The crystal structure of R,S,R,S-(1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane)nickel( II ) bis(trifluoromethanesulphonate)–acetone hydrate, [Ni(tmtactd)][CF ₃ SO ₃ ] ₂ ·Me ₂ CO·H ₂ O, and a strain-energy minimization analysis of four-, five-, and six-co-ordinate nickel( II )–tmtactd solvento complexes

The crystal structure of [Ni(tmtactd)][CF3SO3]2·Me2CO·H2O has been determined by X-ray diffraction methods. The crystals are triclinic, space group P, with a= 9.142(1), b= 13.674(2), c= 13.694(2)Å, α= 61.07(1), β= 83.14(1), γ= 84.54(1)°, and Z= 2. The complex cation is four-co-ordinate with a tetrahedral distortion from square-planar geometry. Strain-energy minimization analysis by the molecular mechanics method shows that for four-co-ordinate complexes the R,S,R,S isomer is preferred, while for six-co-ordinate complexes the R,S,R,S isomer is preferred.