The first oxygen-bridged diorganoarsenic(V) compound: the crystal structure of AsMe2(S)OAs(S)Me-2

The oxidation of tetramethyldiarsinedisulfide, (AsMe2S)(2), with t-BuOOH under anhydrous conditions leads to both AsMe2(S)-S-As(O)Me-2 1 and AsMe2(S)-O-As(S)Me-2 2. The formation of the oxygen-bridged isomer 2 is unexpected and can he rationalised as resulting from either oxidation of the As(III)/As(III) form of the disulfide, (AsMe2-S-S-AsMe2), or by an oxotropic rearrangement of 1 via a cyclic As2OS transition state. RHF/3-21G* ab initio calculations predict that the ore-bridged species 2 is more stable than the thio-bridged form 1. The molecular structure of 2 has been determined by single crystal X-ray diffraction.