Fluorinated alkoxides. Part XII. Studies on potentially tridentate fluorinated diols; zwitterionic and five-coordinate complexes of Ni2+ and Cu2+

1978 ◽  
Vol 56 (17) ◽  
pp. 2369-2373 ◽  
Author(s):  
Stephen J. Loeb ◽  
John W. L. Martin ◽  
Christopher J. Willis
Keyword(s):  
Steric Effects ◽  
Bidentate Ligands ◽  
Tridentate Ligands ◽  
The Third ◽  
Complexing Ability ◽  
Fluorinated Alcohol ◽  
Fluorinated Alkoxides

The complexing ability towards Ni2+ and Cu2+ of the potentially tridentate ligands HOC(CF3)2CH2C(O)CH2C(CF3)2OH, HOC(CF3)2CH2CH(OH)CH2C(CF3)2OH, and HOC(CF3)2CH2CH2N:C(CH3)CH2C(CF3)2OH has been studied. The first two act as bidentate ligands, uninegative or dinegative according to the extent of ionization of the fluorinated alcohol groups; when both were ionized, the complexes had a zwitterionic structure. The third ligand was exclusively tridentate in its complexes; this difference is ascribed to its greater flexibility. Both four- and five-coordinate complexes of nickel were observed, the latter being produced either by choice of co-ligands or by solvation, but no six-coordinate complex was formed in this series. Limitations on coordination for the metal are ascribed to steric effects.

Fluorinated alkoxides. Part XI. Studies on highly fluorinated amino-alcohols and their metal derivatives

1977 ◽  
Vol 55 (13) ◽  
pp. 2465-2472 ◽  
Author(s):  
In-Soon Chang ◽  
Christopher J. Willis
Keyword(s):  
Donor Site ◽  
Amino Alcohols ◽  
Formation Constants ◽  
Intramolecular Proton Transfer ◽  
Nitrogen Donor ◽  
Metal Derivatives ◽  
Fluorinated Alcohol ◽  
Fluorinated Alkoxides ◽  
Trifluoromethyl Groups ◽  
Steric Influence

We describe the synthesis of a number of difunctional molecules in which the fluorinated tertiary alcohol grouping, -C(CF3)20H, is combined with a nitrogen donor site such as an amino-group or a pyridine ring. In all cases, zwitterionic behaviour in solution is found resulting from intramolecular proton transfer from the acidic fluorinated alcohol to the nitrogen, and this sometimes persists in the solid state, e.g. NH2CH2CH2C(CF3)20H exists as the dipolar ion +NH3CH2CH2C(CF3),0-. Measurements of pK values suggest that the behaviour of the fluorinated amino-alcohols may be compared with that of the amino-acids, subject to changes to be expected from the lower acidity of the -C(CF3)20H group. Metal complexes of the fluorinated amino-alcohols form readily; specifically, neutral complexes of Co2+, Ni2+, and Cu2+ of formula M(L),, where L is an ionized amino-alcohol chelating through the ionized hydroxy group and the nitrogen atom. Measurements of formation constants show that the six-membered chelate rings are the most stable, while a comparison of the stabilities of fluorinated amino-alkoxy complexes with those of analogous aminoacids shows that the former are less stable: this is attributed to the steric influence of the trifluoromethyl groups.

scholarly journals Synthesis of Dianionic and Trianionic Chiral, Chelating Ligands Based on Amino Acids

2008 ◽  
Vol 61 (4) ◽  
pp. 297
Author(s):  
Madeleine Schultz ◽  
Jakov Kulis ◽  
Julie Murison ◽  
Genevieve W. Andrews
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Aspartic Acid ◽  
Nitrilotriacetic Acid ◽  
Solution Phase ◽  
Chelating Ligands ◽  
Bidentate Ligands ◽  
Synthetic Route ◽  
Tridentate Ligands ◽  
Amide Coupling

The synthesis of two new families of amino acid-containing chiral ligands, based on methyliminodiacetic acid and nitrilotriacetic acid cores, has been accomplished using a simple protection, solution-phase amide coupling, and deprotection strategy. The amino acids glycine, leucine, aspartic acid, and phenylalanine were used to demonstrate the versatility of the synthetic route, and that no epimerization occurs. The tridentate ligands bear C3 symmetry, whereas the bidentate ligands have C1 symmetry.

Effect of Third Monomer Type and Content on Peroxide Crosslinking Efficiency of EPDM

2003 ◽  
Vol 76 (1) ◽  
pp. 132-144 ◽  
Author(s):  
Martin van Duin ◽  
Herman G. Dikland
Keyword(s):  
Molecular Weight ◽  
Steric Hindrance ◽  
Radical Addition ◽  
Steric Effects ◽  
Low Molecular Weight ◽  
Comprehensive Overview ◽  
Model Studies ◽  
The Third ◽  
Peroxide Curing ◽  
Weight Model

Abstract Peroxide crosslinking of EPDM is commonly applied in rubber practice. Although the presence of a diene termonomer is not a prerequisite for peroxide crosslinking, it does provide a significant increase of the peroxide crosslinking efficiency. Different explanations for the effect of the type and the amount of the third monomer on the peroxide curing efficiency have been put forward; but, a comprehensive overview and an acceptable explanation of all the effects observed are still lacking. In the present paper, this gap is filled by combining results from low-molecular-weight model studies and rheometer experiments with information from the literature. It is shown that peroxide crosslinking of EPDM proceeds via the combination of two EPDM macro-radicals and the addition of an EPDM macro-radical to the residual EPDM unsaturation. The extent to which the latter radical addition occurs, is governed by the amount of the third monomer and by the steric hindrance of the residual unsaturation of the EPDM, i.e. the lower the number of ipso- and β- alkyl substituents on the unsaturation, the higher the rate of addition. This explains why EPDMs containing termonomers with terminal unsaturations are more reactive than those with internal unsaturations. The same approach was followed to assess the peroxide curing efficiency of polydiene elastomers. It was found that the same steric effects govern peroxide crosslinking of polydiene elastomers, such as NR, IR and BR.

Steric Effects in Aluminum Compounds Containing Monoanionic Potentially Bidentate Ligands:  Toward a Quantitative Measure of Steric Bulk

1999 ◽  
Vol 18 (21) ◽  
pp. 4399-4416 ◽  
Author(s):  
Julie A. Francis ◽  
C. Niamh McMahon ◽  
Simon G. Bott ◽  
Andrew R. Barron
Keyword(s):  
Quantitative Measure ◽  
Steric Effects ◽  
Bidentate Ligands ◽  
Aluminum Compounds

Fluorinated alkoxides. Part XIII. The reduction of β-imino-alkoxy complexes to give stable, polydentate, amino-alcohols; their coordination to Co2+, Ni2+, and Cu2+

1978 ◽  
Vol 56 (23) ◽  
pp. 2966-2969 ◽  
Author(s):  
John W. L. Martin ◽  
C. J. Willis
Keyword(s):  
Metal Atom ◽  
Amino Alcohols ◽  
Fluorinated Alcohol ◽  
Fluorinated Alkoxides

The amino-alcohols HOC(CF3)2CH2CH(CH3)NH(CH2)3NHCH(CH3)CH2C(CF3)2OH and HOC(CF3)2CH2CH(CH3)NH(CH2)3NH(CH2)3NHCH(CH3)CH2C(CF3)2OH have been prepared by reduction of the corresponding imino-alcohols coordinated to, e.g., Cu2+, by use of LiAlH4. The products are capable of acting as polydentate, dinegative, ligands (following ionization of the fluorinated alcohol groups) and the second compound gives stable, neutral, complexes of Co2+, Ni2+, and Cu2+ in which the metal atom is five-coordinate.

A study of the effect of axial ligand steric hindrance

2018 ◽  
Vol 22 (07) ◽  
pp. 588-595 ◽  
Author(s):  
Chuanjiang Hu ◽  
Allen G. Oliver ◽  
Ilona Turowska-Tyrk ◽  
W. Robert Scheidt
Keyword(s):  
Steric Hindrance ◽  
Axial Ligand ◽  
Molecular Structures ◽  
Steric Effects ◽  
X Ray ◽  
The Third ◽  
Porphyrin Ligand ◽  
Structure Determinations

The molecular structures of three porphyrinate derivatives have been determined by X-ray studies. Two derivatives, [Fe(TTP)(1-MeIm)[Formula: see text]] · 2C[Formula: see text]H[Formula: see text] and [Fe(T-[Formula: see text]-OCH[Formula: see text]PP)(BzHIm)[Formula: see text]] are iron(II) derivatives, whereas the third, [Fe(TMP)(BzHIm)[Formula: see text]]ClO[Formula: see text] · 2CHCl[Formula: see text], is an iron(III) species. The structure determinations provide evidence of the importance of steric effects, either from the axial ligand or the porphyrin ligand, in defining the overall stereochemistry.

Binding energies and stabilities of potassium ion complexes with ethylene diamine and dimethoxyethane (glyme) from measurements of the complexing equilibria in the gas phase

1976 ◽  
Vol 54 (16) ◽  
pp. 2594-2599 ◽  
Author(s):  
W. R. Davidson ◽  
P. Kebarle
Keyword(s):  
Phase Equilibria ◽  
Gas Phase ◽  
Ion Source ◽  
Potassium Ion ◽  
Binding Energies ◽  
Ethylene Diamine ◽  
Bidentate Ligands ◽  
Source Pressure ◽  
The Third ◽  
Monodentate Ligands

The temperature dependence of the gas phase equilibria [Formula: see text] where en = ethylene diamine were measured for n = 1 to n = 3. The equilibrium K+ + dimethoxyethane [Formula: see text] K+(dimethoxyethane) was also determined. The measurements were made with a high ion source pressure mass spectrometer equipped with a thermionic potassium ion emitter. The resulting ΔH0, ΔG0, and ΔS0 values are compared with the corresponding values for monodentate ligands like H2O, NH3, CH3OCH3 etc. determined in earlier work. As expected, the bidentate ligands lead to considerably stronger (0,1) interactions. Dimethoxyethane leads to a stronger complex than ethylene diamine. The third molecule of ethylene diamine leads to much weaker binding than is observed for the first two molecules. Explanation of the observed effects is given on basis of electrostatic and steric arguments.

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