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-(PhP)CH}E(Me); E = Ge or Sn) were synthesized through the phosphine exchange reaction accompanied by selective E-C bond cleavage. The ligand precursors {o-(PhP)C H}EMe (E = Ge or Sn) were readily obtained in excellent yields by treating {o-(PhP)C H}Li with 0.5 equivalents of Me ECl. Tris(triphenylphosphine)rhodium(i) carbonyl hydride M(H)(CO)(PPh) (M = Rh, Ir) cleaved one of the E-Me bonds of {o-(PhP)CH}EMe exclusively to afford the trigonal bipyramidal (TBP) complexes, [PEP]M(CO)(PPh). Square-planar rhodium complexes [PEP]Rh(PPh ) were also prepared from the reactions of tetrakis(triphenylphosphine)rhodium(i) hydride Rh(H)(PPh) with {o-(PhP)CH} EMe. Further, the trans influence of group 14 elements E (E = Si, Ge, Sn) in [PEP]Rh(PPh) is discussed in terms of the J coupling constants, indicating that E exhibited a stronger trans labilizing effect in the order Sn < Ge < Si. © 2013 The Royal Society of Chemistry.