Organolead(IV) derivatives of oxophosphorus ligands.: X-ray structures of monomeric R2Pb[(OPPh2)2N]2 (R=Me, Ph) and tetrameric [Me3Pb(O2PPh2)]4

The reaction of R4−nPbCln with Na[(OPPh2)2N] or K[(OPPh2)(SPPh2)N] afforded isolation of Ph2Pb[(OPPh2)2N]2 (1), Ph2Pb[(OPPh2)(SPPh2)N]2 (2), Me3Pb[(OPPh2)2N] (3) and Ph3Pb[(OPPh2)(SPPh2)N] (4). Attempts to grow crystals of Me3Pb[(OPPh2)2N] (3) led to isolation of Me2Pb[(OPPh2)2N]2 (5), as a result of decomposition. Me3Pb(O2PPh2) (6) was obtained from Me3PbCl and Na(O2PPh2). The compounds were characterized by IR and multinuclear NMR spectroscopy. The molecular structures of 1, 5 and 6 were determined by single-crystal X-ray diffraction. The crystal of 5 contains two independent molecules in the unit cell. In both compounds the imidodiphosphinato ligands act as monometallic biconnective units, resulting in a spiro-bicyclic system with six-membered PbO2P2N rings of distorted boat conformation. The coordination geometry around the metal atom is distorted octahedral, with CPbC angles close to 180° [178.9(2)° for 1; 173.4(3)° and 178.7(4)° for molecules 5a and 5b, respectively]. The crystal of the trimethyllead(IV) phosphinate (6) contains discrete tetrameric units, [Me3Pb(O2PPh2)]4, with bridging phosphinato ligands [range: PbO 2.373(3)–2.402(6) Å, PO 1.495(6)–1.512(6) Å], thus resulting in a sixteen-membered Pb4O8P4 inorganic ring. The coordination geometry at lead atoms is distorted trigonal bipyramidal, with oxygen atoms in trans positions [range: OPbO 174.7(2)–177.6(3)°].