Synthesis, Characterization, and Stability of Dealkylated Salen-Supported Aluminum Phosphates

Three salen aluminum bromide compounds salen(Bu)AlBr (1) (salen = N,N'-ethylenebis(3,5-di-tert-butylsalicylideneimine)), salpen(Bu)AlBr (2) (salpen = N,N'-propylenebis(3,5-di-tert-butylsalicylideneimine)), and salophen(Bu)AlBr (3) (salophen = N,N'-o-phenylenenebis(3,5-di-tert-butylsalicylideneimine) were evaluated for their potential use as dealkylation agents with a series of organophosphates. These reactions led to the aluminum phosphate compounds containing six-coordinate aluminum centers and hydrolytically stable P-O-C bonds: 4 = [salen(Bu)AlOP(O)(OMe)₂], 5 = [salen(Bu)AlOP(O)(OEt)₂], 6 = [salen(Bu)AlOP(O)(OPh)₂], 7 = [salophen(Bu)AlOP(O)(OMe)₂], 8 = [salpen(Bu)AlOP(O)(OPr)₂]₂, 9 = (salen(Bu)AlO)₃PO, 10 = (salpen(Bu)AlO)₃PO, 11 = (salophen(Bu)AlO)₃PO. All the compounds were characterized by ¹H, ¹³C, ²⁷Al, and ³¹P NMR, IR, and mass spectrometry. Furthermore, compounds 4-8 were structurally characterized by single-crystal X-ray diffraction. The potential hydrolysis of these compounds was modeled with 4 and demonstrated the unique stability of the final product and ease of isolation.