Exchange reactions by NMR without variable temperature. An experiment using allyl-palladium complexes

1978 ◽  
Vol 55 (2) ◽  
pp. 131 ◽  
Author(s):  
Trevor G. Appleton ◽  
John D. Cotton
Keyword(s):  
Variable Temperature ◽  
Palladium Complexes ◽  
Exchange Reactions

Fluxional behaviour of potentially bidentate phenanthroline, naphthyridine, and phthalazine ligands in palladium complexes

1978 ◽  
Vol 56 (7) ◽  
pp. 950-953 ◽  
Author(s):  
J. Bradley Brandon ◽  
Michael Collins ◽  
Keith R. Dixon
Keyword(s):  
Nmr Spectra ◽  
Variable Temperature ◽  
Palladium Complexes ◽  
Exchange Mechanism ◽  
Heterocyclic Ligands ◽  
Planar Structures ◽  
Square Planar ◽  
Intramolecular Process

The synthesis of a series of palladium complexes, cis-[PdCl(PEt3)2L][Y]; L = 1,10-phenanthroline, 1,8-naphthyridine, or phthalazine; Y = BF4− or ClO4−; is reported. Variable temperature 1H and 31P nmr spectra are discussed in terms of square planar structures in which the heterocyclic ligands are essentially monodentate and fluxional with the palladium exchanging between the two nitrogen atoms. Above ca. −10 °C a dissociative exchange mechanism operates in all three complexes and, when L = 1,10-phenanthroline or 1,8-naphthyridine, exchange continues at lower temperatures by an intramolecular process.

CYCLOBUTADIENE–METAL COMPLEXES: PART VIII. SYNTHESIS OF TETRAPHENYLCYCLOBUTADIENE NICKEL HALIDES BY LIGAND-EXCHANGE REACTIONS

1966 ◽  
Vol 44 (22) ◽  
pp. 2673-2677 ◽  
Author(s):  
D. F. Pollock ◽  
P. M. Maitlis
Keyword(s):  
Metal Complex ◽  
Metal Complexes ◽  
Ligand Exchange ◽  
Palladium Complexes ◽  
Exchange Reactions ◽  
Reaction Proceeds ◽  
Halide Complexes

The preparation of cyclobutadiene nickel halide complexes (R4C4NiX2)2, where R is phenyl or substituted phenyl, by reaction of the palladium complexes, [R4C4PdX2]2, with a tert-phosphine metal complex, e.g. (n-Bu3P)2NiX2, is described. The reaction proceeds according to the equation[Formula: see text]Possible mechanisms are suggested.

scholarly journals Synthesis of N,O-Chelating Hydrazidopalladium Complexes from 1,2-Bis(trifluoroacetyl)hydrazine

Inorganics ◽  
2021 ◽  
Vol 9 (10) ◽  
pp. 76
Author(s):  
Yoshihito Kayaki ◽  
Tomohiro Hayakawa ◽  
Takao Ikariya
Keyword(s):  
Crystal Structure ◽  
Structure Determination ◽  
Nmr Spectra ◽  
Structural Changes ◽  
Variable Temperature ◽  
Palladium Complexes ◽  
Electron Donors ◽  
Crystal Structure Determination ◽  
X Ray ◽  
Square Planar

N,O-chelating dicarbonylhydrazido-palladium complexes were synthesized by treatment of 1,2-bis(trifluoroacetyl)hydrazine with a mixture of a Pd(0) source, [Pd(dba)2] (DBA = dibenzylideneacetone), and four-electron donors including 1,3-bis(diphenylphosphino)propane (DPPP), N,N,N’,N’-tetramethylethylenediamine (TMEDA), and two equivalents of triphenylphosphine. The same products from DPPP and TMEDA could be obtained alternatively by using Pd(OAc)2 through deprotonation of the diacylhydrazine. The five-membered chelate structure was confirmed by NMR spectra and X-ray crystal structure determination. The X-ray structures indicate that the products are formally considered as Pd(II) complexes with a hydrazido(2–) ligand. In the case of the triphenylphosphine-coordinated complex, a fluxional behavior in dichloromethane-d2 was observed by variable temperature NMR experiments, possibly due to structural changes between the square planar and pseudo-tetrahedral geometries.

Methyl group exchange reactions of trimethylaluminium dimer

1973 ◽  
Vol 26 (4) ◽  
pp. 749 ◽  
Author(s):  
EM Krankovits ◽  
RJ Magee ◽  
KS Murray ◽  
MJ O'Conner
Keyword(s):  
Liquid Helium ◽  
Low Temperatures ◽  
Variable Temperature ◽  
Magnetic Behaviour ◽  
Exchange Reactions ◽  
Methyl Group ◽  
Ferromagnetic Behaviour ◽  
Cluster Interaction ◽  
Square Planar ◽  
Temperature Susceptibility

Variable temperature susceptibility measurements have been made on a number of bis(N,N-dialkylmonothiocarbamato)nickel(II) complexes. The results are characteristic of ferromagnetically coupled NiII clusters. Within the range 300-80 K the susceptibilities can be fitted extremely well to a number of possible cluster models and it is not possible to distinguish the exact molecularity. ��� Measurements on one of the complexes down to liquid helium temperatures confirm the ferromagnetic behaviour and demonstrate inter- cluster interaction at very low temperatures. The magnetic behaviour of these complexes contrasts with the diamagnetism of the square planar bis(N,N-dialkyldithiocarbamato) analogues.

Isotope exchange reactions of benzene with deuterium catalyzed by palladium complexes

1976 ◽  
Vol 25 (2) ◽  
pp. 461-461
Author(s):  
A. S. Berenblyum ◽  
L. I. Lakhman ◽  
I. I. Moiseev ◽  
E. D. Radchenko ◽  
V. E. Zolotukhin ◽  
...  
Keyword(s):  
Isotope Exchange ◽  
Palladium Complexes ◽  
Exchange Reactions

scholarly journals Mechanistic insights into the tropo-inversion of the biphenyl moiety in chiral bis-amido phosphites and in their palladium(ii) complexes

2018 ◽  
Vol 47 (7) ◽  
pp. 2292-2305 ◽  
Author(s):  
Alessandro Passera ◽  
Anna Iuliano ◽  
Jesús J. Pérez-Torrente ◽  
Vincenzo Passarelli
Keyword(s):  
Nmr Spectroscopy ◽  
Dft Calculations ◽  
Variable Temperature ◽  
Palladium Complexes

The tropo-inversion of the biphenyl moiety in chiral bis-amido phosphites and in their palladium complexes has been elucidated by means of variable temperature NMR spectroscopy and DFT calculations.

Determination of Kinetic Order of Reaction for its Duration in the Study of Solvation Factor Effect on Cyclohexene Hydrocarbomethoxylation Catalyzed by Palladium-Phosphine Systems

2019 ◽  
pp. 103-116
Author(s):  
N.T. Sevostyanova ◽  
S.A. Batashev
Keyword(s):  
Elevated Temperatures ◽  
Catalyst Deactivation ◽  
Initial Rate ◽  
Palladium Complexes ◽  
Methanol Concentration ◽  
Exchange Reactions ◽  
Kinetic Order ◽  
Rate Region ◽  
Factor Effect ◽  
Solvation Factor

The purpose of the study was to investigate homogeneous catalytic reaction of cyclohexene hydrocarbomethoxylation leading to the methyl cyclohexanecarboxylate formation. Pd(PPh3)2Cl2 and Pd(OAc)2 which were promoted by free PPh3 and p-toluenesulfonic acid were used as catalytic precursors. In the temperature range 358--393 K, we studied the methanol concentration effect on the value of kinetic order of the reaction with respect to cyclohexene for the duration of the reaction. Findings of research show that the kinetic order increased from 1 to 10 with temperature increase and methanol concentration rise. We compared the kinetic order values for the duration of the reaction and the concentration order with respect to cyclohexene, which is equal to 1, set for the initial rate region. Based on this comparison, it was suggested that the formation of inactive palladium complexes is progressed by the action of excess methanol at elevated temperatures. We found that the regularities of methanol effect on the cyclohexene hydrocarbomethoxylation rate for the duration of the reaction were agreed with the regularities discovered for the initial rate region. With consideration of the data about enthalpy change in the ligand exchange reactions between the palladium complexes with participation of CH3OH, СО and PPh3, we draw the conclusion about the dominant contribution of specific solvation to the catalyst deactivation in the conditions of high methanol concentrations

Exchange reactions and electrolytic dissociation

1948 ◽  
Vol 45 ◽  
pp. 147-149 ◽  
Author(s):  
C. C. Evans ◽  
S. Sugden
Keyword(s):  
Exchange Reactions ◽  
Electrolytic Dissociation

Modeling of photosynthesis light curves by linear splines

2019 ◽  
pp. 20-29
Author(s):  
Alexander S. Lelekov ◽  
Rudolf P. Trenkenshu
Keyword(s):  
Experimental Data ◽  
Chlorophyll A ◽  
Skeletonema Costatum ◽  
Light Flux ◽  
Photosynthesis Rate ◽  
Light Curves ◽  
External Irradiation ◽  
Exchange Reactions ◽  
Cell Adaptation ◽  
Linear Splines

The paper presents an example of the linear splines use to describe the photosynthesis light curves for microalgae culture. The main mathematical models of the relationship between photosynthesis rate and light are listed. Based on the previously formulated basic principles of modeling microalgae photobiosynthesis, a mathematical model is proposed that describes the dependence of the assimilation number of chlorophyll a on the value of the light flux by linear splines. The advantage of the proposed approach is a clear definition of the point of change of the limiting factor. It is shown that light-limited photosynthesis rate is determined not only by external irradiation, but also by the concentration of chlorophyll a. The light-saturated rate depends on the amount of a key enzyme complex, which limits the rate of energy exchange reactions in the cell. Verification of the proposed model on the example of the diatom microalgae Skeletonema costatum was carried out. It is shown that the higher the degree of cell adaptation to high irradiation, the better the photosynthesis curve is described by linear splines. If S. costatum cells are adapted to low irradiation, deviations of experimental data from the idealized broken line are observed, which are caused by changes in the pigment composition. When the experimental data are normalized, the cell adaptation factor is reduced, all points are described by a single broken line, which indicates the universality of the proposed approach.

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