Facile synthesis of rhodium and iridium complexes bearing a [PEP]-type ligand (E = Ge or Sn) via E-C bond cleavage

Rhodium and iridium complexes bearing a tridentate [PEP] type ligand ([PEP] = {o-(Ph2P)C6H4}(2)E(Me); E = Ge or Sn) were synthesized through the phosphine exchange reaction accompanied by selective E-C bond cleavage. The ligand precursors {o-(Ph2P)C6H4}(2)EMe2 (E = Ge or Sn) were readily obtained in excellent yields by treating {o-(Ph2P)C6H4}(2)Li with 0.5 equivalents of Me2ECl2. Tris(triphenylphosphine) rhodium(I) carbonyl hydride M(H)(CO)(PPh3)(3) (M = Rh, Ir) cleaved one of the E-Me bonds of {o-(Ph2P) C6H4}(2)EMe2 exclusively to afford the trigonal bipyramidal (TBP) complexes, [PEP] M(CO)(PPh3). Square-planar rhodium complexes [PEP] Rh(PPh3) were also prepared from the reactions of tetrakis(triphenylphosphine) rhodium(I) hydride Rh(H)(PPh3)(4) with {o-(Ph2P) C6H4}(2)EMe2. Further, the trans influence of group 14 elements E (E = Si, Ge, Sn) in [PEP] Rh(PPh3) is discussed in terms of the (1)J(Rh) (P) coupling constants, indicating that E exhibited a stronger trans labilizing effect in the order Sn < Ge < Si.