Variable Nitric Oxide
Reactivity of Tropocoronand
Cobalt(III) Nitrite Complexes as a Function of the Polymethylene Linker
Chain Length
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Abstract
The size-dependent reactivity of cobalt tropocoronands
[TC-<i>n</i>,<i>n</i>]<sup>2–</sup> is
manifest in
the NO chemistry of the cobalt(III) nitrite complexes [Co(η<sup>2</sup>-NO<sub>2</sub>)(TC-<i>n</i>,<i>n</i>)]
(<i>n</i> = 4–6), the synthesis and characterization
of which are reported for the first time. Complete conversion of [Co(η<sup>2</sup>-NO<sub>2</sub>)(TC-4,4)] to the cobalt mononitrosyl [Co(NO)(TC-4,4)]
occurs upon exposure to NO(g). In contrast, addition of NO(g) to [Co(η<sup>2</sup>-NO<sub>2</sub>)(TC-5,5)] generates both cobalt mono- and
dinitrosyl adducts, and addition of nitric oxide to [Co(η<sup>2</sup>-NO<sub>2</sub>)(TC-6,6)] converts this complex to the dicobalt
tetranitrosyl species [Co<sub>2</sub>(NO)<sub>4</sub>(TC-6,6)]. In
the latter complex, two tetrahedral cobalt dinitrosyl units are bound
to the aminotroponeiminate poles of the [TC-6,6]<sup>2–</sup> ligand. These results significantly broaden the chemistry of cobalt
tropocoronands with nitric oxide and the nitrite anion
