Aluminum(III) Halide Complexes based on a Bis‐(benzoxazol‐2‐yl)methane Ligand

Abstract

Low‐valent aluminum(I) heterocycles that are specified as metal carbenes can be applied as catalysts and in small molecule activation. Thus, the synthesis of new types of metal carbenes is a rewarding task we set out to contribute. The reactive aluminum compounds should be obtained by reduction of an aluminum(III) halide precursor coordinated to a suitable ligand. The bis(benzoxazol‐2‐yl)methanide ligand HCBOX2 (BOX = benzoxazol‐2‐yl) mimics the beneficial features of the omni‐present nacnac ligand. Two new aluminum halide complexes [(HCBOX2)AlX2] (X = Cl, I) were synthesized in a salt elimination reaction with the corresponding metal halide and the lithiated ligand [(HCBOX2)Li(Et2O)2], derived from H2CBOX2 [bis‐(benzoxazol‐2‐yl)methane]. The complexes [(HCBOX2)AlCl2] (1) and [(HCBOX2)AlI2] (2) were characterized by NMR spectroscopy from solution, mass spectrometry and single‐crystal X‐ray diffraction. 1 crystallizes in the monoclinic space group P21/n and crystals of complex 2 were obtained in the triclinic crystal system with space group P1. Especially [(HCBOX2)AlI2] (2) is a promising precursor for the synthesis of new low‐valent aluminum(I) compounds because especially the Al–I bond is prone to reduction.