Cleavage of tin-aryl bond(s) by monohalocarboxylic acids: The steric factor role

All four tin-carbon bonds of tetra-p-tolyltin can be successively cleaved b y iodoacetic acid. Reactions with tetra-m-tolyltin are sluggish and only on e tin-carbon bond is cleaved, even in the presence of an excess of the acid . Tetra-o-tolyltin does not react under similar conditions. Steric factors are thought to be responsible for this difference in reactivity of tetratol yltins. The monocarboxylates were not isolated in case of Ph,Sn (except wit h CCl3COOH). Tetraphenylgermanium gives only the monocarboxylates Ph3GeOOCR ', (R' = CH2Cl, CH2Br, CH2I), but all the Ph-Pb bonds in tetraphenyllead ma y be successively cleaved. Tri-p-tolyltin chloride reacts with iodoacctic a cid to give a mixed chloro halocarboxylate, (p-MeC6H4)(2)SnCl(OOCCH2I), but attempts to prepare a mixed carboxylate by reacting (p-MeC6H4)(3)SnOOCCH2C l with HOOCCH2I failed.