Reactions of diphenylphosphoric acid (DPPA) with AlMe3, AlEt3, Al(tBu)3, and boehmite have been studied. The reaction with Al(tBu)3 yields the molecular complex ([(tBu)2AlO2P(OPh)2]2) (1), which in the solid state exists as a centrosymmetric dimer consisting of two four-coordinate Al centers linked by diphenyl phosphate (DPP) bridges. The ligand bite distance Al···Al in 1 is equal to 4.75 Å. Reactions with AlMe3 or AlEt3 lead to polymeric aluminum organophosphates ({Al[O2P(OC6H5)2]3} n ) (2). These polymers were characterized by elemental analysis, in addition to XRD, TGA, FT-IR, SEM, and MAS NMR techniques. The results of MAS NMR and FT-IR studies have shown that Al(OP)6 units are the basic chain building blocks that produce condensed structures. The same type of Al environment was observed in aluminophosphate phase found in the products of the reaction with boehmite. This phase reveals a fibrous structure attributed to the close-packed hexagonal columnar structure consisting of polymeric chains of catena-Al(DPP)3 with the unit cell parameters α = 15.14(4) Å and c = 14.44(3) Å (V = 2870 Å3). The number of molecules in the crystallographic unit (Z) is 3. According to this model the mean diameter of the chain is equal to the parameter α (15.14 Å) while the distance between adjacent Al atoms linked by three phosphate bridges can be estimated as c/3 = 4.81 Å. The latter value matches perfectly the value of the Al···Al distance determined for compound 1.

Several aluminum tris(diorganophosphates) have been synthesized and characterized via elemental analysis, NMR, FT-IR and Raman spectroscopy, as well as powder XRD, and SEM. Single-crystal X-ray diffraction studies revealed that the aluminum tris(diethylphosphate) crystal structure comprises two crystallographically nonequivalent catena-Al[O2P(OEt)2]3 chains propagating along the c-axis. Their parallel orientation favors the formation of closely packed hexagonal domains. PXRD data suggest that other homologues have a similar structure, with the interchain distance closely corresponding to the dimensions of organic ligands. They are also susceptible to a reversible dissociation to ionic species under the effect of primary amines. This feature can be utilized for the synthesis of epoxy nanocomposites.