Synthesis and structural elucidation of some novel aluminium(III) complexes with Schiff bases: Crystal and molecular structure of [Al{O(C6H4)CHNC6H5}2{HO(C6H4)CHNC6H5}2]Br

Reactions of Et3Al · Et2O with bidentate Schiff base ligands in 1:1 and 1:2 molar ratios in diethyl ether yield Et2Al{O(C6H4)CHNC6H5}, EtAl{O(C6H4)CHNC6H5}2, Et2Al{OC(R)CHC(R1)NC6H5} and EtAl{OC(R)CHC(R1)NC6H5}2 (where R = R1CH3, C6H5; R = CH3, R1 = C6H5). The reaction of Et2AlBr with HO(C6H4)CHNC6H5 in a 1:4 molar ratio in diethyl ether yields [Al{O(C6H4)CHNC6H5}2{HO(C6H4)CHNC6H5}2]Br. All the above complexes are soluble in common organic solvents and have been characterized by elemental analysis, as well as IR and multinuclear NMR (1H, 13C and 27Al) spectroscopy. Molecular weight measurements in refluxing benzene show the monomeric nature of the monoethyl complexes and dimeric nature of the diethyl complexes, which is further supported from the FAB mass spectra of three representative compounds, Et2Al{O(C6H4)CHNC6H5}, Et2Al{OC(CH3)CHC(CH3)NC6H5}and EtAl{O(C6H4)CHNC6H5}2. 27Al NMR spectra show that in both types of complex, the aluminium is pentacoordinated. The crystal structure of [Al{O(C6H4)CHNC6H5}2{HO(C6H4)CHNC6H5}2]Br displays a unique octahedral symmetry with the ligand bonded in two different patterns to the aluminium(III) center.

Graphical abstractReaction of Et3Al · Et2O/Et2AlBr with bidentate Schiff base ligands (LH) in different molar ratios yield Et2AlL, EtAlL2 and [Al{O(C6H4)CHNC6H5}2{HO(C6H4)CHNC6H5}2]Br (9). These are characterized by elemental analyses, FAB mass, IR and NMR spectral studies. The crystal structure of 9, indicates the presence of hexa coordination around central aluminium(III) atom.Figure optionsDownload full-size imageDownload as PowerPoint slide