X-ray crystal structure* and kinetics of oxidation of 1,4,8,11-tetraazaundecanenickel(II), [Ni-II(2,3,2-tet)](2+) by peroxodisulphate

While macrocyclic ligands are well-known to stabilize tervalent nickel, it is very unusual to form stable nickel(III)-amine species in aqueous solution. We describe the kinetics of oxidation of 1,4,8,11-tetraazaundecanenickel(II), [Ni-II(2,3,2-tet)](2+) by peroxodisulphate in aqueous solution to the tervalent state. The reaction follows a second order rate law, first order in [Ni-II(2,3,2-tet)](2+) and first order in peroxodisulphate. The activation enthalpy and entropy are 55 +/- 3 kJ mol(-1) and -38 +/- 10 J K-1 mol(-1) respectively. The X-ray crystal structure of the [Ni-II(2,3,2-tet)](2+) cation is also described. The title compound crystallizes in the monoclinic space group P2(1)/n. The cation has a slightly distorted square planar structure, with the bite angle of the 5-membered chelate rings being slightly less than 90 degrees, and that of the 6-membered chelate ring being correspondingly greater than 90 degrees.PT: J; CR: ANICHINI A, 1977, INORG CHIM ACTA, V24, L21 ARORA K, 1990, J CHEM SOC DA, P1257 BANERJEE P, 1981, Z ANORG ALLG CHEM, V473, P224 BENKO J, 1993, TRANSIT METAL CHEM, V18, P551 BOSNICH B, 1966, J CHEM SOC A, P1331 BRODOVITCH JC, 1981, CAN J CHEM, V59, P1610 BURGESS J, 1966, J CHEM SOC A, P1772 CHEN MH, 1996, INORG CHEM, V35, P2627 COOK DF, 1978, INORG CHIM ACTA, V31, P59 CURTIS NF, 1974, AUST J CHEM, V27, P1167 FABBRIZZI L, 1979, INORG CHIM ACTA, V36, L391 FAWCETT TG, 1980, INORG CHEM, V19, P941 FREEMAN HC, 1969, INORG CHEM, V6, P129 GAVRISH SP, 1996, J COORD CHEM, V38, P295 HAINES RI, 1980, INORG CHEM, V19, P719 HAINES RI, 1981, COORDIN CHEM REV, V39, P77 HAINES RI, 1992, CAN J CHEM, V70, P2785 HAINES RI, 1993, CAN J CHEM, V71, P976 HAINES RI, 1998, TRANSIT METAL CHEM, V23, P763 HOLBA V, 1987, TRANSIT METAL CHEM, V12, P121 HORI F, 1977, B CHEM SOC JPN, V50, P138 LATI J, 1972, INORG CHEM, V11, P2393 LINDOY LF, 1989, CHEM MACROCYCLIC LIG, P176 LOVECCHIO FV, 1974, J AM CHEM SOC, V96, P3109 MARONGIU G, 1969, INORG CHEM, V8, P2763 MCAULEY A, 1983, CAN J CHEM, V61, P1120 MCPHERSON A, 1971, J COORD CHEM, V1, P39 OHASHI K, 1976, B CHEM SOC JPN, V49, P2440 SIEKLUCKA B, 1996, TRANSIT METAL CHEM, V21, P200 SUH MP, 1997, ADV INORG CHEM, V44, P93 TAUBE H, 1952, CHEM REV, V50, P69 VOLLAROVA O, 1986, COLLECT CZECH CHEM C, V51, P1049 ZEIGERSON E, 1981, INORG CHEM, V20, P3988; NR: 33; TC: 5; J9: TRANSIT METAL CHEM; PG: 6; GA: 369VYSource type: Electronic(1