Formation and Stability of Gaseous WS 2 Cl 2 , WS 2 Br 2 and WS 2 I 2 – A Combined Experimental and Theoretical Study

Gaseous WS 2 Cl 2 and WS 2 Br 2 are formed by the reaction of solid WS 2 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 WS 2 Cl 2 and WS 2 Br 2 have been determined by means of mass spectrometry (MS) and quantum chemical calculations (QC). WS 2 I 2 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:, Δ f H 0 298 (WS 2 Cl 2 ) = –230.8 kJ · mol –1 (MS), Δ f H 0 298 (WS 2 Cl 2 ) = –235.0 kJ · mol –1 (QC),, S 0 298 (WS 2 Cl 2 ) = 370.7 J · K –1 · mol –1 (QC) and, c p 0 T (WS 2 Cl 2 ) = 103.78 + 7.07 × 10 –3 T – 0.93 × 10 5 T –2 – 3.25 × 10 –6 T 2 (298.15 K < T < 1000 K) (QC). Δ f H 0 298 (WS 2 Br 2 ) = –141.9 kJ · mol –1 (MS), Δ f H 0 298 (WS 2 Br 2 ) = –131.5 kJ · mol –1 (QC),, S 0 298 (WS 2 Br 2 ) = 393.9 J · K –1 · mol –1 (QC) and, c p 0 T (WS 2 Br 2 ) = 104.84 + 5.32 × 10 –3 T – 0.75 × 10 5 T –2 – 2.45 × 10 –6 T 2 (298.15 K < T < 1000 K) (QC). Δ f H 0 298 (WS 2 I 2 ) = –18.0 kJ · mol –1 (QC), S 0 298 (WS 2 I 2 ) = 409.9 J · K –1 · mol –1 (QC) and, c p 0 T (WS 2 I 2 ) = 105.17 + 4.77 × 10 –3 T – 0.67 × 10 5 T –2 – 2.19 × 10 –6 T 2 (298.15 K < T < 1000 K) (QC). These molecules have the expected C 2 v ‐symmetry.