Addition der schweren Chalkogen-Atome und Halogenonium-Ionen an Carbodiphosphorane / Addition of the Heavy Chalkogen Atoms and Halogenonium Ions to Carbodiphosphoranes

Abstract

Hexaphenylcarbodiphosphorane Ph3P=C=PPh3 (1) forms deeply coloured, crystalline 1:1 ad- ducts with elemental sulfur, selenium and tellurium (2, 3 and 7, respectively). A superior method of synthesis for 7 is the reaction of Na2Te with (Ph3P)2CCl⊕Cl⊖. All three compounds are thermally unstable and decompose at or below room temperature. A selenium adduct 5 was also obtained with Me3P = C = PPh, (4). The compounds 2 and 3 can be alkylated at the chalkogen atoms using MeOSO2F or PhCH2Cl. Oxydation of 3 leads to Se - Se coupling. Addition of elemental iodine to 1 in molar ratios 1:1. 2:3 and 1:2 affords salt-like products composed of the (Ph2P)2Cl⊕ cation associated with I⊖ and/or I3 ⊖ anions (8a-c). The crystal and molecular structures of 3 and 8b have been determined by single crystal X-ray diffraction. 3′, containing one half equivalent of disordered tetrahydrofuran, crystallizes in the monoclinic space group P21/n (a = 10.848(6), b = 17.433(8). c = 16.848(9) Å, β = 91.51(5)°. V = 3185.07 Å3, ϱx = 1359 gcm-3, Z = 4). Based on 3488 structure factors, the final R value was 0.103. The selenium is attached to the ylidic carbon atom without major changes of the Ph3P=C=PPh3 skeleton (C - Se = 1.99 Å). 8b crystallizes in the triclinic space group P1̄ (a = 9.935(2). b = 11.507(2), c = 16.646(3) Å, α = 90.91(1), β = 112.00(1), γ = 96.60(1)°, V = 1749.15 A3, ϱx = 1.741 gcm-3, Z = 2). Refinement of 382 parameters on 5096 structure factors converged at R = 0.043. The molecular structure shows close similarities to the selenium adduct 3 (C-I = 2.12 Å).