Search

Careful analysis of the crystals formed in the reduction of AriPr8AlI2 (AriPr8=C6H-2,6-(C6H2-2,4,6-iPr3)2-3,5-iPr2) with sodium on sodium chloride showed them to contain the long sought-after dialuminene AriPr8AlAlAriPr8 (1) that forms alongside the previously characterized alanediyl :AlAriPr8. The single crystal X-ray structure of 1 revealed a nearly planar, trans-bent C(ipso)AlAlC(ipso) core with an Al-Al distance of 2.648(2) Å. The molecular and electronic structure of 1 are consistent with an Al-Al double dative interaction augmented with diradical character and stabilized by dispersion interactions. Density functional theory calculations showed that the reactivity of :AlAriPr8 with dihydrogen involves 1, not :AlAriPr8, as the reactive species. In contrast, the reaction of :AlAriPr8 with ethylene gave two products, the 1,4-dialuminacyclohexane AriPr8Al(C2H4)2AlAriPr8 (2) and the aluminacyclopentane AriPr8Al(C4H8) (3), that can both form from the aluminacyclopropane intermediate AriPr8Al(C2H4). Although the [2+2+2] cycloaddition of 1 with two equivalents of ethylene was also calculated to be exergonic, it is likely to be kinetically blocked by the numerous isopropyl substituents surrounding the Al-Al bond. Attempts to fine-tune the steric bulk of the terphenyl ligand to allow stronger Al-Al bonding were unsuccessful, leading to the isolation of the sodium salt of a cyclotrialuminene, Na2[AlAriPr6]3 (4), instead of AriPr6AlAlAriPr6.

Careful analysis of the crystals formed in the reduction of AriPr8AlI2 (AriPr8=C6H‐2,6‐(C6H2‐2,4,6‐iPr3)2‐3,5‐iPr2) with sodium on sodium chloride showed them to contain the long sought‐after dialuminene AriPr8AlAlAriPr8 (1) that forms alongside the previously characterized alanediyl :AlAriPr8. The single crystal X‐ray structure of 1 revealed a nearly planar, trans‐bent C(ipso)AlAlC(ipso) core with an Al−Al distance of 2.648(2) Å. The molecular and electronic structure of 1 are consistent with an Al−Al double dative interaction augmented with diradical character and stabilized by dispersion interactions. Density functional theory calculations showed that the reactivity of :AlAriPr8 with dihydrogen involves 1, not :AlAriPr8, as the reactive species. In contrast, the reaction of :AlAriPr8 with ethylene gave two products, the 1,4‐dialuminacyclohexane AriPr8Al(C2H4)2AlAriPr8 (2) and the aluminacyclopentane AriPr8Al(C4H8) (3), that can both form from the aluminacyclopropane intermediate AriPr8Al(C2H4). Although the [2+2+2] cycloaddition of 1 with two equivalents of ethylene was also calculated to be exergonic, it is likely to be kinetically blocked by the numerous isopropyl substituents surrounding the Al−Al bond. Attempts to fine‐tune the steric bulk of the terphenyl ligand to allow stronger Al−Al bonding were unsuccessful, leading to the isolation of the sodium salt of a cyclotrialuminene, Na2[AlAriPr6]3 (4), instead of AriPr6AlAlAriPr6. [ABSTRACT FROM AUTHOR]

Careful analysis of the crystals formed in the reduction of AriPr8AlI2 (AriPr8=C6H‐2,6‐(C6H2‐2,4,6‐iPr3)2‐3,5‐iPr2) with sodium on sodium chloride showed them to contain the long sought‐after dialuminene AriPr8AlAlAriPr8 (1) that forms alongside the previously characterized alanediyl :AlAriPr8. The single crystal X‐ray structure of 1 revealed a nearly planar, trans‐bent C(ipso)AlAlC(ipso) core with an Al−Al distance of 2.648(2) Å. The molecular and electronic structure of 1 are consistent with an Al−Al double dative interaction augmented with diradical character and stabilized by dispersion interactions. Density functional theory calculations showed that the reactivity of :AlAriPr8 with dihydrogen involves 1, not :AlAriPr8, as the reactive species. In contrast, the reaction of :AlAriPr8 with ethylene gave two products, the 1,4‐dialuminacyclohexane AriPr8Al(C2H4)2AlAriPr8 (2) and the aluminacyclopentane AriPr8Al(C4H8) (3), that can both form from the aluminacyclopropane intermediate AriPr8Al(C2H4). Although the [2+2+2] cycloaddition of 1 with two equivalents of ethylene was also calculated to be exergonic, it is likely to be kinetically blocked by the numerous isopropyl substituents surrounding the Al−Al bond. Attempts to fine‐tune the steric bulk of the terphenyl ligand to allow stronger Al−Al bonding were unsuccessful, leading to the isolation of the sodium salt of a cyclotrialuminene, Na2[AlAriPr6]3 (4), instead of AriPr6AlAlAriPr6. [ABSTRACT FROM AUTHOR]

Careful analysis of the crystals formed in the reduction of AriPr8AlI2 (AriPr8=C6H‐2,6‐(C6H2‐2,4,6‐iPr3)2‐3,5‐iPr2) with sodium on sodium chloride showed them to contain the long sought‐after dialuminene AriPr8AlAlAriPr8 (1) that forms alongside the previously characterized alanediyl :AlAriPr8. The single crystal X‐ray structure of 1 revealed a nearly planar, trans‐bent C(ipso)AlAlC(ipso) core with an Al−Al distance of 2.648(2) Å. The molecular and electronic structure of 1 are consistent with an Al−Al double dative interaction augmented with diradical character and stabilized by dispersion interactions. Density functional theory calculations showed that the reactivity of :AlAriPr8 with dihydrogen involves 1, not :AlAriPr8, as the reactive species. In contrast, the reaction of :AlAriPr8 with ethylene gave two products, the 1,4‐dialuminacyclohexane AriPr8Al(C2H4)2AlAriPr8 (2) and the aluminacyclopentane AriPr8Al(C4H8) (3), that can both form from the aluminacyclopropane intermediate AriPr8Al(C2H4). Although the [2+2+2] cycloaddition of 1 with two equivalents of ethylene was also calculated to be exergonic, it is likely to be kinetically blocked by the numerous isopropyl substituents surrounding the Al−Al bond. Attempts to fine‐tune the steric bulk of the terphenyl ligand to allow stronger Al−Al bonding were unsuccessful, leading to the isolation of the sodium salt of a cyclotrialuminene, Na2[AlAriPr6]3 (4), instead of AriPr6AlAlAriPr6. [ABSTRACT FROM AUTHOR]

Careful analysis of the crystals formed in the reduction of AriPr8AlI2 (AriPr8=C6H‐2,6‐(C6H2‐2,4,6‐iPr3)2‐3,5‐iPr2) with sodium on sodium chloride showed them to contain the long sought‐after dialuminene AriPr8AlAlAriPr8 (1) that forms alongside the previously characterized alanediyl :AlAriPr8. The single crystal X‐ray structure of 1 revealed a nearly planar, trans‐bent C(ipso)AlAlC(ipso) core with an Al−Al distance of 2.648(2) Å. The molecular and electronic structure of 1 are consistent with an Al−Al double dative interaction augmented with diradical character and stabilized by dispersion interactions. Density functional theory calculations showed that the reactivity of :AlAriPr8 with dihydrogen involves 1, not :AlAriPr8, as the reactive species. In contrast, the reaction of :AlAriPr8 with ethylene gave two products, the 1,4‐dialuminacyclohexane AriPr8Al(C2H4)2AlAriPr8 (2) and the aluminacyclopentane AriPr8Al(C4H8) (3), that can both form from the aluminacyclopropane intermediate AriPr8Al(C2H4). Although the [2+2+2] cycloaddition of 1 with two equivalents of ethylene was also calculated to be exergonic, it is likely to be kinetically blocked by the numerous isopropyl substituents surrounding the Al−Al bond. Attempts to fine‐tune the steric bulk of the terphenyl ligand to allow stronger Al−Al bonding were unsuccessful, leading to the isolation of the sodium salt of a cyclotrialuminene, Na2[AlAriPr6]3 (4), instead of AriPr6AlAlAriPr6. [ABSTRACT FROM AUTHOR]

2‐tetrelavinylidenes (C=EH2; E=Si, Ge) are according to quantum chemical studies the least stable isomers on the [E,C,2H] potential energy hypersurface isomerizing easily via the trans‐bent tetrelaacetylenes HE≡CH to the thermodynamically most stable 1‐tetrelavinylidenes (E=CH2). Consequently, experimental studies on 2‐tetrelavinylidenes (C=ER2) and their derivatives are lacking. Herein we report experimental and theoretical studies of the first N‐heterocyclic carbene (NHC) supported 2‐silavinylidene (NHC)C=SiBr(Tbb) (1‐Si: NHC=C[N(Dipp)CH]2, Dipp=2,6‐diisopropylphenyl, Tbb=2,6‐bis[bis(trimethylsilyl)methyl]‐4‐tert‐butylphenyl) and the isovalent 2‐germavinylidenes (NHC)C=GeBr(R) (1‐Ge, 1‐GeMind: R=Tbb, Mind (1,1,3,3,5,5,7,7‐octamethyl‐s‐hydrindacene‐4‐yl)). The NHC‐supported 2‐tetrelavinylidenes were obtained selectively from the 1,2‐dibromoditetrelenes (E)‐(R)BrE=EBr(R) using the diazoolefin (NHC)CN2 as vinylidene transfer reagent. 1‐E (E=Si, Ge) have a planar vinylidene core, a bent‐dicoordinated vinylidene carbon atom (CVNL), a very short E=CVNL bond and an almost orthogonal orientation of the NHC five‐membered ring to the vinylidene core. Quantum chemical analysis of the electronic structures of 1‐E suggest a significantly bent 1‐tetrelaallene and tetrelyne character. NMR studies shed light into the dynamics of 1‐E involving NHC‐rotation around the CVNL−CNHC bond with a low activation barrier. Furthermore, the synthetic potential of 1‐E is demonstrated by the synthesis and full characterization of the unprecedented NHC‐supported bromogermynes BrGe=C(EBr2Tbb)(NHC) (2‐SiGe: E=Si; 2‐GeGe: E=Ge). [ABSTRACT FROM AUTHOR]

We describe our efforts to access a compound with an Al=P double bond by reaction of Al(Nacnac) towards [H2CN(Dipp)]2P(PCO) (Nacnac=HC[C(Me)N(Dipp)]2; Dipp=2,6‐iPr2C6H3). Our observations are consistent with the formation of a transient phosphanyl‐phosphaalumene at low temperatures (−70 °C), however this species was found to readily undergo intramolecular C−H activation of the β‐diketiminato ligand upon warming to room temperature. The reactivity of the transient complex toward small molecules including dihydrogen, carbon dioxide, phosphaketenes, amines and silanes could be explored at low temperatures, showcasing that the target compound can react as both a frustrated Lewis pair (via the pendant phosphanyl moiety) or in hydroelementation reactions of the Al=P bond. The elusive target molecule could be trapped by addition of a Lewis base (tetrahydrofuran) affording an isolable molecular species that reacts in an analogous fashion to the base‐free compound. [ABSTRACT FROM AUTHOR]

Due to the unique properties of C−F bonds, organofluorine compounds occupy a privileged space in the pharmaceutical, agrochemical, and polymer industries. Carbofluorination reactions involve the formation of a C−C and a C−F bond, typically across a π‐bond or another unsaturated functionality that is revealed upon in situ activation. The design of tailored substrates and new catalyst systems has enabled carbofluorination chemistry to emerge as a promising manifold for the synthesis of unique fluorinated scaffolds. This review covers the application of nucleophilic and electrophilic fluorinating reagents in this chemistry, in addition to recently developed atom‐economical carbofluorination reactions using organofluorine compounds as dual reagents. [ABSTRACT FROM AUTHOR]

α‐Functionalized phosphorus compounds are an important class of biologically relevant molecules. The synthesis of these compounds often proceeds through the hydrophosphorylation of a C=E bond, with the most well‐known transformation being the Kabachnik‐Fields reaction. The nature of the phosphorus reagent is an important aspect of the hydrophosphorylation reaction. The Kabachnik‐Fields reaction uses H‐phosphonates (RO)2P(O)H, and similarities are often applied to 2° phosphine chalcogenides (R2P(Ch)H). However, the reactivities of the P−C and P−OR molecules differ quite dramatically, which changes the operative mechanism as well as subsequent downstream chemistry. We provide an in‐depth analysis of hydrophosphorylation of C=E (E=O, N) bonds with organophosphine chalcogenides. Additional discussion and a critical appraisal are provided on the similarities and differences between the H‐phosphonate and phosphine chalcogenide chemistry. [ABSTRACT FROM AUTHOR]

A neutral silylyne complex with a Cr≡Si triple bond was prepared by dehydrogenation of a chromium silylene complex with Cr−H and Si−H bonds, and was isolated as monomeric crystals, unlike dimeric forms of its tungsten and molybdenum congeners. The strong Cr(δ−)−Si(δ+) bond polarity was revealed by the reaction with MeOH and DFT calculations. The chromium silylyne complex reacted with H2 under LED (365 nm) irradiation to reproduce the precursor silylene complex with a (H)Cr=Si(H) moiety, as a result of 1,2‐H−H addition across the Cr≡Si triple bond. Similarly, the chromium silylyne complex reacted with benzene under irradiation to afford an 1,2‐addition product with a (H)Cr=Si(Ph) moiety, via benzene C−H bond activation accompanied by Si−C bond forming. [ABSTRACT FROM AUTHOR]

Understanding free radical addition to multiple bonds is important to elucidating the mechanistic details of addition polymerization reactions, albeit the fleeting radical intermediates are very difficult to detect by conventional methodologies. Muon spin spectroscopy (μSR) is a highly sensitive method that can detect radical species at 106 spins (cf. EPR: 1012 spins, NMR: 1018 spins). Herein, we employ μSR to detect the radical‐addition products from three 1‐phosphabutadiene monomers, P‐analogues of isoprene. We show that muonium (Mu), a "light" H‐atom surrogate, adds predominantly at the C4 position of the P1=C2−C3=C4 moiety to give unprecedented 1‐phosphaallyl radicals as the major products. Our structural assignments are supported by assignment of muon, phosphorus and proton hyperfine coupling constants using DFT‐calculations. A minor radical product is also detected that is tentatively assigned to an PC3‐heterocyclic free radical. On the basis of DFT‐predictions, we speculate that its formation may involve initial addition of Mu+ at the C3 position followed by electron capture. These studies provide rare insights into the prospective radical (or cationic) polymerization of 1‐phosphabutadienes, which have previously been polymerized using anionic initiation. [ABSTRACT FROM AUTHOR]

Reactions of a chromium complex, featuring a Cr≡Si triple bond, with alkynes and butadiene were investigated. The former reaction yielded 4-membered metallasilacycles with a homoaromatic character through [2+2] cycloaddition, while the latter reaction afforded silacyclopentenyl complexes through [2+4] cycloaddition. [ABSTRACT FROM AUTHOR]

Group 13 oxyfluorides OMF2 were produced by the reactions of laser‐ablated group 13 atoms M (M=B, Al, Ga and In) with OF2 and isolated in excess neon or argon matrices at 5 K. These molecules were characterized by matrix‐isolation infrared spectroscopy and isotopic substitution experiments in conjunction with quantum‐chemical calculations. The calculations indicate that the OMF2 molecules have a 2B2 ground state with C2v symmetry. The computed molecular orbitals and spin densities show that the unpaired electron is mainly located at the terminal oxygen atom. Oxo monofluorides OMF were only observed in solid argon matrices and exhibit a linear structure in the singlet ground state. The M−O bonding in the OMF molecules can be rationalized as highly polar multiple bonds based on the calculated bond lengths and natural resonance theory (NRT) analyses. In particular, the molecular orbitals of OBF exhibit the character of a triple bond B−O resulting from two degenerate electron‐sharing π bonds and an O→B dative σ bond formed by the oxygen 2p lone pair which donates electron density to the boron empty 2p orbital. [ABSTRACT FROM AUTHOR]

A series of new alkynylamidinate complexes of selected first and second row transition metals has been synthesized and fully characterized. Treatment of MCl2 precursors (M=Mn, Fe, Co) with 2 equiv. of the lithium alkynylamidinates Li[c‐C3H5−C≡C−C(NR′)2] ⋅ THF (R′=iPr (2), Cy (cyclohexyl) (2)) afforded a series of binuclear complexes of the type M2[c‐C3H5−C≡C−C(NR)2‐κN:κN′]2[c‐C3H5−C≡C−C(NR)2‐κ2N,N′]2 (3: M=Mn, R=Cy; 4 a: M=Fe, R=iPr; 4 b: M=Fe, R=Cy; 5: M=Co, R=iPr) with no significant metal‐metal bonding. In marked contrast, a similar reaction of CrCl2 with 2 equiv. of 1 afforded the homoleptic dinuclear chromium(II) complex Cr2[c‐C3H5−C≡C−C(NiPr)2‐κN:κN′]4 (6) which supposedly comprises a Cr−Cr quadruple bond. Complex 6 could also be prepared in a more rational way and in better yield (61 %) by using dichromium(II) tetraacetate, Cr2(OAc)4, as starting material. Related reactions employing dimolybdenum(II) tetraacetate, Mo2(OAc)4, and 2 or 3 equiv. of 1 afforded the mixed‐ligand paddle wheel‐type complexes trans‐Mo2(OAc‐κO:κO′)2([c‐C3H5−C≡C−C(NiPr)2‐κN:κN′]2 (7) and Mo2(OAc‐κO:κO′)([c‐C3H5−C≡C−C(NiPr)2‐κN:κN′]3 (8). All title compounds were structurally characterized through single‐crystal X‐ray diffraction and spectroscopic techniques (NMR, IR, Raman). [ABSTRACT FROM AUTHOR]

Boron‐boron multiple bonds, such as those found in diborenes and diborynes, are typically stabilized by σ‐donor ligands that furnish electron density to these otherwise electron‐deficient species. These compounds are not only of fundamental importance in the study of chemical bonding, but can also activate small molecules in a chemistry reminiscent of that carried out by transition metals. In the pursuit of designing new and improved σ‐donor ligands to stabilize diborenes and diborynes suitable to activate small molecules, we performed density functional calculations to evaluate the Lewis basicity of a series of σ‐donor ligands. For this evaluation, we analysed the interaction between the boranes and the σ‐donor ligands in model systems L→BX3 (X=F and Me) using energy decomposition analyses. We found that electronic bond energies of the L→BX3 adducts correlate well with the ionization energies of the ligands and that ligands with high or medium basicity stabilize diborynes better than ligands with low basicity. We also learnt that beryllium‐based ligands are promising since they are able to stabilize L→B≡B←L diborynes without significantly reducing the triple bond character of the B≡B bond. [ABSTRACT FROM AUTHOR]

Borylation has become a powerful method to synthesize organoboranes as versatile building blocks in organic synthesis, medicinal chemistry, and materials science. Copper-promoted borylation reactions are extremely attractive due to the low cost and non-toxicity of the copper catalyst, mild reaction conditions, good functional group tolerance, and convenience in chiral induction. In this review, we mainly updated recent advances (from 2020 to 2022) in the synthetic transformations in C=C/C≡C multiple bonds, and C=E multiple bonds mediated by copper boryl systems. [ABSTRACT FROM AUTHOR]

The simplest diphosphene HPPH and isomeric diphosphinyldene PPH2 features prototype phosphorus‐phosphorus multiple bonding properties that have been of long‐standing interest in main‐group chemistry. Herein, we report the observation of cis‐HPPH, trans‐HPPH, and PPH2 among the respective laser photolysis products of phosphine (PH3) and diphosphine (P2H4) in solid N2‐ and Ar‐matrices at 10 K. The identification of these P2H2 isomers with matrix‐isolation IR and UV/Vis spectroscopy is supported by D‐isotope labeling and the quantum chemical calculations at the CCSD(T)‐F12a/cc‐pVTZ‐F12 level using configuration‐selective vibrational configuration interaction theory (VCI). Bonding analyses suggest that the two conformers of HPPH contain standard PP double bonds, whereas, PPH2 resembles P2 in having partial PP triple bond due to the H2P←P π bonding interaction. [ABSTRACT FROM AUTHOR]

The simplest diphosphene HPPH and isomeric diphosphinyldene PPH2 features prototype phosphorus‐phosphorus multiple bonding properties that have been of long‐standing interest in main‐group chemistry. Herein, we report the observation of cis‐HPPH, trans‐HPPH, and PPH2 among the respective laser photolysis products of phosphine (PH3) and diphosphine (P2H4) in solid N2‐ and Ar‐matrices at 10 K. The identification of these P2H2 isomers with matrix‐isolation IR and UV/Vis spectroscopy is supported by D‐isotope labeling and the quantum chemical calculations at the CCSD(T)‐F12a/cc‐pVTZ‐F12 level using configuration‐selective vibrational configuration interaction theory (VCI). Bonding analyses suggest that the two conformers of HPPH contain standard PP double bonds, whereas, PPH2 resembles P2 in having partial PP triple bond due to the H2P←P π bonding interaction. [ABSTRACT FROM AUTHOR]

We report a broad theoretical study on [(PMe3)3MER]+ complexes, with M = Ni, Pd, Pt, E = C, Si, Ge, Sn, Pb, and R = ArMes, Tbb, (ArMes = 2,6-dimesitylphenyl; Tbb = C6H2-2,6-[CH(SiMe3)2]2-4-tBu). A few years ago, our group succeeded in obtaining heavier homologues of cationic group 10 carbyne complexes via halide abstraction of the tetrylidene complexes [(PMe3)3M=E(X)R] (X = Cl, Br) using a halide scavenger. The electronic structure and the M-E bonds of the [(PMe3)3MER]+ complexes were analyzed utilizing quantum-chemical tools, such as the Pipek–Mezey orbital localization method, the energy decomposition analysis (EDA), and the extended-transition state method with natural orbitals of chemical valence (ETS-NOCV). The carbyne, silylidyne complexes, and the germylidyne complex [(PMe3)3NiGeArMes]+ are suggested to be tetrylidyne complexes featuring donor–acceptor metal tetrel triple bonds, which are composed of two strong π(M→E) and one weaker σ(E→M) interaction. In comparison, the complexes with M = Pd, Pt; E = Sn, Pb; and R = ArMes are best described as metallotetrylenes and exhibit considerable M−E−C bending, a strong σ(M→E) bond, weakened M−E π-components, and lone pair density at the tetrel atoms. Furthermore, bond cleavage energy (BCE) and bond dissociation energy (BDE) reveal preferred splitting into [M(PMe3)3]+ and [ER] fragments for most complex cations in the range of 293.3–618.3 kJ·mol−1 and 230.4–461.6 kJ·mol−1, respectively. Finally, an extensive study of the potential energy hypersurface varying the M−E−C angle indicates the presence of isomers with M−E−C bond angles of around 95°. Interestingly, these isomers are energetically favored for M = Pd, Pt; E = Sn, Pb; and R = ArMes over the less-bent structures by 13–29 kJ·mol−1. [ABSTRACT FROM AUTHOR]

The simplest diphosphene HPPH and isomeric diphosphinyldene PPH2 features prototype phosphorus‐phosphorus multiple bonding properties that have been of long‐standing interest in main‐group chemistry. Herein, we report the observation of cis‐HPPH, trans‐HPPH, and PPH2 among the respective laser photolysis products of phosphine (PH3) and diphosphine (P2H4) in solid N2‐ and Ar‐matrices at 10 K. The identification of these P2H2 isomers with matrix‐isolation IR and UV/Vis spectroscopy is supported by D‐isotope labeling and the quantum chemical calculations at the CCSD(T)‐F12a/cc‐pVTZ‐F12 level using configuration‐selective vibrational configuration interaction theory (VCI). Bonding analyses suggest that the two conformers of HPPH contain standard PP double bonds, whereas, PPH2 resembles P2 in having partial PP triple bond due to the H2P←P π bonding interaction. [ABSTRACT FROM AUTHOR]

The simplest diphosphene HPPH and isomeric diphosphinyldene PPH2 features prototype phosphorus‐phosphorus multiple bonding properties that have been of long‐standing interest in main‐group chemistry. Herein, we report the observation of cis‐HPPH, trans‐HPPH, and PPH2 among the respective laser photolysis products of phosphine (PH3) and diphosphine (P2H4) in solid N2‐ and Ar‐matrices at 10 K. The identification of these P2H2 isomers with matrix‐isolation IR and UV/Vis spectroscopy is supported by D‐isotope labeling and the quantum chemical calculations at the CCSD(T)‐F12a/cc‐pVTZ‐F12 level using configuration‐selective vibrational configuration interaction theory (VCI). Bonding analyses suggest that the two conformers of HPPH contain standard PP double bonds, whereas, PPH2 resembles P2 in having partial PP triple bond due to the H2P←P π bonding interaction. [ABSTRACT FROM AUTHOR]

We report the direct synthesis of the terminal pnictidenes [An(TrenTCHS)(PnH)][M(2,2,2‐cryptand)] (TrenTCHS={N(CH2CH2NSiCy3)3}3−; An/Pn/M=Th/P/Na 5, Th/As/K 6, U/P/Na 7, U/As/K 8) and their conversion to the pnictides [An(TrenTCHS)(PnH2)] (An/Pn=Th/P 9, Th/As 10, U/P 11, U/As 12). Use of the super‐bulky TrenTCHS ligand was essential to accessing complete families, and 6 is an unprecedented example of a terminal thorium‐arsinidene complex and only the second structurally authenticated parent terminal arsinidene complex of any metal. Comparison of the terminal Th=AsH unit of 6 to the bridging ThAs(H)K linkage in structurally analogous [Th(TrenTIPS){μ‐As(H)K(15‐crown‐5)}] (TrenTIPS={N(CH2CH2NSiPri3)3}3−) reveals a stronger Th−As bond in the former compared to the latter, and a large response overall to the nature of the Th=AsH bonding upon removal of the electrostatically‐bound K‐ion; the σ‐bond changes little but the π‐bond is significantly perturbed. [ABSTRACT FROM AUTHOR]

Phosphaborenes are P/B analogs of alkynes. Herein, we describe the isolation of a phosphaborene stabilized by an intramolecular Lewis base. This species is achieved via the installation of the phosphaborene with a sterically encumbering phosphino substituent. Although this species features an aromatic P2B three‐membered ring, the ring strain allows the hemi‐labile behavior of the P−B donor‐acceptor bond, thereby exhibiting frustrated Lewis pair reactivity. Our finding paves the way for further exploration of the reactivity patterns of monomeric phosphaborenes. [ABSTRACT FROM AUTHOR]

The stabilization of elusive monomeric species containing multiple boron‐chalcogen bonds has motivated the investigation of sophisticated ligand systems in the past few years. Recently, a series of neutral, Lewis acid‐free chalcogenboranes were prepared by incorporation of an amido imidazoline‐2‐imine as the supporting ligand (Frank et al., Angew. Chem. Int. Ed. 2021, 60, 4633), resulting in well‐defined molecular entities with pronounced multiple bond character, B=X (X=O, S, Se, Te). In view of the potential use of N‐heterocyclic boranes (NHB=X) as ligands in catalysis and fine chemistry, we evaluated in this work the bonding properties of the new B=X compounds based on a π‐backdonation model. The electronic properties of systems in question were modulated via systematic modifications of the NHB ring with respect to ligand variation, saturation, size, and heteroatom substitutions. Investigations into the B=X bond length and order, calculated by means of density functional theory methods, reveal enhanced B=X bonding properties for NHB rings with high electron delocalization in the NHB ring and bearing electron‐withdrawing substituents; a fact that was also confirmed by computational assessment of electron interactions of the B=X species with a dicarbonyl manganese complex. We expect that the analysis will contribute to the rational optimization of existing ligands as well as the development of new moieties, which would further allow for exploration of new boron chemistry. [ABSTRACT FROM AUTHOR]

We describe a facile synthesis of the cyapho‐cyanamide salt [Na(18‐crown‐6)][N(CN)(CP)] from reaction of [Na(18‐crown‐6)][PH2] (18‐crown‐6=1,4,7,10,13,16‐hexaoxacyclooctadecane) with dimethyl N‐cyanocarbonimidate, (MeO)2C=N(CN). The reaction proceeds with elimination of two equivalents of methanol. Careful tuning of the reaction conditions allowed for the isolation and characterization of the N‐cyano(carboximidate)phosphide intermediate [HP{C(OMe)N(CN)}]−. Due to the adverse effects of methanol in these reaction mixtures, a bulk scale synthesis of [Na(18‐crown‐6)][N(CN)(CP)] could be achieved by addition of a base (LiHMDS) to neutralize the resulting alcohol. Further reactivity studies of this anion reveal that functionalization at the phosphorus atom is viable to yield a new family of cyanide‐functionalised phosphorus heterocycles. [ABSTRACT FROM AUTHOR]

Dialumenes are neutral AlI compounds with Al=Al multiple bonds. We report the isolation of an amidophosphine‐supported dialumene. Our X‐ray crystallographic, spectroscopic, and computational DFT analyses reveal a long and extreme trans‐bent Al=Al bond with a low dissociation energy and bond order. In solution, the dialumene can dissociate into monomeric AlI species. Reactivity studies reveal two modes of reaction: as dialumene or as aluminyl monomers. [ABSTRACT FROM AUTHOR]

We thank the Fonds der Chemischen Industrie (Liebig fellowship for D.M.), the German‐American Fulbright Commission (Fulbright‐Cottrell Award for D.M.) as well as the Bavarian Equal Opportunities Sponsorship – Realization of Equal Opportunities for Women in Research and Teaching (fellowship for A.G.) for financial support. We thank the RRZ Erlangen for computational resources. [ABSTRACT FROM AUTHOR]

The reactivity of the phosphanyl‐phosphagallene, [H2C{N(Dipp)}]2PP=Ga(Nacnac) (Nacnac=HC[C(Me)N(Dipp)]2; Dipp=2,6‐iPr2C6H3) towards a series of reagents possessing E−H bonds (primary amines, ammonia, water, phenylacetylene, phenylphosphine, and phenylsilane) is reported. Two contrasting reaction pathways are observed, determined by the polarity of the E−H bonds of the substrates. In the case of protic reagents (δ−E−Hδ+), a frustrated Lewis pair type of mechanism is operational at room temperature, in which the gallium metal centre acts as a Lewis acid and the pendant phosphanyl moiety deprotonates the substrates. Interestingly, at elevated temperatures both NH2iPr and ammonia can react via a second, higher energy, pathway resulting in the hydroamination of the Ga=P bond. By contrast, with hydridic reagents (δ+E−Hδ−), such as phenylsilane, hydroelementation of the Ga=P bond is exclusively observed, in line with the polarisation of the Si−H and Ga=P bonds. [ABSTRACT FROM AUTHOR]

Multiply bonded lanthanide oxo groups are rare in coordination compounds and have not previously been reported for a surface termination of a lanthanide oxide. Here we report the observation of a Ce=O terminated ceria surface in a CeO2(111)‐(3 ×3)R30° reconstruction of ≈3 nm thick ceria islands prepared on Pt(111). This is evidenced by scanning tunnelling microscopy (STM), low energy electron diffraction (LEED) and high‐resolution electron energy loss spectroscopy (HREELS) measurements in conjunction with density functional theory (DFT) calculations. A Ce=O stretching frequency of 775 cm−1 is observed in HREELS, compared with 766 cm−1 calculated by DFT. The calculations also predict that the Ce=O bond is weak, with an oxygen vacancy formation energy of 0.85 eV. This could play an important role in the facile removal of lattice oxygen from CeO2, accompanied by the reduction of CeIV to CeIII, which is a key attribute of ceria‐based systems in connection with their unique catalytic properties. [ABSTRACT FROM AUTHOR]

Multiply bonded lanthanide oxo groups are rare in coordination compounds and have not previously been reported for a surface termination of a lanthanide oxide. Here we report the observation of a Ce=O terminated ceria surface in a CeO2(111)‐(3 ×3)R30° reconstruction of ≈3 nm thick ceria islands prepared on Pt(111). This is evidenced by scanning tunnelling microscopy (STM), low energy electron diffraction (LEED) and high‐resolution electron energy loss spectroscopy (HREELS) measurements in conjunction with density functional theory (DFT) calculations. A Ce=O stretching frequency of 775 cm−1 is observed in HREELS, compared with 766 cm−1 calculated by DFT. The calculations also predict that the Ce=O bond is weak, with an oxygen vacancy formation energy of 0.85 eV. This could play an important role in the facile removal of lattice oxygen from CeO2, accompanied by the reduction of CeIV to CeIII, which is a key attribute of ceria‐based systems in connection with their unique catalytic properties. [ABSTRACT FROM AUTHOR]

Multiply bonded lanthanide oxo groups are rare in coordination compounds and have not previously been reported for a surface termination of a lanthanide oxide. Here we report the observation of a Ce=O terminated ceria surface in a CeO2(111)‐(3 ×3)R30° reconstruction of ≈3 nm thick ceria islands prepared on Pt(111). This is evidenced by scanning tunnelling microscopy (STM), low energy electron diffraction (LEED) and high‐resolution electron energy loss spectroscopy (HREELS) measurements in conjunction with density functional theory (DFT) calculations. A Ce=O stretching frequency of 775 cm−1 is observed in HREELS, compared with 766 cm−1 calculated by DFT. The calculations also predict that the Ce=O bond is weak, with an oxygen vacancy formation energy of 0.85 eV. This could play an important role in the facile removal of lattice oxygen from CeO2, accompanied by the reduction of CeIV to CeIII, which is a key attribute of ceria‐based systems in connection with their unique catalytic properties. [ABSTRACT FROM AUTHOR]

Multiply bonded lanthanide oxo groups are rare in coordination compounds and have not previously been reported for a surface termination of a lanthanide oxide. Here we report the observation of a Ce=O terminated ceria surface in a CeO2(111)‐(3 ×3)R30° reconstruction of ≈3 nm thick ceria islands prepared on Pt(111). This is evidenced by scanning tunnelling microscopy (STM), low energy electron diffraction (LEED) and high‐resolution electron energy loss spectroscopy (HREELS) measurements in conjunction with density functional theory (DFT) calculations. A Ce=O stretching frequency of 775 cm−1 is observed in HREELS, compared with 766 cm−1 calculated by DFT. The calculations also predict that the Ce=O bond is weak, with an oxygen vacancy formation energy of 0.85 eV. This could play an important role in the facile removal of lattice oxygen from CeO2, accompanied by the reduction of CeIV to CeIII, which is a key attribute of ceria‐based systems in connection with their unique catalytic properties. [ABSTRACT FROM AUTHOR]

We report the synthesis and characterization of the first terminal imido complex of an Fe–S cluster, (IMes)3Fe4S4=NDipp (2; IMes=1,3‐dimesitylimidazol‐2‐ylidene, Dipp=2,6‐diisopropylphenyl), which is generated by oxidative group transfer from DippN3 to the all‐ferrous cluster (IMes)3Fe4S4(PPh3). This two‐electron process is achieved by formal one‐electron oxidation of the imido‐bound Fe site and one‐electron oxidation of two IMes‐bound Fe sites. Structural, spectroscopic, and computational studies establish that the Fe–imido site is best described as a high‐spin Fe3+ center, which is manifested in its long Fe−N(imido) distance of 1.763(2) Å. Cluster 2 abstracts hydrogen atoms from 1,4‐cyclohexadiene to yield the corresponding anilido complex, demonstrating competency for C−H activation. [ABSTRACT FROM AUTHOR]

The first example of a triply bridging (μ3‐P) phosphine ligand has been discovered in the crown‐shaped [Cu3(μ2‐Hal)3L] (Hal=Cl, Br, or I) complexes supported by tris[2‐(2‐pyridyl)ethyl]phosphine (L). Theoretical analysis completely confirms the observed μ3‐P‐bridging pattern, revealing the interaction of the same lone pair of phosphorus with three valence 4s‐orbitals of Cu atoms. The presented complexes exhibit outstanding blue phosphorescence (λem=442–465 nm) with the quantum efficiency reaching 100 %. The complex [Cu3(μ2‐I)3L] also exhibits remarkable thermo‐ and mechanochromic luminescence resulting in a sharp change in the emission colour upon external stimuli. These findings essentially contribute to coordination chemistry of the pnictine ligands. [ABSTRACT FROM AUTHOR]

The chemistry of transition metal carbynes, LnM≡CR, has historically been dominated by species bearing hydrocarbyl or amino 'R' substituents, with other elements appearing only sporadically. In recent years, carbynes and related 'C1' species bearing other main‐group substituents, particularly heavier elements of the p‐block, have begun to emerge. This review details the chemistry of heavier pnictogen‐functionalised C1 ligands, MCARn (A=P, As, Sb, Bi; n=0–3), including their syntheses, properties and reactivities, and how these are distinguished from more traditional carbyne complexes. Recent developments in the closely related phospha‐isonitrile LnM(CPR), cya‐phosphide and cya‐arside ligands, LnM(C≡A) (A=P, As), are also discussed. [ABSTRACT FROM AUTHOR]

Since the discovery that the so‐called "double‐bond" rule could be broken, the field of molecular main group multiple bonds has expanded rapidly. With the majority of homodiatomic double and triple bonds realised within the p‐block, along with many heterodiatomic combinations, this Minireview examines the reactivity of these compounds with a particular emphasis on small molecule activation. Furthermore, whilst their ability to act as transition metal mimics has been explored, their catalytic behaviour is somewhat limited. This Minireview aims to highlight the potential of these complexes towards catalytic application and their role as synthons in further functionalisations making them a versatile tool for the modern synthetic chemist. [ABSTRACT FROM AUTHOR]

An N‐heterocyclic‐carbene‐stabilized diboryne undergoes rapid, high‐yielding and catalyst‐free hydroamination reactions with primary amines, yielding 1‐amino‐2‐hydrodiborenes, which can be considered boron analogues of enamines. The electronics of the organic substituent at nitrogen influence the structure and further reactivity of the diborene product. With electron‐rich anilines, a second hydroamination can occur at the diborene to generate 1,1‐diamino‐2,2‐dihydrodiboranes. With isopropylamine, the electronic influence of the alkyl substituent upon the diborene leads to an unprecedented boron‐mediated intramolecular N‐dearylation reaction of an N‐heterocyclic carbene unit. [ABSTRACT FROM AUTHOR]

Oxidative coupling methodology is widely applied for the formation of carbon‐carbon and carbon‐heteroatom bonds. This review focuses on methods for oxidative sulfonylation of multiple bonds involving sulfonyl hydrazides, sulfinic acids and their salts as sulfonylation reagents. Under oxidative conditions, they generate sulfonyl radicals, trapped by multiple carbon‐carbon bonds resulting in a variety of SO2‐containing products: mainly, vinyl and alkynyl sulfones, hydroxy‐, keto, and halo‐substituted sulfones, sulfonylated derivatives of carbo‐ and heterocycles. This exhaustive review summarizes 321 references from 1996 to 2020 with the specialization of the studies of the last five years, and is divided into the chapters according to the classes of compounds being sulfonylated. [ABSTRACT FROM AUTHOR]

This Minireview examines the synthesis and characterization of late metal (i.e., groups 8–12) terminal sulfides, along with a discussion of their electronic structures. We discuss both examples where a terminal sulfide was isolated, as well as those examples where a terminal sulfide was invoked as an unobserved intermediate. Additionally, where appropriate, we contextualize our discussion by comparisons to either early metal sulfide chemistry or metal sulfide cluster chemistry. Finally, we describe several possible avenues for future investigation. Late metal terminal sulfides are exceptionally rare – only a handful examples have been isolated – and those examples are either stabilized by hydrogen‐bonding or dative interactions to alkali metals. It is our hope that this Minireview will spur further developments in this exciting, but underexplored field. [ABSTRACT FROM AUTHOR]

In contrast to the ubiquity of transition‐metal carbonyl, and (to a lesser extent) thiocarbonyl complexes, transition‐metal complexes of carbon monoselenide LnMCSe and monotelluride LnMCTe remain scarce. The last few years, however, have seen notable steps towards expanding this chemistry, specifically with regards to new systematic studies on homologous sets of chalcocarbonyl complexes LnMCE (E=O, S, Se, Te), the first reports of new bi‐ and polynuclear CSe and CTe bridging complexes and a confluence with metal carbido chemistry. Herein the properties, syntheses and reactions of these rare but fundamentally intriguing compounds are discussed. [ABSTRACT FROM AUTHOR]

Visible‐light‐photocatalyzed methods employed in synthetic transformations present attractive properties such as environmentally friendly, safety, availability and excellent functional group tolerance. In this regard, research on the visible‐light photocatalytic incorporation of the trifluoromethyl CF3 moiety into organic substrates, in particular, has contributed to a clear evolution of the field of photocatalysis. Although this particular area is constantly evolving and has been reviewed, the last five years have experienced an outburst of seminal and significant photocatalytic trifluoromethylation examples that are leading the way and opening new synthetic avenues. Recent review articles on Ru‐ and Ir‐based photocatalytic trifluoromethylation reactions have borne witness of this evolution. Although this account will show the new Ru‐ and Ir‐based photocatalytic trifluoromethylations, Sections 2 and 3 will also illustrate other photocatalytic systems, such as organic dyes, organic semiconductors and newly‐developed all‐organic photocatalysts. All the known and reviewed strategies for photocatalytic trifluoromethylation reactions of olefins and (hetero)aromatic compounds will not be discussed but will be summarized in two figures (Figures 4 and 5), and new examples (2015–present) will be presented and discussed. [ABSTRACT FROM AUTHOR]

We present herein an in‐depth study of complexes in which a molecule containing a boron‐boron triple bond is bound to tellurate cations. The analysis allows the description of these salts as true π complexes between the B−B triple bond and the tellurium center. These complexes thus extend the well‐known Dewar‐Chatt‐Duncanson model of bonding to compounds made up solely of p block elements. Structural, spectroscopic and computational evidence is offered to argue that a set of recently reported heterocycles consisting of phenyltellurium cations complexed to diborynes bear all the hallmarks of π‐complexes in the π‐complex/metallacycle continuum envisioned by Joseph Chatt. Described as such, these compounds are unique in representing the extreme of a metal‐free continuum with conventional unsaturated three‐membered rings (cyclopropenes, azirenes, borirenes) occupying the opposite end. [ABSTRACT FROM AUTHOR]

Addition of MesN3 (Mes=2,4,6‐Me3C6H2) to germylene [(NONtBu)Ge] (NONtBu=O(SiMe2NtBu)2) (1) gives germanimine, [(NONtBu)Ge=NMes] (2). Compound 2 behaves as a metalloid, showing reactivity reminiscent of both transition metal‐imido complexes, undergoing [2+2] addition with heterocumulenes and protic sources, as well as an activated diene, undergoing a [4+2] cycloaddition, or "metallo"‐Diels–Alder, reaction. In the latter case, the diene includes the Ge=N bond and π‐system of the Mes substituent, which is reactive towards dienophiles including benzaldehyde, benzophenone, styrene, and phenylacetylene. [ABSTRACT FROM AUTHOR]

Reaction of NacNacAl (NacNac=[DippNC(Me)CHC(Me)NDipp]−) with one equivalent of benzophenone affords a ketylate species NacNacAl(η2(C,O)‐OCPh2) that undergoes easy cyclization reactions with unsaturated substrates. The scope of substrates included benzophenone, aldimine (PhNC(Ph)H), quinoline, phenyl nitrile, trimethylsilyl azide, and a saturated cyclic thiourea. The latter substrate reacted by an unusual C−N cleavage that left the C=S functionality intact. The new products were characterized by NMR spectroscopy and X‐ray diffraction analysis. [ABSTRACT FROM AUTHOR]

The deoxygenative conversion of carbon dioxide to carbon monoxide is promoted by the aluminyl anion [Al(NONAr)]− (NONAr=[O(SiMe2NAr)2]2−, Ar=2,6‐iPr2C6H3). The reaction proceeds via the isolable monoalumoxane anion [Al(NONAr)(O)]−, containing a terminal aluminum‐oxygen bond. This species reacts with a second equivalent of carbon dioxide to afford the carbonate [Al(NONAr)(CO3)]−, and with nitrous oxide to generate the hyponitrite anion, [Al(NONAr)(κ2O,O′‐N2O2)]−. [ABSTRACT FROM AUTHOR]

Boryl radicals have recently contributed to the development of organoboron chemistry, but synthetic application of boryl radicals is still limited compared with other radical species. The recent development of new reagents and catalytic systems has expanded the practicality of boryl radicals in synthetic chemistry, and it has enabled addition reactions of boryl radicals to multiple bonds such as alkenes, alkynes, carbonyl groups and their derivatives. Boryl radical additions to multiple bonds can create not only novel organoboron compounds but also unusual chemical transformations. This review summarizes recently developed addition reactions of boryl radicals, which are roughly categorized by the strategy for formation of boryl radicals: (1) B–H bond cleavage and (2) B–B bond cleavage. Also, the reaction mechanism is outlined in order to understand the design and concept of each reaction. [ABSTRACT FROM AUTHOR]

We report the anion [Al(NONAr)(Se)]− (NONAr=[O(SiMe2NAr)2]2−, Ar=2,6‐iPr2C6H3), which is an isoelectronic Group 13 metal analogue of the carbonyl group containing an aluminium–selenium multiple bond. It was synthesized in a single step from the reaction of the aluminyl anion [Al(NONAr)]− with elemental selenium. Spectroscopic, crystallographic, and computational analysis confirmed multiple bonding between aluminium and selenium. Addition of a second equivalent of selenium afforded the diselenirane, [Al(NONAr)(κ2‐Se2)]−, which is an isoelectronic analogue of the dioxirane group. [ABSTRACT FROM AUTHOR]

Borasilenes, that is complexes which contain a boron–silicon double bond, have scarcely been isolated to date. In pursuit of such species, (Me3Si)3SiB(Cl)NHI (2, NHI=bulky N‐heterocyclic imine) was prepared and treated with KOtBu to achieve formal extrusion of ClSiMe3. The formation of an elusive borasilene (3int) is postulated and it was verified by isolation of the N‐heterocyclic carbene adduct (Me3Si)2SiB(IMe4)NHI (4, IMe4 =1,3,4,5‐tetramethyl‐imidazolin‐2‐ylidene). X‐ray crystallographic study and theoretical calculations on 4 diagnosed a boron–silicon double bond with marked zwitterionic character. The negative charge resides at the Si atom which marks the apex of a trigonal pyramid. Structural comparison of 4 with boron cation congeners (5+, 6+) suggests that the positive charge is mainly located at the trigonal planar‐coordinated B center. The conversion of 4 with pinacolborane (HBpin, 2 equiv) resulted in cleavage of the double bond to produce (Me3Si)2Si(Bpin)2 and (NHI)BH2(IMe4). [ABSTRACT FROM AUTHOR]