Mixed‐Valent Selenium Ligands in the Uncharged Iridium Complexes [Ir4Se10Br16] and [Ir6Se8Cl30]. Issue 26 (17th August 2015) - Stolze, Karoline
Abstract: The reaction of Ir with Se and SeBr4 at 200 °C yields shiny vermillion slate‐like crystals of the new compound Ir4 Se10 Br16 . Single‐crystal X‐ray diffraction revealed an orthorhombic unit cell, space group Pccn, with lattice parameters a = 1515.0(1) pm, b = 1534.4(1) pm, and c = 1514.5(1) pm at 296(1) K. The crystal structure consists of uncharged tetranuclear iridium complexes [Ir4 Se10 Br16 ] with C 2 symmetry. In the [(Ir 3+ )4 (μ4 ‐η 2 ‐Se2 2– )2 (μ‐η Se ‐[SeBr] – )2 (η Se ‐SeBr2 )4 (μ‐Br – )2 (Br – )4 ] complex, each of the iridium atoms is coordinated octahedrally by four selenium and two bromine atoms. Selenium adopts three different oxidation states: –I in the fourfold‐bonded diselenide dumbbell, ±0 in the bridging [SeBr] – unit, and +II in the terminal SeBr2 ligand. An analogous reaction with SeCl4 at 300 °C yields orange air‐stable crystals of Ir6 Se8 Cl30 . The triclinic crystal structure [space group P $\bar {1}$, a = 891.2(1) pm, b = 1064.6(1) pm, c = 1263.0(1) pm, α = 94.458(3)°, β = 106.900(3)°, and γ = 101.410(3)° at 296(1) K] consists of uncharged hexanuclear iridium complexes with the structured formula [(Ir 3+ )6 (μ‐η Se ‐[SeCl] – )2 (η Se ‐SeCl2 )6 (μ‐Cl – )10 (Cl – )6 ] and shows structural motifs similar to Ir4 Se10 Br16 and IrSeCl5 . The triclinic structure of IrSeCl5 [P$\bar {1}$, a = 1223.4(1) pm, b = 1408.7(1) pm, c = 1499.5(1) pm, α = 115.72(1)°, β = 106.05(1)°, and γ = 96.38(1)° at 296(1) K] is homeotypic to monoclinic RhSCl5 . Abstract : The tetra‐ and hexanuclear ring‐shaped iridium molecules [Ir4 Se10 Br16 ] and [Ir6 Se8 Cl30 ] are among the largest complexes in the category of halogen‐rich chalcogen halides of the platinum‐group metals. They feature unusual [SeBr] – or [SeCl] – ligands as well as diverse oxidation states of selenium in one molecule.