This paper demonstrates the possibilities and advantages of low-temperature infrared (IR) spectroscopy in investigating active labile catalytic complexes, intermediates, and reaction mechanisms, taking aluminum halide complexes as an example. The intermolecular interactions between aluminum chloride and nitromethane, 1-nitropropane and nitrobenzene were studied both by the low-temperature IR spectroscopy and quantum-chemical methods. Three kinds of molecular species have been found in these systems: complexes of monomer AlCl3 1:1 and 1:2 composition and 2:1 dimer Al2Cl6 ones, existing as trans-and gauche-conformers. Their structure, thermal stability, and catalytic activity were investigated. The aluminum chloride complexes with nitroalkanes are more active than the ones with nitrobenzene in catalytic hydrocarbon cracking.