scholarly journals Experimental study of speciation and mechanistic implications when using chelating ligands in aryl-alkynyl Stille coupling

2020 ◽  
Vol 49 (32) ◽  
pp. 11336-11345
Author(s):  
Ana M. Gallego ◽  
Marconi N. Peñas-Defrutos ◽  
Guillermo Marcos-Ayuso ◽  
Jose M. Martin-Alvarez ◽  
Jesús M. Martínez-Ilarduya ◽  
...  
Keyword(s):  
Experimental Study ◽  
Chelating Ligands ◽  
Stille Coupling ◽  
Chelate Complexes ◽  
Leaving Group

The leaving group and the solvent are critical for transmetalation of alkynyl to Pd chelate complexes in a Stille process.

ChemInform Abstract: An Experimental Study of Special Leaving Group Behavior in the Reaction of Arylidenebarbituric Acids with Carbon Nucleophiles.

ChemInform ◽  
2011 ◽  
Vol 42 (20) ◽  
pp. no-no
Author(s):  
Mohammad A. Bigdeli ◽  
Enayatollah Sheikhhosseini ◽  
Azizollah Habibi ◽  
Saeed Balalaie
Keyword(s):  
Experimental Study ◽  
Group Behavior ◽  
Carbon Nucleophiles ◽  
Leaving Group

Chelate complexes of molybdenum. I. Thiolo-bridged molybdenum(III) complexes with low magnetic moments

1965 ◽  
Vol 18 (10) ◽  
pp. 1549 ◽  
Author(s):  
LF Lindoy ◽  
SE Livingstone ◽  
TN Lockyer
Keyword(s):  
Magnetic Moment ◽  
Magnetic Moments ◽  
Thiol Group ◽  
Molybdenum Atom ◽  
Chelating Ligands ◽  
Chelate Complexes ◽  
Metal Interaction ◽  
Metal Metal ◽  
Multinuclear Complexes ◽  
Bridging Groups

Thiolo-bridged complexes of molybdenum(III) have been obtained from the reaction in alcohol of lithium hexachloromolybdate(III) enneahydrate with a number of chelating ligands containing a thiol group. These multinuclear complexes have three bridging groups--either three thiolo-bridges or two thiolo-bridges and one chloro-bridge-linking the molybdenum atoms which, except in one complex, are probably eight-coordinate, Only two complexes were obtained from the reaction of the ligands with potassium hexabromomolybdate(III) in alcohol. The bromo-derivatives were similar to but less stable than their chloro-analogues. All the complexes have anomalously low magnetic moments ranging from 0.3 to 1.56 BAT. per molybdenum atom, owing to metal-metal interaction either directly or via the bridging atoms. A monomeric five-coordinate molybdenum(1v) complex MoO[(PriO)2PS2]2 with a low magnetic moment (μ 0.9 B.M.) is also described.

Nitrogenous chelate complexes of transition metals. VII. Complexes of silver(I) and silver(II) with tridentate chelating ligands

1970 ◽  
Vol 23 (6) ◽  
pp. 1125 ◽  
Author(s):  
CM Harris ◽  
TN Lockyer
Keyword(s):  
Aqueous Solution ◽  
Schiff Base ◽  
Absorption Band ◽  
Magnetic Moments ◽  
Chelating Ligands ◽  
Chelate Complexes ◽  
Complex Ions ◽  
Strong Absorption Band ◽  
Stable Species ◽  
Complexes Of Transition Metals

Silver(1) complexes of 2,2',2"-terpyridine and a related Schiff base chelate 8-(or-pyridylmethyleneamino)quinoline have been prepared. They are of the type Ag(chelate)X, where X = NO3, ClO4, and PF6. Both Ag(terpy)+ and Ag(pmq)+ are stable in solution and conductance measurements have been obtained. Ag(terpy)PF6 is monomeric in nitrobenzene. Reaction of the above complex ions with pyridine or triphenylphosphine affords stable species of the form [Ag(chelate)(py)]+ and [Ag(chelate)(Ph3P)]+ which have been isolated as their perchlorate salts. Both Ag(chelate)+ and [Ag(ohelate)L]+ involve unusual stereochemistry for AgI. The known paramagnetic AgII complexes Ag(terpy)X2 (X = NO3, ClO4, �S2O8) have been reprepared. They are unstable in solution and reduce readily to AgI. They all show magnetic moments in the range 1.7-1.9 B.M. Ag(terpy)2+ in an aqueous solution of CeIv shows a strong absorption band at 470 mμ (880).

Phosphinsubstituierte Chelatliganden, XXV [1] Diastereoselektive Komplexierung chiraler Phosphinothioformamide mit entferntem Asymmetriezentrum

1987 ◽  
Vol 42 (7) ◽  
pp. 860-866 ◽  
Author(s):  
Udo Kunze ◽  
Roland Burghardt
Keyword(s):  
Amino Acid ◽  
Complex Formation ◽  
Bond Distance ◽  
Phosphine Ligands ◽  
Asymmetric Induction ◽  
Amino Acid Esters ◽  
Chelating Ligands ◽  
Chelate Complexes ◽  
Equilibrium Ratio ◽  
Acid Esters

Abstract For further studies of the diastereoselective complex formation of ambidentate chiral chelating ligands, we prepared the racemic phosphinothioformamides. Ph2P(X )C(S)NHC*HR 1R2, with X = 2e- (R1 = Ph,R2 = Et: 1a;R1 = Ph,R2 = iPr:2a; R2 = Me,R2 = Et:3a) and X = O (1b ,2b ) according to a previously reported route. The coordination of 1a -3a to CpM (CO)3Cl (M = Mo, W) in m ethanol gives the diastereomeric P.S-chelate complexes, (Mo: 4-6, W: 7-9). In solution, epimerisation proceeds to an equilibrium ratio of B/A = 1,5 in case of 4, 5, 7, and 8, but less than 1,1 with 6 and 9. A reduced diastereoselectivity (d.e. 10 -20%) is also observed during the formation of the analogous molybdenum complexes 10a-d with phosphine ligands derived from α-amino acid esters. Ph2PC(S)NHC*H(R)COOMe [R = Me (L-Ala), CH2Ph (L-Phe). CHMe2 (L-Val). Ph (D-phenylglycine)]. The results indicate a significant asymmetric induction despite of the four bond distance of the chiral centres.

Structure correlation study of four-coordinate copper(I) and (II) complexes

2000 ◽  
Vol 56 (3) ◽  
pp. 444-454 ◽  
Author(s):  
Paul R. Raithby ◽  
Gregory P. Shields ◽  
Frank H. Allen ◽  
W. D. Samuel Motherwell
Keyword(s):  
Principal Component ◽  
Correlation Study ◽  
Chelating Ligands ◽  
Bidentate Ligands ◽  
Chelate Complexes ◽  
Tetrahedral Symmetry ◽  
Square Planar ◽  
Structural Database ◽  
Structure Correlation ◽  
Polymeric Structures

The geometries of four-coordinate CuI and CuII complexes in the Cambridge Structural Database (CSD) have been analysed systematically and compared using symmetry-deformation coordinates and principal component analysis. The observed stereochemistries have been rationalized in terms of the d-electron configurations, interligand repulsion and π-bonding effects. The results confirm that the majority of four-coordinate copper(I) complexes in the CSD adopt tetrahedral geometries and deviations from tetrahedral symmetry are caused by the presence of chelating ligands or by the incorporation of copper centres into dimeric or polymeric structures. Four-coordinate copper(II) complexes generally adopt geometries close to square planar; this is particularly evident for bis(chelate) complexes where π-bonding is important. Distortions towards tetrahedral geometries are attributable to steric interactions of bulky substituents in the bidentate ligands.

scholarly journals A computational and experimental study of O-glycosylation. Catalysis by human UDP-GalNAc polypeptide:GalNAc transferase-T2

2014 ◽  
Vol 12 (17) ◽  
pp. 2645-2655 ◽  
Author(s):  
Hansel Gómez ◽  
Raúl Rojas ◽  
Divya Patel ◽  
Lawrence A. Tabak ◽  
José M. Lluch ◽  
...  
Keyword(s):  
Experimental Study ◽  
Nucleophilic Attack ◽  
Front Side ◽  
Leaving Group

GalNAc-T2 catalyses GalNAc O-glycosylation via a front-side nucleophilic attack in which stabilization of the UDP leaving group is crucial.

An Experimental Study of Special Leaving Group Behavior in the Reaction of Arylidenebarbituric Acids with Carbon Nucleophiles

Heterocycles ◽  
2011 ◽  
Vol 83 (1) ◽  
pp. 107 ◽  
Author(s):  
Enayatollah Sheikhhosseini ◽  
Mohammad A. Bigdeli ◽  
Azizollah Habibi ◽  
Saeed Balalaie
Keyword(s):  
Experimental Study ◽  
Group Behavior ◽  
Carbon Nucleophiles ◽  
Leaving Group

Experimental study on the restoration from a tilt-azimuth series for improvement in resolution

1995 ◽  
Vol 53 ◽  
pp. 636-637
Author(s):  
Norio Baba ◽  
Norihiko Ichise ◽  
Syunya Watanabe
Keyword(s):  
Experimental Study ◽  
Spherical Aberration ◽  
Incident Beam ◽  
Optical Parameters ◽  
Beam Tilting ◽  
Illumination Method ◽  
Restoration Method ◽  
Illumination Mode

The tilted beam illumination method is used to improve the resolution comparing with the axial illumination mode. Using this advantage, a restoration method of several tilted beam images covering the full azimuthal range was proposed by Saxton, and experimentally examined. To make this technique more reliable it seems that some practical problems still remain. In this report the restoration was attempted and the problems were considered. In our study, four problems were pointed out for the experiment of the restoration. (1) Accurate beam tilt adjustment to fit the incident beam to the coma-free axis for the symmetrical beam tilting over the full azimuthal range. (2) Accurate measurements of the optical parameters which are necessary to design the restoration filter. Even if the spherical aberration coefficient Cs is known with accuracy and the axial astigmatism is sufficiently compensated, at least the defocus value must be measured. (3) Accurate alignment of the tilt-azimuth series images.

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