Reactivity of "Eu(OiPr)2" with phenols:: Formation of linear Eu3, square pyramidal Eu5, cubic Eu8, and capped cubic Eu9 polymetallic europium complexes

The direct reaction of europium with 2-propanol and phenols has been investigated under a variety of conditions. The reaction of europium metal with 2,6-dimethylphenol and 2,6-diisopropylphenol in 2-propanol at reflux revealed that polymetallic europium complexes could be generated by this method. H-x[Eu8O6(OC6H3Me2-2,6)(12)((OPr)-Pr-i)(8)], 1, and H-5[Eu5O5((OC6H3Pr2)-Pr-i-2,6)(6)(NCCH3)(8)], 2, were isolated by recrystallization in the presence of hexanes and acetonitrile, respectively, and characterized by X-ray crystallography. Complex 1 has a cubic arrangement of europium ions with face-bridging mu(4)-O donor atoms, edge-bridging mu-O(phenoxide/phenol) ligands, and terminal O(isopropoxide/2-psopanol) ligands. Complex 2 is mixed valent and has a square pyramidal europium core with four Eu(II) ions at the basal positions and one Eu(III) ion at the apex. Since these reactions gave complicated mixtures of products from which 1 and 2 could only be obtained in low yields, direct reactions under less forcing reaction conditions were investigated. Europium reacts slowly at room temperature to form arene-soluble divalent [Eu((OPr)-Pr-i)(2)(THF)(x)](n), 3. Complex 3 reacts with 2,6-dimethylphenol to form the arene-insoluble complex {H[Eu(OC6H3Me2)(2)((OPr)-Pr-i)]}(n), 4. Recrystallization of 4 in the presence of THF results in the crystallographically characterizable divalent trimetallic complex [Eu(OC6H3Me2-2,6)(2)(THF)(2)](3), 5, which has an unusual linear metal geometry. In the presence of (HOPr)-Pr-i at ambient conditions in the glovebox, crystals of 5 slowly convert to the mixed valent H-10[Eu8O8(OC6H3Me2-2,6)(10)((OPT)-P-i)(2)(THF)(6)], 6, which was found to have a cubic arrangement of europium atoms similar to 1 by X-ray crystallography. Complex 4, upon heating under vacuum, followed by reaction with THF, forms the arene-soluble divalent complex H-18{[Eu9O8(OC6H3Me2-2,6)(10)(THF)(7)][Eu9O9(OC6H3Me2-2,6)(10)(THF)(6)]}, 7, which contains two types of capped cubic arrangements of europium ions in the solid state.