A lithium-aluminium heterobimetallic dimetallocene.

Homobimetallic dimetallocenes exhibiting two identical metal atoms sandwiched between two η bonded cyclopentadienyl rings is a narrow class of compounds, with representative examples being dizincocene and diberyllocene. Here we report the synthesis and structural characterization of a heterobimetallic dimetallocene, accessible through heterocoupling of lithium and aluminylene fragments with pentaisopropylcyclopentadienyl ligands. The Al-Li bond features a high ionic character and profits from attractive dispersion interactions between the isopropyl groups of the cyclopentadienyl ligands.

Gauging ambiphilicity of pseudo-halides beryllium-trispyrazolylborato compounds.

The ambiphilicity of pseudo-halides has been the object of extensive debate. Herein, we use a series of trispyrazolylborato beryllium pseudo-halido complexes [TpBe(X')] with X' = CN, N, NCO and NCS to explore the origins of the preferred isomers. Thus, we have synthesised and characterised through NMR and IR spectroscopy as well as single crystal X-ray diffraction these complexes.

The first HyDRA challenge for computational vibrational spectroscopy.

Vibrational spectroscopy in supersonic jet expansions is a powerful tool to assess molecular aggregates in close to ideal conditions for the benchmarking of quantum chemical approaches. The low temperatures achieved as well as the absence of environment effects allow for a direct comparison between computed and experimental spectra. This provides potential benchmarking data which can be revisited to hone different computational techniques, and it allows for the critical analysis of procedures under the setting of a blind challenge.

Phosphorus derivatives of mesoionic carbenes: synthesis and characterization of triazaphosphole-5-ylidene → BF adducts.

Trimethylsilyl-substituted triazaphospholes were synthesized by a [3+2] cycloaddition reaction between organic azides and (CH)Si-CP. In an attempt to isolate their -alkylated products, the formation of BF adducts of unprecedented triazaphosphol-5-ylidenes was found. The nature of the carbon-boron bond was investigated within the DFT framework, revealing a strong donation of electrons from the carbene carbon atom to the boron atom combined with weak back-bonding.

Revisiting the origin of the bending in group 2 metallocenes AeCp (Ae = Be-Ba).

Metallocenes are well-established compounds in organometallic chemistry, and can exhibit either a coplanar structure or a bent structure according to the nature of the metal center (E) and the cyclopentadienyl ligands (Cp). Herein, we re-examine the chemical bonding to underline the origins of the geometry and stability observed experimentally. To this end, we have analysed a series of group 2 metallocenes [Ae(CR)] (Ae = Be-Ba and R = H, Me, F, Cl, Br, and I) with a combination of computational methods, namely energy decomposition analysis (EDA), polarizability model (PM), and dispersion interaction densities (DIDs).

Merging the Energy Decomposition Analysis with the Interacting Quantum Atoms Approach.

Energy decomposition analysis (EDA) is a well-established approach to dissect the interaction energy into chemically sound components. Despite the inherent requirement of reference states has been a long-standing object of debate, the direct relation with the molecular orbital analysis helps in building up predictive models. The alternative molecular energy decomposition schemes that decompose the total energy into atomic and diatomic contributions, such as the interacting quantum atoms (IQA), has no external reference requirements and also the intra- and intermolecular interactions are treated on equal footing.

σ,π-Conjugated Bis(germylene) Adducts with NHC and CAACs.

Heavier tetrylenes attract attention for their potential in synthesis, catalysis and small molecule activation. The coordination by N-heterocyclic carbenes (NHCs) and cyclic (alkyl)(amino)carbenes (CAACs) results in substantial structural and electronic differences although typically only one of these yields stable derivatives for one and the same tetrylene. We now report both NHC- and CAAC-coordination to a bridged bis(germylene) motif.

Stable Silapyramidanes.

Starting from tetrakis(trimethylsilyl)cyclobutadiene and an amidinate-supported silylene of the Roesky-type, a sequence of addition and reduction cleanly gives the elusive silapyramidane via an isolable cyclobutene intermediate with an exocyclic Si═C bond. The silapyramidane features an unusually shielded Si NMR resonance at -448.3 ppm for the apex silicon atom.

Reply to the 'Comment on "The oxidation state in low-valent beryllium and magnesium compounds"' by S. Pan and G. Frenking, , 2022, , DOI: 10.1039/D2SC04231B.

A recent article by Pan and Frenking challenges our assignment of the oxidation state of low valent group 2 compounds. With this reply, we show that our assignment of Be(+2) and Mg(+2) oxidation states in Be(cAAC) and Mg(cAAC) is fully consistent with our data. Some of the arguments exposed by Pan and Frenking were based on visual inspection of our figures, rather than a thorough numerical analysis.

Evidence of Al Radical Addition to Benzene.

Electrophilic Al species have long dominated the aluminum reactivity towards arenes. Recently, nucleophilic low-valent Al aluminyl anions have showcased oxidative additions towards arenes C-C and/or C-H bonds. Herein, we communicate compelling evidence of an Al radical addition reaction to the benzene ring.

Formation of exceptional monomeric YPhos-PdCl complexes with high activities in coupling reactions.

The use of well-defined palladium(ii) complexes as precatalysts for C-X cross-coupling reactions has improved the use of palladium catalysts in organic synthesis including large-scale processes. Whereas sophisticated Pd(ii) precursors have been developed in the past years to facilitate catalyst activation as well as the handling of systems with more advanced monophosphine ligands, we herein report that simple PdCl complexes function as efficient precatalysts for ylide-substituted phosphines (YPhos). These complexes are readily synthesized from PdCl sources and form unprecedented monomeric PdCl complexes without the need for any additional coligand.

Crystalline Anions Based on Classical N-Heterocyclic Carbenes.

Herein, the first stable anions K[SIPr ] (4 a-K) and K[IPr ] (4 b-K) (SIPr =BpC{N(Dipp)CH } , IPr =BpC{N(Dipp)CH} ; Bp=4-PhC H ; Dipp=2,6-iPr C H ) derived from classical N-heterocyclic carbenes (NHCs) (i.e. SIPr and IPr) have been isolated as violet crystalline solids.

The oxidation state in low-valent beryllium and magnesium compounds.

Low-valent group 2 (E = Be and Mg) stabilized compounds have been long synthetically pursued. Here we discuss the electronic structure of a series of Lewis base-stabilized Be and Mg compounds. Despite the accepted zero(0) oxidation state nature of the group 2 elements of some recent experimentally accomplished species, the analysis of multireference wavefunctions provides compelling evidence for a strong diradical character with an oxidation state of +2.

Isolation of an Arsenic Diradicaloid with a Cyclic C As -Core.

Herein, we report on the synthesis, characterization, and reactivity studies of the first cyclic C As -diradicaloid {(IPr)CAs} (6) (IPr = C{N(Dipp)CH} ; Dipp = 2,6-iPr C H ). Treatment of (IPr)CH (1) with AsCl affords the Lewis adduct {(IPr)CH }AsCl (2). Compound 2 undergoes stepwise dehydrochlorination to yield {(IPr)CH}AsCl (3) and {(IPr)CAsCl} (5 a) or [{(IPr)CAs} Cl]OTf (5 b).

Metathesis Reactions of a NHC-Stabilized Phosphaborene.

The BP unsaturated unit is a very attractive functional group as it provides novel reactivity and unique physical properties. Nonetheless, applications remain limited so far due to the bulky nature of B/P-protecting groups, required to prevent oligomerization. Herein, we report the synthesis and isolation of a N-heterocyclic carbene (NHC)-stabilized phosphaborene, bearing a trimethylsilyl (TMS) functionality at the P-terminal, as a room-temperature-stable crystalline solid accessible via facile NHC-induced trimethylsilyl chloride (TMSCl) elimination from its phosphinoborane precursor.

Cage-size effects on the encapsulation of P by fullerenes.

The classic pnictogen dichotomy stands for the great contrast between triply bonding very stable N molecules and its heavier congeners, which appear as dimers or oligomers. A banner example involves phosphorus as it occurs in nature as P instead of P , given its weak π-bonds or strong σ-bonds. The P synthetic value has brought Lewis bases and metal coordination stabilization strategies.

Path-dependency of energy decomposition analysis & the elusive nature of bonding.

Here, we provide evidence of the path-dependency of the energy components of the energy decomposition analysis scheme, EDA, by studying a set of thirty-one closed-shell model systems with the symmetry point group. For each system, we computed EDA components from nine different pathways and numerically showed that the relative magnitudes of the components differ substantially from one path to the other. Not surprisingly, yet unfortunately, the most significant variations in the relative magnitudes of the EDA components appear in the case of species with bonds within the grey zone of covalency and ionicity.

Diarylpnictogenyldialkylalanes─Synthesis, Structures, Bonding Analysis, and CO Capture.

Several new diphenylamino- and diphenylphosphanyldialkylalanes are reported, which were characterized in solution and in the solid state, assisted by in-depth bonding analysis within the DFT framework. In the case of bulky alkyl substituents on the aluminum atom, the species are stable in their monomeric form and were structurally characterized by single crystal X-ray diffraction, expanding the relatively small field of monomeric pnictogenylalanes. In the case of oligomeric diphenylpnictogenyldimethylalanes, their reactivity toward different σ-donor ligands was studied, and several examples of monomeric adducts could be structurally characterized, including the first cyclic(alkyl)(amino)carbene complexes.

Unveiling the Electronic Structure of the Bi(+1)/Bi(+3) Redox Couple on NCN and NNN Pincer Complexes.

Low-valent group 15 compounds stabilized by pincer ligands have gained particular interest, given their direct access to fine-tune their reactivity by the coordination pattern. Recently, bismuth has been employed in a variety of catalytic transformations by taking advantage of the (+1/+3) redox couple. In this work, we present a detailed quantum-chemical study on the electronic structure of bismuth pincer complexes from two different families, namely, bis(ketimine)phenyl (NCN) and triamide bismuthinidene (NNN).

A Cyclic Iminoborane-NHC Adduct: Synthesis, Reactivity, and Bonding Analysis.

Lewis-base coordinated iminoborane adducts, in contrast to their isoelectronic analogue imines, remain largely unexplored given the lack of efficient synthetic strategies for generating robust compounds. Herein, we report the preparation of a cyclic amino iminoborane carbene complex obtained in quantitative yield by adding NHC to the 1,8-(trimethylsilyl)aminonaphthalene complex of boron to induce the elimination of trimethylsilyl chloride (TMSCl). The iminoborane-NHC adduct shows unprecedented thermal stability both in the solid and solution phases, due to the rigid, pre-established geometry of the 1,8-diaminonaphthalene scaffold.

Isolation of 1,4-Diarsinine-1,4-diide and 1,4-Diarsinine Derivatives.

1,4-Diarsinine-1,4-diide compound [(ADC )As] (5) (ADC ={C(DippN)} CPh, Dipp=2,6-iPr C H ) with a planar C As ring fused between two 1,3-imidazole scaffolds has been isolated as a red crystalline solid. Compound 5, formally comprising an 8π-electron C As ring, is antiaromatic and undergoes 2e-oxidation with AgOTf to form the 6π-electron aromatic system [(ADC )As] (OTf) (6).

Chemical Bonding in Silicon Carbonyl Complexes.

Although silylene-carbonyl complexes are known for decades, only recently isolable examples have been accomplished. In this work, the bonding situation is re-evaluated to explain the origins of their remarkable stability within the Kohn-Sham molecular orbital theory framework. It is shown that the chemical bond can be understood as CO interaction with the silylene via a donor-acceptor interaction: a σ-donation from the σ into the empty p-orbital of silicon, and a π-back donation from the sp lone pair of silicon into the π* antibonding orbitals.

Metalloradical Cations and Dications Based on Divinyldiphosphene and Divinyldiarsene Ligands.

Metalloradicals are key species in synthesis, catalysis, and bioinorganic chemistry. Herein, two iron radical cation complexes (3-E)GaCl [(3-E) = [{(IPr)C(Ph)E} Fe(CO) ] , E = P or As; IPr = C{(NDipp)CH} , Dipp = 2,6-iPr C H ] are reported as crystalline solids. Treatment of the divinyldipnictenes {(IPr)C(Ph)E} (1-E) with Fe (CO) affords [{(IPr)C(Ph)E} Fe(CO) ] (2-E), in which 1-E binds to the Fe atom in an allylic (η -EEC ) fashion and functions as a 4e donor ligand.

Isolation of a 16π-Electrons 1,4-Diphosphinine-1,4-diide with a Planar C P Ring.

Herein, we report the first 1,4-diphosphinine-1,4-diide compound [(ADC )P] (5-Ph) (ADC =PhC{(NDipp)C} ; Dipp=2,6-iPr C H ) derived from an anionic dicarbene (ADC ) as a red crystalline solid. Compound 5-Ph containing a 16π-electron planar fused-tricyclic ring system was obtained by the 4e reduction of [(ADC )PCl ] (4-Ph) with Mg (or KC ) in a quantitative yield. Experimental and computational results imply that the central 8π-electrons C P ring of 5-Ph, which is fused between two 6π-electrons C N aromatic rings, is antiaromatic.