STRUCTURAL-PROPERTIES OF E)(1,4,8,11-TETRAAZACYCLOTETRADECANE)RUTHENIUM(II) TETRAFLUOROBORATE, TRANS-[RUCL(CYCLAM)(4-ACPY)](BF4), BY X-RAY-DIFFRACTION AND NMR-SPECTROSCOPY

The X-ray structural analysis of trans-[RuCl(cyclam)(4-acpy)](BF4) (cy clam = 1,4,8,11-tetraazacyclotetradecane; 4-acpy = 4-acetylpyridine) s howed that the crystals are monoclinic, space group I2/a, with a = 19. 216(2), b = 11.345(1), c = 20.336(2) Angstrom, beta = 96.30(1)degrees, V = 4407(1) Angstrom(3) and Z = 8. The complex adopts the trans geome try, with the macrocycle in the chair conformation. Ru-N(cyclam) inter atomic distances range from 2.085(6) to 2.118(7) Angstrom, and their v alues are smaller than those in other Ru(II) amine complexes and are c loser to Ru(III)-N(amine) interatomic distances. The Ru(II)-N(4-acpy) interatomic distance is 2.057(7) Angstrom and is longer than expected when compared with pyrazine, bis(isonicotinamide) or 1-methylpyraziniu m Ru(II) ammine complexes, and based on the 4-acpy back-bonding abilit y as deducted from reduction potentials and metal-to-ligand charge-tra nsfer absorption bands. Cl-H(N4) and Cl-H(N8) interatomic distances ar e smaller than the sum of the van der Waals radii of H and Cl, indicat ing a bonding interaction. C-13 and H-1 NMR spectra in d(6)-dimethyl s ulfoxide and d(6)-acetone showed the same geometry and conformation of the macrocycle in solution.