Syntheses, theoretical studies, and crystal structures of [ni(Ii)ssrrl](pf6)2 and [ni(ii)srsrl](cl)(pf6) that contains anagostic interactions

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Department of Chemistry


The syntheses of two square planar nickel complexes containing the condensation and subsequently reduced products obtainedbyreacting[Ni(en)3](BF4)2 andacetonearereported. Thecomplexes5,5,7,12,12,14-hexamethyl-1(S),4(S),8(R),11(R)-tetraazacy-clotetradecane-nickel(II)[PF6]2 and 5,5,7,12,12,14-hexamethyl-1(S),4(R),8(S),11(R)-tetraazacyclotetradecane-nickel(II)[Cl][PF6] labelled as [Ni(II)SSRRL](PF6)2 and [Ni(II)SRSRL](Cl)(PF6), respectively, were found to have slightly different solubilities that allowed for their purification. The complexes were characterized by FTIR,1H NMR, and UV–vis spectra. Redox potentials, determined by cyclic voltammetry, established that [Ni(II)SSRRL](PF6)2 exhibits a reversible oxidation (E1/2(ox) = 0.85 V) and reduction (E1/2(red) = 1.59 V), whereas [Ni(II)SRSRL](Cl)(PF6) displays an irreversible oxidation (Epa(ox) = 1.37 V) and reversible reduction (E1/2(red) = 1.62 V) relative to the ferrocene couple at 0.0 V. Single crystal X-ray determinations established that one of the compounds, [Ni(II)SSRRL](PF6)2, contained two PF6 anions, whereas the other compound, [Ni(II)SRSRL](Cl)(PF6), contained one Cl and one PF6 anion. In the solid state, compound [Ni(II)SSRRL](PF6)2 was held together by H-bonds between H atoms on the Ni containing dication and F atoms in the PF6 anion. Compound [Ni(II)SRSRL](Cl)(PF6) crystallized in the form of dimers held together by interactions between H atoms attached to N atoms on adjacent cations binding to two Cl anions in the middle with these dimers held together by further H-bonding to interstitial PF6 anions. Complex [Ni(II)SRSRL](Cl)(PF6) was found to contain anagostic interactions on the bases of NMR (downfield shift in C–H protons) and structural data (2.3 < d(H-Ni) < 2.9 Å), as well as theoretical calculations.

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© 2021, Canadian Science Publishing. All rights reserved. Publisher’s version of record: https://doi.org/10.1139/cjc-2020-0136

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Canadian Journal of Chemistry