High-Energy Ball-Milling of Alloys and Compounds

Hyperfine Interactions - After outlining some characteristics of high-energy ball-milling, we discuss selected examples of phase transformation and of alloy synthesis which focus on deviations from...     

Catalytic reactivity of a zirconium(IV) redox-active ligand complex with 1,2-diphenylhydrazine

Two-electron reactivity of [N2O2red]ZrL3 (1a, N2O2(red) = N,N'-bis(3,5-di-tert-butyl-2-phenoxy)-1,2-phenylenediamide, L = THF) was explored with halogens and 1,2-diphenylhydrazine. Despite a formal d0 zirconium(IV) metal center, halogen oxidative addition occurred to form [N2O2(ox)]ZrCl2(THF) (2) with two-electron oxidation of the ligand. This ligand redox activity allows catalytic reactivity with 1,2-diphenylhydrazine resulting in disproportionation to form aniline and azobenzene via a putative zirconium-imide intermediate.     

The crystal structures of (p-ClPh)3PO and (p-OMePh)3PO, including an analysis of the P-O bond in triarylphosphine oxides

The crystal structures of the compounds tris(para-chlorophenyl)phosphine oxide {(p-ClPh)₃PO} and tris(para-methoxyphenyl)phosphine oxide {(p-OMePh)₃PO} were determined by X-ray diffraction methods. (p-ClPh)₃PO crystallizes in the space group P-1 (no. 2) with a = 11.828(2), b = 12.645(2), c = 14.072(2) Å, = 97.90(1), = 109.45(1), = 115.43(1), V = 1692.3(2) ų and Z = 4. The mean O–P and C–P distances are 1.481(6) and 1.806(2) Å, respectively, and the mean C–P–C angle is 106.5(1.1). (p-OMePh)₃PO crystallizes in the space group P2₁/c (no. 14) with a = 18.8642 (10), b = 10.3999(5), c = 21.3462(16) Å, = 115.414(6)°, V= 3782.6(4) ų, and Z = 8. The mean O–P and C–P distances are 1.484(5) and 1.798(4) Å, respectively, and the mean C–P–C angle is 106.5(1.0). These two structures were analyzed along with the previously determined structures of triphenylphosphine oxide {Ph₃PO} and tri-p-tolylphosphine oxide {(p-MePh)₃PO}, and IR data were collected on all four compounds. Both the observed P–O distances and the IR stretching frequencies for these triarylphosphine oxides support the interpretation of the P–O bond as having substantial multiple-bond character, with a bond order between 1.7 and 1.8. The para-substituents on these triarylphosphines were shown to have a statistically insignificant effect on the P–O bond.     

Varying the Lewis base coordination of the Y2N2 core in the reduced dinitrogen complexes {[(Me3Si)2N]2(L)Y}2(μ-η2:η2-N2) (L = benzonitrile, pyridines, triphenylphosphine oxide, and trimethylamine N-oxide)

The effect of the neutral donor ligand, L, on the Ln(2)N(2) core in the (N═N)(2-) complexes, [A(2)(L)Ln](2)(μ-η(2):η(2)-N(2)) (Ln = Sc, Y, lanthanide; A = monoanion; L = neutral ligand), is unknown since all of the crystallographically characterized examples were obtained with L = tetrahydrofuran (THF). To explore variation in L, displacement reactions between {[(Me(3)Si)(2)N](2)(THF)Y}(2)(μ-η(2):η(2)-N(2)), 1, and benzonitrile, pyridine (py), 4-dimethylaminopyridine (DMAP), triphenylphosphine oxide, and trimethylamine N-oxide were investigated. THF is displaced by all of these ligands to form {[(Me(3)Si)(2)N](2)(L)Y}(2)(μ-η(2):η(2)-N(2)) complexes (L = PhCN, 2; py, 3; DMAP, 4; Ph(3)PO, 5; Me(3)NO, 6) that were fully characterized by analytical, spectroscopic, density functional theory, and X-ray crystallographic methods. The crystal structures of the Y(2)N(2) cores in 2-5 are similar to that in 1 with N-N bond distances between 1.255(3) ? and 1.274(3) ?, but X-ray analysis of the N-N distance in 6 shows it to be shorter: 1.198(3) ?.