Hypervalence at tin(IV) by transannular bonding of sulfur in an eight-membered ring: The case of dibenzostannocines [{S(C6H4S)2}Sn]

Treatment of Ph2SnCl2 with S(C6H4SH)2 in benzene leaded to the formation of [{S(C6H4S)2}SnPhCl] (1); the same reaction with 1,4-diazabicyclo-[2.2.2]-octane leaded [{S(C6H4S)2}SnPh2] (4). The compounds [{S(C6H4S)2}SnPhHal] (Hal = Br, 2; I, 3) have been synthesized by halogen exchange from 1 and the corresponding potassium halide. The compound [{S(C6H4S)2}SnCl2] (5) was obtained from S(C6H4SH)2 and SnCl4. The reaction of 1 with NaS2CNEt2·3H2O yielded [{S(C6H4S)2}SnPh{S2CNEt2}] (6). X-ray structure determinations of dibenzostannocines 1–6 revealed that the tin atom acts as an acceptor atom displaying an intramolecular transannular interaction with the sulfur (thioether-like) atom. The local geometry of the Sn atom in the compounds 1–5 is described as distorted trigonal bipyramidal with a TBP character spanning from 81% to 73%. In 6 the tin atom is six-coordinate with a distorted octahedral geometry.

The synthesis of [{S(C6H4S)2}SnL1L2] compounds (L1 = Cl, Br, I, Ph; L2 = Ph, Cl, S2CNEt2) is described. The nature of the ligands L is a determinant factor in the enhancing of the intramolecular interaction S⋯⋯Sn, leading to several coordination numbers at the tin atom.Figure optionsDownload as PowerPoint slide