Zinc complexes amides

IR and Raman spectroscopy have been commonly used and, for example, the effects of pressure on the Raman spectrum of a zinc compound with a N2C12 coordination sphere around the metal, have been investigated.28 IR spectroscopy has been utilized in studies of the hydration of zinc in aqueous solution and in the hydrated perchlorate salt.29 Gas phase chemistry of zinc complexes has been studied with some gas phase electron diffraction structures including amide and dithiocarbamate compounds.30-32... 

The zinc complexes with diphenyl-2-pyridylmethane, ZnL2Cl2 and ZnL2Br2, have been characterized by IR spectroscopy and conductivity measurements.107 The [(pyridyl)2P(NSi Mc3)2] ligand forms an aminoiminophosphoranate complex with zinc which structural characterization shows to be four-coordinate bound to two pyridyl and two amide nitrogen donors (3).108... 

The complexes formed from salicylhydroxamic acid and acetylsalicylhydroxamic acid (104) with zinc show loss of one ligand proton and loss of two ligand protons respectively. The zinc complex of the acetyl derivative appears to show coordination via the deprotonated amide and phenolate oxygen of the ligand. IR studies are presented.849... 

The zinc complex of a tripodal N2S20 pentadentate ligand undergoes amide alcoholysis of a coordinated amide group.893 Examples of amide hydrolysis are known for other ligand systems.894... 

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... 

There are several other examples of zinc complexes that are closely related to amides but not within the scope of this survey. These include derivatives of diaminocyclophospha-... 

Insertion of carbodiimides into Zi -C bonds is also observed. Also, zinc bis-amides react with one equivalent of carbodiimide to give a zinc guanidate complex. ... 

As was seen in the CD competition study (Section 3.4) copper displaced zinc from patellamide C and when a mixture of the two metals was added only copper species were formed. When copper was added to a solution containing predominantly the two zinc complex [PatCfij + Zn2Cl3] at m/z 995 formed by adding a large excess of zinc, this was displaced and the two copper complex [PatCHa + Cu2Cl2] at m/z 957 became the dominant species present. A further competition experiment was carried out with copper bound patellamide C in the presence of acid. The solution of copper and patellamide C was diluted with 2% formic acid and then introduced into the mass spectrometer. No copper species of any kind were detected because the amide NH s were fully protonated at low pH so no binding to Cu was possible. 

As with amide hydrolysis reactions, extensive mechanistic studies of metal-mediated phosphate monoester hydrolysis reactions have been performed using exchange inert mononuclear Co(III) complexes.9,188-202 To date, only a few zinc complexes that promote phosphate monoester hydrolysis have been reported. A binuclear zinc complex supported by a macrocyclic cryptate ligand (Fig. 36)... 

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... 

Model studies of carboxypeptidase A are limited. It is found that some zinc complexes can hydrolyze the carboxylic ester, however, there is no suitable functional model that demonstrates the hydrolysis of normal carbox-amide by [Zn—OH]" species. 

Rapid amide hydrolysis by copper and zinc complexes of a ligand which mimics the carboxypeptidase active site (7) has been observed. The metal is held perpendicular to the amide plane, and at pH 7.6 and 50 °C hydrolysis occurs 2 X 10 times faster in the presence of zinc than in its absence. Copper is a more potent catalyst. A metal-dependent pliTa ( 8.5 for Zn and 7.6 for Cu +) is consistent with a mechanism in which the amide carbonyl is attacked by a co-ordinated hydroxyl nucleophile. A more sophisticated model with a [20]paracylcophane which has a nucleophilic and a metal binding site attached (8) catalyses the hydrolysis of p-nitrophenyl hexadecanoate. The mechanism... 

The trigonal planar zinc phenoxide complex [K(THF)6][Zn(0-2,6-tBu2C6H3)3] is formed by the reaction of a zinc amide complex, via a bis phenoxide, which is then further reacted with potassium phenoxide. TheoX-ray structure shows a nearly perfect planar arrangement of the three ligands with zinc only 0.04 A out of the least squares plane defined by the three oxygen atoms.15 Unlike the bisphenoxide complexes of zinc with coordinated THF molecules, these complexes are not cataly-tically active in the copolymerization of epoxides with C02. The bisphenoxide complex has also been structurally characterized and shown to be an effective polymerization catalyst. 43... 

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