1H N.m.r. Chemical shifts and hydrogen exchange rates oftrans-[Co(en)2XY]n+ complexes in liquid ammonia

Balt, S.; Gamelkoorn, Hendrikus J.; Lammers, Koene R.

doi:10.1007/bf00620663

Cited by 5 publications

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“…We believed this to be a misinterpretation of the facts based on an incorrect assignment , for the syn or anti protons in either the reactant trans -[Co(en) 2 (OSMe 2 )(N 3 )] 2+ or product trans -[Co(en) 2 (NH 3 )(N 3 )] 2+ complexes. Herein we redress both these issues.…”

Section: Introductionmentioning

confidence: 99%

Secondary Deuterium Kinetic Isotope Effect for Aquation, Solvolysis, and Isomerization Reactions of trans-[Co(en)₂(OSMe₂)N₃]²⁺, and the Resolution of a Mechanistic Anomaly

Jackson

2004

Inorg. Chem.

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The two closely spaced NH signals in the (1)H NMR spectrum of trans-[Co(en)(2)(OSMe(2))(N(3))](2+) have been reassigned using 2D NMR and other techniques. Thus, the unusual syn to anti (to Co-N(3)) NH rearrangement on base catalyzed substitution of the selectively deuterated complex in ND(3)(l) has been reinterpreted as "normal", with inversion of the effective deprotonation site accompanying the act of substitution. The re-examination of this system required a repeat study of the secondary isotope effect for the acid hydrolysis reaction, previously used to assign syn and anti amine sites, and this has been extended to other solvents (Me(2)SO, MeCN). The relative NH proton exchange rates are also reconsidered. A systematic rate reduction for Me(2)SO substitution is observed for deuterium incorporation into the cis-NH centers, irrespective of whether these are syn or anti, and the effect is much greater in Me(2)SO than in water. The results are interpreted in terms of zero point energy effects and coupled vibrations.

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Section: Introductionmentioning

confidence: 99%

Secondary Deuterium Kinetic Isotope Effect for Aquation, Solvolysis, and Isomerization Reactions of trans-[Co(en)₂(OSMe₂)N₃]²⁺, and the Resolution of a Mechanistic Anomaly

Jackson

2004

Inorg. Chem.

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“…Our interest in the kinetic isotope effect for hydrolysis reactions stems from a paper by Balt and Gamelkoorn on the ammoniolysis of an elusive complex we synthesized in 1976, trans -[Co(en) 2 (N 3 )(OSMe 2 )] 2+ . This ion has two distinct kinds of NH protons, one adjacent to the azide ligand and one remote . The two kinds of NH protons observed in the 1 H NMR spectrum were assigned by Balt et al using the spectra for the “parent” ions, trans -[Co(en) 2 (OSMe 2 ) 2 ] 3+ and trans -[Co(en) 2 (N 3 ) 2 ] + .…”

Section: Introductionmentioning

confidence: 99%

Stereoselectivity of the Secondary Isotope Effect in the Aquation of [Co(NH₃)₅Cl]²⁺

Jackson

2002

Inorg. Chem.

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A careful kinetic study of the acid hydrolysis of [Co(NH(3))(5)Cl](2+) and the selectively deuterated species trans-[Co(NH(3))(4)(ND(3))Cl](2+), trans-[Co(ND(3))(4)(NH(3))Cl](2+), and [Co(ND(3))(5)Cl](2+) reveals that N-deuteration reduces the hydrolysis rate at both the cis and trans sites. On a per-D basis, the rate reduction is three times more effective for trans-Cl deuteration. This result is contrary to conventional wisdom but has never been tested previously. It appears to be the first example of significant stereoselectivity for the secondary isotope effect in a substitution reaction, in either inorganic or organic systems. An explanation is offered in terms of the effect of D-substitution on zero point energies, the different extents of coupling of NH(D) and Co-Cl vibrational modes according to their stereochemical relationship, and the view that the rate of acid hydrolysis of the [Co(NH(3))(5)Cl](2+) involves an aberrant Co-Cl vibration component.

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Dictionary of Inorganic Compounds

Macintyre¹,

Daniel²,

Stirling³

1992

Dictionary of Inorganic Compounds

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1H N.m.r. Chemical shifts and hydrogen exchange rates oftrans-[Co(en)2XY]n+ complexes in liquid ammonia

Cited by 5 publications

References 24 publications

Secondary Deuterium Kinetic Isotope Effect for Aquation, Solvolysis, and Isomerization Reactions of trans-[Co(en)₂(OSMe₂)N₃]²⁺, and the Resolution of a Mechanistic Anomaly

Secondary Deuterium Kinetic Isotope Effect for Aquation, Solvolysis, and Isomerization Reactions of trans-[Co(en)₂(OSMe₂)N₃]²⁺, and the Resolution of a Mechanistic Anomaly

Stereoselectivity of the Secondary Isotope Effect in the Aquation of [Co(NH₃)₅Cl]²⁺

Dictionary of Inorganic Compounds

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1H N.m.r. Chemical shifts and hydrogen exchange rates oftrans-[Co(en)2XY]n+ complexes in liquid ammonia

Cited by 5 publications

References 24 publications

Secondary Deuterium Kinetic Isotope Effect for Aquation, Solvolysis, and Isomerization Reactions of trans-[Co(en)2(OSMe2)N3]2+, and the Resolution of a Mechanistic Anomaly

Secondary Deuterium Kinetic Isotope Effect for Aquation, Solvolysis, and Isomerization Reactions of trans-[Co(en)2(OSMe2)N3]2+, and the Resolution of a Mechanistic Anomaly

Stereoselectivity of the Secondary Isotope Effect in the Aquation of [Co(NH3)5Cl]2+

Dictionary of Inorganic Compounds

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Secondary Deuterium Kinetic Isotope Effect for Aquation, Solvolysis, and Isomerization Reactions of trans-[Co(en)₂(OSMe₂)N₃]²⁺, and the Resolution of a Mechanistic Anomaly

Secondary Deuterium Kinetic Isotope Effect for Aquation, Solvolysis, and Isomerization Reactions of trans-[Co(en)₂(OSMe₂)N₃]²⁺, and the Resolution of a Mechanistic Anomaly

Stereoselectivity of the Secondary Isotope Effect in the Aquation of [Co(NH₃)₅Cl]²⁺