Synthesis and structure of sterically overloaded tetra-coordinated yttrium and lanthanum disiloxides

Synthesis and Characterization of Solvated Lanthanide Tris(trimethylsilyl)siloxides

In an effort to develop precursors for the production of lanthanide silicate (LnSiO_x) materials, the reactions of [Ln(NR₂)₃] (R = SiMe₃) with three equivalents of tris(trimethylsilyl)silanol (H-OSi(SiMe₃)₃) or H-SST) in tetrahydrofuran (THF) were undertaken. The products were crystallographically characterized as [Ln(SST)₃(THF)₂] (where Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu). In general, these compounds are similar to the previously reported [Gd(SST)₃(THF)₂] complex, where each metal center of the monomeric species is found to adopt a trigonal bipyramidal (TBP; τ = av 0.95) geometry; however, the crystallographic structure solutions for these crystals invoke a much larger unit cell that reveals the complex disorder of the axial THF ligands. Using incompletely washed H-SST, the tetrahedrally (T-4) bound [Ln(SST)₃(NEt₃)] (Ln-NEt₃ = Pr-NEt₃, Ho-NEt₃; NEt₃ = triethylamine) compounds were isolated from the same reaction run in toluene. Rational syntheses of amine derivatives were realized by performing the same reaction with pure H-SST in toluene containing the appropriate amine and [Ln(NR₂)₃] with the final products identified as [Tm(SST)₃(NEt₃)] (Tm-NEt₃) or [Tm(SST)₃(NHPr₂ⁱ)] (NHPr₂ⁱ = di-iso-propylamine; Tm-NHPr₂ⁱ). The products isolated from reactions undertaken in pyridine (py) were identified as [Ln(SST)₃(py)₂] (Ln-py = Ce-py, Eu-py, and Tm-py). The Ln-py structures exhibit the larger unit cell noted for the THF derivatives with each Ln adopting a TBP (τ = av 0.98) metal center possessing equatorial SST and axial py ligands. The same reaction run in toluene led to the isolation of [(η⁶-tol)Tm(SST)₃] (Tm-tol). Multinuclear NMR (¹H and ²⁹Si) data support the retention of the solid-state structures of all of these compounds in solution. Photoluminescent measurements of Tb, Sm, Dy, and Eu were found to display emission and lifetime profiles in the visible range due to f-f transitions, consistent with trivalent lanthanide metal centers.

Reactivity of the carbodiphosphorane, (Ph3P)2C, towards main group metal alkyl compounds: coordination and cyclometalation

The carbodiphosphorane, (Ph3P)2C, reacts with Me3Al and Me3Ga to afford the adducts, [(Ph3P)2C]AlMe3 and [(Ph3P)2C]GaMe3, which have been structurally characterized by X-ray diffraction. (Ph3P)2C also reacts with Me2Zn and Me2Cd to generate an adduct but the formation is reversible on the NMR time scale. At elevated temperatures, however, elimination of methane and cyclometalation occurs to afford [κ2-Ph3PC{PPh2(C6H4)}]ZnMe and [κ2-Ph3PC{PPh2(C6H4)}]CdMe. Analogous cyclometalated products, [κ2-Ph3P{CPPh2(C6H4)}]ZnN(SiMe3)2 and [κ2-Ph3P{CPPh2(C6H4)}]CdN(SiMe3)2, are also obtained upon reaction of (Ph3P)2C with Zn[N(SiMe3)2]2 and Cd[N(SiMe3)2]2. The magnesium compounds, Me2Mg and {Mg[N(SiMe3)2]2}2, likewise react with (Ph3P)2C to afford cyclometalated derivatives, namely [κ2-Ph3PC{PPh2(C6H4)}]MgN(SiMe3)2 and {[κ2-Ph3PC{PPh2(C6H4)}]MgMe}2. While this reactivity is similar to the zinc system, the magnesium methyl complex is a dimer with bridging methyl groups, whereas the zinc complex is a monomer. The greater tendency of the methyl groups to bridge magnesium centers rather than zinc centers is supported by density functional theory calculations.

Crystal structure of poly[tetraaqua-(μ4-oxalato-κ4 O,O′:O′′,O′′′)-(μ8-benzene-1,2,4,5-tetracarboxylato-κ8 O 1:O 2:O 3:O 4:O 5:O 6:O 7:O 8)yttrium(III)], C6H5O8Y

C6H5O8Y, triclinic, P1̄ (no. 2), a = 6.2090(17) Å, b = 8.573(4) Å, c = 8.863(2) Å, α = 111.018(6)°, β = 109.850(4)°, γ = 91.866(6)°, V = 407.8(2) Å3, Z = 2, R gt(F) = 0.0435, wR ref(F 2) = 0.1332, T = 296(2) K.

Synthesis and structural study of new metallasilsesquioxanes of potassium and uranium

The first metallasilsesquioxanes comprising potassium and uranium have been synthesized and structurally characterized by single-crystal X-ray diffraction.