Well‐Defined, Mononuclear Bi^I and Bi^II Compounds: Towards Transition‐Metal‐Like Behavior

Abstract

Mononuclear BiI and BiII compounds remained elusive for a long time, but recently, the isolation and characterization of such species were reported. They can be handled in solution at ambient temperature and show exceptional properties, which are expected to reveal new reactivity patterns, enabling the development of new catalytic processes. TEMPO=2,2,6,6‐tetramethyl‐1‐piperidinyl N‐oxide.

Applications of electron paramagnetic resonance spectroscopy to heavy main-group radicals

“…In my experience, low temperatures are required to overcome the fast electron relaxation behaviour of these heavy radical centres, reflecting their metal-like character. 39,40 However, substantial amounts of main-group radical characterization have relied only on solution-phase EPR characterization and hyperfine analysis. 1,13,19,22 In room-temperature EPR spectroscopy, the rapid tumbling of the molecule averages the anisotropic contributions to the spectrum and directly measures g iso and a iso values.…”

“…An emerging area of interest is the isolation and characterization of stable bismuth radicals which exhibit metal-like bevahior. 40 To date, only a few bismuth radicals have been characterized 19,22,25,26 and their EPR spectra recorded. 25,26 Isolation of low-valent bismuth centres is difficult to achieve as these complexes are prone to overreduction and disproportionation reactions.…”

From stable Sb- and Bi-centered radicals to a compound with a Ga=Sb double bond

“…1) 24 . Laser-ablated Sb and Bi atoms react with hydrogen and methane to give short-lived Sb(II) and Bi(II) radicals H 2 E· and HMeE· (E = Sb, Bi) 25,26 and persistent cAAC-stabilized stibinyl ( a ) 27 and bismuthinyl radicals ( b ) were synthesized in solution 27,28 .…”

A Redox‐Confused Bismuth(I/III) Triamide with a T‐Shaped Planar Ground State

“…[4] Thec onfluence of al one pair and av acant p orbital at the central atom in the transition state unlocks ambiphilic reactivity akin to that of transition metals, [3a] with 10-P-3 compounds finding applications in catalytic reductions [5] and activation of challenging substrates like NH 3 . [6] Ther einvigorated interest in 10-E-3 complexes drew our attention to the conspicuous absence of bismuth in Scheme 1c and the general paucity of mononuclear Bi I compounds.T his absence is particularly surprising because bismuth exhibits low toxicity, [7] al arge coordination sphere, [8] multiple stable redox states, [9] and ah igh p-affinity [10] -features that are appealing in the context of toxic-metal-free catalysis.Several Bi III complexes also show stoichiometric activation of CÀH bonds and small molecules such as CO and CO 2 . [11] Previous attempts to generate a1 0-Bi-3 center using geometric constraints and electron-rich ligands were foiled by the small steric profile of the O-N-O ligand, resulting in attachment of multiple ligand equivalents to give ah ypercoordinate 20-Bi-9 complex.…”