The reactivity of europium in liquid ammonia with 2,6-disubstituted phenols has been surveyed and the effect of the 2,6 substituents on the bridging ability of the aryloxides has been examined. Monomeric and tetrameric complexes of Eu II have been isolated with tert-butyl and isopropyl substituents, Eu(OC 6) 2 (µ 3 -OH) 2 (NCMe) 6 2, respectively, which can be compared to the previously reported bimetallic complex, (dme) 2 Eu(µ-OC 6 H 3 Me 2 -2,6) 3 Eu(OC 6 H 3 Me 2 -2,6)(dme) 3, isolated with methyl substituents (dme = 1,2-dimethoxyethane). Acetonitrile has been found to be an excellent solvating ligand for the formation of crystalline complexes in this series. Complex 1 crystallizes from acetonitrile in the monoclinic space group P2 1 /c with a = 11.7117( 14), b = 17.616(2), c = 18.263(2) Å, β = 91.318(8)Њ, U = 3766.8(7) Å 3 and D c = 1.282 Mg m Ϫ3 for Z = 4. Complex 2 crystallizes from acetonitrile in the monoclinic space group P2 1 /n with a = 13.676(3), b = 20.325(4), c = 32.632(6) Å, β = 91.068(12)Њ, U = 9069(3) Å 3 and D c = 1.429 Mg m Ϫ3 for Z = 4.

The europium and ytterbium complexes of formula [(C5Me5)Ln]2(μ-η8:η8-C8H8) have been synthesized and structurally characterized to determine the dependence of the (ring centroid)−metal−(ring centroid) angles on the size and electron configuration of the metal. YbI2(THF)2 reacts with KC5Me5 and K2C8H8 in THF to form [(C5Me5)Yb(THF)]2(μ-η8:η8-C8H8), 1, in 80% yield. 1 can be readily desolvated at 30 °C and 10-7 Torr to afford [(C5Me5)Yb]2(μ-η8:η8-C8H8), 2, in 80% yield. 2 crystallizes from toluene and consists of two divalent [(C5Me5)Yb]+ moieties bridged by a (C8H8)2- unit with 159° and 161° (C5Me5 ring centroid)−Yb−(C8H8 ring centroid) angles. [(C5Me5)Eu(THF)2]2(μ-η8:η8-C8H8), 3, can be desolvated at 55 °C and 10-7 Torr to afford [(C5Me5)Eu]2(μ-η8:η8-C8H8), 4, in 90% yield. 4 crystallizes with a molecule of toluene and has 149.3° and 148.9° (C5Me5 centroid)−Eu−(C8H8 centroid) angles. Complex 2 reacts with 1,3,5,7-cyclooctatetraene to form (C5Me5)Yb(C8H8), 5.

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. Hx[Eu8O6(OC6H3Me2-2,6)12(OiPr)8], 1, and H5[Eu5O5(OC6H3iPr2-2,6)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-propanol) 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(OiPr)2(THF)x]n, 3. Complex 3 reacts with 2,6-dimethylphenol to form the arene-insoluble complex (H[Eu(OC6H3Me2)2(OiPr)])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 HOiPr at ambient conditions in the glovebox, crystals of 5 slowly convert to the mixed valent H10[Eu8O8(OC6H3Me2-2,6)10(OiPr)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 H18([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.

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Europium reacts with 2-methoxyethanol at room temperature to form arene-soluble [Eu(OCH2CH2OMe)2] n , 1. Reaction of 1 with 2,6-dimethylphenol or 2,6-diisopropylphenol forms the tetrametallic complexes {[Eu(μ3-η2-OCH2CH2OMe)(η2-OCH2CH2OMe)(OC6H3R2-2,6)-][H+]}4 (R = Me, 2; R = i Pr, 3). Magnetic measurements of 1−3 in solution are consistent with the presence of divalent europium. 2 and 3 are isostructural and contain a tetrahedral arrangement of europium atoms. Coordinated to each seven-coordinate metal are one terminal bidentate alkoxide, one bridging bidentate alkoxide, which bridges through its alkoxide oxygen to two other europium atoms, a terminal aryloxide, and two bridging oxygen atoms from other such units. The presence of protons in 2 was probed by reaction with Al2Me6, which forms hexametallic [Me3Al(μ-η2-OCH2CH2OMe)Eu(μ-η2-OCH2CH2OMe)2AlMe2]2, 4. Each six-coordinate europium in 4 is surrounded by three bidentate 2-methoxyethoxide ligands, which bridge via their alkoxide oxygen atoms. One ligand bridges to one AlMe3 unit, and the other two ligands bridge to AlMe2 units.