A SOLID-STATE NMR-STUDY OF ALUMINUM LEWIS ACID ADDUCTS WITH TRIMETHYLPHOSPHINE IN ZEOLITE-Y - MAGIC ANGLE SPINNING SIDE-BAND ANALYSIS OF DIPOLAR AND J-COUPLED MULTIPLET SYSTEM

The adsorption of trimethylphosphine (TMP) on a mixture consisting of a H-Y zeolite and aluminum chloride results in AlCl3-P(CH3)3 coordination complexes which exists as a family of structures with different stoichiometries. These complexes have been characterized by Al-27 and P-31 solid-state NMR. Two significant phases are formed with AlCl3:(CH3)3P ratios of 1:1 and 1:2. In the 1:1 adduct the aluminum is tetrahedrally coordinated and is directly bonded to phosphorus. The 1:2 adduct involves P-Al-P type bonding as suggested by the P-31 NMR sideband line shape and multiplet structure. Here aluminum is likely to be fivefold coordinated with trigonal-bipyramidal geometry (D3h). The two trimethylphosphine molecules are believed to be trans axial. From an analysis of the sample spinning sidebands multiplet, the Al-P distances were found to be 2.58 +/- 0.02 angstrom for the 1:1 complex and 2.96 +/- 0.02 angstrom for the 1:2 complex. These values are in good agreement with values obtained from crystal structure studies of the individual phases. From a comparison of samples with different TMP loadings, it is concluded that an equilibrium can be established between these two major phases in the presence of a H-Y zeolite, in a manner similar to that which occurs in the solution phase or in the solid state.