Synthesis of triphenylphosphonopropionbetainetriorganotin(IV) salts [(C 6H 5) 3P(CH 2) 2CO 2SnR 3] +X −, by nucleophilic displacement of anions from triorganotins

Abstract

Trimethyl- and triphenyl-tin(IV) hydroxide act on triphenyl(2-carboxyethyl)-phosphonium hydrochloride, which is made from 3-chloropropionic acid and triphenylphosphine, to release water in the presence of dimethylformamide (DMF) as a catalyst. The water is azeotropically distilled to drive the reaction forward and produce triphenylphosphonopropionbetainetrimethyl- and triphenyl-tin(IV) chlorides in high yield. The latter product also results from the displacement of chloride from triphenyltin(IV) chloride by the phosphobetaine, (C 6H 5) 3P(CH 2) 2CO 2, which is made by treating the phosphonium hydrochloride with bicarbonate, and the compounds [(C 6H 5) 3P(CH 2) 2CO 2Sn(C 6H 5) 3] +X − where X = Cl, Br, I, N 3, NCS, NO 3, B(C 6H 5) 4 and Co(CO) 4 are made in the same way. The acetate salt results from metathesis from the chloride and lead(II) acetate. A double salt, [(C 6H 5) 3P(CH 2) 2CO 2SnR 3] + [R 3SnX 2] −, is formed for X = Cl, Br and N 3 by adding additional (C 6H 5) 3SnX to the already-formed simple salts. Double salts are also obtained from the 1 1 reactions between the phosphobetaine and triphenyltin(IV) isocyanate and methyldiphenyltin(IV) chloride. The phosphonium chloride double salt could be converted to the thiophosphonium derivative by heating with elemental sulfur in ethanol. The products of these novel nucleophilic displacement reactions are high melting solids. Tin-119m Mössbauer data are consistent with five-coordinated, triorganotin(IV) formulations with the exception of the diphenyl(8-hydroxyquinolinato)tin(IV) chloride salt in which the tin atom is six-coordinated, and the diphenyltin system cis-oriented. The parameters otherwise do not change with the nature of the X group, which is the tetracarbonylcobaltate derivative is tetrahedral by infrared, establishing the ionicity of the products. The chloride exhibits a molar conductivity indicative of a 1 1 electrolyte in DMF. A bridging acetate structure in the solid is consistent with the lowered ν(CO 2) frequencies. The Mössbauer spectra of the double salts give simple doublets of lowered isomer shift (IS) and raised quadrupole splitting (QS) which may arise from a cross-linking ion pairing of the polymer chains in the solid, and the NMR spectra of the two methyltin derivatives shows only a single resonance line and tin satellites which is rationalized by a dynamic exchange process. The products are formulated as associated in carboxylate polymers with dangling triphenylphosphonium cations.