Transition metal coordination chemistry ofN,N-bis(2-{pyrid-2-ylethyl})hydroxylamine.

Although directly relevant to metal mediated biological nitrification as well as the coordination chemistry of peroxide, the metal complexes of hydroxylamines and their functionalized variants remain largely unexplored. The chelating hydroxylamine ligand N,N-bis(2-{pyrid-2-ylethyl})hydroxylamine can be readily generated via a solvent free reaction in high purity; however, the ligand is prone to decomposition which can hamper metal reaction. N,N-bis(2-{pyrid-2-ylethyl})hydroxylamine forms stable complexes with chromium(III), manganese(II), nickel(II), and cadmium(II) ions, coordinating in a side-on mode in the case of chromium and via the nitrogen in the case of the latter three metal ions. The hydroxylamine ligand can also be reduced to form N,N-bis(2-{pyrid-2-ylethyl})amine upon exposure to a stoichiometric amount of the metal salts cobalt(II) nitrate, vanadium(III) chloride, and iron(II) chloride. In the reaction with cobalt nitrate, the reduced ligand then chelates to the metal to form [N,N-bis(2-{pyrid-2-ylethyl})amine]dinitrocobalt(II). Upon reaction with vanadium(III) chloride and iron(III) chloride, the reduced ligand is isolated as the protonated free base, resulting from a metal-mediated decomposition reaction.

Reactions of the Re(CO)3(H2O)3(+) synthon with monodentate ligands under aqueous conditions.

The reactions of ammonia, pyridine (py), N-methyl imidazole (N-MeIm), tetrahydrothiophene (tht), and piperidine (pip) with Re(CO) 3(H 2O) 3 (+), 1 ( + ), were investigated employing aqueous conditions under atmospheric dioxygen. The reaction of [ 1]Br in aqueous ammonia led to [Re(CO) 3(NH 3) 3]Br ([ 2]Br) as the only product isolated. For the aqueous reactions of [ 1]Br with py, N-MeIm, and tht, mixtures of products are formed because of competition between the bromide and added ligand, even when the ligand is present in excess. Substitution of the PF 6 (-) anion for Br (-) leads to the clean formation of [Re(CO) 3L 3][PF 6] ([ 3][PF 6]-[ 5][PF 6]) for py, N-MeIm, and tht, respectively, as the only products observed. Reaction of [ 1][PF 6] with pip produces the dimeric species, (pip)(CO) 3Re(micro-OH) 2Re(CO) 3(pip), 6. Reactions of [ 1]Br were also performed in methanol for comparison purposes. The reaction with pip in this solvent led to the analogous dimer, (pip)(CO) 3Re(micro-OMe) 2Re(CO) 3(pip), 7; however, reactions with py, N-MeIm, and tht gave Re(CO) 3L 2Br, 8- 10, respectively, as the only products. The crystal structures of compounds [ 2]Br- 10 are reported.

The synthesis and toxicity of tripodal tricarbonyl rhenium complexes as radiopharmaceutical models.

We report the synthesis and toxicity of a series of rhenium(I) tricarbonyl complexes incorporating the trisaminomethylethane (TAME) ligand. Compounds with the (TAME)Re(CO)(3)(+) cation were synthesized via several routes, including by use of Re(CO)(5)X precursors as well as the aqueous cation Re(CO)(3)(H(2)O)(3)(+). Salts of the formula [(TAME)Re(CO)(3)]X where X=Br(-), Cl(-), NO(3)(-), PF(6)(-) and ClO(4)(-) were evaluated using two cell lines: the monoclonal S3 HeLa line and a vascular smooth muscle cell line harvested from mice. All compounds have isostructural cations and differ only in the identity of the non-coordinating anion. None of the complexes exhibited any appreciable toxicity in the HeLa line up to the solubility limit. In the vascular smooth muscle cell line, the bromide salt exhibited some cytotoxicity, but this observation most likely results from the presence of bromide anion, which has been shown to have limited toxicity.

C-H bond activation and ring oxidation in nickel carbahemiporphyrazines.

The first nickel complexes of two carbon-substituted phthalocyanine analogues are reported; both exhibit direct Ni-C bonding and oxygen activation chemistry is observed.

Rhenium(I) compounds bound by tripodal ligands of pyridine and N-methylimidazole.

The reaction of Re(CO)(5)Br with tris(2-pyridyl)methanol (tpmOH) leads to unexpectedly complex chemistry with three new compounds forming instead of a single product. In compound 1, the tpmOH ligand binds to the metal in the N,N',N''-mode; 2 has tpmO(-) bound in the N,N',O-mode; while 3 is a dimer with the tpmO(-) ligand utilizing each of the four donor atoms to bridge the two metal centers. The analogous methyl ether ligands, tris(2-pyridyl)methoxymethane (tpmOMe) or tris[2-(l-methylimidazolyl)]methoxymethane (timmOMe), each yielded a single product, 4 and 5, respectively, bound in the N,N',N''-mode, and are new leads for potential radiotherapeutic agents. All compounds have been structurally characterized.