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Dibasic 3,30-dinitro-4,40-bipyrazole-1,10-diides of K, Rb and Cs reveal metal-selective ring-p over ring-π coordination.

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Title: Dibasic 3,30-dinitro-4,40-bipyrazole-1,10-diides of K, Rb and Cs reveal metal-selective ring-p over ring-π coordination.
Authors: Domasevitch, Kostiantyn V.1 dk@univ.kiev.ua, Ponomarova, Vira V.
Source: Acta Crystallographica Section E: Crystallographic Communications. Jun2026, Vol. 82 Issue 6, p683-691. 24p.
Subjects: Alkali metal ions, Pyrazolates, Coordinate covalent bond, Alkali metals
Abstract: Three new alkali metal pyrazolate salts, namely, poly[[.-3,30-dinitro-4,40-bipyrazole-1,10-diido]dipotassium], [K2(C6H2N6O4)]n, (1), its rubidium analogue [Rb2(C6H2N6O4)]n, (2), and poly[[[1-3,30-dinitro-4,40-bipyrazole-1,10-diido]-dicaesium] monohydrate], {[Cs2(C6H2N6O4)]·H2O}n, (3), suggest that the electron-depleted nitropyrazolates may be still functional as efficient 1-donors toward late alkali metal ions. The three-dimensional structures of 1 and 2 are very similar, being governed by k4-k¹:k¹:k¹:k¹ coordination of the pyrazolate anions as hard Lewis bases [K--N = 2.783 (3)-2.956 (3); Rb--N = 2.930 (4)-3.194 (4) A ° ]. In contrast, the structure of 3 reveals a dominant significance for the pyrazolate-1 coordination, which produces two distinct motifs in the forms of finite Cs--1 arrangement [Cs--ring centroid distance = 3.389 (3) A ° ] and onedimensional --Cs--(1--Cs)n-- sandwiches with slightly larger Cs--1 separations at 3.474 (3) and 3.587 (3) A °. Weaker ion-dipole interactions with the nitro-O donors, at the distances approaching the sums of corresponding ionic radii, are relevant for the entire series and they complete typically high coordination numbers of the metal ions [CN = 8, 9]. These findings may find use in the construction of ion-selective receptors since the existing examples for the coordinative discrimination of the late alkali metal ions, beyond the ion-cavity size match considerations, are still rare. [ABSTRACT FROM AUTHOR]
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Abstract:Three new alkali metal pyrazolate salts, namely, poly[[.-3,30-dinitro-4,40-bipyrazole-1,10-diido]dipotassium], [K2(C6H2N6O4)]n, (1), its rubidium analogue [Rb2(C6H2N6O4)]n, (2), and poly[[[1-3,30-dinitro-4,40-bipyrazole-1,10-diido]-dicaesium] monohydrate], {[Cs2(C6H2N6O4)]·H2O}n, (3), suggest that the electron-depleted nitropyrazolates may be still functional as efficient 1-donors toward late alkali metal ions. The three-dimensional structures of 1 and 2 are very similar, being governed by k4-k¹:k¹:k¹:k¹ coordination of the pyrazolate anions as hard Lewis bases [K--N = 2.783 (3)-2.956 (3); Rb--N = 2.930 (4)-3.194 (4) A ° ]. In contrast, the structure of 3 reveals a dominant significance for the pyrazolate-1 coordination, which produces two distinct motifs in the forms of finite Cs--1 arrangement [Cs--ring centroid distance = 3.389 (3) A ° ] and onedimensional --Cs--(1--Cs)n-- sandwiches with slightly larger Cs--1 separations at 3.474 (3) and 3.587 (3) A °. Weaker ion-dipole interactions with the nitro-O donors, at the distances approaching the sums of corresponding ionic radii, are relevant for the entire series and they complete typically high coordination numbers of the metal ions [CN = 8, 9]. These findings may find use in the construction of ion-selective receptors since the existing examples for the coordinative discrimination of the late alkali metal ions, beyond the ion-cavity size match considerations, are still rare. [ABSTRACT FROM AUTHOR]
ISSN:20569890
DOI:10.1107/S2056989026005037