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A study on the reactions of organic azide with transition metal complexes is presented. Experiments are carried out, which reveal that addition of azides to defined chemicals produce a tetra-azazirconacycle complex.

A new redox-active, tris(amido) ligand platform, bis(2-isopropylamino-4-methoxyphenylamine), is prepared and used in the preparation of tantalum(V) complexes. The ligand is prepared in its protonated form by using a three-step procedure from commercially available 4-methoxy-2-nitroaniline and 1-iodo-4-methoxy-2-nitrobenzene.

The study of the oxidative reactivity of zirconium(IV) complexes with redox-active [pda.sup.2-] ligands (where [pda.sup.2-] = N,N-bis(neo-pentyl-ortho-phenylenediamide) is reported. This halogen oxidative-addition reaction provides access to new zirconium(IV) complexes with two [disq.sup.-] ligands.

A new type of catalyst is described for the two-electron disproportionation of diphenylhydrazine to azobenzene and aniline. The electrophilic properties of the zirconium center coupled with the redox properties of the ligand have enabled catalytic turnover in the system.

A series of six-coordinate zirconium(IV) dianions are synthesized by treating the neutral zirconium complex with either 2 equi of LiX or by reaction of ap[Li.sub.2] and LiX with Zr[Cl.sub.4]. The complexes are recovered as lithium-etherate salts and studied by nuclear magnetic resonance (NMR) spectroscopy and single-crystal X-ray diffraction.

The reaction of the redox-active ligand 2,4-di-tert-butyl-6-tert-butylamidophenolate (ap) with ZrCl4(THF)(sub 2) affords the new complex Zr(super IV)(ap)(sub 2)(THF)(sub 2), also called zirconium(IV), and its exposure to chlorine gas results in swift chlorine addition at the zirconium metal center via one-electron oxidation of each ap ligand. The diradical product, Zr(super IV)Cl(sub 2)(isq)(sub 2) (isq = 2,4-di-tert-butyl-6-tert-butyliminosequinone), is characterized.

The new complex, [Zr(pda)2]n (1, pda2- = N,N′-bis(neo-pentyl)-ortho-phenylenediamide, n = 1 or 2), prepared by the reaction of 2 equiv of pdaLi2 with ZrCl4, reacts rapidly with halogen oxidants to afford the new product ZrX2(disq)2 (3, X = Cl, Br, I; disq- = N,N′-bis(neo-pentyl)-ortho-diiminosemiquinonate) in which each redox-active ligand has been oxidized by one electron. The oxidation products 3a-c have been structurally characterized and display an unusual parallel stacked arrangement of the disq- ligands in the solid state, with a separation of ~3 Å. Density functional calculations show a bonding-type interaction between the SOMOs of the disq- ligands to form a unique HOMO while the antibonding linear combination forms a unique LUMO. This orbital configuration leads to a closed-shell-singlet ground-state electron configuration (S = 0). Temperature-dependent magnetism measurements indicate a low-lying triplet excited state at ~750 cm-1. In solution, 3a-c show strong disq-based absorption bands that are invariant across the halide series. Taken together these spectroscopic measurements provide experimental values for the one- and two-electron energies that characterize the π-stacked bonding interaction between the two disq- ligands. [ABSTRACT FROM AUTHOR]