Isolation and characterization of bis(silylene)-stabilized antimony(I) and bismuth(I) cations

Abstract

Monovalent group 15 cations L2Pn + (L = σ-donor ligands, Pn = N, P, As, Sb, Bi) have attracted significant experimental and theoretical interest because of their unusual electronic structures and growing synthetic potential. Herein, we describe the synthesis of a family of antimony(I) and bismuth(I) cations supported by a bis(silylene) ligand [(TBDSi2)Pn][BArF4] (TBD = 1, 8, 10, 9-triazaboradecalin; ArF = 3,5-CF3-C6H3; Pn = Sb, (2); Bi, (3)). The structures of 2 and 3 have been unambiguously characterized spectroscopically and by X-ray diffraction analysis and DFT calculations. They feature bis-coordinated Sb and Bi atoms which exhibit two lone pairs of electrons. The reactions of 2 and 3 with methyl trifluoromethane sulfonate provide a approach for the preparation of dicationic antimony(III) and bismuth(III) methyl complexes. Compounds 2 and 3 serve as 2e donors to group 6 metals (Cr, Mo), giving rise to ionic antimony and bismuth metal carbonyl complexes 6–9.

Stabilizing Monoatomic Two-Coordinate Bismuth(I) and Bismuth(II) Using a Redox Noninnocent Bis(germylene) Ligand

“…The Ge1–Bi1–Ge2 angles of 103.981(12)° ( 4 [BAr F ]) and 104.67(3)° ( 4 [OTf]) are quite similar to those of 3 [BAr F ] (103.895(14)°) but slightly smaller than those of 2 (109.244(18)°) and 3 [OTf] (106.995(10)°), respectively. However, the Ge1–Bi1–Ge2 angles are significantly larger than the Si1–Bi1–Si2 angle of the Bi I cation complex B (82.10(3)°) due to the larger ring size …”

“…The Bi III center adopts a trigonal pyramidal geometry due to methyl coordination. The Bi–C distance of 2.247(7) Å is shorter than that of [(TBDSi 2 )­BiMe]­[BAr F ] 2 (2.300 Å) . The Ge–Bi distances in 8 of 2.7393(7) and 2.7426(7) Å are longer than those in the two-coordinate Bi I complex 4 and radical dication 5 (2.6627(4)–2.7147(3) Å), but shorter than those in the four-coordinate 2 , 3 , and 7 (2.7497(6) to 2.8035(5) Å), respectively.…”

“…The Bi−C distance of 2.247 (7) Å is shorter than that of [(TBDSi 2 )BiMe][BAr F ] 2 (2.300 Å). 23 The Ge−Bi distances in 8 of 2.7393(7) and 2.7426 (7) Å are longer than those in the two-coordinate Bi I complex 4 and radical dication 5 (2.6627(4)−2.7147(3) Å), but shorter than those in the four-coordinate 2, 3, and 7 (2.7497 (6) We are currently applying these redox-ligand-active Bi I and Bi II complexes in photoredox single-electron transfer catalysis in our laboratory. We believe that the stabilization of Bi I cations and Bi II radical dication complexes by using redox noninnocent ligands is a promising strategy to gain access to related low-valent p-block metal complexes that are otherwise very difficult to tame.…”

“…Compounds containing heavy p-block group 14 and 15 elements E in uncommon low oxidation states are of paramount interest because they provide multiple new opportunities for the design of main-group element species mimicking transition-metal-like reactivity with respect to small molecule activation and catalysis. − However, the synthesis of such isolable species is challenging and requires suitable ligation around the low-valent E atom to prevent E–E bond oligomerization and disproportionation. Recent developments in this direction have paved the way to zerovalent monatomic complexes of the group 14 elements named tetrylones with the general formula L:→E 0 ←:L (E = C, Si, Ge, Sn, Pb). − Utilizing the bis­(silylene)­xanthene, we achieved the whole series of heavier tetrylones previously. ,,, The central E 0 atom is two-coordinated by two sufficient donor ligands and obeys the octet rule, retaining its four valence electrons as two lone pairs. , The various tetrylones stabilized by sufficient Lewis bases show an unparalleled reactivity toward small molecules. − Monovalent group 15 element complex cations of the type L 2 E + (L = donor, E = N, P, As, Sb, Bi) − are known isoelectronic species but particularly difficult to tame for the heaviest pnictogen, bismuth. Compared with the lighter congeners, low-valent bismuth compounds possess exceptional features such as strong spin–orbit coupling (SOC) due to relativistic effects, , low redox potentials and transition-metal-like properties in redox catalysis. − It should be noted here that the peculiar electronic features of low-valent Bi play also a decisive role in rare earth metal–bismuth coordination compounds that are single-molecule magnets. − …”

Ultrafast charge transfer of stiboviologens for electrochromism and visible light-induced α-amino C(sp3)–H functionalization

“…In recent years, there has been growing interest in incorporating the Sb element into organic systems in order to achieve unique properties. 37–41 Organic antimony compounds often exist in the trivalent or pentavalent form due to the electron configuration of Sb. These compounds, characterized by their heavier atoms, distinctive electron configuration, and certain biocompatibility, 42,43 have been widely applied in organic synthesis, 44–46 photocatalysis, 47–49 and coordination chemistry.…”