Synthesis of extended acyclic azathienes. Crystal and molecular structure of two compounds, Ar(SNSN)nSiMe3 (Ar 2-O2NC6H4; n 1,2)

The 1:1 reaction of (Me3SiNSN)2S with ArSCl gives Ar(SNSN)2SiMe3, while the 1:2 reaction gives (ArSN)2S and (SN)4 if Ar = Ph, and (ArSNSN)2S if Ar = nitrophenyl. Thus, the aromatic nitro groups inhibit spontaneous shortening of azathiene chains of (ArSNSN)2S, but they do not stabilize the compounds containing a chain of 17 alternating nitrogen and sulphur atoms [Ar(SNSN)2SiMe3 + SCl2, 2:1] which are shortened to (ArSNSN)2S. As shown by X-ray structure analysis, the configuration of the azathiene chains in the compounds Ar(SNSN)nSiMe3 (Ar = 2- O2NC6H4; n = 1, 2) is similar to that of (SN)x macromolecules: Z, E, n = 1; Z, E, Z, E, n = 2. At n = 1 the molecule is planar, at n = 2 (the longest oligomer azathiene chain with established real geometry) the non-hydrogen atoms lie on the cylindrical surface with a radius of ca 50 A.