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 [W 2 L 2 (μ 2 OH) 2 Br 2 ]Br 2 · 2H 2 O and of Trimeric [W 3 L 3 (μ 3 0)(μ 2 ‐0) 3 ][ZnBr 4 ] 2

Reactions of WL(CO) 3 (L = 1, 4, 7‐triazacyclononane; C 6 H 15 N 3 ) with bromine under different conditions afford the monomeric W VI compound, WO 2 LBr 2 , or the monomeric W V complex, WOLBr 3 . The former dimerizes in aqueous solution, yielding the [W 2 O 5 L 2 ] 2+ cation. Two diamagnetic isomers of the W V ‐dimer, [W 2 O 4 L 2 ] 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 W IV ‐trinuclear cluster, [W 3 O 4 L 3 ] 4+ , has been isolated as the tetrabromozincate(2‐) salt and its structure has been determined by single crystal X‐ray diffraction. [W 3 O 4 L 3 ][ZnBr 4 ] 2 crystallizes in the monoclinic space group P2 1 /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 Å 3 , d ealed . = 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 R 1 = 0.089 and R 2 = 0.096. The structure consists of [W 3 L 3 O 4 ] 4+ cations of the M 3 X 13 cluster type and isolated ZnBr 4 2− anions. Three tungsten atoms occupy the corners of an equilateral triangle bridged by three μ 2 ‐oxo‐ and one μ 3 ‐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 W III complex, [W 2 L 2 (μOH) 2 Br 2 ]Br 2 · 2 H 2 O, has been prepared by reduction of monomeric WLOBr 3 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 Å 3 , d calcd. = 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 R 1 = 0.062 and R 2 = 0.084. The structure consists of dimeric cations [W 2 L 2 (μOH) 2 Br 2 ] 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 μ 2 ‐hydroxo bridges (edge sharing), respectively. The bromide ligands are in trans‐positions with respect to each other. The four‐membered W 2 (μOH) 2 ring is planar. The WW distance of 2.477(3) Å together with its diamagnetism imply the presence of a strong metal‐metal bond between the tungsten(II1) centers (σ 2 π 2 δ 2 ).