A cyclic osmastannyl complex, Os(κ2(Sn,P)-SnMe2C6H4PPh2)(κ2-S2CNMe2)(CO)(PPh3) derived from the osmastannol complex, Os(SnMe2OH)(κ2-S2CNMe2)(CO)(PPh3)2

Treatment of the six-coordinate trimethylstannyl complex, Os(SnMe3)(κ2-S2CNMe2)(CO)(PPh3)2 (1) with SnMe2Cl2 produces Os(SnMe2Cl)(κ2-S2CNMe2)(CO)(PPh3)2 (2), which in turn reacts readily with hydroxide ion to give, Os(SnMe2OH)(κ2-S2CNMe2)(CO)(PPh3)2 (3). The osmastannol complex 3 undergoes a reaction with 2 equivalents of tBuLi, in which one of the phenyl rings of a triphenylphosphine ligand is “ortho-stannylated”, without cleavage of the Os–Sn bond, to give the cyclic complex, Os(κ2(Sn,P)-SnMe2C6H4PPh2)(κ2-S2CNMe2)(CO)(PPh3) (4). This novel cyclic complex is selectively functionalised at the tin atom by reaction with SnMe2Cl2 which exchanges one methyl group for chloride giving the diastereomeric mixture, Os(κ2(Sn,P)-SnMeClC6H4PPh2)(κ2-S2CNMe2)(CO)(PPh3) (5a/5b). Crystal structure determination reveals that both diastereomers occur in the unit cell. The mixture, 5a/5b, undergoes reaction with hydroxide ion to give the diastereomeric osmastannol complexes, Os(κ2(Sn,P)-SnMeOHC6H4PPh2)(κ2-S2CNMe2)(CO)(PPh3) (6a/6b) and with sodium borohydride to give the corresponding tin-hydride mixture, Os(κ2(Sn,P)-SnMeHC6H4PPh2)(κ2-S2CNMe2)(CO)(PPh3) (7a/7b). Crystal structure determinations for 2, 4, and 5a/5b have been obtained.