Synthesis, characterization and X-ray structure of stannocanes substitutedwith a cyclic dithiophosphate ligand X(CH2CH2S)(2)(SnBu)-Bu-n[S2P(OCH2C(Et-2)CH2O)], (X = O, S): a study about the conformational tendencies and the relationship with the anomeric effect of the stannocane rings

The preparation and conformational study of two stannocanes, 5-n-butyl-5-(5 ',5'-diethyl-2'-thioxo-1',3',2'-dioxaphosphorinane-2'-thiolate)-1-oxa-4,6-d ithia-5-stannocane. O(CH2CH2S)(2)(SnBu)-Bu-n[S2P(OCH2CEt2CH2O)] (1) and 2-n -butyl-5-(5'5'-diethyl-2'-thioxo-1',3',2'-dioxaphosphorinane-2-thiotate)-1, 3,6-trithia-2-stannocane S(CH2CH2S)(2)(SnBu)-Bu-n[S2P(OCH2CEt2CH2O)] (2) is reported. These compounds were prepared from the corresponding chloro-oxa and -thia-stannocanes and the sodium salt of dithiophosphoric acid (2-merca pto-2-thiono-1,3,2-dioxaphosphorinane) in ethanol. Compounds 1 and 2 were c haracterized by IR, EI-MS and multinuclear NMR (H-1, C-13, P-31). The molec ular structures were determined by X-ray analyses. The eight-membered ring in both compounds has a boat-chair conformation with a 1,5 transannular Sn ... O (2.468 Angstrom), Sn ... S (2.94 Angstrom) interaction. The 1,3,2-dio xaphosphorinane ring in 1 and 2 present a chair conformation with the stann ocane in the axial position, in accordance with the anomeric effect. The co ordination of the Sn-atoms is trigonal-bipyramidal in 1 and intermediate be tween trigonal-bipyramidal and a bicapped tetrahedral arrangement in 2. (C) 2000 Elsevier Science S.A. All rights reserved.