PS2Br and AsS2X (X = Br, I): similar molecules with completely different shapes--a combined experimental and theoretical study

• Published in: Dalton transactions : an international journal of inorganic chemistry Vol. 42; no. 5; pp. 1417 - 1426
• Main Authors: Milke, E, Köppe, R, Binnewies, M
• Format: Journal Article
• Language: English
• Published: England 07.02.2013
• ISSN: 1477-9234
• DOI: 10.1039/c2dt31547e

By the reaction of solid As(4)S(4) with gaseous Br(2) at a temperature of 410 K gaseous AsSBr and AsS(2)Br are formed; the reaction with gaseous I(2) at 468 K leads to the formation of AsSI, AsS(2)I, As(2)S(2)I(2) and As(2)S(3)I(2). Thermodynamic data on these novel species are obtained by mass spectrometry. The experimental findings are extended and confirmed by ab initio quantum chemical calculations. Undoubtedly the molecules AsSX (X = Br, I) and As(2)S(2)I(2) contain As-atoms in the formal oxidation state III. Unexpectedly, in AsS(2)X arsenic is not of formal oxidation state +V but +III: due to the absence of As-S π-bonding, the molecular structure of AsS(2)X is arranged as a dithia-arsirane with an AsS(2) three-membered ring. For comparison with AsS(2)X, PS(2)Br is investigated for the first time. This high temperature species is planar with symmetry C(2v) and phosphorus of the formal oxidation state +V in which the two P=S π-bonds are realized due to their strength over one S-S σ-bond. As(2)S(3)I(2) contains a five-membered As(2)S(3)-ring with one S-S-bond. The ionization energies are determined and compared with those obtained from calculations; they serve as a further indication for the structures realized in these molecules.