Zinc complexes aniline

A A -coordi nation was found in the zinc complex of 2,2 -dipyridyl diselenide, [ZnLCl2].214 The tridentate ligand 6-(2-aminophenyl)-2,2 -bipyridine contains two pyridyl and one aniline donor ligand to form a complex of the form [ZnL2]2+. The X-ray structure shows a distorted octahedral metal center with each ligand twisting from planar to accommodate the meridional binding.215... 

H NMR studies of the zinc complex formed with the hexadentate aniline functionalized triazacyclononane ligand (70) showed C3 symmetry in solution. It is suggested a six-coordinate complex is formed with all A-donors bound.664 This compares with the benzyl amino derivative,... 

In Figure 2, a series of traces of the NMR spectra of the aromatic protons of aniline in carbon tetrachloride with increasing concentrations of Co(II)trispyrazolylborate is shown. All the lines are shifted to high field with increasing cobalt concentrations. That this eflFect is attributable to the paramagnetic dipolar interactions was demonstrated by carrying out similar experiments with the analogous zinc complex. In the latter case, the shifts are very much smaller (1 or 2 Hz compared with 40 or... 

One of the drawbacks of the Skraup/Doebner-von Miller reaction is the isolation of the desired product from the starting aniline and co-formed alkyl anilines and 1,2,3,4-tetrahydroquinaldine. Isolation can be simplified greatly by addition of one equivalent of zinc chloride at the end of the reaction all of the basic products were precipitated. Washing the brown solids with 2-propanol removed all impurities and left the desired quinoline as a 2 1 complex with zinc chloride in yields of 42-55%. 

The aniline-zinc porphyrin interaction has also been exploited to form dimers. Hunter (60) reported the dimerization of porphyrins functionalized at one meso position with ortho or meta aniline groups (47, 48, Fig. 15). Both compounds showed concentration-dependent H NMR spectra with large upfield shifts for the aniline protons. The dimerization constants are 160 and 1080 M-1 respectively for 47 and 48, and these values are an order of magnitude higher than the association constants of simple reference complexes (K — 10 and 130 M 1 respectively), which is indicative of cooperative self-assembly. The complexa-tion-induced changes in chemical shift were used to obtain three-dimensional structures of the dimers. 

Hunter (60) reported a self-assembled open polymer formed by a zinc porphyrin bearing one para-aniline substituent at the meso position. The ortho- and mela-analogs discussed above form closed dimers, but the geometry of the para-derivative precludes this, and polymerization is the only alternative (76, Fig. 31). Although the dilution experiments could be fitted to a non-cooperative polymerization model with a pairwise association constant (K = 190 M 1) practically identical to that found for simple aniline-zinc porphyrin complexes (K = 130 M 1), broadening of the 4H NMR spectrum at high concentrations is characteristic of oligomerization. 

Ferrocene-containing sulfur ligands have been used in complex formation with zinc. 3-Ferro-cenyl-3-mercaptopropenale and l,l -bis(3-mercaptopropenale)ferrocene (112) form stable complexes as do their Schiff base derivatives with aniline or 1,2-ethylenediamine. The Fen/Fein redox couple shows only minor metal dependence, this is attributed to tetrahedral distortion.884... 

A large variety of aromatic amines react with isatins to give anils (132).169,232,269,305,312,411 413 The imine from isatin and o-hydroxy-aniline forms complexes with copper acetate and zinc iodide.413 Reaction of these anils (132) with phenylhydrazine gives the isatin-3-phenylhydrazone.411 The imine 132 (R = 5-Me, R = H, Ar = p-tolyl)... 

Other suitable catalysts for the carboxymethylation of aromatic amines are zinc or copper carbamates. In 1997 it was patented a process " for the preparation of carbamates Ifom an aromatic amine and DMC in the presence of N,N-substituted carbamate complexes of zinc and copper. Table 6 summarises results reported in some of the patent examples, high selectivity was reported with aniline, while with MDA a considerable amount of N-methyl derivatives was foimd. 

It is often unnecessary to use a condensing agent. Hickinbottom476 prepared monoalkylanilines in about 75% yield by boiling propyl, isopropyl, and butyl bromide for several hours with 2.5-4 times the quantity of aniline to separate the excess of aniline from the resulting mixture of bases, an aqueous solution of zinc chloride is added, for this gives a water-resistant complex only with the primary amine this complex can thus be filtered off after some hour s storage. 

Furthermore, porphyrins react like extremely electron-rich aromatic compounds, comparable to phenol, aniline, or pyrrole. Central metal ions, in particular zinc(II) and copper(II), further activate them in electrophilic substitution reactions, l pical examples of the di- and tetrachlorination, mono- and dinitration, and most important Vilsmeier mono me o-formylation are given (Scheme 6.4.3) (Bonnett and Stephenson, 1965). Vilsmeier formylation of tetraphenylpor-phyrins gives mono (3-formyl products, which have been used to attach side chains to an imidazole end. Five coordinated metal complexes thus become accessible (not shown). 

Aromatic amines form addition compounds and complexes with many inorganic substances, such as zinc chloride, copper chloride, uranium tetrachloride, or boron trifluoride. Various metals react with the amino group to form metal anilides and hydrochloric, sulfuric, or phosphoric acid salts of aniline are important intermediates in the dye industry. 

The aforementioned type of complex was also useful to prepare chiral a-amino phosphonates 46, which are a-amino acid mimics with interesting biological activities (73-93% yield, 81-87% ee) [52]. The same enantioselective Kabachnik-Fields hydrophosphorylation starting with aldehydes 9, dialkyl phosphites 45, and anilines 38 could be performed using chiral imidazolidine-type ligands in combination with a zinc salt (Scheme 11.18) [53]. 

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