The relationship between transannular secondary bonding strength and conformation in diphenyldithiophosphinate stibocanes X(CH2CH2S)2SbS2PPh2 (X = O, S)

Article abstract of DOI:10.1002/zaac.19966220819

The two stibocanes 1-oxa-4,6-dithia-5-stibocane diphenyldithiophosphinate O(CH₂CH₂S)₂SbS₂PPh₂1 and 1,3,6-trithia-2-stibocane diphenyldithiophosphinate S(CH₂CH₂S)₂ · SbS₂PPh₂ 2 were prepared from the corresponding chloro oxa-and thia-stibocanes 3 and 6, and the ammonium salt of diphenyldithiophosphinic acid in CH₂Cl₂. 1 and 2 were characterized by IR, EI-MS and multinuclear NMR (¹H, ¹³C, ³¹P{¹H}). The crystalline state of 1 features two Sb1 ... S1 intermolecular interactions [3.987(2) A] that results in a dimer. Alongside 1 displays both an endocyclic, transannular Sb1 ... O1 interaction [2.555(6) A] and an exocyclic Sb1 ... S4 secondary interaction [3.327(2) A]. The coordination geometry at the antimony could be described as AX₄YE ψ-trigonal bipyramid geometry with A = Sb, X = S1, S2, S3,O1; Y = S4; S1, S2 and the lone pair lays on the equatorial plane with O1 and S4 in axial positions. The Sb1 ... S4 secondary bonding is face capping one of the planes form by the lone pair, S2 and S3 of the trigonal bipyramid. 2 also displays both an endocyclic, transannular Sb1 ... S2 interaction [2.949(3) A] and an exocyclic Sb1 ... S5 secondary interaction [3.216(3) A]. The antimony becomes five-coordinate, giving the AX₄YE ψ-trigonal bipyramid geometry with S1, S3 and the lone pair laying on the equatorial plane with S2 and S4 in axial positions. The Sb1 ... S5 also here is face capping the plane form by the lone pair, S3 and S4 of the trigonal bipyramid. The conformation of the eight membered ring in 2 is boat-chair. In 1 the main conformation is chair-planar. Johann Ambrosius Barth 1996.