Phosphane- and phosphorane Janus Head ligands in metal coordination

Our principal strategy to include the substituent periphery of phosphanides and phosphoranates in metal coordination is outlined. Rather than providing merely bulk or stereo information like in classical phosphane ligands to d-block metal centres the 2-pyridyl substituted species supply a second coordination site. Additional to the found cy/n coordination site selectivity these Janus Head ligands might serve as anionic staples in mixed Group 13/d-block metal complexes in homogeneous catalysis. The classical NP(Ph-2)N- chelating ligand is converted into a NP(Py-2)N- tripodal ligand. The pyridyl substitution has not only considerable impact on the metal coordination but also on the reactivity, emphasising the fact that this heteroaromatic substituent cannot simply be regarded as eka-phenyl. It facilitates double P-C bond cleavage and reduction of iminophosphoranes to phosphanamines in a one-pot reaction. Even P=N bond cleavage is observed. Several new routes to multidentate ligands in metal side-arm coordination were established. (C) 2002 Elsevier Science B.V. All rights reserved.