Mononuclear rhodium(III) complexes with N,N ',N ''-trimethyl-1,1,1-tris(aminomethyl)ethane (Me-3-tame). Preparations, characterization and configurational isomerization. Crystal structure of meso-[Rh(Me-3-tame)(2)](ReO4)(3)center dot 1.2H(2)O

The reaction of RhCl3. aq with N,N',N"-trimethyl-1,1,1-tris (aminomethyl) e thane (Me-3-tame) in aqueous solution results in the formation of two isome rs of [Rh(Me-3-tame)Cl-3] with C-3 and C-1 symmetry, respectively. The corr esponding isomeric triaqua complexes were prepared from these trichloro com plexes by mercury(II)/silver(I)-assisted aquation. Isomerization between th e two isomers takes place in basic solution, and an equilibrated isomer mix ture can be quenched by acidification. C-13 NMR was used to distinguish bet ween the isomers. The compound meso-[Rh(Me-3-tame)(2)](CF3SO3)(3) was synth esized from [Rh(Me-3-tame) (H2O)(3)](CF3SO3)(3) (the isomer with C-3 symmet ry), and by metathesis crystals of meso-[Rh(Me-3-tame)(2)](ReO4)(3). 1.2H(2 )O, suitable for single-crystal X-ray diffraction, were obtained. This comp ound crystallizes in the centrosymmetric triclinic space group P (1) over b ar with a=10.184(2), b=17.559(4), c= 9.161(4) Angstrom and alpha=90.68(3), beta = 112.57(3), gamma = 87.78(2)degrees and Z = 2. The geometries around the nitrogen atoms deviate considerably from ideal tetrahedral symmetry, an d the rhodium-nitrogen bond lengths are relatively long [2.104(4)-2.120(5) Angstrom]. In accordance with this, the biscomplex exhibits an unusually lo w ligand field strength, as determined from the electronic absorption spect rum.