An unprecedented neutral "masked" non-external-donor-stabilized diborene is generated via intramolecular arene dearomatization of an N-heterocyclic imine (NHI)-supported free diborene. The free diborene intermediate is photochemically accessible from the masked form, as supported experimentally through chalcogenation reactions. Computational studies elucidate an alkyne-like bonding pattern and a triplet ground state with a ΔES-T = +1.2 kcal mol-1 for the NHI-supported free diborene. Remarkably, the "masked" diborene activates pyridines, promoting transition-metal-free C-C bond formation with high C2 regioselectivity to afford homocoupling products under mild conditions. Mechanistic investigations reveal that stepwise coordination and B-C bond cleavage produce a bis-pyridine diborene intermediate, which undergoes reductive coupling via intrinsically strong double single-π-electron transfer from the B═B unit to the intramolecular pyridine ligands. Furthermore, oxidation with p-benzoquinone allows the release of free 2,2'-bipyridine derivatives. These findings provide access to insight into a hitherto elusive free diborene species, establish a previously unknown reactivity mode for diborenes, and demonstrate that this "masked" diborene functions as an exceptionally powerful double single-electron donor with the potential to mimic transition-metal behavior in the construction of organic molecules.

The utilization of two electronically distinct elements for the cooperative activation of white phosphorus (P4) is a promising route to novel and reactive polyphosphido complexes. Herein, the preparation of cyclooctadiene Co–Zn complexes and their application in the activation of white phosphorus (P4) to synthesize new phosphorus‐rich sandwich complexes are reported. The complexes [Zn{Co(tBu2C2P2)(COD)}2] (1, COD = cycloocta‐1,5‐diene), [(acac)Zn{Co(tBu2C2P2)(COD)}] (2, acac = acetylacetonate), [(Dippnacnac)Zn{Co(tBu2C2P2)(COD)}] (3, Dippnacnac = CH({2,6‐iPr2‐C6H3}NCMe)2), and [(Ar)Zn{Co(tBu2C2P2)(COD)}] (4, Ar = C6H3‐2,6{C6H3‐2,6‐iPr2}2) are prepared by transmetalation of [(Depnacnac)Mg{Co(tBu2C2P2)(COD)}] (F, Depnacnac= CH({2,6‐Et2‐C6H3}NCMe)2) with zinc(II) salts. Complex 1 reacts with cyclohexyl isonitrile (CyNC) to afford isonitrile complexes [ZnCo2(tBu2C2P2)2(COD)(CyNC)2] (5) and [Zn{Co(tBu2C2P2)(CyNC)2}2] (6). Single‐crystal X‐ray diffraction data and quantum chemical studies employing Atoms In Molecules and Natural Bond Orbital methods reveal weak covalent Co–Zn interactions in complexes 1—6. Compound 1 reacts with P4 to produce [Zn2Co4(μ‐P2)2(tBu2C2P2)4(COD)2] (7) and subsequently [Zn2Co4(μ‐P2)4(tBu2C2P2)4] (8), featuring bridging diphosphorus ligands. A stepwise mechanism for the formation of 8 is elucidated through 31P nuclear magnetic resonance spectroscopic monitoring studies. Chemical oxidation of 8 generates the triple‐decker sandwich complex [{Co(tBu2C2P2)}2(μ‐P4)] (9) with a cyclo‐P4 middle deck.

The di-N-heterocyclic carbene (NHCs) stabilized stannyliumylidene, [MesTerSn(IMe4)2][BArF], (MesTer = 2,6-Mes2C6H3, Mes = 2,4,6-Me3-C6H2, IMe4 = 1,3,4,5-tetramethylimidazol-2-ylidene, BArF = (3,5-(CF3)2-C6H5)4B), was isolated from the reaction of (MesTer)SnCl with two equivalents of IMe4, followed by one equivalent of Na[BArF]. This stannyliumylidene acts as a precatalyst for the homogeneous hydrosilylation of CO2. Experimental mechanistic studies and quantum chemical calculations have been conducted to elucidate the catalytically active species and the mechanism for the transformation, revealing the stannyliumylidene [MesTerSn(CO2IMe4)2][BArF], which is formed in the presence of CO2, as the catalytically active species.

Multiple bonds between heavy elements have been shown to be not only stable but also offer divergent reactivity. Accordingly, there has been a drive in research to isolate such species. Here we report on the synthesis of a compound containing an aluminium–carbon double bond (alumene). The alumene was formed by exposing a dialane to a CO atmosphere. Experimental data and quantum chemical calculations confirm the existence of a π-bond between the aluminium and carbon centre. The mechanism for the formation of the alumene was calculated and indicated a heterocyclic intermediate, which we were able to observe spectroscopically. Treating the alumene with excess CO leads to CO homologation, forming a C3O2 chain initiated by interaction of a CO molecule with the π-bond of Al=C. Multiple bonds involving heavier elements were considered impossible but have recently been shown to be stable and offer divergent reactivity. Here the isolation of an alumene (a compound containing an Al=C bond) via direct CO reduction is described. Analysis of the alumene and its ability to homologate CO is reported.

We report on the utilization of the ethylene-bridged bis[(dialkylamino)cyclopropenimine] (bisCPI) ligand, LCPI, to give access to new main-group E(II) halide complexes (E = Ge, Sn, Pb; 1, 2, 3). Subsequent reduction with Collman's reagent (Na2Fe(CO)4 • dioxane) enables the isolation of a series of zero-valent tetrylone-tetracarbonyl iron complexes, (LCPI)E(Fe(CO)4 (E = Ge (4), Sn (5), Pb (6)). Compounds 4 - 6 were reacted further with iron pentacarbonyl to yield the bis-tetracarbonyl iron complexes (LCPI)E[(Fe(CO)4]2 (E = Ge (7), Sn (8), Pb (9)). The electronic structure of these complexes was studied by 57Fe Mössbauer spectroscopy and computationally by density functional theory calculations.

The terphenyl amido stannylene-NHC adducts, HMDS(MesTer)Sn(NHC), (MesTer = 2,6-Mes2C6H3, Mes = 2,4,6-Me3-C6H2, HMDS = N(SiMe3)2, NHC = IMe4, IEt, IMe4 = 1,3,4,5-tetramethylimidazol-2-ylidene, Iet = 1,3-diethyl-4,5-dimethylimidazol-2-ylidene), were reacted with benzaldehyde resulting in the formation of HMDS(MesTer)Sn(OCH(Ph)NHC). In the presence of acetophenone, deprotonation occurs to afford the tin enolate (MesTer)Sn(NHC)(OPhC=CH2), via the release of hexamethyldisilamine. This stannylene-NHC adduct is a catalyst for the homogeneous hydrosilylation of aldehydes and ketones under ambient conditions.

We show that countercations exert a remarkable influence on the ability of anionic cobaltate salts to catalyze challenging alkene hydrogenations. An evaluation of the catalytic properties of [Cat][Co(η4 -cod)2 ] (Cat=K (1), Na (2), Li (3), (Dep nacnac)Mg (4), and N(n Bu)4 (5); cod=1,5-cyclooctadiene, Dep nacnac={2,6-Et2 C6 H3 NC(CH3 )}2 CH)]) demonstrated that the lithium salt 3 and magnesium salt 4 drastically outperform the other catalysts. Complex 4 was the most active catalyst, which readily promotes the hydrogenation of highly congested alkenes under mild conditions. A plausible catalytic mechanism is proposed based on density functional theory (DFT) investigations. Furthermore, combined molecular dynamics (MD) simulation and DFT studies were used to examine the turnover-limiting migratory insertion step. The results of these studies suggest an active co-catalytic role of the counterion in the hydrogenation reaction through the coordination to cobalt hydride intermediates.

Isocyanides, being isoelectronic and isolobal to carbon monoxide, are an important class of compounds in organic synthesis and coordination chemistry. In terms of reactivity, the severing of R-NC bonds has gained particular interest recently, as the cleaved moieties can be used as a CN/R source in cross -coupling reactions. Herein, we disclose Ar-NC bond cleavage and subsequent transformation of aryl isocyanides to silylcyanide and diaryldiiminodisilenes, utilizing the ambiphilic acyclic imino(silyl)silylene 1. A proposed reaction mechanism for the aryl and silyl group exchange, based on experimental evidence and supported by quantum chemical calculations, proposes an initial insertion of aryl isocyanide into the Si-Si bond of 1 and a subsequent aryl transfer to the silylene center via aryl C-N bond cleavage.

The formation of phosphorus-rich alanes featuring butterfly-like geometries is achieved. The two-electron reduction products feature a unique P4 2- structure and can act as a source of P3-. The treatment of these phosphorus containing products with electrophiles under mild conditions results in the formation of different phosphines. This approach eliminates the need for high temperatures and/or high pressures, which are commonly required in industrial processes for the preparation of useful phosphines.The activation and further functionalization of white phosphorus (P4) by main group complexes has become an increasingly studied topic in recent times. Herein, we report the controlled formation of phosphorus-rich alanes featuring butterfly-like geometries from the selective reaction of P4 with dialumenes, ([L(IiPr)Al]2) (1: L=Tripp=2,4,6-iPr3C6H2; 2: L=tBu2MeSi; IiPr=[MeCN(iPr)]2C)). The two-electron-reduction product of P4 features a P4 2- structure and is shown to be able to act as a source of P3-. Treatments of different electrophiles (e.g., chlorotrimethylsilane (Me3SiCl), iodotrimethylsilane (Me3SiI), HCl, or acetyl chloride (CH3COCl)) with these alanes under mild conditions gave the corresponding phosphines (e.g., P(SiMe3)3, PH3, or P(COCH3)3).

A heteroleptic amino(imino)stannylene (TMS2 N)(It BuN)Sn: (TMS=trimethylsilyl, It Bu=C[(N-t Bu)CH]2 ) as well as two homoleptic NHI-stabilized tetrylenes, (It BuN)2 E: (NHI=N-heterocyclic imine, E=Ge, Sn) are presented. VT-NMR investigations of (It BuN)2 Sn: (2) reveal an equilibrium between the monomeric stannylene at room temperature and the dimeric form at -80 °C as well as in the solid state. Upon reaction of the homoleptic tetrylenes with CO2 , both compounds insert two equivalents of CO2 , however differing bonding modes can be observed. (It BuN)2 Sn: (2) inserts one equivalent of CO2 into each Sn-N bond, giving carbamato groups coordinated κ2 O,O' to the metal center. With (It BuN)2 Ge: (3), the Ge-N bonds stay intact upon activation, being bridged by one molecule of CO2 respectively, forming 4-membered rings. Furthermore, the reactivity of 2 towards N2 O was investigated, resulting in partial oxidation to form stannylene dimer [((It BuN)3 SnO)(It BuN)Sn:]2 (6).

A running thread in contemporary chemical research is that of sustainability. Using highly abundant material as feedstocks for useful products is highly desirable in the modern world and will be a necessity looking towards the future. One major chemical in abundance is that of carbon dioxide, a waste material from energy production and a main contributor to climate change. A shared goal in academia and industry is transforming carbon dioxide into valuable carbon containing compounds. One such avenue is doing this chemically with abundant and reactive compounds, with prime candidates being silicon and aluminium. There has been a meteoric rise in main group chemistry of late, especially with silicon and aluminium containing compounds, exhibiting reactivity at once thought not possible. One such reaction is the direct activation of carbon dioxide, without the aid of any metal catalyst or additive. In this last half century, a wealth of remarkable silicon/aluminium compounds have been isolated in unprecedented oxidation states and bonding modes. This has translated into unique interactions with carbon dioxide resulting in fundamentally interesting compounds and isolable intermediates in industrially relevant processes, with new prospects into CO2 functionalisation.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

The reaction of Cp*Sn[OTf] (Cp*=C5Me5; OTf=O3SCF3) with one equivalent of IPrNLi (IPrN=bis(2,6-diisopropylphenyl)imidazolin-2-iminato) resulted in the binuclear [OTf]-bridged tin complex 1. Similarly, the [BF4]-bridged bimetallic complex 2 was synthesized by the reaction of Cp*Sn[BF4] with IPrNLi (1 eq.). It was also possible to prepare 1 from 2 via an anion exchange reaction. The high-yield conversion of 2 into the binuclear iodostannylene [IPrNSnI](2) 3 was accomplished by treatment with LiI. The catalytic potential of 1 and 2 was demonstrated in the hydroboration of carbonyls.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Phosphorus analogues of the ubiquitous cyclopentadienyl (Cp) are a rich and diverse family of compounds, which have found widespread use as ligands in organometallic complexes. By contrast, phospholes incorporating heaviear group 14 elements (Si, Ge, Sn, and Pb) are hardly known. Here, we demonstrate the isolation of the first metal complexes featuring heavy cyclopen-tadienyl anions (SnP4)2─ and (PbP4)2─. The complexes [(η4-tBu2C2P2)2Co2(μ,η5:η5-P4Tt)] [Tt = Sn (6), Pb (7)] are formed by reaction of white phosphorus (P4) with cyclooctadiene cobalt complexes [Ar′TtCo(η4-P2C2tBu2)(η4-COD)] [Sn (2), Pb (3), Ar′ = C6H3-2,6{C6H3¬-2,6-iPr2}2, COD = cycloocta-1,5-diene] and Tt{Co(η4-P2C2tBu2)(COD)}2 [Tt = Sn (4), Pb (5)]. While the (SnP4)2− complex 6 was isolated as a pure and stable compound, compound 7 eliminates Pb(0) below room temper-ature to afford [(η4-tBu2C2P2)2Co2(μ,η4:η4-P4) (8), which is a rare example of a tripledecker complex with a (P4)2─ middle deck. The electronic structures of 6-8 are analysed using theoretical methods, including an analysis of intrinsic bond orbitals and magnetic response theory. Thereby the aromatic nature of (P5)− and (SnP4)2− was confirmed, while for (P4)2− a specific type of symmetry-induced weak paramagnetism was found which is distinct from conventional antiaromatic species.

The germanium iron carbonyl complex 3 was prepared by the reaction of dimeric chloro(imino)germylene [IPrNGeCl]2 (IPrN=bis(2,6-diisopropylphenyl)imidazolin-2-iminato) with one equivalent of Collman's reagent (Na2 Fe(CO)4 ) at room temperature. Similarly, the reaction of chloro(imino)stannylene [IPrNSnCl]2 with Na2 Fe(CO)4 (1 equiv) resulted in the Fe(CO)4 -bridged bis(stannylene) complex 4. We observed reversible formation of bis(tetrylene) and tetrylene-tetrylone character in complexes 3 vs. 5 and 4 vs. 6, which was supported by DFT calculations. Moreover, the Li/Sn/Fe trimetallic complex 12 has been isolated from the reaction of [IPrNSnCl]2 with cyclopentadienyl iron dicarbonyl anion. The computational analysis further rationalizes the reduction pathway from these chlorotetrylenes to the corresponding complexes.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.