Crystal and solution structure of the palladium(II) bis(1,4,7-triazacyclononane) ion: Evidence for rapid fluxional behavior in a macrocyclic complex
An unusual example of fluxionality at the normally inert Pd(II) center is described. The preparation and x-ray crystal structure of the Pd(non)/sub 2//sup 2+/ ion (non = 1,4,7-triazacyclononane) are presented. Pd(non)/sub 2/(PF/sub 6/)/sub 2/ crystallizes in the space group P2/sub 1//c with cell dimensions of a = 7.150 (1) /angstrom/, b = 16.675 (6) /angstrom/, c = 9.542 (3) /angstrom/, and /beta/ = 97.37 (2)/degree/ (Z = 2). In the solid state the ion displays square-planar geometry, Pd-N = 2.057 /angstrom/, with the third (noncoordinated) nitrogen atom in a configuration remote (/approximately/3.5 /angstrom/) from the metal center and the rings in an anti conformation. However, in solution at ambient temperatures, /sup 13/C NMR shows only a single resonance, explicable only by a rapid ring hopping of the Pd(II) around the triaza macrocycle. This is considered to be the first example of such behavior for a Pd(II) amine complex. Temperature-dependence studies have permitted identification of syn and anti conformations in equilibrium (K/sub eq/ /approx/ 2). Rate data for the interconversion have been obtained, and a possible mechanism is proposed. The fluxional behavior of this ion explains the ready oxidation by air in aqueous medium to a very stable hexacoordinate Pd(III) ion. 41 refs., 6 figs., 3 tabs.
- Research Organization:
- Univ. of Victoria, British Columbia (Canada)
- OSTI ID:
- 5826258
- Journal Information:
- Inorg. Chem.; (United States), Vol. 27:15
- Country of Publication:
- United States
- Language:
- English
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Bis(1,4,7-triazacyclononane)palladium(III): characterization and reactions of an unusually stable monomeric palladium(III) ion
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CYCLOALKANES
CHEMICAL PREPARATION
ORGANIC NITROGEN COMPOUNDS
ORGANOMETALLIC COMPOUNDS
PALLADIUM COMPLEXES
CARBON 13
EXPERIMENTAL DATA
NMR SPECTRA
ALKANES
CARBON ISOTOPES
COMPLEXES
DATA
EVEN-ODD NUCLEI
HYDROCARBONS
INFORMATION
ISOTOPES
LIGHT NUCLEI
NUCLEI
NUMERICAL DATA
ORGANIC COMPOUNDS
SPECTRA
STABLE ISOTOPES
SYNTHESIS
TRANSITION ELEMENT COMPLEXES
400201* - Chemical & Physicochemical Properties
400202 - Isotope Effects
Isotope Exchange
& Isotope Separation