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  • 1
    ISSN: 0044-2313
    Keywords: Rhenium Bromide ; Crystal Structure ; Halogen Exchange ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Halogen Exchange at Re3-Clusters: A New Synthetic Route to Binary and Ternary Rhenium(III) Bromides. Crystal Structures of Cs2[Re3Br11] and Cs3[Re3Br3Cl9]The substitution of “inner” ligands in transition metal clusters in aqueous HX solutions is hitherto unknown. For the first time the substitution of bridging and terminal chloride for bromide ions was observed at rhenium clusters, [Re3(μ-Cli,b)3(Cl6o,t)(Cli,t)(3-x)(H2Oi,t)x](3-x)- (x = 0-3), via the reaction of “ReCl3 · 2 H2O” in hot hydrobromic acid solution under an inert gas atmosphere. This establishes a new synthetic route to ternary Re(III) bromides as well as to ReBr3. However, ternary Re(IV) bromides, A2ReBr6 (A = Rb, Cs), are dominating in the presence of oxygen, rhenium(III) bromides are only by-products. Dark brown rods of Cs2[Re3Br11] are obtained from argon saturated, hot hydrobromic acid solutions of “ReCl3 · 2 H2O” and CsBr. The crystal structure (orthorhombic, Pnma (Nr. 62); a = 955.51(5); b = 1 610.29(10); c = 1 372.70(9); Z = 4; Vm = 318.0(2) cm3mol-1; R = 0.084, Rw = 0.058) consists of defect clusters [Re3Br3i,bBr6o,tBr2i,t□i,t]2- in which one in plane, terminal position is not occupied. The substitution of “inner” ligands has been observed in the case of chloride for bromide only, the Bri,b and Ii,b ligands in ReBr3 and ReI3, respectively, are not substituted in hydrochloric acid even at temperatures as high as 100°C. Bordeaux red square pyramids of CsReBrCl3 = Cs3[Re3(μ-Bri,b)3Cl6o,tCl3i,t] are obtained from hot hydrochloric acid solutions of ReBr3 · 2/3 H2O upon evaporation. CsReBrCl3 (orthorhombic, C2cm (Nr. 40); a = 1 419.0(1); b = 1 419.2(1); c = 1 080.30(8) pm; Z = 4; Vm = 327.6(3) cm3mol-1; R = 0.033, Rw = 0.028) is isostructural to the corresponding chloride CsReCl4.
    Notes: Die bislang nicht beobachtete Substitution von „inneren“ Liganden in Übergangsmetallclustern in wäßriger Halogenwasserstoffsäure gelingt bei der Umsetzung von „ReCl3 · 2H2O“ mit heißer, konz. Bromwasserstoffsäure. Unter Schutzgas werden verbrückende und terminale Chloridionen in den Baugruppen [Re3(μ-Cli,b)3(Cl6o,t)(Cli,t)(3-x)(H2Oi,t)x](3-x)- (x = 0-3) durch Bromid ersetzt. Dies eröffnet einen neuen Syntheseweg für ternäre Re(III)-bromide und ReBr3. In Gegenwart von Sauerstoff dominieren ternäre Re(IV)-bromide, A2ReBr6 (A = Rb, Cs), Rhenium(III)-bromide entstehen nur als Nebenprodukte. Aus argongesättigter, bromwasserstoffsaurer Lösung von „ReCl3 · 2H2O“ und CsBr wurden dunkel-braune Stäbchen von Cs2[Re3Br11] erhalten. In der Kristallstruktur (orthorhombisch, Pnma (Nr. 62); a = 955,51(5); b = 1 610,29(10); c = 1 372,70(9); Z = 4; Vm = 318,0(2) cm3mol-1; R = 0,084; Rw = 0,058) liegen defekte Baueinheiten [Re3Br3i,bBr6o,tBr2i,t□i,t]2- vor. Der Austausch von inneren Liganden wird nur im Falle von Chlorid gegen Bromid beobachtet, die Bri,b- und Ii,b-Liganden in ReBr3 bzw. ReI3 bzw. ReI3 werden selbst bei 100°C in konz. Salzsäure nicht substituiert. Aus heißer, salzsaurer Lösung von ReBr3 · 2/3 H2O erhält man beim Eindunsten bordeauxrote, quadratische Pyramiden von CsReBrCl3 = Cs3[Re3(μ-Bri,b)3Cl6o,tCl3i,t] (orthorhombisch, C2cm (Nr. 40); a = 1 419,0(1); b = 1 419,2(1); c = 1080,30(8) pm; Z = 4; Vm = 327,6(3) cm3mol-1; R = 0,033; Rw = 0,028; isotyp zu CsReCl4).
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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