Monomere und dimere Oxotrihalogenoselenate(IV): Darstellung, Struktur und Eigenschaften von [As(C₆H₅)₄]SeOCl₃ und [N(C₂H₅)₄]SeOCl₃ / Monomerie and Dimeric Oxotrihalogenoselenates(IV): Preparation, Structure and Properties of [As(C₆H₅)₄]SeOCl₃ and [N(C₂H₅)₄]SeOCl₃

Abstract

Abstract The monomeric SeOCl 3 - ion, which can be prepared as the tetraphenylarsonium salt from SeOCl 2 and As(C 6 H 5 ) 4 Cl, was structurally characterized by a low-temperature single crystal X-ray diffraction analysis. [As(C 6 H 5 ) 4 ]SeOCl 3 is monoclinic, space group P2 1 /c, with a = 9,332(3), b = 13,761(4), c = 18,985(6) Å, β = 110,97(3)° (at -135 °C), Z = 4; it contains a novel type of ψ-trigonal bipyramidal oxotrichloroselenate(IV) anion which is not associated to dimers or polymer chains as in known structures. The equatorial positions are occupied by doubly bonded oxygen (Se-O 1,601(3) Å) and by one Cl(Se-Cl 2,234(1) Å), the axial Se-Cl bonds (2,430(1) and 2,475(1) Å) being significantly longer. [N(C 2 H 5 ) 4 ]SeOCl 3 , which was obtained as crystals by oxidation of trichloroselenate(II), is triclinic, space group P1̄, with a = 10,607(3), b = 8,950(2), c = 8,862(2) Å, α = 119,79(2)°, β = 101,07(2)°, γ = 96,28(2)°, Z = 2. The X-ray structure analysis shows the anions to be present as centrosymmetric dimers Se 2 O 2 Cl 6 2- like in the [P(C 6 H 5 ) 4 ] + salt, with two tetragonal SeOCl 4 pyramids linked through a Cl···Cl edge and the lone pairs trans to the axial Se-O bonds (1,589(4) Å). Se-Cl bond lengths are 2.270(1) and 2,351(2) Å (terminal); 2,698(1) and 2,920(1) Å (bridging). The results show that the nature of the reaction products of the Lewis acid SeOCl 2 with halogenides as bases changes very sensitively with small variations in cations and environment. The vibrational spectra are discussed.