Oxotrihalogenoselenate(IV): Darstellung, Struktur und Eigenschaften von P(C₆H₅)₄SeOCl₃, P(C₆H₅)₄SeOBr₃ und As(C₆H₅)₄SeOBr₃

Abstract

The novel oxotribromosolcnate(IV) SeOBr 3- anion was prepared from the reaction of stoichiometric quantities of SeOBr 2 and bromide in acetonitrile solution, and it was isolated as the tetraphenylphosphonium and -arsonium salts in crystalline form. For the synthesis of the analogous SeOCl 3- as P(C 6 H 5 ) 4 SeOCl 3 , SeCl 4 was reacted in the presence of a small quantity of H 2 O with P(C 6 H 5 ) 4 Cl in acetonitrile. Complete X-ray structural analyses of P(C 6 H 5 ) 4 SeOCl 3 (space group P1̄, a = 10.981(3), b = 11.0511(3), c = 10.358(3) Å, α = 73.77(2)°, β = 83.33(2)°, γ = 80.51(2)°, V = 1187.9(6) Å 3 ) and of P(C 6 H 5 ) 4 SeOBr 3 (space group P 2 1 /c, a = 11.719(4), b = 16.088(4), c = 13.124(4) Å, β = 94.72(3)°, V = 2400(1) Å 3 ) show dimeric centrosymmetric Se 2 O 2 Cl 6 2- and Se 2 O 2 Br 6 2- anions being present in the solid. In the anions two square-pyramidal (Ψ-octahedral) SeOHal 4 groups are connected through a common Hal-Hal edge. The axial oxygen ligands (So-O: 1.597(4) and 1.584(0) Å) cause a pronounced stereochemical trans-activation of the inert pairs at the Se atoms. As(C 6 H 5 ) 4 SeOBr 3 is isotypic with P(C 6 H 5 ) 4 SeOCl 3.