Catalytic dehydrogenation of aliphatic amines to nitriles,imines,or vinylamines and dealkylation of tertiary aliphatic amines over halide cluster catalysts of group 5 and 6 transition metals

摘要

A molybdenum halide cluster,(H_3O)_2[I(Mo_6CI_8)Cl_6] centre dot 6H_2O,with an octahedral metal framework was used as a catalyst in a gas-flow reactor under hydrogen or helium.Diethylamine started to react above 300 deg C,and dehydrogenation to N-ethylideneethylamine proceeded selectively above 350 deg C.Dibutylamine yielded the corresponding dehydrogenation product,and pyrrolidine and piperidine were dehydrogenated to 1-pyrroline and 2,3,4,5-tetrahydropyridine.Dehydrogenation of primary amines yielded the corresponding nitriles and the condensation product N-alkylidenealkylamine.Tripropylamine and tributylamine were dehydrogenated to yield,for the most part,N-vinyldialkylamines.In contrast,triethylamine was dealkylated to diethylamine.Thus,the halide cluster exhibited a characteristic catalysis for aliphatic amines:nitrogen-bonded hydrogens were removed completely to yield nitrile or imine,and when there was no such hydrogen,a neighboring hydrogen or the nitrogen-bonded alkyl group was removed.Niobium,tantalum,and tungsten chloride clusters of the same metal framework were also active catalysts for dealkylation and dehydrogenation of diethylamine.