Diastereoisomerism and diastereoselectivity in metal complexes

Bernauer, Klaus

doi:10.1007/bfb0050151

Cited by 29 publications

(6 citation statements)

References 112 publications

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“…In fact, this complex is generally considered less stable than Fe-EDDHA and for this reason its use as a soil fertilizer has decreased in recent years. Finally, the increase of the length of the chain linking the two nitrogen (N) atoms is responsible for the lower stability of the Fe-PDDHA complex compared with that of Fe-EDDHA (Bernauer, 1976;Lucena et al, 1996).…”

Section: Stability Of the Chelates: Ligand Competition With Dtpamentioning

confidence: 99%

Synthetic Iron Chelates as Substrates of Root Ferric Chelate Reductase in Green Stressed Cucumber Plants

Lucena

Chaney

2006

Journal of Plant Nutrition

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This work studied the behavior of different iron (Fe)-chelates as substrates of ferric chelate reductase (FCR) and their ability as Fe suppliers for mildly chlorotic plants. FCR activity and Fe concentration in xylem sap were determined in green stressed cucumber plants with different stress levels using different synthetic chelates as substrates. Both reduction and Fe concentration in the xylem sap were higher for the less-stable Fe chelates, except for Fe-EDTA, which presented a relatively low Fe concentration in sap. It was concluded that a high stability of the chelate in the nutrient solution reduces the Fe reduction, but other factors, such as the complexation of the Fe(II) by the chelating agents, should be considered when the complete process of Fe uptake is studied. The use of both indexes together, i.e., FCR determination and xylem sap concentration, is useful for understanding the Fe uptake from different Fe chelates.

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Section: Stability Of the Chelates: Ligand Competition With Dtpamentioning

confidence: 99%

Synthetic Iron Chelates as Substrates of Root Ferric Chelate Reductase in Green Stressed Cucumber Plants

Lucena

Chaney

2006

Journal of Plant Nutrition

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“…By serving as bridging linkers or terminal blocks, the amine moieties in an aminophenolate ligand architecture play a key role in establishing a specific coordination environment around the metal center. Moreover, the prochiral nitrogen atom of an amine moiety would turn into chiral after coordination, which, in combination with other inherent chirality within the ligand, the helicity of the ligand wrapping the metal center, as well as the stereogenic metal center in a four- or five-coordinate metal complex, brings versatile distereoselective control in complex synthesis, hence influencing the stereoselectivity in polymerization. For instance, zinc complexes bearing achiral aminophenolate ligands reported by Tolman’s group (Chart , I ) and our group (Chart , II ) , are racemic mixtures both in solution and in the solid state, despite the presence of the stereogeneity at the amine donor and the metal center.…”

Section: Introductionmentioning

confidence: 99%

Exploring Steric Effects in Diastereoselective Synthesis of Chiral Aminophenolate Zinc Complexes and Stereoselective Ring-Opening Polymerization of rac-Lactide

Wang

Yang

2016

Inorg. Chem.

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A series of tridentate chiral aminophenol proligands and corresponding zinc complexes, LZnX (L = (S)-2-{[(1-R(4)-2-pyrrolidinyl)CH2N(R(3))-]CH2}-6-R(1)-4-R(2)-C6H2O, X = N(SiMe3)2, R(3) = (n)Bu, R(4) = Bn: R(1) = R(2) = Cl (1), R(1) = R(2) = Me (2), R(1) = R(2) = (t)Bu (3); X = N(SiMe3)2, R(1) = trityl, R(2) = Me: R(3) = n-octyl, R(4) = Bn (4), R(3) = Bn, R(4) = Bn (5), R(3) = (n)Bu, R(4) = naphthalen-1-ylmethyl (6), R(3) = (n)Bu, R(4) = (i)Pr (7); R(1) = R(2) = cumyl, R(3) = Et, R(4) = Bn: X = N(SiMe3)2 (8), X = O(t)Bu (9), X = Et (10), X = Cl (11)), have been synthesized. Complexes 4, 6, and 11 were obtained as enantiopure products (4 and 6 as enantiopure a; 11 as enantiopure b), while complexes 1-3, 5, and 7-10 as a pair of diastereomers, but in different ratios, which have been proved by X-ray diffraction and NMR spectroscopic studies. When exposed to the ring-opening polymerization of rac-lactide, most of these complexes can effectively produce PLAs with narrow polydispersities, desirable molecular weights, and moderate to high isotacticities. The structure-selectivity relationships, including the relationships of structure-synthesis diastereoselectivity and structure-polymerization stereoselectivity, have been further investigated. Consistent trends of diastereoselectivity and stereoselectivity are observed with the variations of the R(1) group at the ortho-position of the phenolate ring and the R(3) group in the pyrrolidinyl moiety. The decrease of the steric bulkiness of the R(4) group on the central amine has less influence on the diastereoselectivity, but leads to considerable loss of the stereoselectivity, whereas the decrease of the steric bulkiness of the X group results in a reverse of the diastereoselectivity, but shows no influence on the stereoselectivity. There is probably no direct relationship between the diastereoselectivity in complex synthesis and the stereoselectivity of the complex toward the ROP of rac-LA. The stereocontrol of these complexes might largely rely on the substituents in the ligand framework rather than their diastereomer ratios.

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“…Distortion of the copper(II) coordination polyhedron is a central problem of its stereochemistry (Gažo, 1974;Gažo et al, 1976;Bernauer, 1976;Eggleston et al, 1997). However, distortion of the coordination polyhedron of copper(II) and other elements can be described and calculated in many ways (Kepert, 1982;Raos, 1997), by using the method of reaction paths (Muetterties & Guggenburger, 1974), by measuring the distortion along the Berry coordinate (Berry, 1960;Holmes & Deiters, 1977;Raos, 1996), and by using distortion indices (Baur, 1974;Addison et al, 1984), the distortion vector (Murray-Rust et al, 1978a,b, 1979, tensors (Petruševski & Trenčevski, 1990), and various functions of the volume of the coordination polyhedron and the volume of its circumscribed sphere (Makovicky & Balić-Ž unić, 1998).…”

Section: Introductionmentioning

confidence: 99%

Theoretical analysis of apical bonding in copper(II) chelates with amino acids

Miličević

Raos

2009

J Appl Cryst

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The interdependence between the side of apical coordination (H2O, >C=O, dimethyl sulfoxide and Cl−) and steric crowding at the apical positions was investigated for a set of 20 copper(II) bis complexes with naturally occurring amino acids. As a measure of steric crowding the overlapping volumes, V*, were used, calculated by the modified overlapping spheres method. It was found that the apically coordinated side of a complex is more hindered by the side‐chain atoms. In addition, if both sides are apically coordinated, the apical bond is shorter at the more crowded side. The interdependence between the length of the apical bond and distortion of the coordination polyhedron was also studied. The apical bond length shows sigmoidal dependence on the magnitude of distortion, and is also dependent on the kind of distortion (square‐pyramidal or tetrahedral).

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Diastereoisomerism and diastereoselectivity in metal complexes

Cited by 29 publications

References 112 publications

Synthetic Iron Chelates as Substrates of Root Ferric Chelate Reductase in Green Stressed Cucumber Plants

Synthetic Iron Chelates as Substrates of Root Ferric Chelate Reductase in Green Stressed Cucumber Plants

Exploring Steric Effects in Diastereoselective Synthesis of Chiral Aminophenolate Zinc Complexes and Stereoselective Ring-Opening Polymerization of rac-Lactide

Theoretical analysis of apical bonding in copper(II) chelates with amino acids

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