Synthesis of methyltrioxorhenium(VII) arylamine complexes and mono-and bis(ortho)-chelated arylaminorhenium(VII) trioxides

From the reaction of MeReO₃ with the neutral arylamine C₆H₅CH₂NMe₂ and the aryldiamine C₆H₄(CH₂NMe₂)₂-1,3, have been isolated in good yields the 1/1 adduct complex [MeReO₃ · C₆H₅CH₂NMe₂], 1, and the 2/1 adduct complex [(MeReO₃)₂ · C₆H₄(CH₂NMe₂)₂-1,3], 2, respectively. The X-ray molecular structure of 2 shows that both rhenium centres have a trigonal bipyramidal geometry and in the axial positions of each rhenium centre are one of the NMe₂ units of the aryldiamine ligand and a methyl group. The mono(ortho)-chelated arylaminorhenium trioxide complex [ReO₃{C₆H₄CH₂NMe₂-2}], 3, can be synthesized by a transmetallation reaction of ClReO₃ with [Zn{C₆H₄CH₂NMe₂-2}₂] in a 2:1 molar ratio. In a similar way the bis(ortho)-chelated arylaminorhenium trioxide complex [ReO₃{C₆H₃(CH₂NMe₂)₂-2,6}], 4, can be synthesized by addition of a mixture of [Li₂{C₆H₃(CH₂NMe₂)₂-2,6}₂] and ZnCl₂ to ClReO₃. Complexes 3 and 4 have been isolated as white solids in 66% and 81% yields respectively. The rhenium centre in complex 4 has a bicapped tetrahedral geometry in which the monoanionic {C₆H₃(CH₂NMe₂)₂-2,6}^- ligand is pseudo-facially bonded with a characteristic N1-Re-N2 angle of 107.7(3)°, a Re-C_ipso bond length of 2.112(11) Å and Re-N1 and Re-N2 bond lengths of 2.518(9) Å and 2.480(8) Å respectively.