THE CRYSTAL-STRUCTURE OF POTASSIUM -N,N'-DIACETATO-N,N'-DI-3-PROPIONATOCOBALTATE(III) TRIHYDRATE AND CONSIDERATION OF RING STRAIN, KTRANS(O-6)-[CO(1,3-PDDADP)]CENTER-DOT-3H(2)O

The crystal structure of Ktrans(O-6)-[Co(1,3-pddadp)]. 3H(2)O (1,3-pdd adp = N,N'-diacetate-N,N'-diacetate-N,N'-di-3-propionate ion) was dete rmined by single crystal X-ray diffraction techniques. The complex ani on is a trans (O-6) isomer in which the cobalt(III) ion is surrounded octahedrally by the two nitrogen and four oxygen atoms of 1,3-pddadp w ith the two six-membered beta-alaninate chelate rings in trans positio ns. This result confirms the assignment made on the basis of electroni c absorption, circular dichroism and NMR spectroscopy. The complex Ktr ans(O-6)-[Co(1,3-pddadp)]. 3H(2)O crystallizes in the space group P2(1 )/c of the monoclinic crystal system with unit cell parameters a = 9.2 98(2), b = 11.780(4), c = 16.771(5) Angstrom, beta = 90.97(2)degrees a nd Z = 4. The structure converged to R = 0.031 for 3019 reflections. C onsiderations of strains favor the trans (O-6) isomer of [Co(1,3-pddad p)](-).