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Bis(1,4,7-triazacyclononane)palladium(III): characterization and reactions of an unusually stable monomeric palladium(III) ion

Journal Article · · Inorg. Chem.; (United States)
DOI:https://doi.org/10.1021/ic00291a010· OSTI ID:5852994
;
The synthesis of the monomeric palladium(III) ion (Pd((9)aneN/sub 3/)/sub 2/)/sup 3+/ ((9)aneN/sub 3/: 1,4,7-triazacyclononane) as the hexafluorophosphate salt is described. Solutions of this ion exhibit exceptional kinetic stability in aqueous media as shown by the ESR spectrum of the d/sup 7/ ion. With Pd/sup II/((9)aneN/sub 3/)/sub 2//sup 2+/, electrochemical oxidation yields two one-electron cyclic voltammograms associated with oxidation to the Pd(III) and Pd(IV) states. A detailed analysis of the pH dependences of the electrode potentials is provided. An isotropic ESR signal is observed at low ionic strength. However, in saturated Li/sub 2/SO/sub 4/, a pseudoaxial spectrum is derived, owing to ion-pair formation. Stopped-flow kinetic experiments have been carried out with both Pd((9)aneN/sub 3/)/sub 2//sup 3+/ and Pd((9)aneN/sub 3/)/sub 2//sup 2+/ as reagents. Rates of reduction of the Pd(III) ion with Co((9)aneN/sub 3/)/sub 2//sup 2+/ and Co(sepulchrate)/sup 2+/ and rates of oxidation of the Pd(II) ion with Ni((9)aneN/sub 3/)/sub 2//sup 3+/ and Ni(Me(9)aneN/sub 3/)/sub 2//sup 3+/, when analyzed by using a Marcus cross-correlation, led to a value of (2 /plus minus/ 1) /times/ 10/sup /minus/6/ M/sup /minus/1/ s/sup /minus/1/ for the Pd((9)aneN/sub 3/)/sub 2//sup 3+/2+/ couple. The origin of this exceptionally low rate lies in the inner-sphere reorganization required to provide axial interaction of the noncoordinated nitrogens with the normally square-planar d/sup 8/ Pd(II) ion. This rate constant is contrasted with that of (7 /plus minus/ 3) /times/ 10/sup 2/ M/sup /minus/1/ s/sup /minus/1/ for the Pd((9)aneN/sub 3/)/sub 2//sup 4+/3+/ couple where both reagents are octahedral in configuration. 32 references, 4 figures, 6 tables.
Research Organization:
Univ. of Victoria, British Columbia (Canada)
OSTI ID:
5852994
Journal Information:
Inorg. Chem.; (United States), Journal Name: Inorg. Chem.; (United States) Vol. 27:18; ISSN INOCA
Country of Publication:
United States
Language:
English

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Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
400202 -- Isotope Effects
Isotope Exchange
& Isotope Separation
ALKANES
BARYONS
CARBON 13
CARBON ISOTOPES
CHEMISTRY
COMPLEXES
CYCLOALKANES
DATA
ELECTROCHEMISTRY
ELEMENTARY PARTICLES
EVEN-ODD NUCLEI
EXPERIMENTAL DATA
FERMIONS
HADRONS
HYDROCARBONS
INFORMATION
ISOTOPES
LIGHT NUCLEI
NMR SPECTRA
NUCLEI
NUCLEONS
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PALLADIUM COMPLEXES
PROTONS
SPECTRA
STABLE ISOTOPES
SYNTHESIS
TRANSITION ELEMENT COMPLEXES