Synthesis and Crystal Structure of Bis(methyltriphenylphosphonium) Hexabromotellurate(IV)‐bis{dibromoselenate(II)}, [PMePh 3 ] 2 [TeBr 6 (SeBr 2 ) 2 ], the Salt of a Mixed‐valence Bromotellurate(IV)‐Selenate(II) Anion

Brown crystals of [PMePh 3 ] 2 [TeBr 6 (SeBr 2 ) 2 ] ( 1 ) were obtained when selenium and bromine (1:1) react in acetonitrile solution in the presence of tellurium(IV) bromide and methyltriphenylphosphonium bromide. The salt 1 crystallizes in the triclinic space group P1¯ with the cell dimensions a = 10.3630(14)Å, b = 11.5140(12)Å, c = 11.7605(17)Å, α = 108.643(9)°, β = 106.171(10)° and γ = 99.077(9)° (296 K). In the solid state the [TeBr 6 (SeBr 2 ) 2 ] 2— anion contains a nearly regular [TeBr 6 ] octahedron where the four equatorial bromo ligands each have developed a bond to the Se II atom of a SeBr 2 molecule. The contacts between the bridging bromo and the Se II atoms of the SeBr 2 molecules are observed in the range 3.11—3.21Å, and can be interpreted as bonds of the donor‐acceptor type with the bridging bromo ligands as donors and the SeBr 2 molecules as acceptors. The Te IV —Br distances are in the range 2.67—2.72Å, and the Se II —Br bond lengths in coordinated SeBr 2 molecules in the range 2.33—2.34Å.