Formation and Stability of Gaseous WS2Cl2, WS2Br2 and WS2I2 – A Combined Experimental and Theoretical Study

Abstract

AbstractGaseous WS2Cl2 and WS2Br2 are formed by the reaction of solid WS2 with chlorine resp. bromine at temperatures of about 1000 K. This could be shown by mass spectrometric measurements. The heats of formation and entropies of WS2Cl2 and WS2Br2 have been determined by means of mass spectrometry (MS) and quantum chemical calculations (QC). WS2I2 could not be detected by experimental methods. This is in line with the quantum chemically determined equilibrium constant of the formation reaction. The following values are given:, ΔfH0298(WS2Cl2) = –230.8 kJ·mol–1 (MS), ΔfH0298(WS2Cl2) = –235.0 kJ·mol–1 (QC),, S0298(WS2Cl2) = 370.7 J·K–1·mol–1 (QC) and, cp0T(WS2Cl2) = 103.78 + 7.07 × 10–3 T – 0.93 × 105 T–2 – 3.25 × 10–6 T2 (298.15 K < T < 1000 K) (QC). ΔfH0298(WS2Br2) = –141.9 kJ·mol–1 (MS), ΔfH0298(WS2Br2) = –131.5 kJ·mol–1 (QC),, S0298(WS2Br2) = 393.9 J·K–1·mol–1 (QC) and, cp0T(WS2Br2) = 104.84 + 5.32 × 10–3 T – 0.75 × 105 T–2 – 2.45 × 10–6 T2 (298.15 K < T < 1000 K) (QC). ΔfH0298(WS2I2) = –18.0 kJ·mol–1 (QC), S0298(WS2I2) = 409.9 J·K–1·mol–1 (QC) and, cp0T(WS2I2) = 105.17 + 4.77 × 10–3 T – 0.67 × 105 T–2 – 2.19 × 10–6 T2 (298.15 K < T < 1000 K) (QC). These molecules have the expected C2v‐symmetry.