Amido-Bridged Dinuclear Chromium(III) Complexes with 1,4,7-Triazacyclononane.

Andersen, Peter; Glerup, Jørgen; Gumm, Andreas; Nielsen, Karen Margrethe; Lönnberg, Harri; Yan, Shi‐Ping; Yao, Xin‐Kan; Wang, Honggen; Tuchagues, J. P.; Ögren, Mattias

doi:10.3891/acta.chem.scand.53-0391

Cited by 3 publications

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“…In connection with the first amido bridge cleavage, reaction (1), another reaction was observed. This reaction, most marked at higher temperatures, is a loss of ammonia from complex 4 under the formation of [(tacn)Co(-NH 2 ) 2 (-OH)Co(tacn)] 3+ (a similar irreversible reaction has been described for the chromium analogue 18 ). ESMS of an isolated product (perchlorate, see Experimental) showed a mixture of this complex and complex 4 (deprotonated) after 30-60 min in 1.0 M HClO 4 at 70 °C.…”

Section: [(Tacn)co(-nh 2 ) 2 {-Tacn(−h)}co(nh 3 )] 3+ (3)mentioning

confidence: 69%

“…The complex [(NH 3 ) 4 Co(-NH 2 )(-OH)Co(NH 3 ) 4 ] 4+ in Table 3 is another example showing an increased rate for water substitution of ammonia. 26 By prolonged treatment of [(tacn)Co(-NH 2 ) 3 Co(tacn)] 3+ in 1.0 M HClO 4 (1-4 h at 70 °C) the reaction proceeds, as for the chromium(III) analogue, 18 and [(tacn)Co(-NH 2 )(-OH) 2 Co(tacn)] 3+ is formed (FPLC and ESMS). In addition these reactions are accompanied by bridge cleavage of the triply bridged species to form doubly bridged species, which may exist as cis-and trans-isomers, making the whole system rather complicated.…”

Section: [(Tacn)co(-nh 2 ) 2 {-Tacn(−h)}co(nh 3 )] 3+ (3)mentioning

confidence: 99%

“…Peak areas (UV detection at 254 nm) were determined using a program developed by Ole Mønsted, 34 and further details concerning the FPLC separation (of similar chromium(III) complexes) are described elsewhere. 18,21 Acid dissociation constants were determined 18 on a Radiometer PHM52 instrument as described by Mønsted and Mønsted. 35 Single crystal X-ray diffraction data were collected at 122 K on a Nonius KappaCCD area-detector diffractometer equipped with an Oxford Cryostreams low-temperature device.…”

Section: Description Of the Crystal Structure Of The Perchlorate Of T...mentioning

confidence: 99%

“…14 Whereas an acid-accelerated path for the cleavage of a hydroxo bridge can be explained by H + binding to the bridging atom, [15][16][17] this is not possible for the co-ordinatively saturated amido bridge. Nevertheless, acid-accelerated amido bridge cleavage was observed recently 18 also for the chromium(III) analogue, [(NH 3 ) 3 Cr(-NH 2 ) 3 -Cr(NH 3 ) 3 ] 3+ , and for [(tacn)Cr(-NH 2 ) 3 Cr(tacn)] 3+ and [(tacn)Cr(-NH 2 ) 2 (-OH)Cr(tacn)] 3+ (tacn = 1,4,7-triazacyclononane).…”

Section: Introductionmentioning

confidence: 99%

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Dinuclear 1,4,7-triazacyclononane (tacn) complexes of cobalt(iii) with amido and tacn bridges. Synthesis, characterization and reversible acid-accelerated bridge cleavage

et al. 2004

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Amido-bridged dinuclear cobalt(III) complexes with 1,4,7-triazacyclononane (tacn) were synthesized from [Co(tacn)(O3SCF3)3] by treatment with potassium amide in liquid ammonia at 100 degrees C. Two isomeric triply bridged complexes, [(tacn)Co(mu-NH2)3Co(tacn)]3+ and [(tacn)Co(mu-NH2)2[mu-tacn(-H)]Co(NH3)]3+, were isolated as perchlorates, and the crystal structure of the perrhenate of the latter complex was determined by X-ray diffraction. In this compound a nitrogen atom (deprotonated) from one of the tacn ligands forms a third bridge together with two amido bridges. In 1.0 M (Na,H)ClO4 ([H+] 0.1-1.0 M) the two isomers undergo acid-accelerated amido bridge cleavage, as earlier found for chromium(III) analogues, in spite of the fact that such bridges are co-ordinatively saturated. The triamido-bridged isomer is in this acid medium in equilibrium with [(H2O)(tacn)Co(mu-NH2)2Co(tacn)(NH3)]4+. An isolated perchlorate of this complex appeared to be the salt of the trans-ammineaqua isomer as determined by X-ray diffraction. Equilibration from both sides fits the first-order rate constant dependence k(obs)=6.2(3) x 10(-5)[H+] + 2.1(2) x 10(-5)(s(-1)) at 40 degrees C. Prolonged treatment of the two triply bridged isomers in 1.0 M HClO4 at elevated temperature produces primarily triply bridged dinuclear species where one or two amido bridges have been replaced by hydroxo bridges.

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Section: [(Tacn)co(-nh 2 ) 2 {-Tacn(−h)}co(nh 3 )] 3+ (3)mentioning

confidence: 69%

Section: [(Tacn)co(-nh 2 ) 2 {-Tacn(−h)}co(nh 3 )] 3+ (3)mentioning

confidence: 99%