Clusters as ligands, part 3 generation of tricobalt cluster carboxylate-bridged iron—cobalt and manganese—cobalt mixed-metal alkoxide cubes from iron and manganese tricobalt cluster metal carboxylates

Abstract

The reaction of the cluster-substituted carboxylic acid, (CO) 9Co 3CCOOH, with M(CH 3CO 2) 2 permits the isolation of M 2{(CO) 9Co 3CCO 2} 4(THF) 2, M = Mn ( 1), Fe ( 2), Co ( 3) respectively. Single crystals could not be obtained directly from any of these compounds; however, the slow redox degradation of Hg{(CO) 9Co 3CCO 2} 2 in THF leads to crystalline [Co 2((CO) 9Co 3CCO 2) 4(THF) 2], which has been characterized by single crystal X-ray structure analysis. Both compounds 1 and 2 react with methanol and the products [M 2 IIICo 2 II(MeO) 6(MeOH) 2{(CO) 9Co 3CCO 2} 4] · 2MeOH, M = Mn ( 4), Fe ( 5) respectively, have been isolated as crystalline solids. The formulation of these new mixed-metal cubane clusters is based on analytical data, single crystal X-ray structure analysis, and the Mössbauer spectrum of 5. The inner Co II centers are derived from sacrificial decomposition of the tricobalt clusters during precipitation of the product. For both 4 and 5 the magnetic susceptibility data show high room temperature magnetic moments which decrease with decreasing temperature consistent with weak antiferromagnetic coupling between the core metal centers and with S = 0 ground states. The formation of these unusual carboxylate coordinated mixed-metal alkoxide cubes derives from the properties of a transition metal cluster as a substituent as well as its tendency to engage in redox chemistry with other metal species.