Synthesis of the N1-bonded (5-methyltetrazolato)pentaamminecobalt(III) complex utilizing sodium azide enriched in 15N at the terminal nitrogen has produced a complex enriched specifically at the N2 and N4 ring positions. This has permitted the assignment of all four nitrogen signals in the natural-abundance 15N NMR spectrum of the complex. A similar natural-abundance NMR spectrum for a novel chelated amidine complex which is also N1 bonded is reported along with its synthesis and purification. Following the 15N NMR of the linkage isomerization of the enriched complex in solution to the N2-bonded form has also permitted an η5 and certain η3 transition-state structures to be eliminated from consideration for the isomerization process. The data suggest an η2 transition state is utilized. A subsequent N2-to-N3 isomerization of the N2-bonded complex has also been discovered from the 15N NMR study. The enrichment study also indicates that previous assignments of ring nitrogen signals N1 and N4 in similar N2-bonded tetrazolato complexes of cobalt(III) may be in error.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry