Zinc complexes acetate

Zeise s salt, 353, 403 Zinc, 925-1022 metallocnzymcs, 1001, 1002 biomimetic modelling, 1021 X-ray crystallography, 1002 zinc-carbonyl mechanism, 1003 zinc-hydroxide mechanism. 1003 Zinc complexes acetate, 969 alcohols, 964 amides, 944 amine oxides, 964 amines, 933 amino acids, 938... 

Many carbamates have been used as protective groups. They are arranged in this chapter in order of increasing complexity of stmcture. The most useful compounds do not necessarily have the simplest stmctures, but are /-butyl (BOC), readily cleaved by acidic hydrolysis benzyl (Cbz or Z), cleaved by catalytic hy-drogenolysis 2,4-dichlorobenzyl, stable to the acid-catalyzed hydrolysis of benzyl and /-butyl carbamates 2-(biphenylyl)isopropyl, cleaved more easily than /-butyl carbamate by dilute acetic acid 9-fluorenylmethyl, cleaved by /3-elimination with base isonicotinyl, cleaved by reduction with zinc in acetic acid 1-adamantyl, readily cleaved by trifluoroacetic acid and ally], readily cleaved by Pd-catalyzed isomerisation. 

The zinc complex formed with V,V -diphenylformamidinate is structurally analogous to the basic zinc acetate structure, as [Zn4(/i4-0)L6], and the basic beryllium acetate structure. It is prepared by hydrolysis of zinc bis(diphenylformamidinate).184 Mixed metal zinc lithium species were assembled from dimethyl zinc, t-butyl lithium, V.iV -diphenylbenzamidine and molecular oxygen. The amidinate compounds formed are dependent on the solvent and conditions. Zn2Li2 and... 

Di-t-butyl phosphate complexes of zinc were synthesized as precursors for ceramic material formation. A tetrameric zinc complex was characterized from the treatment of zinc acetate with the phosphate resulting in a compound with a bridging oxo at the center, [Zn4(/i4-0)(di-t-butyl phosphate)6]. In the presence of auxiliary donor ligands such as imidazole or ethylenediamine, monomeric complexes are formed, [Zn(di-t-butyl phosphate)2(imidazole)4]. It is also possible to convert the tetramer into the monomer by treating with a large excess of imidazole.41... 

Bimetallic zinc complexes formed with hexaazamacrocycles were studied in the hydrolysis of activated carboxyesters. Potentiometric titration demonstrated the dominant presence of a dinuclear hydroxo bridged species at pH >7. /)-Nitrophenyl acetate is hydrolyzed with no loss of catalytic activity for at least 2.7 catalytic cycles 4... 

Phosphate ester crystal structures have been determined of zinc 1,5,9-triazacyclononane including an interesting structure containing an oligophosphate bridged zinc unit.450 The zinc complex of 1,5,9-triazacyclododecane was studied as a hydrolysis catalyst for substituted phenyl acetates.451 Kinetic analysis suggested that hydrolysis occurs by a mechanism involving hydroxide attack of a metal-bound carbonyl. 

A tridentate N02 donor set complex was formed from 2-pyridinecarboxaldehyde N-oxide and 2-aminophenol and gave mononuclear and trinuclear compounds. The trinuclear zinc complex was structurally characterized and revealed bridging acetate groups, [ZnLZn(OAc)4ZnL].865... 

Diiminatc zinc complexes are highly active catalysts in the copolymerization of epoxides and C02. Complexes that are catalytic are of the form ZnLX, where X is alkoxide, acetate, or bis(tri-methylsilyl)amide. Changing the ligand geometries of the complexes allows variation in the catalytic behavior and activity.941 The polymerization of lactide with diiminate zinc has also been studied.942... 

It was shown that 2,5-bis(phenoxy)-3,3aA4,4-trithia-l,6-diazapentalene 182 reacts with , v-diami nopolyether nucleophiles 183 in a 1 1 molar ratio to form novel pentaleno crown ethers 184 (see Scheme 21 and Table 24) <1997AG(E)1648>. Macrocycles 184 were readily reduced by treatment with zinc in acetic acid to form the corresponding thioureas 185. The reoxidation is quantitative in the presence of atmospheric oxygen. The complex formation of the starting pentalene 182 and the new crown ether compounds 184 and 185 was investigated (see Section 12.11.7.2). 

On treating diisobutene with acetic anhydride and anhydrous zinc chloride, A. C. Byrns and T. F. Doumani had isolated in 1943 a crystalline compound to which they had ascribed the structure of a zinc complex with a 1,3-diketone 40 the correct pyrylium chlorozincate structure was established by A. T. Balaban et al.41 in 1961, after extended investigation on the formation of pyrylium salts by alkene diacylation.42 This formation again had remained undetected for many decades during which alkenes had been acylated but only the water-insoluble monoacylation products had been investigated, whereas the water-soluble pyrylium salts went into the sink with the Lewis or Bronsted acid catalysts that had been used in the acylation. 

Insulin suspensions. When the hormone is injected as a suspension of insulin-containing particles, its dissolution and release in subcutaneous tissue are retarded (rapid, intermediate, and slow insulins). Suitable particles can be obtained by precipitation of apolar, poorly water-soluble complexes consisting of anionic insulin and cationic partners, e.g the polycationic protein protamine or the compound aminoqui-nuride (Surfen). In the presence of zinc and acetate ions, insulin crystallizes crystal size determines the rate of dissolution. Intermediate insulin preparations (NPH or isophane, lente or zinc insulin) act for 18 to 26 h, slow preparations (protamine zinc insulin, ultralente or extended zinc insulin) for up to 36 h. 

Under conventional dechlorination conditions (20 equiv of zinc dust, acetic acid, 25°C or 50°C) the reduction of 4,4-dichlorocyclobutenones affords complex mixtures of products which include the desired cyclobutenones as well as significant amounts of partially reduced byproducts. He have found that the desired transformation can be accomplished cleanly provided that the reduction is carried out at room temperature in alcoholic solvents (preferably ethanol) in the presence of 5 equiv each of acetic acid and a tertiary amine (preferably tetramethylethylenediamine). Zinc dust has proven to be somewhat superior to zinc-copper couple for this reduction. The desired cyclobutenones are obtained in somewhat higher yield using this procedure as compared to the related conditions reported by Dreiding [Zn(Cu), 4 1 AcOH-pyridine, 50-60 C] for the same transformation. ... 

The reaction involves the catalyst-substrate complex (158). Molecular models show that in the mixed ligand complex (158), the N—O- group is in a position to attack the acetyl group of (157). The zinc complex (156) is also an excellent catalyst for the hydrolysis of p-nitrophenyl acetate in fact it is comparable in reactivity to hydroxide ion, although its p.Ka is only 6.5, (Table 29). 

Mukaiyama s group also reported the catalytic asymmetric aldol reaction of ketene silyl acetals (28) promoted by chiral zinc complexes. These complexes are prepared in situ from... 

Zn2+ correlate can be obtained, as pyridinium salt, by reaction of corrole with zinc acetate in pyridine [25] in a procedure similar to that reported for the preparation of nickel and palladium complexes of corrole [11]. The zinc derivative is not paramagnetic and its formulation has been made on the basis of its proton NMR spectrum. Attempts to isolate the neutral zinc complex have been unsuccessful. 

In 1982, Krautler and Hilpert reported on the preparation of (D-didehydrocorrinate)(dicyano)Co(III) by non-oxidative photocyclization of 19-cyanosecocorrin (Fig. 24a (R = = CH2, R = R" = CN) to the corresponding 1-methyl-19-cyanocorrinate Cd2+ [73]. Demetallation, subsequent insertion of cobalt and careful thermal elimination of the 19-cyano group affords the didehydrocorrinato cobalt complex as illustrated in Fig. 25. The complex has been converted into the corresponding corrinate by treatment with zinc in acetic acid. 

The zinc organo-lialide is prepared for use by heating together the zinc-copper couple, the alkyl or aiyl halide, ethyl acetate, and toluene for about an hour, the reaction being started if necessary with a ciystal of iodine. All the reagents must be well dried, and the colomdess viscous liquid which results is ntilised by adding to it the acid chloride dissolved in toluene, and when the required amount has been added the intermediate zinc complex is decomposed by the addition of dilute sulphuric acid.1... 

Ethanol was used, for example, in preparation of zinc complex of 2-hydroxy-1-(N-phenylaminomethyl) 673 [246] and copper complexes of hydrazoneimines of the type 674 [247], whose structures were determined by x-ray diffraction. The complexes of salicylidenthiocarbonylhydrazones of the type 675-677 were synthesized in the same solvent [248]. The complexes 675 are formed from metal acetates [Cu(II)], 676 from nitrates [Ni(II)], and 677 from chlorides [Fe(III)] ... 

In a difference from above, the nickel and copper ICC 874 (X = O) with coordination unit MN202 evidently have tetrahedral structure, which is also characteristic for analogous cobalt and zinc complexes [169], as proved for a zinc complex by x-ray diffraction. In this respect we note a nonstandard behavior of manganese. As a result of the interaction of the ligand 873 (X = 0, R = H, N02 Ar = C6H4R, R =H, OMe, N02) and the acetate of the metal in methanol, together with an expected ICC of type 874 (X = O, M = Mn) [17], tetrameric cluster structures are formed (4.46) [171] ... 

Following the detailed mechanistic study using BDI zinc complexes, Coates subsequently reported a dinucleating BDI ligand the p-oxo-5-diimine (BODDI) ligands (Fig. 20) [149]. The reaction of the corresponding dinuclear zinc ethyl complexes with acetic acid afforded zinc acetate systems (with a Zn-Zn distance of 3 A), but no catalytic activity was reported. 

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