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

Abstract

Organotin(IV) derivatives of the type R 2Sn[(OPMe 2)(OPPh 2)N] 2 (R=Me, Bu n , Bz, Ph) were prepared by metathesis reactions between R 2SnCl 2 and the potassium salt of the imidodiphosphinic acid, in toluene. Me 3SnCl and K[(OPMe 2)(OPPh 2)N] (1:1 molar ratio) in chloroform at room temperature gives Me 3Sn[(OPMe 2)(OPPh 2)N], while the NMR studies indicate that the corresponding triphenyltin(IV) derivative disproportionates gradually in solution to give Ph 2Sn[(OPMe 2)(OPPh 2)N] 2. Attempts to grow crystals of the trimethyltin(IV) derivative also gives Me 2Sn[(OPMe 2)(OPPh 2)N] 2 as a redistribution product. The compounds were characterized by IR and multinuclear NMR spectroscopy. The crystal and molecular structures of R 2Sn[(OPMe 2)(OPPh 2)N] 2 [R=Me ( 1), Bu n ( 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 OPR 2 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.