Catalytic deuterium exchange reactions with organics. XLII. The picolines, lutidines, thiophen, and furan on unsupported Group VIII transition metals

1968 ◽  
Vol 21 (5) ◽  
pp. 1221 ◽  
Author(s):  
GE Calf ◽  
JL Garnett
Keyword(s):  
Transition Metals ◽  
Lone Pair ◽  
Nickel Chloride ◽  
Platinum Oxide ◽  
Transition Metal Catalysts ◽  
The Novel ◽  
Group Viii ◽  
Exchange Reactions ◽  
Alkyl Groups ◽  
Nitrogen Lone Pair

The picolines (methylpyridines), lutidines (dimethylpyridines), thiophen, and furan have been exchanged with heavy water on a variety of Group VIII transition metals. Platinum is the most reactive general labelling catalyst for the picolines and lutidines, whereas cobalt catalyses exchange exclusively in the positions α to the nitrogen atom. The labelling pattern in the picolines and lutidines is similar to that of the alkylbenzenes in that (i)positions ortho to a methyl group are severely deactivated and (ii)positions flanked by two methyl groups are completely deactivated. Compensation effects are observed involving steric hindrance to adsorption from the alkyl groups and enhanced strength of adsorption from the nitrogen lone pair. The compensation effect in this charge-transfer adsorption slightly favours the nitrogen lone pair. Thiophen and furan generally do not exchange appreciably with pre-reduced Group VIII transition metal catalysts. Thiophen exchanges rapidly on self-activated platinum oxide whereas self-activated iridium oxide is the most useful for furan. With nickel chloride, furan exchanges exclusively in the or positions. A theory is proposed to account for the novel exchange in both thiophen and furan.

Catalytic deuterium exchange reactions with organics. XIII. Characteristic reactions of the Group VIII transition metals

1965 ◽  
Vol 18 (7) ◽  
pp. 1003 ◽  
Author(s):  
JL Garnett ◽  
WA Sollich
Keyword(s):  
Transition Metal ◽  
Hydrogen Exchange ◽  
Deuterium Oxide ◽  
Metal Catalysts ◽  
Transition Metal Catalysts ◽  
Group Viii ◽  
Exchange Reactions ◽  
Substitution Mechanism ◽  
Π Complex ◽  
Complex Adsorption

Activation procedures and hydrogen exchange reactions with six Group VIII transition metal catalysts (Pt, Pd, Ru, Rh, Ir, Ni) are reported for three characteristic reaction systems: (i) deuterium oxide/benzene, (ii) deuterium oxide/naphthalene, and (iii) deuterium oxide/n-octane. Results of these exchange reactions indicate that both π-complex adsorption and the dissociative π-complex substitution mechanism previously established for platinum are applicable to other Group VIII transition metal catalysts. For general catalytic labelling with isotopic hydrogen, platinum was found to be the most efficient of the catalysts investigated.

Carbonyl halides of the Group VIII transition metals. II. Aquo adducts of Halobis(triphenylphosphine)dicarbonyls of cobalt(I)

1968 ◽  
Vol 21 (4) ◽  
pp. 891 ◽  
Author(s):  
JA Bowden ◽  
R Colton
Keyword(s):  
Solid State ◽  
Transition Metals ◽  
Group Viii ◽  
Exchange Reactions

Aquo adducts of halobis(triphenylphosphine)dicarbonylcobalt(1), Co(CO)2- (PPh3)2(H2O)X (X = Cl, Br, I), have been prepared by direct halogenation of the cation CO(CO)3(PPh3)2+, followed by addition of water. All of the compounds are stable in the solid state but they appear to undergo exchange reactions in solution.

Catalytic deuterium exchange reactions with organics. XXVII. The alkylbenzenes on self-activated Group VIII transition metals

1966 ◽  
Vol 19 (12) ◽  
pp. 2299 ◽  
Author(s):  
BD Fisher ◽  
JL Garnett
Keyword(s):  
Transition Metal Oxides ◽  
Exchange Process ◽  
Kinetic Studies ◽  
Platinum Oxide ◽  
Activation Process ◽  
Group Viii ◽  
Exchange Reactions ◽  
Π Complex ◽  
Cis And Trans ◽  
In Cis

Exchange reactions between heavy water and the alkylbenzenes have been investigated on the following self-activated Group VIII transition metal oxides: PtO2,2H2O; PdO; Rh2O3; IrO2,2H2O; RuO2,H2O; ReO2; and Ni2O3. All oxides except Ni2O3 are self-activated by benzene up to 180�. Order of ease of self-activation is Pt > Pd > Rh, Ru, Ir > Re > Ni. Trends in deuteration rates of the alkylbenzenes on self-activated platinum oxide are generally similar to those obtained on hydrogen prereduced platinum. At 130�, some differences in reactivity are observed and these are attributed to reagent displacement effects from the presence of small percentages of dimer (1%) associated with the self-activation process. Compared with hydrogen prereduced catalysts, significant differences in isotope orientation are observed with certain alkylbenzenes on self-activated catalysts. Multiple deuteration effects which are accentuated on self-activated catalysts have been used to confirm isotope orientation and also the participation of a π-complex mechanism for the exchange process. Isomerization and exchange in cis- and trans-stilbenes on self-activated platinum have also been interpreted by the dissociative n-complex substitution mechanism. The advantages of self-activated catalysts in general deuterium and tritium labelling work have been evaluated. Possible correlations between exchange results and electron spin resonance data for charge-transfer adsorption on the above oxides are discussed. Preliminary kinetic studies with self-activation are also reported.

Catalytic deuterium exchange reactions with organics. XL. Pyridine, the quinolines, azines, and aniline on unsupported Group VIII transition metals

1968 ◽  
Vol 21 (4) ◽  
pp. 961 ◽  
Author(s):  
GE Calf ◽  
JL Garnett ◽  
VA Pickles
Keyword(s):  
Charge Transfer ◽  
Transition Metals ◽  
Heavy Water ◽  
Heterocyclic Compounds ◽  
Group Viii ◽  
Borohydride Reduction ◽  
Exchange Reactions ◽  
Catalyst Activation ◽  
Π Complex ◽  
Sodium Borohydride Reduction

Pyridine, the quinolines, pyridazine, pyrimidine, pyrazine, s-triazine, and aniline have been exchanged with heavy water on the following Group VIII transition metals: Fe, Co, Ni, 0s. Ru, Rh, Pd, Ir, and Pt. Three types of catalyst activation have been used, including self-activation, hydrogen and sodium borohydride reduction of the inorganlo salts. Platinum is the most useful catalyst for general exchange whereas cobalt possesses valuable specificity for selective a exchange in a large number of the heterocyclic compounds. A kinetic study of the deuteration of pyridine on platinum has been performed. The exchange results have been rationalized in terms of charge-transfer adsorbed intermediates. E.s.r. has been used to support this conclusion for the interaction between pyridine and potassium chloropalladite. π-Complex mechanisms have been proposed to explain the observed deuteration behaviour.

Bond-length distributions for ions bonded to oxygen: Metalloids and post-transition metals

2017 ◽  
Author(s):  
Olivier Charles Gagné ◽  
Frank Christopher Hawthorne
Keyword(s):  
Transition Metal ◽  
Transition Metals ◽  
Metal Ions ◽  
Bond Length ◽  
Lone Pair ◽  
Transition Metal Ions ◽  
Oxygen Lone Pair

Bond-length distributions are examined for thirty-three configurations of the metalloid ions and fifty-six configurations of the post-transition-metal ions bonded to oxygen. Lone-pair stereoactivity is discussed.

Bond-length distributions for ions bonded to oxygen: Metalloids and post-transition metals

2017 ◽  
Author(s):  
Olivier Charles Gagné ◽  
Frank Christopher Hawthorne
Keyword(s):  
Transition Metal ◽  
Transition Metals ◽  
Metal Ions ◽  
Bond Length ◽  
Lone Pair ◽  
Transition Metal Ions ◽  
Oxygen Lone Pair

Bond-length distributions are examined for thirty-three configurations of the metalloid ions and fifty-six configurations of the post-transition-metal ions bonded to oxygen. Lone-pair stereoactivity is discussed.

Catalytic deuterium exchange reactions with organics. XXIV. Electron spin resonance studies of adsorption on platinum oxide

1966 ◽  
Vol 19 (4) ◽  
pp. 529 ◽  
Author(s):  
IT Ernst ◽  
JL Garnett ◽  
WA Sollich-Baumgartner
Keyword(s):  
Transition Metal Oxides ◽  
Hydrogen Exchange ◽  
Platinum Oxide ◽  
Active Species ◽  
Paramagnetic Species ◽  
Charge Transfer Complexes ◽  
Severe Reaction ◽  
Exchange Reactions ◽  
Spin Resonance ◽  
Solid Liquid

The formation of paramagnetic species on catalyst surfaces at room temperature through the interaction of polynuclear aromatics in solid, liquid, or solute form with hydrated platinum oxide (PtO2,2H2O) is reported. The results are attributed to the formation of charge-transfer complexes, where the transferred electrons couple weakly, forming essentially a "diradicaloid" complex with a low-lying, thermally populated, triplet state. The effect of solvent, particle size, oxygen, water of crystallization, and temperature on the generation and stability of these e.s.r. active species has been investigated. The possible importance of these paramagnetic species in catalytic self-activation and hydrogen exchange reactions has been discussed. The following Group VIII transition metal oxides gave no e.s.r. spectra under relatively severe reaction conditions such as 1 hr at 120�: PdO; Ru02,2H20; RuO2; Rh2O3; IrO2,2H2O; ReO2; and NiO.

Structure and bonding in cyclic phosphoramidates as determined by carbon-13 magnetic resonance

1979 ◽  
Vol 57 (1) ◽  
pp. 21-26 ◽  
Author(s):  
Gerald W. Buchanan ◽  
Frederick G. Morin
Keyword(s):  
Magnetic Resonance ◽  
Nitrogen Atom ◽  
Electron Pair ◽  
Chemical Shifts ◽  
Lone Pair ◽  
Ring Conformation ◽  
Delocalized Electron ◽  
Nitrogen Lone Pair ◽  
Structure And Bonding

13C chemical shifts and 13C–31P couplings are reported for 11 cyclic phosphoramidates of ring sizes from four to nine. Vicinal couplings are compared with those of carbocyclic analogs and provide insight regarding the degree of nitrogen lone pair derealization into the N—P bond. For six-membered and larger rings, there appears to be nearly complete lone pair delocalization, i.e., a trigonal planar nitrogen atom. In azetidine derivatives the nitrogen lone pair remains localized, giving rise to a highly puckered ring conformation. Pyrrolidine derivatives are viewed as having a nitrogen with a partially delocalized electron pair.

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