AsS2Cl—an Arsenic(v) Compound? Formation, Stability and Structure of gaseous AsSCl and AsS2Cl—a combined experimental and theoretical study

Abstract

By reaction of solid As₄S₄ with gaseous Cl₂ at a temperature of 410 K gaseous AsSCl and AsS₂Cl are formed. Unexpectedly in AsS₂Cl the arsenic is not of formal oxidation state +V but +III: the molecular structure of AsS₂Cl is arranged as a 1-chloro-dithia-arsirane and comprises an hitherto unknown AsS₂ three-membered ring. Thermodynamic data on AsSCl and AsS₂Cl are obtained by mass spectrometry (MS). The experimental data are extended and confirmed by ab initio quantum chemical calculations (QC). The following values are given: Δ_fH⁰₂₉₈(AsSCl) = −5.2 kJ mol⁻¹ (MS), Δ_fH⁰₂₉₈(AsSCl) = 1.7 kJ mol⁻¹ (QC), S⁰₂₉₈(AsSCl) = 296.9 J K⁻¹ mol⁻¹ (QC) and c_p⁰_T(AsSCl) = 55.77 + 3.97 × 10⁻³T − 4.38 × 10⁵T⁻² − 1.83 × 10⁻⁶T² and Δ_fH⁰₂₉₈(AsS₂Cl) = −39.0 kJ mol⁻¹ (MS), Δ_fH⁰₂₉₈(AsS₂Cl) = −20.2 kJ mol⁻¹ (QC), S⁰₂₉₈(AsS₂Cl) = 321.3 J K⁻¹ mol⁻¹ (QC) and c_p⁰_T(AsS₂Cl) = 80.05 + 5.09 × 10⁻³T − 7.61 × 10⁵T⁻² − 2.35 × 10⁻⁶T² (298.15 K < T < 1000 K) (QC). The ionization energies are determined (IP(AsSCl) = 10.5, IP(AsS₂Cl) = 10.2 eV). The IR spectrum of AsSCl is detected by means of matrix isolation spectroscopy. The estimated force constant f(AsS) = 4.47 mdyn·Å⁻¹ gives rise to an AsS double bond.