Synthetic, structural and electrochemical studies of cationic chromium(VI) and molybdenum(VI) bis(imido) complexes supported by 1,4,7-triazacyclononane macrocycles

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review

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Detail(s)

Original languageEnglish
Pages (from-to)3197-3201
Journal / PublicationJournal of the Chemical Society - Dalton Transactions
Issue number18
Publication statusPublished - 21 Sep 1999
Externally publishedYes

Abstract

Treatment of [Cr(NtBu)2Cl2] or [Mo(NtBu)2Cl2(dme)] with 1,4,7-triazacyclononane (tacn) in THF, followed by metathesis using NaClO4 in aqueous medium, readily afforded [M(tacn)(NtBu)2Cl]ClO4 (M = Cr 1 or Mo 2); [M(Me3tacn)(NtBu)2Cl]Cl (M = Cr 3 or Mo 4) were similarly prepared using the metal precursors and 1,4,7-trimethyl-1,4,7-triazacyclononane (Me3tacn). Complexes 1-4 are resistant to hydrolysis, but do not mediate imido group transfer reactions. Distinctive UV-vis absorption bands are tentatively assigned to imido-to-metal LMCT transitions. The crystal structures of 1 and 2·CH3CN show that the 3 nitrogen atoms of tacn are not equidistant from the respective metal centres. A severely distorted imido moiety (imido angle 151.8(4)°) has been observed in the structure of 1 but not 2·CH3CN, and is attributed to steric and crystal packing factors rather than electronic effects. Metathesis of both chloride groups in 3 using AgOTf(OTf = SO3CF3) yielded [Cr(Me3tacn)(NtBu)2(OTf)]OTf 5. The cyclic voltammograms of 1-5 in acetonitrile consist of a quasi-reversible couple (+0.86 to +1.20 V vs. Cp2Fe0/+) and an irreversible wave (-1.04 to -2.08 V vs. Cp2Fe0/+); the former couple is assigned to an imido-centred oxidation. © The Royal Society of Chemistry 1999.

Citation Format(s)

Synthetic, structural and electrochemical studies of cationic chromium(VI) and molybdenum(VI) bis(imido) complexes supported by 1,4,7-triazacyclononane macrocycles. / Chan, Michael C. W.; Lee, Fu-Wa; Cheung, Kung-Kai; Che, Chi-Ming.

In: Journal of the Chemical Society - Dalton Transactions, No. 18, 21.09.1999, p. 3197-3201.

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review