ISSN:
0044-2313
Keywords:
Chemistry
;
Inorganic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Description / Table of Contents:
Synthesen monomerer, dimerer und trimerer Komplexe des Wolframs(VI), (V), (IV) und (III) mit dem Liganden 1,4,7-Triazacyclononan (L). Die Kristallstrukturen von [W2L2(μ—OH)2Br2]Br2 · 2 H20 und von [W3L3(μ3—0) (μ2—O)3] [ZnBr4]2Die Reaktionen von WL(CO)3 (L = 1,4,7-Triazacyclononan; C5H15N3) mit Brom ergeben je nach Reaktionsführung monomeres WO2LBr2 oder WOLBr3. Ersteres dimerisiert in wäßriger Lösung zum [W205L2]2+-Kation. Zwei diamagnetische Isomere des [W2O4L2]2+ wurden dargestellt: eine gelbe Form mit zwei terminalen 0 × 0-Gruppen in cis-Position und eine rote Form mit trans-Position dieser 0 × 0-Gruppen. Ein kationischer Cluster des WIV wurde als Tetrabromozinkat isoliert: [W3O4L3][ZnBr4]2. Dieses Salz kristallisiert in der Raumgruppe P21/c mit a =12,698(2) Å, b = 21,267(6) Å, c = 15,687(7) Å, β = 92,94(3)º und V = 4222 Å3, dber. = 2,79 g/cm3 für Z = 4. Die Struktur wurde mittels direkter Methoden gelöst mit 7399 unabhängigen Reflexen (R1 = 0,089; R2 = 0,096). Der kurze W-W-Abstand in der trimeren Einheit W3O4 von 2,52 Å und der beobachtete Diamagnetismus weisen auf W-W-Bindungen hin. Die Reduktion von WLOBr3, mit Zn in stark saurer, wäßriger Lösung führt zum grünen, zweikernigen Komplex des Wolfram(III): [W2L2(μ—OH)2Br2]Br2 · 2 H20. Dieses Salz kristallisiert in der Raumgruppe Pnnm mit a = 13,83.7(5) Å, b = 11,657(6) Å, c = 7,832(4) Å und V = 1263 Å3; dber. = 2,67 g/cm3 für Z = 2. Die Struktur wurde mittels direkter Methoden gelöst mit 783 unabhängigen Reflexen (R1 = 0,062; R2 = 0,084). Der viergliedrige Ring W2(μ—OH)2 ist planar. Der kurze W—W-Abstand von 2,477(3) Å und der beobachtete Diamagnetismus deuten auf eine starke W—W-Mehrfachbindung (σ2π2δ2).
Notes:
Reactions of WL(CO)3 (L = 1, 4, 7-triazacyclononane; C6H15N3) with bromine under different conditions afford the monomeric WVI compound, WO2LBr2, or the monomeric WV complex, WOLBr3. The former dimerizes in aqueous solution, yielding the [W2O5L2]2+ cation. Two diamagnetic isomers of the WV -dimer, [W2O4L2]2+, have been prepared : a yellow form with terminal oxo groups in cis-positions with respect to each other and a red species containing two terminal oxo-groups in trans-positions. The cationic WIV -trinuclear cluster, [W3O4L3]4+, has been isolated as the tetrabromozincate(2-) salt and its structure has been determined by single crystal X-ray diffraction. [W3O4L3][ZnBr4]2 crystallizes in the monoclinic space group P21/c with a = 12.698(2) Å, b = 21.267(6) Å, c = 15.687(7) Å, β = 92.94(3)0, and V = 4222 Å3, dealed. = 2.79 g cm-3 for Z = 4, and mol wt 1773.2. The structure was solved by direct methods using 7399 unique reflections with I≥ 2.5 σ (I). Final residuals were R1 = 0.089 and R2 = 0.096. The structure consists of [W3L3O4]4+ cations of the M3X13 cluster type and isolated ZnBr42- anions. Three tungsten atoms occupy the corners of an equilateral triangle bridged by three μ2-oxo- and one μ3-oxo-ligands; each tungsten atom has a distorted octahedral environment of three oxygen and three nitrogen atoms. The short W - W distances of 2,52 Å and the diamagnetism indicate metal-metal bonding.The green, diamagnetic binuclear WIII complex, [W2L2(μ—OH)2Br2]Br2 · 2 H2O, has been prepared by reduction of monomeric WLOBr3 in strongly acidic solution with zinc powder. The complex has been characterized by a single-crystal X-ray diffraction study; it crystallized in the orthorhombic space group Pnnm with a = 13.837(5) Å, b = 11.657(6) Å, c = 7.832 Å, and V = 1263 Å3, dcalcd. = 2.67 g cm-3 for Z = 2, and mol wt 1015.8. The structure was solved by direct methods using 783 unique reflections with I ≥ 2.5 σ(1). Final residuals were R1 = 0.062 and R2 = 0.084. The structure consists of dimeric cations [W2L2(μ—OH)2Br2]2+, bromide anions and molecules of water of crystallization. The tungsten centers are in a distorted octahedral environment of the tridentate N-donor igand, one coordinated bromide and two μ2-hydroxo bridges (edge sharing), respectively. The bromide ligands are in trans-positions with respect to each other. The four-membered W2(μ—OH)2 ring is planar. The W—W distance of 2.477(3) Å together with its diamagnetism imply the presence of a strong metal-metal bond between the tungsten(II1) centers (σ2π2δ2).
Additional Material:
3 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/zaac.19855210204
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