RESUMEN
By reacting 1,2-diketones and ortho- diphenylphosphinoyl aniline in the presence of zinc(ii) as a templating agent, cationic zinc(ii) complexes of novel phosphine oxide functionalized 1,4-diaza-1,3-butadiene ligands are acessible. Herein the zinc(ii) site is bound to all four donor atoms of the ligand. Depending on the flexibility of the 1,4-diaza-1,3-butadiene backbone, the bonds to zinc(ii) from the 1,4-diaza-1,3-butadiene donors can be broken. Reaction with oxalate cleaves the zinc(ii) coordination completely and makes accessible the free ligands possessing orthogonal (N,N: soft; O,O: hard) sets of donor sites. This allows for the specific coordination of soft and hard Lewis acids and thus for the generation of heterobimetallic complexes, here exemplarily shown for the combination of palladium(ii) (soft) and zinc(ii) (hard) centres.
RESUMEN
The preparation, molecular structures and physical properties of novel heavy group 13 metal formazanido complexes are described. The trimethyl derivatives MMe3 (M = Al, Ga, In) react with 1,3,5-triphenylformazan (Htpf) in a 1 : 1 ratio to give methane and metallacycles of the type [M(tpf)Me2]. While [Al(tpf)Me2] and [Ga(tpf)Me2] are mononuclear compounds with six-membered rings and coordination number 4 in solution and in the crystalline state, indium derivative [In(tpf)Me2] forms oligomers in non-coordinating solvents according to NMR studies, these are probably N-bridged dimers with coordination number 5 at indium. The oligomer is cleaved by addition of one equivalent of pyridine or 4-dimethylaminopyridine (DMAP). The complexes [M(tpf)Me2] (M = Al, Ga) and [In(tpf)Me2(DMAP)] are characterized by XRD analyses. They are unique examples of main group metal formazane ring systems of the third and higher periods. The UV-Vis solution spectra of the neutral ligand Htpf and its metallated compounds [M(tpf)Me2] (M = Al, Ga, In) are discussed.
RESUMEN
The activity of microsomal NADPH-cytochrome-P-450-reductase and NADH-cytochrome-b5-reductase are inhibited after the addition of an aqueous extract of a pharmaceutical preparation of garlic (Allium sativum, L.) to buffer-suspended microsomes. Incubation of garlic extract with isolated pig liver microsomes also decreases the activity of cytochrome P-450-dependent ethoxycoumarin deethylation. As measured by malondialdehyde release, the effects on the enzyme system are evidently not due to lipid peroxidation. No loss of cytochrome P-450 pigment is observed. Moreover, it could be shown that addition of garlic extract displays no protective effect on microsomal lipids when oxidation occurs spontaneously or is enforced by short-wave UV-irradiation. The above findings were reproduced after applying a HPLC-purified preparation of alliin to the incubation mixtures, suggesting that alliin is the active principle for the inhibitory effects observed in vitro.