Unsymmetrically substituted triazacyclohexanes and their chromium complexes

The unsymmetrically N-substituted N,N'-Ar-2-N ''-R-1,3,5-triazacyclohexanes 1-4 (Ar = ortho- or parr,fluorophenyl, R = n- or iso-propyl) can be obtained in good yields from a one-step condensation reaction with excess amine. Solid state structures of 1-4 resemble closely those of their triaryl-substituted analogues. The condensation reaction to 4 was looked at by detailed NMR investigations and revealed that amine/aniline exchange is occurring in solutions containing free aniline even at ambient conditions setting up an equilibrium between all possible symmetrical and unsymmetrical triazacylcohexanes. Selective crystallisation of 4 from the solution drives the reaction to high yields of 4. Complexes 1-4 react readily with CrCl3 or CrCl3(THF)(3) to form the corresponding CrCl3 complexes. The complexes are insoluble in non-polar solvents and decompose under decomplexation in coordinating solvents.