Mn/Ce clusters from the use of pivalate and chelate ligands: MnIII8CeIV, MnIII2CeIV2, and MnIII4CeIII2 products

The reaction system MnII/CeIII/IV/(CH3)3CCO2− has been investigated and has yielded four MnxCey and one MnIII4 compounds. Reactions in the presence of NBun4MnO4 afforded a MnIII8CeIV compound [Mn8CeO8(ButCO2)12(DMF)4] (1), consisting of a CeIV atom inside a loop of eight MnIII ions. Reactions also containing 1,10-phenanthroline (phen) or 2,2′-bipyridine (bpy) gave [Mn2Ce2O2(OH)2(ButCO2)4(NO3)4(phen)2] (2) or [Mn2Ce2O2(OH)2(ButCO2)4(NO3)4(bpy)2] (3), respectively, containing the MnIII2CeIV2O2 core. In contrast, reactions in the presence of 2-(hydroxymethyl)pyridine (hmpH) yielded the MnIII4CeIII2 cluster [Mn4Ce2O2(ButCO2)5(NO3)5(hmp)4] (4), with an unprecedented [Mn4Ce2(μ4-O)2] core, and a homometallic, butterfly-like MnIII4 cluster [Mn4O2(ButCO2)6(pic)2(H2O)2] (5), in which oxidation of hmp− to picolinate (pic−) has occurred. Variable-temperature, dc and ac measurements were performed on polycrystalline samples of 1–5. Fitting of the obtained magnetization (M) versus field (H) and temperature (T) data by matrix diagonalization, and including only axial anisotropy (zero-field splitting, ZFS), gave a ground state spin of S = 5 for 1·2DMF. The magnetic susceptibility data for 2·2Et2O and 3 up to 300 K were fit and revealed very weak ferromagnetic interactions between the MnIII ions; J =  +0.5(2) cm−1 for 2·2Et2O, and J =  +0.3(1) cm−1 for 3. Complexes 4·3MeCN and 5·2ButCO2H have S = 0 ground states.

The MnII/CeIII or CeIV/pivalate reaction system in the presence or absence of N,N′- or N,O-chelates has yielded four MnxCey clusters, some of which are new structural types in Mn/Ce coordination chemistry, and a MnIII4 cluster. The magnetic properties of all the compounds have been studied.Figure optionsDownload as PowerPoint slide