A new pyrazolylborate zinc hydroxide complex capable of cleaving esters, amides and phosphates

Ruf, Michael; Weis, K. H.; Vahrenkamp, Heinrich

doi:10.1039/c39940000135

Cited by 54 publications

(41 citation statements)

References 8 publications

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“…Our results for the second-order rate constants are in agreement with tertiary amines generating more nucleophilic LZnϪOH species than secondary amines due to the hydrophobicity of the former, [30] which precludes charge delocalisation among solvated species. When comparing complexes 5 and 7, both with tertiary amines, at a given pH it is found that 5 has higher k NA values than 7 even though the latter has four more methylenic groups.…”

Section: Hydrolytic Activitysupporting

confidence: 80%

Synthesis, Structure and Hydrolytic Properties of a Family of New Zn Complexes Containing Hexaazamacrocyclic Ligands

et al. 2004

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The synthesis, structure and spectroscopic properties of a family of Zn complexes containing a dinucleating hexaazamacrocyclic ligand (L) and anionic ligands (X) of general for-n+ (1−8; L = H2p, H3p, Me2p, Me2m, Me3p, Me3m; X = Cl, n = 0; X = NO 3 , n = 2) have been investigated. The solid-state structural characterisation has been performed by means of X-ray diffraction analysis for complexes 3, 5, 7·1/3CH 2 Cl 2 and 8. The Zn complexes 5, 7·1/ 3CH 2 Cl 2 and 8 containing chloride ligands present a distorted N 2 Cl 2 tetrahedral coordination with two non-coordinated N atoms of the macrocyclic ligand. On the other hand, complex 3, which contains nitrate ligands, displays an N 3 O 2 pentacoordination with all the N atoms of the macrocyclic

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Section: Hydrolytic Activitysupporting

confidence: 80%

Synthesis, Structure and Hydrolytic Properties of a Family of New Zn Complexes Containing Hexaazamacrocyclic Ligands

et al. 2004

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“…We believe this ligand has promise since Tp Ar,Me ZnOH complexes have been used as a functional models for hydrolytic enzymes [37,38] and carbonic anhydrase [39] and to elucidate how drugs with inhibitory activity bind to metalloproteins [40]. However, Ttz ligands are much more than just Tp substitutes since they display a propensity for forming extensive hydrogen bonding networks and improved solubility properties in mixtures of water and hydrophilic solvents.…”

Section: Which Has Bond Lengthsmentioning

confidence: 95%

Tris(triazolyl)borate ligands of intermediate steric bulk for the synthesis of biomimetic structures with hydrogen bonding and solubility in hydrophilic solvents

Gardner¹,

Papish²,

Monillas³

et al. 2008

Journal of Inorganic Biochemistry

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“…Materials: The [Tp'ZnÀOH] complexes [16,18,19] were prepared according to the published procedures. Esters and organophosphates were obtained commercially or prepared as cited in ref.…”

Section: Methodsmentioning

confidence: 99%

“…[42,43] We have contributed, to this field, the synthesis of the stable pyrazolylborate ± zinc hydroxide complexes 1 ± 5, [14,16,18,19] experimental proof that the pK a values of the corresponding ZnÀOH 2 complexes are at or below 7, [44] and the hydrolytic reactions of these complexes with CO 2 , [45,46] esters and amides, [47] organophosphates, [48] diphosphates, [49] and sugar phosphates including nucleotide derivatives. [50] In a short communication Kitajima described similar organophosphate cleavages by another [Tp'ZnÀOH] complex.…”

Section: Introductionmentioning

confidence: 99%

Evidence for a Trajectory of Hydrolytic Reactions brought about by [L3Zn−OH] Species

et al. 1999

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A kinetic study has been performed on the hydrolytic cleavage of various triorganophosphates PO-(OR) 2 (OR') by three pyrazolylborate ± zinc hydroxide complexes [Tp'Zn À OH] to form [Tp'Zn À OPO(OR) 2 ] and HOR'. The nature of the reactions (first order both in the zinc complex and the phosphate) and the strongly negative activation entropies (À 54 to À 126 J mol) indicate an intimate association of the ZnÀOH and PO functions in the rate-determining step. Some ester cleavages by [Tp'Zn À OH] show the same kinetic pattern and similar activation parameters. The observations are in accord with a four-center arrangement (ZnOPO or ZnOCO) in the activated complex, that is, the hybrid mechanism discussed for zinc enzyme as well as zinc complex catalyzed hydrolyses. A trajectory for reactions passing through this intermediate has been constructed with the Bürgi ± Dunitz structure correlation method, based on the geometries of 30 [Tp'Zn(X)(Y)] species with truly five-coordinate zinc centers. Its first step is the approach of the substrates oxygen atom to the tetrahedral L 3 ZnÀOH species along the axis of a trigonal bipyramid. In the resulting four-center intermediate with five-coordinate zinc a Berry pseudorotation describes the synchronous formation of the Zn À O-(substrate) and breaking of the ZnÀO-(OH) bonds. The concluding step in the coordination sphere of zinc is the expulsion of the former OH oxygen, now part of the substrate, again along the axis of a trigonal bipyramid. This mechanism, which is applicable to phosphate as well as to ester, amide, and carbon dioxide hydrolysis, is in accord with theoretical models of carbonic anhydrase action.

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A new pyrazolylborate zinc hydroxide complex capable of cleaving esters, amides and phosphates

Cited by 54 publications

References 8 publications

Synthesis, Structure and Hydrolytic Properties of a Family of New Zn Complexes Containing Hexaazamacrocyclic Ligands

Synthesis, Structure and Hydrolytic Properties of a Family of New Zn Complexes Containing Hexaazamacrocyclic Ligands

Tris(triazolyl)borate ligands of intermediate steric bulk for the synthesis of biomimetic structures with hydrogen bonding and solubility in hydrophilic solvents

Evidence for a Trajectory of Hydrolytic Reactions brought about by [L3Zn−OH] Species

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