Controlled Thiolate Coordination and Redox Chemistry: Synthesis, Structure, Axial-Binding, and Electrochemistry of Dinickel(II) Dithiolate Macrocyclic Complexes
✍ Scribed by Sally Brooker; Paul D. Croucher; Tony C. Davidson; Geoffrey S. Dunbar; Corina U. Beck; S. Subramanian
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- English
- Weight
- 550 KB
- Volume
- 2000
- Category
- Article
- ISSN
- 1434-1948
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✦ Synopsis
A single crystal X-ray analysis of [Ni 2 L1](ClO 4 ) 2 • MeCN • 1/ thiocyanate ions, forming [Ni 2 L1(NCS) 2 ] 4 and [Ni 2 L2(NCS) 2 ] 5 respectively, whereas 3 does not. Single crystal X-ray 4 H 2 O, 1a [formed directly from a mixture of nickel(II) template ions, 2,6-diformyl-4-methyl-thiophenolate, and 1,4-analyses of complexes 4 • 2 MeCN and 5 • MeCN show that adjacent square-planar and octahedral nickel(II) ions result. diaminobutane] reveals that the nickel(II) ions are in squareplanar N 2 S 2 environments and that the four "bowed"
Two one-electron oxidations and two one-electron reductions are a feature of the electrochemistry of 1-3 in MeCN: dinickel macrocycles in the asymmetric unit pack around a single central perchlorate template ion encapsulating it to curiously, the potentials for the oxidation processes are almost invariant whereas those for the reduction processes form "star" clusters of stoichiometry {[Ni 2 L1] 4 (ClO 4 )} 7+ . These "stars" stack together, via π-π-stacking interactions, vary as anticipated. EPR spectroscopy shows that the first one-electron reduction process and the first one-electron to form two-dimensional sheets, which are separated from one another by layers of the remaining perchlorate anions oxidation process are metal centred. Spectroelectrochemical studies and redox titrations indicate that a purplish-coloured and solvent molecules. Reduction, by NaBH 4 , of the four imine bonds in [Ni 2 L2](ClO 4 ) 2 2a (analogous to 1a but formed complex is produced by one-electron oxidation of 2 (λ = 870 nm, ε = 1320 L mol cm -1 ). The synthesis of a phenolate from 1,3-diaminopropane not 1,4-diaminobutane) or [Ni 2 L2](CF 3 SO 3 ) 2 2b to amine bonds produces the analogue, [Ni 2 LЈ(MeCN) 4 ](ClO 4 ) 2 (6), of the thiophenolate complex 2a is also detailed. Complex 6 undergoes two one-corresponding tetra-amine complex, [Ni 2 L3](ClO 4 ) 2 3. These complexes are shown to contain diamagnetic nickel(II) ions electron oxidations in MeCN, but, in contrast to the thiophenolate complexes 1-3, these occur at much higher by a combination of magnetic, NMR and UV/Vis spectroscopic results. The 1 H NMR spectra of 1-3 run in potentials. Only a single one-electron reduction process is observed and this occurs at a more negative potential than [D 3 ]MeNO 2 and in [D 3 ]MeCN are consistent with increasing axial binding ability in the order: 3 Ͻ 2 Ͻ 1. Thiocyanate ion for any of 1-3. binding studies reveal that 1 and 2 are able to coordinate two ing an understanding of the nature of the redox products [a] Department of Chemistry, University of Otago, tively controlled way. [25] The investigation of the dinickel(II) P. O. Box 56, Dunedin, New Zealand thiolate macrocyclic complexes [Ni 2 Lj]X 2 1؊3 (j ϭ 1Ϫ3