Synthesis and structure of bulky phosphiniminato complexes of zirconium and hafnium: Aryl groups as “non-innocent” substituents in electrophilic systems

Sterically highly hindered phosphiniminato complexes MCl3(NCP) were prepared from MCl4 and Li[NPC] in toluene [M = Zr or Hf; NPC = 4-ButC6H4C(SiMe3)P(Ph)2double bond; length as m-dashNC6H2Me3-2,4,6]. Reaction with methyl lithium readily affords the corresponding zirconium and hafnium trimethyl complexes. The structures of representative zirconium and hafnium complexes MX3(NPC) (X = Cl, M = Zr, Hf; X = Me, M = Hf) were determined by X-ray diffraction. In all cases the NPC ligand acts as C–N chelate, with an additional bonding contribution from the ipso -carbon atom of the C-bound aryl substituent, which results in a η1:η2-coordination mode. The reaction of the hafnium trimethyl complex with View the MathML sourceCPh3+ salts of perfluoroarylborate anions results either in the diastereoselective formation of the binuclear cation [{(NPC)HfMe2}2(μ-Me)]+ or in the formation of the mononuclear cation [(NPC)HfMe2]+, depending on the molar ratio of reagents.