PNNL

Abstract

Dibenzo-7-phosphanorbornadiene Ph3PC(H)PA (1, A = C14H10, anthracene) is reported as a molecular precursor to phosphaethyne (HC=P), produced together with anthracene and triphenylphosphine. HCP generated by thermolysis of 1 has been characterized by molecular beam mass spectrometry (MBMS), laser-induced fluorescence (LIF), microwave spectroscopy, and nuclear magnetic resonance (NMR) spectroscopy. In toluene, fragmentation of 1 has been found to proceed with activation parameters of ?H ‡ = 25.5 kcal/mol and ?S ‡ = -2.43 e.u., and is accompanied by formation of an orange insoluble precipitate. Results from computational studies of the mechanism of HCP generation are in good agreement with experimental data. This high temperature method of HCP generation has pointed to new reaction chemistry with azide anion to produce the 1,2,3,4-phosphatriazolate anion, HCPN3- , for which structural data have been obtained in a single-crystal Xray diffraction study. Negative ion photoelectron spectroscopy has shown the adiabatic detachment energy for this anion to be 3.555(10) eV. The aromaticity of HCPN3- has been assessed using nucleus-independent chemical shift (NICS), quantum theory of atoms in molecules (QTAIM), and natural bond orbital (NBO) methods.