The crystal and molecular structure of di- isothiocyanatolead(II)-di-methyl sulphoxide (1/2)

Abstract

The title compound has four Pb[NCS]₂·2Me₂SO units in a cell with a= 14.876(3), b= 16.373(7), c= 5.866(1)Å, belonging to space group P2₁ab. The absence of a centre of symmetry is supported by the morphology of the crystal. The structure has been refined by the heavy-atom method to R 6.5% for 1 331 observed diffractometer intensities. The lead atom is six co-ordinate with a distorted octahedral co-ordination sphere consisting of two nitrogenatoms [Pb–N 2.45(2),2.42(5)Å: N–Pb–N 80.2(14)°] and two sulphur atoms [Pb–S 2.19(2)Å: S–Pb–S 121.7(4)°] nearly in a plane with the lead atom, while two oxygen atoms [Pb–O 2.50(2), 2.45(3)Å] of co-ordinated dimethyl sulphoxide molecules subtend an angle of 160.1° at lead(II). The structure is explained in terms of an irregular pentagonal bipyramidal arrangement of six bonded atoms and one lone electron-pair, with the latter directed towards a pentagonal corner between the two sulphur atoms. The 80° angles in the pentagonal plane are attributed to non-bonded repulsions of ligand atoms over-riding the repulsive effect of the lone pair which, however, is thought to be strong enough to distort the O–Pb–O angle from 180 to 160°. Each Pb[NCS]₂ unit behaves like a bidentate ligand with a large ‘bite’[S ⋯ S 4.74(2)Å] to form a planar polymeric chain which extends parallel to c.