The first O,C,S-coordinating pincer-type ligand and its application to the synthesis of a triorganotin cation stabilized by two different donor atoms

The syntheses and molecular structures of the bromo-substituted triarylphosphane sulfide (3-Br-5-t-Bu-C6H3) P(S)Ph-2 (1), the arylphosphonic acid di-isopropyl ester {3-t-Bu-5-[P(S)Ph-2]-C6H3}P(O)(O- iPr)(2) (2), its triphenyltin derivative {5-t-Bu-3-[P(S)Ph-2]-2-(SnPh3)-C6H2}P(O)(O-i-Pr)(2) (3), and the corresponding triorganostannylium salt {4-t-Bu-2-[P(O)(O-i-Pr)(2)]-6-[P(S)Ph-2]-C6H2}SnPh2+ PF6- (4) are reported. By reaction with bromide ion, the latter is converted in situ to the intramolecularly coordinated benzoxaphosphastannole derivative [1(P),3(Sn)-SnPh2OP(O)(O-i-Pr)-6-t-Bu-4-P(S)Ph-2]C6H2 (5). Ab initio MO calculations on the ethoxy-substituted analogue of compound 4 indicate a reduced positive charge at the tin atom in comparison with previously reported {4-t-Bu-2,6-[P(O)(OEt)(2)](2)C6H2}SnPh2+PF6-.