ISSN:
0044-2313
Keywords:
Chemistry
;
Inorganic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Description / Table of Contents:
Complexes of Chromium Containing 1,5,9-Triazacyclododecane: Synthesis, Magnetism, and Crystal Structure of Tri-μ-hydroxo-bis[(1,5,9-triazacyclododecane) chromium (III)] tribromide · Dihydrate; Kinetic and Mechanism of its Bridge-cleavage with HydroxideThe oxidative decarbonylation of LCr(CO)3 (L = 1,5,9-triazacyclododecane) with bromine yields green LCrBr3. Base hydrolysis affords red [LCr(μ-OH)3CrL]3+, whereas in the presence of acetate ions [L2Cr2(μ-OH)2(CH3CO2)]3+ is formed. [LCr(μ-OH)3CrL]Br3· 2 H2O crystallizes in the orthorhombic space group P212121 with 8 formula units per unit cell. Two CrIII centers are connected via three OH- bridges; the spins of d3-electronic configuration are coupled intramolecularly, antiferromagnetically (2J = -96 cm-1). With excess OH- but not with protons the tri-μ-hydroxo species is cleaved to give [L2Cr2(OH)2(μ-OH)2]2+. The kinetics of this reaction have been measured using the stopped flow technique. The mechanism is discussed.
Notes:
Oxydative Decarbonylierung von LCr(CO)3 (L = 1,5,9-Triazacyclododecan) mit Brom liefert grünes LCrBr3, dessen alkalische Hydrolyse rotes [LCr(μ-OH)3CrL]Br3·2 H2O ergibt, in Gegenwart von Acetationen aber [L2Cr2(μ-OH)2(μ-CH3CO2)]3+·Bei [LCr(μ-OH)3CrL]Br3·2 H2O (P212121, Z = 8) sind 2 CrIII-Zentren durch drei OH-Brücken verknüpft. Die Spins der d3-Elektronenkonfiguration sind intramolekular antiferromagnetisch gekoppelt (2J = -96 cm-1). Mit überschüssigen OH--Ionen (nicht aber mit H+) tritt eine Spaltung zu [L2Cr2(OH)2(μ-OH)2]2+ ein (2J = -16 cm-1). Die Kinetik wurde mit einer Strömungsapparatur gemessen; der Mechanismus wird diskutiert.
Additional Material:
4 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/zaac.19855270804
