Complexation and chemisorption of trimethylphosphine on Ni zeolites

Abstract

After room temperature saturation of dehydrated NiY with trimethylphosphine two complexes are formed in the supercages. They are identified and quantified by reflectance spectroscopy as 0.9[Ni(PMe₃)₅]²⁺ per unit cell and 6–8[(O₁)₃—Ni—PMe₃]²⁺ per unit cell (O₁ is a lattice oxygen). The former is diamagnetic and trigonal bipyramidal, the latter is paramagnetic and compressed tetrahedral. [Ni(PMe₃)₅]²⁺ is only stable in excess PMe₃, while the mono-phosphine complex is stable to ≈ 383 K in vacuo. On NiX only the paramagnetic compressed tetrahedral complex is formed. The ligand field parameters of this complex were calculated.

Chemisorption on lattice and extralattice oxygens gives strongly held OPMe₃, OP(OMe₃)₃ and a range of decomposition products such as CO, CO₂, H₂O, hydrocarbons and oxygenated P on the surface. These products were qualitatively identified by i.r. and mass spectrometry.