Syntheses of Monomeric, Dimeric, and Trimeric Complexes of Tungsten(VI), (V), (IV), and (III) with the 1,4,7‐Triazacyclononane (L) Ligand. Crystal Structures of Dimeric [W2L2(μ2OH)2Br2]Br2 · 2H2O and of Trimeric [W3L3(μ30)(μ2‐0)3][ZnBr4]2

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).