| 1. |
- Abdel-Magied, Ahmed, et al.
(författare)
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Diastereomeric control of enantioselectivity: evidence for metal cluster catalysis.
- 2014
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Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1364-548X. ; 50:57, s. 7705-7708
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Tidskriftsartikel (refereegranskat)abstract
- Enantioselective hydrogenation of tiglic acid effected by diastereomers of the general formula [(μ-H)2Ru3(μ3-S)(CO)7(μ-P-P*)] (P-P* = chiral Walphos diphosphine ligand) strongly supports catalysis by intact Ru3 clusters. A catalytic mechanism involving Ru3 clusters has been established by DFT calculations.
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| 2. |
- Abdel-Magied, Ahmed F., et al.
(författare)
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Asymmetric hydrogenation of an α-unsaturated carboxylic acid catalyzed by intact chiral transition metal carbonyl clusters-diastereomeric control of enantioselectivity
- 2020
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 49:14, s. 4244-4256
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Tidskriftsartikel (refereegranskat)abstract
- Twenty clusters of the general formula [(μ-H)2Ru3(μ3-S)(CO)7(μ-P-P∗)] (P-P∗ = chiral diphosphine of the ferrocene-based Walphos or Josiphos families) have been synthesised and characterised. The clusters have been tested as catalysts for asymmetric hydrogenation of tiglic acid [trans-2-methyl-2-butenoic acid]. The observed enantioselectivities and conversion rates strongly support catalysis by intact Ru3 clusters. A catalytic mechanism involving an active Ru3 catalyst generated by CO loss from [(μ-H)2Ru3(μ3-S)(CO)7(μ-P-P∗)] has been investigated by DFT calculations.
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| 3. |
- Abdel-Magied, Ahmed F., et al.
(författare)
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Synthesis and characterization of chiral phosphirane derivatives of [(μ-H)4Ru4(CO)12] and their application in the hydrogenation of an α,β-unsaturated carboxylic acid
- 2017
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Ingår i: Journal of Organometallic Chemistry. - : Elsevier BV. - 0022-328X. ; 849-850, s. 71-79
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Tidskriftsartikel (refereegranskat)abstract
- Ruthenium clusters containing the chiral binaphthyl-derived mono-phosphiranes [(S)-([1,1'-binaphthalen]-2-yl)phosphirane] (S)-1a, [(R)-(2'-methoxy-1,1'-binaphthyl-2-yl)phosphirane] (R)-1b, and the diphosphirane [2,2'-di(phosphiran-1-yl)-1,1'-binaphthalene] (S)-1c have been synthesized and characterized. The clusters are [(μ-H)4Ru4(CO)11((S)-1a)] (S)-2, [(μ-H)4Ru4(CO)11((R)-1b)] (R)-3, 1,1-[(μ-H)4Ru4(CO)10((S)-1c)] (S)-4, [(μ-H)4Ru4(CO)11((S)-binaphthyl-P(s)(H)Et)] (S,S p)-5, [(μ-H)4Ru4(CO)11((S)-binaphthyl-P(R)(H)Et)] (S,R p)-6, [(μ-H)4Ru4(CO)11((R)-binaphthyl-P(s)(H)Et)] (R,S p)-7, [(μ-H)4Ru4(CO)11((R)-binaphthyl-P(R)(H)Et)] (R,R p)-8 and the phosphinidene-capped triruthenium cluster [(μ-H)2Ru3(CO)9(PEt)] 9. Clusters 5-8 are formed via hydrogenation and opening of the phosphirane ring in clusters (S)-2 and (R)-3. The phosphirane-substituted clusters were found to be able to catalyze the hydrogenation of trans-2-methyl-2-butenoic acid (tiglic acid), but no enantioselectivity could be detected. The molecular structures of (S)-4, (R,S p)-7 and 9 have been determined and are presented.
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| 4. |
- Abdel-Magied, Ahmed F., et al.
(författare)
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Synthesis, Characterization and Catalytic Activity Studies of Rhenium Carbonyl Complexes Containing Chiral Diphosphines of the Josiphos and Walphos Families
- 2015
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Ingår i: Journal of Cluster Science. - : Springer Science and Business Media LLC. - 1040-7278 .- 1572-8862. ; 26:4, s. 1231-1252
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Tidskriftsartikel (refereegranskat)abstract
- Ten rhenium carbonyl complexes-[Re(H)(CO)(3)(1a)], [Re-3(mu-H)(3)(CO)(10) (1a)], [Re-2(CO)(9)(2a)], [Re-2(CO)(8)(2a)], [Re-2(CO)(9)(2b)], [{Re-2(CO)(9)}(2)(2b)], [Re-2 (CO)(8)(2b)], [Re-2(CO)(8)(1b)], [Re-2(mu-H)(2)(CO)(6)(2b)] and [Re-3(mu-H)(3)(CO)(11)(2b)]-containing different bidentate chiral phosphine ligands of the Josiphos (1a, 1b) and Walphos (2a, 2b) families have been synthesized and fully characterized (1a: (R)-1-{(S-P)-2-[Bis[3,5-bis(trifluoromethyl) phenyl] phosphino] ferrocenyl} ethyldi(3,5-xylyl) phosphine, 1b: (R)-1-{(S-P)-2-[Di(2-furyl) phosphino] ferrocenyl} ethyldi-tert-butylphosphine, 2a: (R)-1-{(R-P)-2-[2-[Bis(4-methoxy-3,5-dimethylphenyl) phosphino] phenyl] ferrocenyl} ethylbis[3,5-bis(trifluoromethyl) phenyl] phosphine and 2b: (R)-1-{(R-P)-2-[2( Diphenylphosphino) phenyl] ferrocenyl} ethyldicyclohexylphosphine). The phosphine-substituted clusters were tested for hydrogenation of tiglic acid [trans-2-methyl-2-butenoic acid]. The catalytic reactions gave reasonable conversion rates (15-88 %) under relatively mild conditions but relatively moderate enantiomeric excesses (8-57 %) were observed. The crystal structures of [ReH(CO)(3)(1a)], [Re-2 (CO)(9)(2a)], [{Re-2(CO)(9)}(2)(2b)] and [Re-2(mu-H)(2)(CO)(6)(2b)] are presented.
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| 5. |
- Abdel-Magied, Ahmed, et al.
(författare)
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[(mu)-Bis(diphenylphosphanyl-kappa P)methane]decacarbonyltri-(mu)-hydrido-trirhenium(I)(3 Re-Re) dichloromethane solvate
- 2011
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Ingår i: Acta Crystallographica Section E: Structure Reports Online. - 1600-5368. ; 67:12, s. 1601-1816
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Tidskriftsartikel (refereegranskat)abstract
- In the title compound, [Re(3)(mu-H)(3)(C(25)H(22)P(2))(CO)(10)]center dot CH(2)Cl(2), the three Re atoms form a triangle bearing ten terminal carbonyl groups and three edge-bridging hydrides. The bis(diphenylphosphanyl) methane ligand bridges two Re atoms. Neglecting the Re-Re interactions, each Re atom is in a slightly distorted octahedral coordination environment. The dichloromethane solvent molecule is disordered over two sets of sites with fixed occupancies of 0.6 and 0.4.
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| 6. |
- Abu-Youssef, Morsy A. M., et al.
(författare)
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Molecular, supramolecular structures combined with hirshfeld and dft studies of centrosymmetric m(Ii)-azido {m=ni(ii), fe(ii) or zn(ii)} complexes of 4-benzoylpyridine
- 2021
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Ingår i: Symmetry. - : MDPI AG. - 2073-8994. ; 13:11
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Tidskriftsartikel (refereegranskat)abstract
- The supramolecular structures of the three metal (II) azido complexes [Fe(4bzpy)4 (N3 )2 ]; 1, [Ni(4bzpy)4 (N3 )2 ]; 2 and [Zn(4bzpy)2 (N3 )2 ]n; 3 with 4-benzoylpyridine (4bzpy) were presented. All complexes contain hexa-coordinated divalent metal ions with a slightly distorted octahedral MN6 coordination sphere. Complexes 1 and 2 are monomeric with terminal azido groups while 3 is one-dimensional coordination polymer containing azido groups with µ(1,1) and µ(1,3) bridging modes of bonding. Hirshfeld analysis was used to quantitatively determine the different contacts affecting the molecular packing in the studied complexes. The most common interactions are the polar O … H and N … H interactions and the hydrophobic C … H contacts. The charges at the M(II) sites are calculated to be 1.004, 0.847, and 1.147 e for complexes 1–3, respectively. The degree of asymmetry is the highest in the case of the terminal azide in complexes 1 and 2 while was found the lowest in the µ(1,1) and µ(1,3) azide bonding modes in the Zn(II) complex 3. These facts were further explained in terms of atoms in molecules (AIM) topological parameters.
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| 7. |
- Carlsson, Håkan, et al.
(författare)
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Hydrolytically active tetranuclear nickel complexes with structural resemblance to the active site of urease
- 2002
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 1520-510X .- 0020-1669. ; 41:20, s. 4981-4983
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Tidskriftsartikel (refereegranskat)abstract
- Reaction of the new asymmetric ligand 2-(N-isopropyl-N-((1-methylimidazolyl)methyl)aminomethyl)-6-(N-carboxylm ethyl-N-((1-methylimidazolyl)methyl) aminomethyl)-4-methylphenol (ICIMP) with nickel perchlorate and diphenylacetic acid leads to the formation of tetranuclear nickel complexes, whose crystal structures reveal that they consist of dimers of dimers in which each Ni-2 unit has a coordination environment that is similar to the active site of urease. One complex has been shown to coordinate urea and catalyze the hydrolysis of an organophosphate monoester.
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| 8. |
- Carlsson, Håkan, et al.
(författare)
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Nickel Complexes of Carboxylate-Containing Polydentate Ligands as Models for the Active Site of Urease
- 2004
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 1520-510X .- 0020-1669. ; 43:26, s. 8252-8262
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Tidskriftsartikel (refereegranskat)abstract
- Two new carboxylate-containing polydentate ligands have been synthesized, the symmetric ligand 2,6-bis[N-(N-(carboxylmethyl)-N-((1-methylimidazol)methyl)amine)methyl]-4-methylphenolate (BCIMP) and the corresponding asymmetric ligand 2-(N-isopropyl-N-((1-aminomethyl)-4-methylphenol (ICIMP). The ligands have been used to prepare model complexes for the active site of the dinuclear nickel enzyme urease, viz. [Ni2(BCIMP)Ac2]- (6), [Ni2(BCIMP)(Ph2Ac)2]- (7), [Ni2(ICIMP)(Ph2Ac)2] (14), [Ni4(ICIMP)2(Ph2Ac)2][ClO4]2 (15), [Ni4(ICIMP)2(Ph2Ac)2(DMF)2][ClO4]2 (16), and [Ni4(ICIMP)2(Ph2Ac)2(urea)(H2O)][ClO4]2 (17), where the latter complex contains urea coordinated in a unidentate fashion through the carbonyl oxygen. The N2O-N2O2 donor set of ICIMP provides a good framework for the preparation of urease models, but in some cases tetranuclear nickel complexes are formed due to coordination of the carboxylate moiety of one dinickel-ICIMP unit to one or both of the nickels of a second Ni2 unit. Reactivity and kinetics studies of 7 and 15 show that these model complexes catalyze hydrolysis of 2-hydroxypropyl p-nitrophenyl phosphate (HPNP) at basic pH. In this assay, complexes based on the asymmetric ligand ICIMP exhibit a significantly faster rate of hydrolysis than the corresponding BCIMP complexes. Magnetic measurements indicate that there are weak antiferromagnetic interactions between the nickel ions in complex 16.
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| 9. |
- Carlsson, Håkan, et al.
(författare)
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Structural and Functional Models of the Active Site of Zinc Phosphotriesterase
- 2004
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 1520-510X .- 0020-1669. ; 43:18, s. 5681-5687
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Tidskriftsartikel (refereegranskat)abstract
- In an attempt to prepare structural and functional models for the active site of the hydrolytic enzyme zinc phosphotriesterase, five new zinc complexes of the ligands 2,6-bis[N-(N-(carboxylmethyl)-N-((1-methylimidazol)methyl)amine)methyl]-4-methylphenolate (BCIMP) and the corresponding asymmetric ligand 2-(N-isopropyl-N-((1-methylimidazolyl)methyl)aminomethyl)-6-(N-carboxylmethyl-N-((1-methylimidazolyl)methyl)aminomethyl)-4-methylphenol (ICIMP) have been synthesized, viz. Na[Zn2(BCIMP)Ac2] (1), [Zn2(BCIMP)(Ph2Ac)] (2), [Zn2(ICIMP)Ac2] (3), [Zn4(ICIMP)2(Me3Ac)2][ClO4]2 (4), and [Zn4(ICIMP)2(Ph2Ac)2][ClO4]2 (5). The X-ray structure of complex 5 has been determined and reveals that the complex is a dimer of dimers in the solid state, which in solution dissociates to potent structural models. Studies using NMR show that only one carboxylate coligand bridges the dizinc units in the case of diphenyl acetate and pivalate, while the steric bulk of acetate is sufficiently small to permit the coordination of two acetates/dizinc unit. Functional studies involving the hydrolysis/transesterification of 2-hydroxypropyl p-nitrophenyl phosphate (HPNP) show that the complex with ICIMP (compound 5) has a significantly higher rate of catalysis than the BCIMP complex (compound 2). This is attributed to the vacant/labile coordination site that is available in the ICIMP complex but not the BCIMP complex.
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| 10. |
- Das, Biswanath, et al.
(författare)
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A Heterobimetallic FeIIIMnII Complex of an Unsymmetrical Dinucleating Ligand : A Structural and Functional Model Complex for the Active Site of Purple Acid Phosphatase of Sweet Potato
- 2014
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Ingår i: European Journal of Inorganic Chemistry. - : Wiley. - 1434-1948 .- 1099-1948 .- 1099-0682. ; 2014:13, s. 2204-2212
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Tidskriftsartikel (refereegranskat)abstract
- The heterodinuclear mixed-valence complex [FeMn(ICIMP)(OAc)(2)Cl] (1) {H2ICIMP = 2-(N-carboxylmethyl)-[N-(N-methylimidazolyl-2-methyl)aminomethyl]-[6-(N-isopropylmethyl)-[N-(N-methylimidazolyl-2-methyl)]aminomethyl-4-methylphenol], an unsymmetrical N4O2 donor ligand} has been synthesized and fully characterized by several spectroscopic techniques as well as by X-ray crystallography. The crystal structure of the complex reveals that both metal centers in 1 are six-coordinate with the chloride ion occupying the sixth coordination site of the Mn-II ion. The phenoxide moiety of the ICIMP ligand and both acetate ligands bridge the two metal ions of the complex. Mossbauer spectroscopy shows that the iron ion in 1 is high-spin Fe-III. Two quasi-reversible redox reactions for the complex, attributed to the (FeMnII)-Mn-III/(FeMnII)-Mn-II (at -0.67 V versus Fc/Fc(+)) and (FeMnII)-Mn-III/(FeMnIII)-Mn-III (at 0.84 V), were observed by means of cyclic voltammetry. Complex 1, with an Fe-III-Mn-II distance of 3.58 angstrom, may serve as a model for the mixed-valence oxidation state of purple acid phosphatase from sweet potato. The capability of the complex to effect organophosphate hydrolysis (phosphatase activity) has been investigated at different pH levels (5.5-11) by using bis(2,4-dinitrophenyl)phosphate (BDNPP) as the substrate. Density functional theory calculations indicate that the substrate coordinates to the Mn-II ion. In the transition state, a hydroxide ion that bridges the two metal ions becomes terminally coordinated to the Fe-III ion and acts as a nucleophile, attacking the phosphorus center of BDNPP with the concomitant dissociation of the leaving group.
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