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A Novel Mixed Macrocycle Complex of Nickel:  Synthesis, Structure, and Redox Chemistry of [NiII([9]aneN3)([9]aneS3)](ClO4)2·CHCl3 ([9]aneN3 = 1,4,7-Triazacyclononane and [9]aneS3 = 1,4,7-Trithiacyclononane)

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posted on 20.08.1998, 00:00 by A. McAuley, S. Subramanian, M. J. Zaworotko, R. Atencio
The mixed macrocycle cation, [Ni([9]aneN3)([9]aneS3)]2+ (where [9]aneN3 = 1,4,7-triazacyclononane and [9]aneS3 = 1,4,7-trithiacyclononane), has been prepared by stepwise complexation of [9]aneN3 and [9]aneS3, respectively, to Ni(II) cation. The intermediate [Ni([9]aneN3)(CH3NO2)3]2+ has been isolated and characterized by mass spectrometry and UV−visible spectroscopy. Cyclic voltammetry of [Ni([9]aneN3)(CH3NO2)3]2+ shows a quasireversible wave for the NiII/III couple (E1/2 = 0.73V vs Fc+/0), and the Ni(III) species exhibits an axial ESR spectrum (g = 2.101 and g = 1.985). The structure of [Ni([9]aneN3)([9]aneS3)](ClO4)2·CHCl3 has been determined. It crystallizes in monoclinic space group P21/c with a = 13.3911(8) Å, b = 14.4430(9) Å, c = 13.6116(8) Å, β = 107.2090(10)°, V = 2514.7(3) Å3, and Z = 4. Of the 15 047 reflections collected, 5765 reflections (I > 2σ(I)) were used in the refinement to obtain a final Rw = 0.0278 and RF = 0.0368. In the cation [Ni([9]aneN3)([9]aneS3)]2+, the two macrocycles occupy the trigonal faces of the Ni2+ ion, imposing a distorted octahedral geometry. Cyclic voltammetry of the complex in CH3CN (Pt electrodes, 0.1 M n-Bu4NClO4, 500 mV) shows a quasireversible wave for the NiII/NiIII couple (E1/2 = 0.86V vs Fc+/0). Chemical oxidation by NOPF6 of the cation [Ni([9]aneN3)([9]aneS3)]2+ generates a Ni(III) species that shows axial ESR spectrum with g = 2.106 and g = 2.063. No characteristic reduction wave was observed in either CH3CN or CH3NO2 media.