ALTERNATE COORDINATION MODES OF (CF3)2C(OH)2 - SYNTHESIS AND STRUCTURE OF 5-COORDINATE NI-2+ AND CU-2+ COMPLEXES DERIVED FROM A CHELATING GEM-DIOL

Two modes of coordination of hexafluoropropane-2,2-diol to transition-metal ions (Ni2+, Cu2+, Mn2+, Co3+, Pd2+, Pt2+) have been found. The diionized gem-diol can form a four-membered chelate ring with amine or phosphine coligands to give neutral complexes LnMOC(CF3)2O. Alternatively, two molecules of the diol may condense to give a six-membered chelate ring LnMOC(CF3)2OC(CF3)2O. By suitable choice of coligands L, the central metal ion may be four-, five-, or six-coordinate. The two types of ring system are not in equilibrium, and the formation of the four-membered ring is favored by bulkier coligands. It is suggested that the six-membered chelate ring is formed by template condensation between two alkoxide ligands on the metal. A complete structural determination has been made on the Ni2+ and Cu2+ complexes with the tridentate macrocycle 2,4,4-trimethyl-1,5,9-triazacyclododec-1-ene as coligand. Both contain a four-membered chelate ring and are formulated as the five-coordinate species (NNN)MOC(CF3)2O (5, M = Cu; 6, M = Ni). The crystals are both isomorphic and isostructural, and they have orthorhombic symmetry in space group Pbca with Z = 8. Cell dimensions are as follows: 5, a = 20.520 (3) Å, b = 15.760 (5) Å, c = 14.380 (5) Å, V = 4650 (3) Å3; 6, a = 20.462 (4) Å, b = 15.759 (3) Å, c = 14.398 (3) Å, V = 4643 (3) Å3. Full-matrix least-squares refinement on F oi 205 variables with 2176 and 2112 unique observations converged at conventional agreement factors of 0.043 and 0.047 for 5 and 6, respectively. In each crystal, a pair of complex molecules linked by pairs of water molecules sits on a crystallographic center of symmetry. One alkoxide oxygen atom is hydrogen bonded to the two water molecules, and the other to an ethanol molecule of solvation. The metal atom is in approximate square-pyramidal coordination; the axial bond in 5 is lengthened by a Jahn-Teller distortion. The chelating gem-diol ligand in 5 and 6 forms almost planar rings, with bite angles of 68.4 (1)°and 67.1 (1)°, respectively. © 1990, American Chemical Society. All rights reserved.