SN-119 NMR-STUDIES ON DIORGANOYLTIN(IV)DIHALIDES AND TRIORGANOYLTIN(IV)HALIDES - FORMATION AND STEREOCHEMISTRY OF ADDUCTS

The reactions of R2SnX2 (R = Ph, Me; X = Cl, Br) with excess halide, tributylphosphine, tricyclohexylphosphine and tributylphosphine oxide have been investigated in dichloromethane solution by tin-119 and phosphorus-31 NMR techniques. R2SnX2 form five coordinate 1:1 adducts with halide and phosphine (phos) ligands whilst both 1:1 and 1:2 adducts are formed with tributylphosphine oxide (L). Tin-119 spectra imply that Ph2SnX2(phos) has the phosphine in the equatorial position of a trigonal bipyramid. At low temperature there is evidence for a slow intramolecular twist mechanism between octahedral isomers of Ph2SnCl2L2. The stereochemistry of the complexes Ph2SnX2L2 differ between chloro and bromo compounds and no mixed halide complex is observed. In the case of the bromo system only, the 1:3 adduct [Ph2SnBrL3]+Br- is formed. Ph3SnCl does not react with phosphines but it does give 1:1 adducts with Cl-, L and pyridine. All the adducts have similar tin-119 chemical shifts which is consistent with the phenyl groups being equatorial in the five coordinate trigonal bipyramidal adducts. Ph4Sn does not form adducts with X-, L or phosphine. © 1988 Elsevier Sequoia.