A 1,2,4-diazaphospholyl radical and its nitrogen-phosphorus coupled dimer: synthesis, X-ray structural characterization, EPR analysis, and computational studies

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

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, κN,κN'-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 η¹,η¹-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.

1,2-Diaza-4-phospholide complexes of chromium(ii): dipotassium organochromates behaving as single-molecule magnets

The 1,2-diaza-4-phospholide (dp^-) dipotassium ate complexes of chromium(ii) {[(η¹-N-3,5-tBu₂dp)₄Cr][(η⁵-(N,N,C,C,P))₂-K(η¹-O-THF)₂]₂} (5) and {[(η¹-N-3,5-Ph₂dp)₄Cr][(η⁵-(N,N,C,C,P))₂-K(η¹-O-THF)₂]₂}_∞ (6) were synthesized and characterized by X-ray single crystal structure analysis. Complex 5 with a near-square planar geometry at the chromium(ii) ion was unambiguously characterized by the high field electron paramagnetic resonance (HF-EPR) technique and magnetic measurements, revealing that it is a field-induced single-molecule magnet (SMM).

1,2,4-Triazolato paddlewheel dibismuth complexes with very short Bi(ii)–Bi(ii) bonds: bismuth(iii) oxidation of 1,2,4-triazolato anions into neutral N-1,2,4-triazolyl radicals

Bismuth(iii) oxidation of 1,2,4-triazolato anions allowed paddlewheel 1,2,4-triazolato dibismuth complexes to be isolated and the reaction involved the neutral N-1,2,4-triazolyl radicals that were evidenced by EPR analysis.

X-ray Absorption Near-Edge Structure Spectroscopy of a Stable 6-Oxoverdazyl Radical and Its Diamagnetic Precursor

The electronic structure of 1,3,5-triphenyl-6-oxoverdazyl, a heteroatom-rich stable organic radical, and its diamagnetic 1,3,5-triphenyl-6-oxotetrazane precursor are probed using X-ray absorption near-edge structure (XANES) spectroscopy. The N K-edge XANES spectra of the 6-oxoverdazyl radical contain strong N 1s → π* resonances for each set of equivalent nitrogen atoms. The fact that these resonances are absent from the analogous spectra of the 6-oxotetrazane, whereas the O K-edge and C K-edge XANES spectra of both species are very similar, demonstrates that the unpaired electron of the radical is localized primarily on the N atoms of the 6-oxoverdazyl heterocycle. The O K-edge XANES spectra of both species contain strong O 1s → π* (C═O) peaks, but the peak of the radical is red-shifted by 0.5 eV relative to that of the 6-oxotetrazane, which indicates that the C═O bond in the radical is part of a larger π-conjugated system. The proposed interpretations of the XANES spectra are aided by density-functional calculations.

A dipotassium 1,2,4-diazaphospholide dianion radical as an organometallic building block: the first 1,2-diaza-4-phosphine ruthenocene

A persistent dipotassium 3,5-diphenyl-1,2,4-diazaphospholide dianion radical {K+2[(3,5-Ph2dp)]˙2-} (2) was synthesized and investigated by EPR analysis and magnetic susceptibility measurement, and it can be used as a transfer agent for the preparation of an unusual 1,2-diaza-4-phosphine ruthenocene (4) with exclusive σ(P)-coordination. A plausible mechanism for the formation of 4 was proposed as one that involves a reactive radical intermediate {K+[(η5-CpMe5Ru)(σ(P),σ(C)-(3,5-Ph2dp)˙]-)} (K+[5A˙]-) with σ(P)-coordination due to the high spin density (SD) at the phosphorus (σ2λ3) atom.

1,2-Diaza-4-phosphaferrocenes: synthesis, structural characterization, 57Fe Mössbauer spectrum analysis, and DFT calculation

Two 1,2-diaza-4-phosphaferrocenes [(η⁵-3,5-R₂dp)Fe(η⁵-CpMe₅)] (R = tBu (3), Ph (4)) with a single η⁵ ring containing two nitrogen atoms are prepared. Mössbauer spectroscopic, electrochemical, and density functional theory (DFT) studies have provided a more detailed understanding of the electronic structures and stabilities of these complexes.

Paddlewheel 1,2,4-diazaphospholide distibines with the shortest antimony-antimony single bonds

One-electron reduction of SbCl3 with the non-innocent 1,2,4-diazaphospholide anion [3,5-R2dp](-) produced straightforwardly three unprecedented paddlewheel distibines [L2(Sb-Sb)L2] (L = η(1),η(1)-3,5-R2dp, R = tBu (4), iPr (5α, 5β), or Cy (6)) with very short Sb-Sb bond lengths (2.6691(8)-2.7451(8) Å). The novel structures were rationalized by DFT calculations.

1,2,4-Diazaphospholide complexes of lanthanum(iii), cerium(iii), neodymium(iii), praseodymium(iii), and samarium(iii): synthesis, X-ray structural characterization, and magnetic susceptibility studies

A few heteroleptic, charge-separated heterobimetallic, and polymeric alkali metalate complexes of 1,2,4-diazaphospholide lanthanum(iii), cerium(iii), neodymium(iii), praseodymium(iii), and samarium(iii) were simply prepared via the metathesis reaction of MCl3 (THF)m (m = 1-2) and K[3,5-R2dp] ([3,5-R2dp](-) = 3,5-di-substituent-1,2,4-diazaphospholide; R = tBu, Ph) in a varied ratio (1 : 3, 1 : 4, and 1 : 5, respectively) at room temperature in tetrahydrofuran. All the complexes were fully characterized by (1)H, (13)C{(1)H}, (31)P{(1)H}, IR, and X-ray single crystal diffraction analysis despite their paramagnetism (excluding La(iii) complexes). The structures of the complexes were found to feature varied coordination modes. The magnetic properties of several compounds were studied by magnetic susceptibility, and the complexes presented the magnetic moments close to or lower than the theoretical values for the free ions in the trivalent oxidation states (Pr(3+), Nd(3+)).

Chromium(III) complexes with 1,2,4-diazaphospholide and 2,6-bis(N-1,2,4-diazaphosphol-1-yl) pyridine ligands: synthesis, X-ray structural characterization, EPR spectroscopy analysis, and magnetic susceptibility studies

Three chromium(III) 1,2,4-diazaphospholide complexes were prepared: 3,5-di-tert-butyl-1,2,4-diazaphospholide chromium(III) dichloride [(η 2-3,5-tBu2dp)Cr(THF)2Cl2] (1), 3,5-di-phenyl-1,2,4-diazaphospholide chromium(III) dichloride [(η 2-3,5-Ph2dp)Cr(THF)2Cl2] (2), and 2,6-bis(N-1,2,4-diazaphosphol-1-yl)pyridine chromium(III) trichloride {[2,6-bis(N-1,2,4-diazaphosphol-1-yl)pyridine]CrCl3} (3). X-ray diffraction analysis has shown that these six-coordinate complexes each have a pseudo-octahedral configuration. Electron paramagnetic resonance (EPR) spectroscopy data for complex 1 for the paramagnetic S = 3/2 system (d 3 electron configuration) confirm a Cr(III) center in the octahedral coordination environment. The magnetic susceptibility of complex 1 followed the Curie–Weiss law well between 25 and 300 K. The magnetic moment of 1 was found to be close to the spin-only magnetic moment expected for three unpaired electrons (3.87 μB).

1,2,4-Diazaphospholide complexes of yttrium(iii), dysprosium(iii), erbium(iii), and europium(ii,iii): synthesis, X-ray structural characterization, and EPR analysis

Several structurally characterized heteroleptic, charge-separated heterobimetallic, and polymeric alkali metal ate complexes of 1,2,4-diazaphospholide Y(iii), Dy(iii), Er(iii), Eu(iii), and Eu(ii) were prepared via the reaction of MCl3 and K[3,5-R2dp] in varied ratios at 200-220 °C (M = Y, Dy, Er, Eu; R = tBu, Ph).

Paddlewheel 1,2,4-diazaphospholide dibismuthanes with very short bismuth-bismuth single bonds

One-electron oxidation of the 1,2,4-diazaphospholide anion [3,5-R2dp](-) by BiCl3 generated several remarkable paddlewheel dibismuthanes [L2(Bi-Bi)L2] (L = η(1),η(1)-3,5-R2dp, R = tBu, iPr, or Ph) with very short Bi-Bi single bond lengths (2.7964(4)-2.8873(3) Å).