Solution and solid state structural investigations of organotin(IV) compounds containing asymmetric imidodiphosphinato ligands. X-ray structures of R′′2Sn[(OPMe2)(OPPh2)N]2 (R=Me, Bun, Ph)

Organotin(IV) derivatives of the type R2Sn[(OPMe2)(OPPh2)N]2 (R=Me, Bun, Bz, Ph) were prepared by metathesis reactions between R2SnCl2 and the potassium salt of the imidodiphosphinic acid, in toluene. Me3SnCl and K[(OPMe2)(OPPh2)N] (1:1 molar ratio) in chloroform at room temperature gives Me3Sn[(OPMe2)(OPPh2)N], while the NMR studies indicate that the corresponding triphenyltin(IV) derivative disproportionates gradually in solution to give Ph2Sn[(OPMe2)(OPPh2)N]2. Attempts to grow crystals of the trimethyltin(IV) derivative also gives Me2Sn[(OPMe2)(OPPh2)N]2 as a redistribution product. The compounds were characterized by IR and multinuclear NMR spectroscopy. The crystal and molecular structures of R2Sn[(OPMe2)(OPPh2)N]2 [R=Me (1), Bun (2), Ph (4)] were established by X-ray diffractometry. The compounds exhibit similar spiro-bicyclic structures, with the tin atom as spiro atom and chelating ligands with the oxygen atoms of the similar OPR2 groups in trans positions. The coordination geometry around the central metal atom is octahedral, with CSnC and OSnO (trans) angles of 180°. No significant differences were noted in the length of the tinoxygen, phosphorusoxygen and phosphorusnitrogen bonds, respectively, in relation to the different organic groups attached to tin or phosphorus atoms in a ligand moiety. The solution and solid state structures of the title compounds are discussed comparatively.