Disulfidoverbrückte Halogenokomplexe von Molybdän(V) Kristallstrukturen von (PPh₃Me)₂[Cl₄Mo(μ‐S₂)₂MoCl₄] · 2 CH₂Cl₂ und (PPh₄)₂[Br₄Mo(μ‐S₂)₂MoBr₄] · 3 CH₂Br₂

Abstract

Mo(S2)Cl3, für das eine verbesserte Synthese und das IR‐Spektrum angegeben werden, reagiert mit (PPh3Me)Cl in Dichlormethanlösung unter Bildung des Komplexes (PPh3Me)2 [Cl4Mo(μ‐S2)2MoCl4]. 2 CH2Cl2. Den Bromokomplex (PPh4)2[BrMo(μ‐S2)2MoBr4]. CH2Br2 erhielten wir durch Umsetzung von MoBr4 mit S7NH und anschließender Reaktion des Produktgemisches mit PPh4Br in CH2Br2‐Lösung. Beide Komplexe haben wir IR‐spektroskopisch und durch röntgenographische Strukturanalysen charakterisiert. (PPh3Me)2[Cl4Mo(μ‐S2)2MoCl4].2CH2Cl2kristallisiert monoklin in der Raumgruppe P21/c mit zwei Formeleinheiten pro Elementarzelle (5268 unabhängige, beobachtete Reflexe, R=4,0%). Die Gitterkonstanten sind: a = 1097, b = 1510, c = 1591 pm, β = 104,4°. (PPh4)2[Br4Mo (μ‐S2)2MoBr4]. 3CH2Br2 kristallisiert triklin in der Raumgruppe P&1macr; mit zwei Formeleinheiten pro Elementrazelle (4806 unabhängige, beobachtete Reflexe, R = 6.9%). Die Gitterkonstanten sind: a = 1328, b = 1573, c = 1719 pm, α = 95,8°, β = 96,3°, γ = 74,1°. Beide Komplexe haben einen ionischen Aufbau mit PPh3Me⊕ ‐ bzw. PPh4⊕ ‐ Kationen und Anionen [X4Mo(μ‐S2)2MoX4]2⊖, die einander sehr ähnlich sind. Die Molybdänatome sind über zwei Disulfidobrücken und durch eine direkte MoMo‐Bindung mit einem Abstand von 286 pm miteinander verknüpft. Die terminalen Halogenatome ergänzen die Koordinationszahl am Molybdän zu neun.

Synthesis and Crystal Structures of Cs5Nb2S4X9 - Double Salts Containing New Cluster Anions [Nb2(μ-S2)2X8]4- (X = Cl, Br)

“…This is very close to 290 pm value found in NbS 2 Cl 2 [2]. Overall the geometry of Nb 2 S 4 core in 1±3 is unexceptional and the Nb±Nb, Nb±S and S±S distances are in a good agreement with those found in Nb 2 S 4 (Et 2 NCS 2 ) 4 [15]. This shows that the cluster core is only marginally affected by the changes in external ligands.…”

“…The coordination polyhedron around the Nb atoms (if the Nb±Nb bond is disregarded) is a distorted square antiprism composed of 4 S atoms and 4 Cl(Br) atoms. This coordination is found in all the Nb 2 S 4 clusters so far reported [2,5,11,15] but in addition in 1±3 each Nb atom has two distinct sets of coordinated halogens. One set includes atoms which are coplanar with the mirror plane passing through two Nb atoms and two midpoints of each S 2 ligand.…”

“…distances. This difference does not exist when H 2 the axial halides are again by about 10 pm farther away from the metal then the equatorial ligands [15,16,18] (Table 6) and M±S eq. distances [20].…”

“…distances [20]. It has been proposed that the axial ligands (X(2)) take up the excess negative charge of the anionic complex [15]. Overall, all the distances in the Nb clusters 1±3 (Nb±Nb, Nb±S, Nb± X) are longer than in the isoelectronic Mo and W clusters.…”

“…Treatment of such solids with sources of Cl ± or Br ± would break the bridges to give corresponding anionic halide complexes, preserving the cluster core, from which other complexes can be further made by ligand substitution reactions. This approach works well for MoS 2 2± (M = Mo, X = Cl, Br [11,12,15,16]; M = W, X = Cl [17]; X = Br [18]). The formation of [Nb 2 S 4 X 8 ] 4± (X = Cl, Br) complexes of some stability was therefore expected at least in concentrated HX solution, but it was difficult to find a suitable countercation and right conditions to precipitate the halide complexes.…”