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. 2023 Mar 15;145(10):5618-5623.
doi: 10.1021/jacs.2c12564. Epub 2023 Feb 28.

Synthesis, Isolation, and Characterization of Two Cationic Organobismuth(II) Pincer Complexes Relevant in Radical Redox Chemistry

Xiuxiu Yang  1 , Edward J Reijerse  2 , Nils Nöthling  1 , Daniel J SantaLucia  1 , Markus Leutzsch  1 , Alexander Schnegg  2 , Josep Cornella  1
Affiliations

Synthesis, Isolation, and Characterization of Two Cationic Organobismuth(II) Pincer Complexes Relevant in Radical Redox Chemistry

Xiuxiu Yang et al. J Am Chem Soc. .

Abstract

Herein, we report the synthesis, isolation, and characterization of two cationic organobismuth(II) compounds bearing N,C,N pincer frameworks, which model crucial intermediates in bismuth radical processes. X-ray crystallography uncovered a monomeric Bi(II) structure, while SQUID magnetometry in combination with NMR and EPR spectroscopy provides evidence for a paramagnetic S = 1/2 state. High-resolution multifrequency EPR at the X-, Q-, and W-band enable the precise assignment of the full g- and 209Bi A-tensors. Experimental data and DFT calculations reveal both complexes are metal-centered radicals with little delocalization onto the ligands.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Figure 1
Figure 1
(A) N,C,N organobismuth(II) complexes formed after Bi(III)–X homolysis; (B) state-of-the-art of known Bi(II) complexes.
Scheme 1
Scheme 1. Syntheses of Cationic Bi(II) Complexes
Figure 2
Figure 2
Solid-state structure of 3 (top) and 4 (bottom), using 50% probability ellipsoids. Solvents, hydrogen atoms (except the ones on C7 and C8), and disordered parts have been omitted for clarity.
Figure 3
Figure 3
EPR at the X-, Q-, and W-band of 3 and 4 (blue) with simulations (red) according to the SH parameters from Table 2. The marked (*) lines at the Q-band originate from a g ∼ 2 impurity.
Figure 4
Figure 4
(A to C) Magnetic field dependent spin energy levels (Breit–Rabi diagrams) along the x-, y-, and z-axis of the g-tensor. X-band EPR transitions are plotted as vertical red lines. (D) Corresponding roadmap representing the angular dependence of EPR resonances (theta: angle between the magnetic field and the z-axis of the g-tensor). Energy levels and EPR spectra have been obtained with SH parameters for 4.
Figure 5
Figure 5
DC magnetic susceptibility data from 2.0 to 300 K (black) and fits from the SH model from 7.6 to 300 K and 2 to 271 K (red traces) for 3 (top) and 4 (bottom), respectively.
See this image and copyright information in PMC

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