Issue 4, 2022

Ion-bearing stairs: alkali metal complexes of 1,2-diaza-4-phospholides

Abstract

In this work, eight alkali metal complexes with 1,2-diaza-4-phospholide ligands were prepared and characterized by X-ray single-crystal structural analysis and NMR spectroscopy. Their structures showed varied coordination motifs: (i) a dimeric 1,2-diaza-4-phospholide lithium complex with exo-bidentate bridging coordination (4) consists of two lithium atoms that are linked via two μ2-bridging, κNN′-coordinated ligands; (ii) the polymeric chain 1,2-diaza-4-phospholide potassium complex (5) showed an ion-bearing stair-shaped chain structure running through axis a, where the steps are η2 interactions, and there is a transition platform between every two stairs; (iii) the polymeric chain 1,2-diaza-4-phospholide potassium complex (6) also presented a polymeric chain structure in the solid state but displayed a head-to-tail arrangement of two 1,2-diaza-4-phospholides; (iv) in comparison to 6, the 1,2-diaza-4-phospholide sodium complex (7) displayed a tetrameric structure, in which the sodium ions are arranged in a distorted tetrahedral fashion and each of them occupies a vertex of the tetrahedron; (v) the polymeric chain 1,2-diaza-4-phospholide potassium complex (8) presented a solvent-free chain structure, in which potassium ions each is η5-bonded by two 1,2-diaza-4-phospholides and η2-coordinated by another, consisting of a stair-shaped chain structure running through axis a but without significant intermolecular contacts between the adjacent stairs in comparison to that of 5; (vi) the polymeric chain 1,2-diaza-4-phospholide sodium complex (9) presented a solvent-free chain structure, in which sodium ions each is η1(N),η2(N,N),η1(P)-bonded by three 1,2-diaza-4-phospholides, consisting of a chain structure running through axis a; and (vii) the treatment complex 8 with elemental sulphur or selenium in the presence of crown ether gave rare thiophosphonato potassium [η3(S,P,S)-3,5-tBu2dp-(μ-K)(S2)([18]crown-6)] (10) or a selenophosphonato potassium [η3(Se,P,Se)-3,5-tBu2dp-(μ-K)(Se2)([18]crown-6)] (11). Both of the complexes crystallized in the orthorhombic space group Pnma as pale-yellow (or red) crystals. The X-ray diffraction analysis revealed 10 or 11 as a terminal complex with the η11-X,X-coordination mode (X = S and Se). The 1H DOSY NMR spectroscopy study of the species 8 in DMSO-d6 suggested that polymeric complexes (4–9) in the solid state should dissociate into the related monomers in the solutions when the donor solvents were used.

Graphical abstract: Ion-bearing stairs: alkali metal complexes of 1,2-diaza-4-phospholides

Supplementary files

Article information

Article type
Paper
Submitted
25 Oct 2021
Accepted
14 Dec 2021
First published
20 Dec 2021

Dalton Trans., 2022,51, 1634-1645

Ion-bearing stairs: alkali metal complexes of 1,2-diaza-4-phospholides

M. Zhao, T. Xue, R. He, J. Ma and W. Zheng, Dalton Trans., 2022, 51, 1634 DOI: 10.1039/D1DT03601G

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