The alkaline-earth elements (Be, Mg, Ca, Sr, and Ba) strongly favor the formation of diamagnetic compounds in the +2 oxidation state. Herein we report a paramagnetic beryllium radical cation, [(CAAC) 2 Be] +• (2) [CAAC = cyclic (alkyl)(amino)carbene], prepared by oxidation of a zero-valent beryllium complex with 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO). Compound 2 was characterized by EPR spectroscopy, elemental analysis, X-ray crystallography, and DFT calculations. Notably, the isolation of 2 represents the first s-block charged radical and the first crystalline beryllium radical.

The long‐sought carbene–bismuthinidene, (CAAC)Bi(Ph), has been synthesized. Notably, this represents both the first example of a carbene‐stabilized subvalent bismuth complex and the extension of the carbene‐pnictinidene concept to a non‐toxic metallic element (Bi). The bonding has been investigated by single‐crystal X‐ray diffraction studies and DFT calculations. This report also highlights the hitherto unknown reducing and ligand transfer capability of a beryllium(0) complex.

We report a combined experimental and theoretical study on the first examples of carbodicarbene (CDC)‐stabilized bismuth complexes, which feature low‐coordinate cationic bismuth centers with C=Bi multiple‐bond character. Monocations [(CDC)Bi(Ph)Cl][SbF6] (8) and [(CDC)BiBr2(THF)2][SbF6] (11), dications [(CDC)Bi(Ph)][SbF6]2 (9) and [(CDC)BiBr(THF)3][NTf2]2 (12), and trication [(CDC)2Bi][NTf2]3 (13) have been synthesized via sequential halide abstractions from (CDC)Bi(Ph)Cl2 (7) and (CDC)BiBr3 (10). Notably, the dications and trication exhibit C⇉ Bi double dative bonds and thus represent unprecedented bismaalkene cations. The synthesis of these species highlights a unique non‐reductive route to C−Bi π‐bonding character. The CDC‐[Bi] complexes (7–13) were compared with related NHC‐[Bi] complexes (1, 3–6) and show substantially different structural properties. Indeed, the CDC ligand has a remarkable influence on the overall stability of the resulting low‐coordinate Bi complexes, suggesting that CDC is a superior ligand to NHC in heavy pnictogen chemistry.

The first examples of carbodicarbene (CDC)-s-block complexes have been synthesized. Unusual C–H bond activation and cyclization discovered.

Cyclic(alkyl)(amino) carbene (CAAC)-stabilized complexes of phosphorus, one of the lightest group 15 elements, are well-established and can often be obtained in high yields. In contrast, analogous CAAC compounds of bismuth, the heaviest nonradioactive member of group 15, are unknown. Indeed, reactivity increases as you descend the group, and as a result there are only a few examples of N-heterocyclic carbene (NHC)-bismuth complexes. Moreover, activated bismuth compounds often readily extrude bismuth metal, making isolation of stable complexes highly challenging. We report that CAACs react with phenylbismuth dichloride (PhBiCl) to afford CAAC-Bi(Ph)Cl and CAAC-Bi(Ph)Cl. Significantly, these complexes represent the first structurally characterized examples of CAAC-coordination to bismuth. The CAAC-stabilized bismuth compounds can also be obtained from air-stable salts, [CAAC-H] [Cl(Ph)Bi(μ-Cl)Bi(Ph)Cl] and [CAAC-H] [Cl(Ph)Bi(μ-Cl)Bi(Ph)Cl], by deprotonation with potassium bis(trimethylsilyl)amide, K[N(SiMe)]. The electronic effects of the ligand on the bismuth center were investigated by comparing the CAAC-Bi(Ph)Cl complexes to the NHC analogues, SIPr-Bi(Ph)Cl(THF) and IPr-Bi(Ph)Cl (SIPr = 1,3-bis(2,6-diisopropylphenyl)-4,5-dihydroimidazole-2-ylidene; IPr = 1,3-bis(2,6-diisopropylphenyl)imidazole-2-ylidene). Interestingly, the "normal" IPr-Bi(Ph)Cl slowly isomerizes to the "abnormal" carbene complex, Cl(Ph)Bi-IPr-H, at -37 °C. In the solid-state, the CAAC-, NHC-, and abnormal NHC-bismuth compounds exhibit Bi atomic centers in unique coordination environments. The complexes were fully characterized by NMR, elemental analysis, and single crystal X-ray diffraction studies. In addition, the bonding was probed by natural bond orbital (NBO) calculations.

In the past two decades, the organometallic chemistry of the alkaline earth elements has experienced a renaissance due in part to developments in ligand stabilization strategies. In order to expand the scope of redox chemistry known for magnesium and beryllium, we have synthesized a set of reduced magnesium and beryllium complexes and compared their resulting structural and electronic properties. The carbene-coordinated alkaline earth−halides, ( Et2 CAAC)-MgBr 2 (1), (SIPr)MgBr 2 (2), ( Et2 CAAC)BeCl 2 (3), and (SIPr)BeCl 2 (4) [ Et2 CAAC = diethyl cyclic(alkyl)(amino) carbene; SIPr = 1,3-bis(2,6-diisopropylphenyl)-4,5-dihydroimidazole-2-ylidene] were combined with an α-diimine [2,2bipyridine (bpy) or bis(2,6-diisopropylphenyl)-1,4-diazabutadiene ( Dipp DAB)] and the appropriate stoichiometric amount of potassium graphite to form singly-and doubly-reduced compounds ( Et2 CAAC)MgBr( Dipp DAB) (5), ( Et2 CAAC)MgBr(bpy) ( 6), ( Et2 CAAC)Mg( Dipp DAB) ( 7), ( Et2 CAAC)Be(bpy) (8), and (SIPr)Be(bpy) (9). The doubly-reduced compounds 7−9 exhibit substantial π-bonding interactions across the diimine core, metal center, and π-acidic carbene. Each complex was fully characterized by UV−vis, FT-IR, X-ray crystallography, 1 H, 13 C, and 9 Be NMR, or EPR where applicable. We use these compounds to highlight the differences in the organometallic chemistry of the lightest alkaline earth metals, magnesium and beryllium, in an otherwise identical chemical environment.

The synthesis and thermal redox chemistry of the first antimony (Sb)– and bismuth (Bi)–phosphaketene adducts are described. When diphenylpnictogen chloride [Ph 2 PnCl (Pn = Sb or Bi)] is reacted with sodium 2-phosphaethynolate [Na[OCP]·(dioxane) x ], tetraphenyldipnictogen (Ph 2 Pn–PnPh 2 ) compounds are produced, and an insoluble precipitate forms from solution. In contrast, when the N -heterocyclic carbene adduct (NHC)–PnPh 2 Cl is combined with [Na[OCP]·(dioxane) x ], Sb– and Bi–phosphaketene complexes are isolated. Thus, NHC serves as an essential mediator for the reaction. Immediately after the formation of an intermediary pnictogen–phosphaketene NHC adduct [NHC–PnPh 2 (PCO)], the NHC ligand transfers from the Pn center to the phosphaketene carbon atom, forming NHC–C(O)P-PnPh 2 [Pn = Sb ( 3 ) or Bi ( 4 )]. In the solid state, 3 and 4 are dimeric with short intermolecular Pn–Pn interactions. When compounds 3 and 4 are heated in THF at 90 and 70 °C, respectively, the pnictogen center Pn III is thermally reduced to Pn II to form tetraphenyldipnictines (Ph 2 Pn–PnPh 2 ) and an unusual bis -carbene-supported OCP salt, [(NHC) 2 OCP][OCP] ( 5 ). The formation of compound 5 and Ph 2 Pn–PnPh 2 from 3 or 4 is unique in comparison to the known thermal reactivity for group 14 carbene–phosphaketene complexes, further highlighting the diverse reactivity of [OCP] − with main-group elements. All new compounds have been fully characterized by single-crystal X-ray diffraction, multinuclear NMR spectroscopy ( 1 H, 13 C, and 31 P), infrared spectroscopy, and elemental analysis ( 1 , 2 , and 5 ). The electronic structure of 5 and the mechanism of formation were investigated using density functional theory (DFT).

A common feature of d‐ and p‐block elements is that they participate in multiple bonding. In contrast, the synthesis of compounds containing homo‐ or hetero‐nuclear multiple bonds involving s‐block elements is extremely rare. Herein, we report the synthesis, molecular structure, and computational analysis of a beryllium imido (Be=N) complex (2), which was prepared via oxidation of a molecular Be0 precursor (1) with trimethylsilyl azide Me3SiN3 (TMS‐N3). Notably, compound 2 features the shortest known Be=N bond (1.464 Å) to date. This represents the first compound with an s‐block metal‐nitrogen multiple bond. All compounds were characterized experimentally with multi‐nuclear NMR spectroscopy (1H, 13C, 9Be) and single‐crystal X‐ray diffraction studies. The bonding situation was analyzed with density functional theory (DFT) calculations, which supports the existence of π‐bonding between beryllium and nitrogen.