Insertion of Isocyanate and Isothiocyanate into the Ln–P σ-Bond of Organolanthanide Phosphides

Abstract

The synthesis, structure, and reactivity of organoyttrium phosphides toward phenyl isocyanate (PhNCO) and phenyl isothiocyanate (PhNCS) are described. Reaction of (TpMe2)CpYCH2Ph(THF) (TpMe2 = tris(3,5-dimethylpyrazolyl)borate; Cp = C5H5) with 1 equiv of HPPh2 in THF at ambient temperature gives an organoyttrium phosphide (TpMe2)CpYPPh2(THF) (1). Treatment of 1 with 1 equiv of PhNCO in THF at ambient temperature results in monoinsertion of PhNCO into the Y–P σ-bond to yield complex (TpMe2)CpY[OC(PPh2)NPh](THF) (2), whereas reaction of 1 with 2 equiv of PhNCO affords the PhNCO diinsertion product (TpMe2)CpY[OC(PPh2)N(Ph)C(O)NPh] (4). However, reaction of 1 with PhNCS under the same conditions is independent of the stoichiometric ratio and gives only the monoinsertion product (TpMe2)CpY[SC(PPh2)NPh] (3). Moreover, 1 can effectively catalyze the cyclotrimerization of PhNCO under mild conditions, but does not catalyze the cyclotrimerization of PhNCS. In addition, the reaction of Cp2LnPPh2(THF) with PhNCS affords the insertion products Cp2Ln[SC(PPh2)NPh](THF) (Ln = Y (6), Er (7), Dy (8)). All new complexes were characterized by elemental analysis, IR, and/or 1H, 13C and 31P NMR, and their solid-state structures, except 4, were determined through single-crystal X-ray diffraction analysis. These reactions represent the first example of isocyanate and isothiocyanate insertions into the Ln–P σ-bond and provide an efficient method for the construction of phosphaureido, phosphadiureido, and phosphathioureido ligands.