Remarkable Effect ofC-Methyl Substitutions on the Ligand Field Strength of a Cobalt(III) Complex Containing a Cyclic Tetraamine with a Foldedcis-Type Configuration

Autor:	Kana Kuroda, Sadao Yoshikawa, Shuji Miura, Morio Yashiro, Makoto Komiyama, Shigenobu Yano
Rok vydání:	1994
Předmět:	Circular dichroism Crystallography 13c nmr spectroscopy Chemistry Stereochemistry Ligand Spectrochemical series chemistry.chemical_element Chelation General Chemistry Optically active Cobalt Dissociation (chemistry)
Zdroj:	Bulletin of the Chemical Society of Japan. 67:3276-3281
ISSN:	1348-0634 0009-2673
DOI:	10.1246/bcsj.67.3276
Popis:	Cobalt(III) complexes containing an optically active 14-membered cyclic tetraamine (R,R-Me6[14]aneN4, 7(R), 14(R)-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane) and a bidentate ligand (glycinato, S-alaninato, or oxalato), in which the tetraamine takes the folded cis-type configuration, were prepared and characterized by elementary analyses, 1H and 13C NMR spectroscopy, and circular dichroism spectroscopy. Electronic absorption and 59Co NMR spectroscopies indicate that stereochemical modification of the 14-membered cyclic ligand with C-methyl groups causes an unusual decrease in the ligand field strength of the complex. Rapid dissociation of the chelated alaninato ligand from the cobalt(III) complex, which is generally inert, was observed for the [Co(S-alaninato)(R,R-Me6[14]aneN4)]2+ complex system. The dependence of the dissociation of the alaninato chelate on the ligand field strength is strongly suggested.
Databáze:	OpenAIRE
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