Facile transformations of a 1,3,5-triphosphacyclohexadienyl anion within the coordination sphere of group 13 and 14 elements: Synthesis of 1,3-diphosphacyclopentadienyl complexes and phosphaorganometallic cage compounds

The reactivity of the lithium triphosphacyclohexadienyl complex Li[1,3,5-MeP3C3Bu3t] toward a range of group 13 and 14 halide complexes has been investigated. The heterocycle reacts with MX (M = Ga, In, or Tl; X = Cl or I) to give the diphosphacyclopentadienyl (i.e., diphospholyl) complexes [M(η5-1, 3-P2C3Bu3t)] in good yield via phosphinidene, PMe, elimination reactions. One complex, M = Tl, has been structurally characterized and found to exist as a one-dimensional polymer in the solid state. Similarly, the reactions of Li[MeP3C 3Bu3t] with MCl2 (M = Sn or Pb) have given the tetraphosphametallocenes [M(η5-1,3-P2C 3Bu3t)2], which have been structurally characterized. These exhibit fluxional behavior in solution, which has been examined by variable-temperature NMR studies. The monomeric guanidinatotin chloride complexes [LSnCl] (L = Cy2NC(NAr) 2- or (cis-2,6-Me2C5H8N)C(NAr) 2-, Cy = cyclohexyl, Ar = C6H 3Pr2i-2,6) have been prepared, structurally characterized, and treated with Li[MeP3C3Bu 3t]. Again, this has yielded diphospholyl complexes [LSn(η1-1,3-P2C3Bu3 t)] via phosphinidene elimination processes. In contrast, the reactions of Ph3ECl, E = Sn or Pb, do not proceed via phosphinidene elimination reactions, but instead by triphosphacyclohexadienyl rearrangement processes that eventually lead to complexes [Ph3M(η2-P,P-MeP 3C3Bu3t], containing five-coordinate metal centers that are P,P-chelated by an anionic bicyclic ligand. In the case of the tin complex, a reaction intermediate has been isolated and shown to contain the first structurally characterized example of a 1,2- diphosphabicyclo[1.1.0]butane fragment. A mechanism for the formation of this intermediate has been proposed. © 2006 American Chemical Society.