Heteroleptic iminopyrrolidinates of aluminium

Abstract

A series of iminopyrrolidine (ip) compounds were synthesized with excellent yields as potential ligands for novel organometallic precursors for atomic layer deposition. The idea behind these ligands was that carbodiimide (CDI) deinsertion would not occur as the quaternary carbon was tethered to one chelate nitrogen. To our advantage a melting point trend was evident within the ip ligands and reflected in the family of heteroleptic aluminium species when the ip ligands were reacted with TMA or TEA. The alkane elimination reaction occurred at room temperature yielding clean products with high yields. Crystal structures were collected for compounds 7 [ipipAlMe₂], 12 [tbipAlMe₂], and 14 [sbipAlEt₂] demonstrating that the heteroleptic aluminium species were dimers. This was also evident in the mass spectra collected for each compound as the parent peak was that of the dimer minus a methyl. Thermolysis studies were carried out on all the ipAlMe₂ species to observe the decomposition at an isotherm over several days. The decay of the methyl peak was monitored as a ratio against TMS within the solution and was shown to be a first order decomposition. From these studies it was clear that nbip (9), iso-bip (10), and tbip (12) were the most stable complexes with half-lives of 24.8, 9.00, and 10.3 days, respectively.