Crystal structure of a [1,2,5]oxaselenazolo[2,3-b][1,2,5]oxaselenazole-7-SeIV: a molecule with ‘short’ intramolecular Se ⋯ O distances, or ‘long’ Se–O bonds

Abstract

The crystal structure of the title compound (IV) has been determined from X-ray diffraction by Patterson and Fourier methods. Crystals are monoclinic with a= 5·837(2), b= 20·337(11), c= 7·971(2)Å, and β= 97° 55(2′), space group P2₁/n, with Z= 4. The structure, including hydrogen atoms, has been refined to R 0·056 for 1154 non-zero reflections. The non-hydrogen atoms in the molecule are almost coplanar except for the CMe₂ group in the six-membered ring. The selenium atom interacts with the oxygen atoms of the two nitroso-groups in the molecule to give Se–O 2·017(9) and 2·030(9)Å; O–Se–O is 199·2(4)°. The lengths of the Se–O, C–Se, C–C, C–N, and N–O bonds all support a bicyclic structure for the O–Se–O–N–C–C–C–N moiety involving three-co-ordinate selenium. In the crystal, the molecules of (IV) are arranged as centrosymmetric dimers with two Se ⋯ O intermolecular distances of 3·20 Å.