THE RELATIONSHIP BETWEEN TRANSANNULAR SECONDARY BONDING STRENGTH AND CONFORMATION IN DIPHENYLDITHIOPHOSPHINATE STIBOCANES X(CH2CH2S)(2)SBS(2)PPH(2) (X=O, S)

The two stibocanes 1-oxa-4,6-dithia-5-stibocane diphenyldithiophosphin ate O(CH2CH2S)(2)SbS(2)PPh(2) 1 and 1,3,6-trithia-2-stibocane diphenyl dithiophosphinate S(CH2CH2S)(2) . SbS(2)PPh(2) 2 were prepared from th e corresponding chloro oxa- and thia-stibocanes 3 and 6, and tile ammo nium salt of diphenyldithiophosphinic acid in CH2Cl2. 1 and 2 were cha racterized by IR, EI-MS and multinuclear NMR (H-1, C-13, P-31([H-1]). The crystalline state of 1 features two Sb1 ... S1 intermolecular inte ractions [3.987(2) Angstrom] that results in a dimer. 1 displays both an endocyclic, transannular Sb1 ... O1 interaction [2.555(6) Angstrom] and an exocyclic Sb1 ... S4 secondary interaction [3.327(2) Angstrom] . The coordination geometry at the antimony could be described as AX(4 )YE psi-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 an d S4 in axial positions. The Sb1 ... S4 secondary bonding is race capp ing one of the planes form by the lone pair, S2 and S3 of the trigonal bipyramid. 2 also displays both an endocyclic, transannular Sb1 ... S 2 interaction [2.949(3) Angstrom] and an exocyclic Sb1 ... S5 secondar y interaction [3.216(3) Angstrom]. The antimony becomes five-coordinat e, giving the AX(4)YE (psi-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 o f the eight membered ring in 2 is boat-chair. In 1 the main conformati on is chair-planar.