Jennifer D. Draper

Crystal structures of aryloxide complexes of zinc embracing sodium aryl group interactions: Na[Zn(2,6-diphenylphenoxide)3(H2O)] and Na[Zn2(2,6-diisopropylphenoxide)4Cl]·3THF

The addition of Na(2,6-diphenylphenoxide) to a diethyl ether solution of the monomeric Zn(2,6-diphenylphenoxide)2(THF)2 derivative affords the trisphenoxide complex, Na[Zn(2,6-diphenylphenoxide)3(H2O)] (1). An X-ray crystal structure analysis of 1 reveals the zinc to possess a distorted tetrahedral geometry and that the sodium counterion is essentially six-coordinate, being bound to the three oxygen atoms of the aryloxide ligands and the aromatic carbon atoms of one of the phenyl substituent on each of these ligands. An additional zinc phenoxide complex, Na[Zn2(2,6-diisopropylphenoxide)4Cl]·3THF (2), was obtained during the synthesis of Zn(2,6-diisopropylphenoxide)2(THF)2 in the presence of NaCl. The X-ray structure of 2 again shows the sodium ion to be six-coordinate, involved in an η6-interaction with the phenoxide π-system and bound to two THF ligands and a chloride ion.

The propensity of alkoxide and aryloxide derivatives of tungsten carbonyls to aggregate in solution. Synthesis and X-ray structures of dinuclear, trinuclear and tetranuclear complexes derived from the MeOW(CO)5− anion

Abstract The complex [Et4N][W(CO)5OMe] (1) has been prepared from the reaction of the photochemically generated W(CO)5THF adduct and [Et4N][OH] in methanol. Complex 1 was shown to undergo rapid CO dissociation in THF to quantitatively provide the dimeric dianion, [W(CO)4OMe]22−. The resulting THF insoluble salt [Et4N]2[W(CO)4OMe]2 (2) has been structurally characterized by X-ray crystallography, with the doubly bridging methoxide ligands being in an anti configuration. Complex 2 was found to subsequently react with excess methoxide ligand in a THF slurry to afford the face-sharing octahedron complex [Et4N]3[W2(CO)6(OMe)3] (3) which contains three doubly bridging methoxide groups. In the absence of excess methoxide ligand complex 2 cleanly yields the tetrameric complex [Et4N]4[W(CO)3OMe]4 (4) which has been structurally characterized as a cubane-like arrangement with triply bridging μ3-methoxide groups and W(CO)3 units. Although complex 3 was not characterized in the solid state, the closely related glycolate derivative [Et4N]3[W2(CO)6(OCH2CH2OH)3] (5) was synthesized and its structure determined by X-ray crystallography. The trianions of complex 5 are linked in the crystal lattice by strong intermolecular hydrogen bonds. Crystal data for 2: space group P21/n, a = 7.696(2), b = 22.019(4), c = 9.714(2) A, β = 92.22(3)°, Z = 4, R = 6.43%. Crystal data for 4: space group Fddd, a = 12.433(9), b = 24.01(2), c = 39.29(3) A, Z = 8, R = 8.13%. Crystal data for 5: space group P212121, a = 11.43(2), b = 12.91(1), c = 29.85(6) A, Z = 8, R = 8.29%. Finally, the rate of CO ligand dissociation in the closely related aryloxide derivatives [Et4N][W(CO)5OR] (R = C6H5 and 3,5-F2C6H3) were measured to be 2.15 × 10−2 and 1.31 × 10−3 s−1, respectively, in THF solution at 5°C. Hence, the value of the rate constant of 2.15 × 10−2 s−1 establishes a lower limit for the first-order rate constant for CO loss in the W(CO)5OMe− anion, since the methoxide ligand is a better π-donating group than phenoxide.