Dihalo bismuth cations: unusual coordination properties and inverse solvent effects in Lewis acidity

Abstract

A series of well-defined cationic hepta-coordinate bismuth halides [BiX2(py)5][B(3,5-(CF3)2-C6H3)4] (X = Cl, Br, I), stabilized only by substitutionally labile solvent molecules, were synthesized and fully characterized. Their apparent D5h symmetry...

Lewis Superacidic Heavy Pnictaalkene Cations: Comparative Assessment of Carbodicarbene-Stibenium and Carbodicarbene-Bismuthenium Ions

“…Enhancing the Lewis acidity at the pnictogen center typically enhances the reactivity of pnictenium ions . The Lewis acidity of p-block compounds has been evaluated using a variety of methods, including FIA, , hydride ion affinity, and the GB method. − The GB method is an experimental technique that measures the change in the 31 P NMR chemical shift of triethylphosphine oxide (OPEt 3 ) after it is added to the sample of interest, which translates to an AN using the following formula AN = 2.21 × [δ­( 31 P NMR) sample – 41.0]. , Comparative methods using softer bases (e.g., S = PMe 3 , Se = PMe 3 ) have also been used to evaluate the Lewis acidity of heavy group 15 complexes. , Greb and Erdmann highlighted that the GB method is most reliable as a comparative tool for complexes that contain the same central elements and comparable ligands …”

“…58,59 Comparative methods using softer bases (e.g., S = PMe 3 , Se = PMe 3 ) have also been used to evaluate the Lewis acidity of heavy group 15 complexes. 60,61 Greb and Erdmann highlighted that the GB method is most reliable as a comparative tool for complexes that contain the same central elements and comparable ligands. 62 Catalytically active antimony and bismuth complexes generally have reported ANs greater than 50 as evaluated using the GB method.…”

Bismuth Cations: Fluoride Ion Abstraction, Isocyanide Coordination, and Impact of Steric Bulk on Lewis Acidity

“…The transformation of neutral bismuth species into cationic congeners has granted access to compounds featuring remarkable structural properties and reactivity patterns. [1] This includes low-coordinate and low-valent compounds (such as [Bi(2,6-Mes 2 C 6 H 3 ) 2 ][B(3,5-(CF 3 ) 2 -C 6 H 3 ) 4 ] (Mes = 2,4,6-Me 3 C 6 H 2 ) and [Bi-(cAAC) 2 ][OTf]), [2,3] species with an unusual coordination chemistry (such as a pentagonal bipyramidal coordination geometry with a stereochemically inactive lone pair at bismuth), [4] ring-strained coordination entities, [5][6][7] and new structural motifs such as bisma-alkene species and Bi!Bi donor-acceptor bonding. [8,9] It can be anticipated that such uncommon structural properties inevitably lead to unforeseen reactivity patterns.…”

“…NMR (500 MHz, CD 2 Cl 2 ): δ = 1.08 ppm (d,3 J H-H = 6 4. Hz, o-CCH(CH 3 ) 2 ), 2.72 (t,3 J H-H = 6 6.…”

Cationic Bismuth Amides Add across Activated C═X Bonds (X = C, N, and S): Pronounced Solvent Effects on Reactivity and Selectivity

“…In contrast, solvent effects in the chemistry of heavy p-block elements are far less explored. Among them, bismuth compounds, in particular, appear to be promising candidates for the exploitation of aggregation phenomena and solvent-induced ion pair formation due to the large ionic radius of bismuth atoms and the considerable soft Lewis acidity of bismuth complexes, which enables a highly flexible coordination environment with coordination numbers of up to nine (based on monodentate ligands) − and inverse solvent effects in Lewis acidity . Additionally, low bond dissociation energies − and the tendency to undergo fast ligand exchange reactions can enable a vast variety of reaction pathways. − Bismuth amides and related species have gained considerable attention in the last years due to their good accessibility, high reactivity, and coordination-chemical flexibility.…”