su bstituent as well as its tendency to engage in redox chemistry with ot her metal species. (C) 1997 Elsevier Science S.A.