Dibenzo-7-phosphanorbornadiene-substituted diazene MesN₂PA (1, where Mes = mesityl, A = anthracene, or C₁₄H₁₀), a synthetic equivalent of mesitylphosphaazide (MesN₂P) and anthracene, was synthesized by treatment of [Ph₃BPA][Na(OEt₂)₂] with [MesN₂]OTf (OTf = CF₃SO₃^-) in thawing tetrahydrofuran (14% isolated yield). Treatment of 1 with unsaturated molecules cyclooctyne, [Na(dioxane)_2.5][OCP] (phosphaethynolate), and Ad-C≡P (Ad = adamantyl) results in the corresponding [3 + 2] phosphaazide-(phospha)alkyne cycloadducts, with concomitant loss of anthracene in 65%, 49%, and 38% isolated yield, respectively. Structural data for the phosphaethynolate cycloadduct ([3][Na(12-crown-4)₂]) were obtained in a single-crystal X-ray diffraction study. A diazatriphosphole was generated by combining 1 with P₂A₂, a thermally activated anthracene-based molecular precursor to diphosphorus (P₂). Thermolysis (33-65 °C) of 1 in benzene-d₆ leads to anthracene extrusion. This process has a unimolecular kinetic profile and proceeds with activation parameters of ΔH^⧧ = 21.6 ± 0.3 kcal/mol and ΔS^⧧= -4.9 ± 0.8 cal/(mol K).

Jan M. Rall

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