Molecular structure of arsabenzene by gas-phase electron diffraction

Vapor-phase molecules of C₅H₅As were found, assuming C_2v symmetry, to have the following structure parameters and uncertainties (2.5σ): r_g(C-As)= 1.850 ± 0.003 Å, r_g(C₂–C₃) = 1.390 ± 0.032 /rA, r_g(C₃–C₄) = 1.401 ± 0.032 /rA, r_g(C-C_ave) = 1.395₄ ± 0.002 Å, ∠CAsC = 97.3 ± 1.7°, ∠AsCC = 125.1 ± 2.8°, and ∠C₃C₃C₄ = 124.2 ± 2.9°. Amplitudes of vibration were also determined. Auxiliary information is more restrictive than pure electron diffraction intensities as evidence that the molecule is rigorously planar. Structural characteristics of arsabenzene reinforce prior indications that the heterocyclic molecule is genuinely aromatic.