Search

A novel bis-CF3-substituted diazaphosphole was synthesized selectively from hexafluoro-2-butyne and a 3H-1,2,3,4-triazaphosphole derivative. The [4+2] cycloaddition and subsequent cycloreversion reaction under elimination of pivaloyl nitrile affords the product in high yield. The heterocycle coordinates via the phosphorus atom to a W(CO)5-fragment and shows stronger π-accepting properties than the triazaphosphole.

Activation of CO2 is the first step towards its reduction to more useful chemicals. Here we systematically investigate the CO2 activation mechanism on Cu3X (X is a first-row transition metal atom) using density functional theory computations. The CO2 adsorption energies and the activation mechanisms depend strongly on the selected dopant. The dopant electronegativity, the HOMO-LUMO gap and the overlap of the frontier molecular orbitals control the CO2 dissociation efficiency. Our calculations reveal that early transition metal-doped (Sc, Ti, V) clusters exhibit a high CO2 adsorption energy, a low activation barrier for its dissociation, and a facile regeneration of the clusters. Thus, early transition metal-doped copper clusters, particularly Cu3Sc, may be efficient catalysts for the carbon capture and utilization process. ispartof: PHYSICAL CHEMISTRY CHEMICAL PHYSICS vol:23 issue:38 pages:21738-21747 ispartof: location:England status: published

The yet unknown 2-amino-substituted λ3 ,σ2 -phosphinines are phosphorus-containing aniline derivatives. Calculations show that the strong interaction of the π-donating NR2 group with the aromatic system results in a high π-density at the phosphorus atom. We could now synthesize 2-N(CH3 )2 -functionalized phosphinines, starting from a 3-N(CH3 )2 -substituted 2-pyrone and (CH3 )3 Si-C≡P. Their reaction with CuBr⋅S(CH3 )2 affords CuI complexes with the first example of a neutral phosphinine acting as a rare bridging μ2 -P-4e donor-ligand between two CuI centers. Our experimental and theoretical investigations show that 2-aminophosphinines are missing links in the series of known 2-donor-functionalized phosphinines.

The base-induced (t-BuOK) rearrangement reactions of 3,4-dihydro-2H-1,2,3-benzothiadiazine 1,1-dioxides result in a ring opening along the N-N bond, followed by ring closure with the formation of new C-N bonds. The position of the newly formed C-N bond can selectively be tuned by the amount of the base, providing access to new, pharmacologically interesting ring systems with high yield. While with 2 equiv of t-BuOK 1,2-benzisothiazoles can be obtained in a diaza-[1,2]-Wittig reaction, with 6 equiv of the base 1,2-benzothiazine 1,1-dioxides can be prepared in most cases as the main product, in a diaza-[1,3]-Wittig reaction. DFT calculations and detailed NMR studies clarified the mechanism, with a mono- or dianionic key intermediate, depending on the amount of the reactant base. Also, the role of an enamide intermediate formed during the workup of the highly basic (6 equiv of base) reaction was clarified. The substrate scope of the reaction was also explored in detail.

Ferrocene-1,1 '-dithiol reacts with PCl3 and P(NMe2)(3) to give [3]ferrocenophanes with SPS-ansa-bridges comprising potentially reactive P-Cl and P-N bonds at the central bridge atom. The products were characterized by NMR data and single-crystal XRD studies. The P-chloro-derivative exists both in the solid state and in solution as a mixture of two energetically nearly degenerate conformers with different stereochemical disposition of the ansa-bridge. Activation parameters for the dynamic equilibration between both isomers in solution were determined by dynamic NMR spectroscopy. Computational studies suggest that the isomerization proceeds via a torsional motion of the bridging SPS-unit rather than via configuration inversion at the phosphorus atom.

Synthesis of the tricyclic 1,3-dithiole-2-thione-derived 1,4-dihydro-1,4-diphosphinine is presented using a base-induced ring formation protocol and chloro(diethylamino)(1,3-dithiole-2-thion-4-yl)phosphane as the starting point. P-oxidation reactions of dihydrodiphosphinine by chalcogens led to bis(P-oxide), bis(P-sulfide), or bis(P-selenide), respectively; all tricyclic compounds were obtained as cis/trans mixtures. 1,4-Dihydro-1,4-diphosphinine was converted into 1,4-dichloro-1,4-dihydro-1,4-diphosphinine. This compound is almost insoluble in organic solvents, furnished selectively the trans-bis(amino) derivative upon a 2-fold P-substitution reaction with the weak nucleophile potassium bis(trimethylsilyl)amide, and reacted also with alcohols ROH (R = nBu, iPr, tBu) to give cis/trans mixtures of the corresponding bis(alkoxy) derivatives. Furthermore, the dichloro derivative could be reduced to a 1,4-diphosphinine using PnBu3, but, unfortunately, the stubbornly insoluble product could be neither purified nor crystallized. Despite this, we achieved a thermal [4 + 2] cycloaddition reaction of this first CPS-ternary compound with diethylacetylene dicarboxylate to obtain the corresponding diphosphabarrelene, thus providing indirect evidence for the aromatic tricyclic diphosphinine. Detailed density functional theory studies on the formation of 1,4-diphosphinine provided insights into formation pathways as well as NMR, IR, and UV/vis data.

International audience; This article presents the synthesis of a new family of naphthyl-fused phosphepines through Ni-mediated C-C coupling. Interestingly, the chlorophosphine oxide intermediate shows strong resistance toward oxidation/hydrolysis owing to a combination of steric hindrance and pnictogen interactions. However, it can undergo substitution reactions under specific conditions. The optical/redox properties and the electronic structure of these new π-systems were studied experimentally (UV/Vis absorption, emission, cyclic voltammetry) and computationally (TD-DFT calculations, NICS investigation). Taking advantage of the luminescence of these derivatives, a blue-emitting OLED has been prepared, highlighting that these novel π-conjugated P-heterocycles appear to be promising building blocks for solid-state lighting applications.

Diels-Alder-reactions of a thiazol-2-thione-based, tricyclic 1,4-di-phosphinine were investigated, showing that the central aromatic π-system can react with various dienophiles. The reaction with 4-phenyl-1,2,4-triazoline-3,5-dione was special as the product revealed a remarkable sensitivity towards light, thus enabling the photochemical deprotection of the tricyclic 1,4-diphosphinine.

International audience; We present the stereospecific synthesis of helicenoid-based phosphepines (7-membered P-rings) as well as chiral P-containing polycyclic aromatic hydrocarbons. In these systems, an axial to central chirality transfer takes place from the BINAP moiety to the P-atom. The impact of the molecular design on the structure, the (chir)optical (including circularly polarized luminescence) and redox properties are investigated.

International audience; Polycyclic Aromatic Hydrocarbons (PAHs) with planar, twisted and negatively curved topologies were obtained from polycyclic phospholes using pericyclic reactions. Deviation from planarity is due to steric interaction between the PAH core and the ester substituents. These structural effects on the optical and redox properties were studied and rationalized through DFT calculations. This synthetic approach thus allows the preparation of topologically diverse PAHs allowing finetuning their electronic properties, with potential applications in organic electronics.

A phosphanido-type bridged bis(imidazolium) salt, readily prepared in two steps via reductive deselenization of a tricyclic 1,4-diphosphinine diselone, affords access to a novel anionic P-functional tricyclic bis(NHC) via deprotonation. The former also offers a P-functionalization/deprotonation sequence to access the first mixed P-substituted tricyclic bis(NHCs), as well as coordination of the phosphorus centers to rhodium(I) fragments.

Detection and characterization of fleeting reaction intermediates and active sites are crucial for molecular-level knowledge of catalysis; insight that is required to understand the catalytic mechanisms, and to design novel high performance catalysts. We report a mass spectrometric study of the reactions of 3d early transition metal (vanadium, [Ar]3d 3 4s 2 ) cationic clusters with methanol in a low-pressure collision cell. For comparison, the reaction of methanol with 3d late transition metal (cobalt, [Ar]3d 7 4s 2 ) cationic clusters were studied as well. In the vanadium case, the main reaction products are fully dehydrogenated species, and partial dehydrogenation and non-dehydrogenation species are observed as minors, for which the relative intensities increase with cluster size and also at low cluster source temperature cooled by liquid nitrogen; while no dehydrogenation products have been observed for cobalt clusters. That demonstrates the strikingly different reactivity of vanadium and cobalt cationic clusters towards methanol. Quantum chemical calculations explored the reaction pathways and revealed that the fully dehydrogenation products of the reaction between V n + and methanol are V n (C)(O) + , in which C and O are separated due to the high oxophilicity of vanadium. The partial dehydrogenation and non-dehydrogenation species observed in the experiment are verified to be reaction intermediates along the reaction pathway, and their most probable structures have been proposed.

International audience; In this paper, we report the synthesis and characterization of a series of phosphanyl-substituted siloles. The chemical modification (oxidation, sulfurization, alkylation and complexation) results in a change in the energy levels of frontier orbitals, which has further been studied by UV-Vis absorption spectroscopy and electrochemistry. Significantly, despite their high "s" 2 character the phosphorus lone pairs of the 2,5-bisphosphanylsilole can combine with the π-system of the silole core resulting in a somewhat destabilized HOMO. The structural aspects of these new siloles have been investigated employing single-crystal X-ray diffraction and DFT calculations.

A hitherto unknown triphosphatricyclo[3.2.1.02,7]oct-3-ene was obtained in high yield by a total of four consecutive pericyclic reactions from di-2-pyrone and excess TMS-C[triple bond, length as m-dash]P. DFT calculations gave insight into the reaction mechanism. The chiral phosphorus cage readily forms coordination compounds with Au(i) and Cu(i).

The stability and the structure of adducts formed between four substituted phosphanes (PX3, X:H, F, Cl, and NMe2) and 11 different carbenes have been investigated by DFT calculations. In most cases, the structure of the adducts depends strongly on the stability of the carbene itself, exhibiting a linear correlation with the increasing dissociation energy of the adduct. Carbenes of low stability form phosphorus ylides (F), which can be described as phosphane → carbene adducts supported with some back-bonding. The most stable carbenes, which have high energy lone pair, do not form stable F-type structures but carbene → phosphane adducts (E-type structure), utilizing the low-lying lowest unoccupied molecular orbital (LUMO) of the phosphane (with electronegative substituents), benefiting also from the carbene-pnictogen interaction. Especially noteworthy is the case of PCl3, which has an extremely low energy LUMO in its T-shaped form. Although this PCl3 structure is a transition state of rather high energy, the large stabilization energy of the complex makes this carbene-phosphane adduct stable. Most interestingly, in case of carbenes with medium stability both F- and E-type structures could be optimized, giving rise to bond-stretch isomerism. Likewise, for phosphorus ylides (F), the stability of the adducts G formed from carbenes with hypovalent phosphorus (PX-phosphinidene) is in a linear relationship with the stabilization of the carbene. Adducts of carbenes with hypervalent phosphorus (PX5) are the most stable when X is electronegative, and the carbene is highly nucleophilic.

Recent studies have shown anomalies with the most studied non-covalent molecularly imprinted polymer, the propranolol imprinted one. This imprinted polymer, like many others, binds more template than the non-imprinted control polymer, but its selectivity in template adsorption is only slightly or not at all improved by imprinting, depending on the compound compared. The reasons for this anomaly are discovered here. Simple experiments show that acid homoassociation in the prepolymerisation complex is the likely cause of the anomaly. The specific conductivity of prepolymerization mixtures at different functional monomer to template ratios follows a pattern observed in homoassociating systems. Analysis of the optimal prepolymerization mixture shows that on average two molecules of the functional monomer are complexed to the basic template, even if the template lacks any other hydrogen bonding functional group than the amino group. Molecular modeling calculations provide the structure and stability of the homoassociated prepolymerization complexes. These results lead to a plausible interpretation of the anomaly, which may not be unique for the propranolol imprinted polymer, but may affect all imprinted polymers made for basic templates by using acidic functional monomers. The analytical applications of the new imprinting model are demonstrated.

Synthesis of the first tricyclic bis(carbenes) with facially opposed imidazole-2-ylidenes and two linking phosphorus centres in different oxidation states is presented using a modular, high-yield synthetic route. The formation of homo bimetallic coinage metal(i) complexes provides a first glimpse on their potential use.

3H-1,2,3,4-Triazaphosphole derivatives can be selectively alkylated with Meerwein's reagent at the most nucleophilic nitrogen atom. According to the principle of valence isoelectronicity, the corresponding phosphorus heterocycle represents the first formal phosphorus analogue of the well-known 1,2,3-triazolylidenes (mesoionic carbenes). Theoretical calculations revealed that the cation in triazaphospholenium tetrafluoroborate is an aromatic system with a high degree of π-conjugation. First investigations showed that the cationic phosphorus heterocycle can stabilize a [Cu2 Br4 ]2- dianion by formation of a neutral coordination compound with an unusual bonding situation between phosphorus and copper(I).

In a search for stable phosphinonitrenes generated by thermally induced decomposition of the azidophosphines8a,b, different cyclodiphosp(V)azene products were generated. While in the case of8athe expected phosphinonitrene dimer10could be obtained, from8b, which has the sterically more demanding TMP substituents, product11, was obtained and characterized. DFT calculations have revealed that the primarily formed phosphinonitrene9bis unstable against loss of TMP˙, and the resulting radical dimerizes to the biradicaloid 1,3-diaza-2,4-diphosphetane-2,4-diyl13. Compound13then dimerizes after ring opening, yielding in the ring system, which provides the final product upon reaction with the starting azidophosphine.

Stable N-heterocyclic carbenes (NHC) are a class of compounds that has attracted a huge amount of interest in the last decade. One way to prepare NHCs is through chemical or electrochemical reduction of 1,3-disubstituted imidazolium cations. We are presenting an in-situ electrochemical X-ray Photoelectron Spectroscopy (XPS) study where electrochemically reduced imidazolium cations lead to production of stable NHC. The electroactive imidazolium species is not only the reactant, but also part of the ionic liquid which serves as the electrolyte, the medium and the electroactive material. This allows us to directly probe the difference between the parent imidazolium ion and the NHC through the use of XPS. The interpretation of the results is supported by both observation of reversible redox peaks in the voltammogram and the density functional theory calculations.

2,4,6-Triphenyl-1-phosphabenzene has a non-planar structure, with the substituent phenyl groups rotated out from the plane of the central ring by about 45°. The rotational barriers are relatively low, and the phenyl groups rotate independently with barriers of about 3 kcal/mol, yielding in two minima (“propeller” and “statistical average”) with nearly identical energy. Altogether, the basically rigid aromatic units form a molecule with increased flexibility. The structural characteristics were compared to the related benzene analog, and also to 2,4,6-triphenyl-1,3,5-triphosphabenzene, as well as to the related nitrogen compounds. It was shown that the steric need of N (characterized by the position of the N lone pair from the ring center) is significantly smaller than that of P, which is slightly larger than the steric need of the CH group. The height of the phenyl rotational barrier in different six-membered rings, decreasing in the order 1,3,5triphosphabenzene > phosphabenzene ~ benzene > pyridine and vanishing completely in 1,3,5triazine, can nicely be explained by this finding. The flexible arrangement of the aromatic rings is found to show advantage for self-assembly by π-stacking effect. For the dimer, a somewhat stronger attractive interaction was calculated than that of the corresponding polycyclic aromatic hydrocarbon (tetracene). The rotational barrier increases in the π-stacked aggregates.

Reactions of P-chloro-1,3,2-diazaphospha[3]ferrocenophanes with ECl3 (E = Al, Ga) under solvent-free conditions and with Na[Mn(CO)(5)] furnished salts featuring a ferrocenophane-based phosphenium cation and neutral phosphenium complexes, respectively. All products were characterized by spectroscopic studies. Single-crystal X-ray diffraction studies confirmed the ionic nature of the phosphenium tetrachloroaluminate and the structural analogy between the phosphenium complexes and Fischer-type carbene complexes. Distinct deviations in the conformation of the ansa bridge suggest electronic stabilization of the electrophilic phosphorus atom by phosphorus-nitrogen pi interactions in the free cation and by phosphorus-metal pi bonding in the complexes. The observation of short intermolecular contacts in the crystalline phosphenium salt and its chemical behavior toward donor solvents attest to the cation having an unusually high degree of Lewis acidity, which was confirmed by DFT studies and related to the presence of a rather large N-P-N angle. Computational studies indicate further that the free phosphenium cation exhibits a closed-shell electronic structure with a formal Fe(II) oxidation state and is thus a true analogue to ferrocenophane-based diaminotetrylenes.

A hitherto unknown triphosphatricyclo[3.2.1.02,7]oct-3-ene was obtained in high yield by a total of four consecutive pericyclic reactions from di-2-pyrone and excess TMS-C[triple bond, length as m-dash]P. DFT calculations gave insight into the reaction mechanism. The chiral phosphorus cage readily forms coordination compounds with Au(i) and Cu(i).

The Front Cover visualizes the thermally induced homolytic cleavage of the central P‐P bond in a phosphorus–rich bis‐ferrocenophane furnishing P‐centered radicals. The bond fission process and conformational dynamics in this compound as well as isolobal analogues obtained by formal replacement of individual P‐atoms by nitrogen atoms or SiH fragments is elucidated from analysis of their variable temperature NMR and EPR spectra and simulated by DFT calculations. The central P(6) unit in the title compound is a structural analog of the connecting unit in Hittorf's violet phosphorus, which links the orthogonally arranged tubular entities. More information can be found in the Full Paper by S. Isenberg et al. on page 1235 in Issue 10, 2019 (DOI: 10.1002/open.201900182).[Image: see text]

The article presents the synthesis of a new family of naphthyl-fused phosphepines through Ni-mediated C-C coupling. Interestingly, the chloro-phosphine-oxide intermediate shows strong resistance toward oxidation/hydrolysis due to a combination of steric hindrance and pnictogen interactions. However it can undergo substitution reactions under specific conditions. The optical / redox properties and the electronic structure of these new pi-systems were studied experimentally and computationally. Taking advantage of the luminescence of these derivatives, a blue emitting OLED has been prepared highlighting that these novel pi-conjugated P-heterocycles appear as promising building blocks for solid-state lightning applications.

A series of bis‐[3]ferrocenophanes of the general type Fe(C5H4E’)2E−E(E'C5H4)2Fe (E=P, SiH and E’=PtBu, NneoPentyl, NSi(CH3)3) with an isolobal molecular framework have been prepared and characterized by heteronuclear NMR spectroscopy and X‐ray crystallography. The thermal dissociation behavior with respect to homolytic fission of the central bond generating phosphorus centered radicals was investigated using EPR spectroscopy and quantum chemical calculations.

This work presents the first example of a dienophilic property of the monovalent group-13 NacNac complexes, which are well-known for their carbene-like reactivity, e.g., addition to multiple bonds, insertion into single bonds, and oxidative cleavage of some multiple bonds. In reactions with imidazole-2-thione based tricyclic 1,4-diphospinine 4, the monovalent compounds NacNacM (M = Al,Ga) showed dienophilic behaviour and produced the corresponding 7-metalla-1,4-diphosphanorbornadienes (5-6), leaving the C[double bond, length as m-dash]S functionality of the imidazole-2-thione intact, while the NacNacIn complex did not show any reactivity because of unfavourable thermodynamics. DFT calculations revealed that for NacNacAl, the cycloaddition was kinetically more favoured (due to a small reaction barrier) than the oxidative cleavage of the C[double bond, length as m-dash]S functionality, despite the fact that the product of the C[double bond, length as m-dash]S bond addition has a somewhat higher stability. For NacNacGa, the cycloaddition reaction was both kinetically and thermodynamically favourable than the cleavage of C[double bond, length as m-dash]S. Furthermore, these reactions were found to be reversible in nature and diphosphinine 4 showed a clear preference towards Al than towards Ga which reflects the better inclination of Ga to stay monovalent than be in the trivalent state.

Condensation of secondary 1,1'-diaminoferrocenes with phosphorus trihalides (PCl3 or PBr3) yielded either P-halo-1,3-diaza-2-phospha[3]ferrocenophanes or 1,1'-diaminoferrocenediyl-bis(dichlorophosphines), respectively. The latter provide controlled access to both [3]- and [4]ferrocene frameworks. Thus, reductive coupling with magnesium gave diaza-diphospha[4]ferrocenophane-annelated tetraphosphetanes, while a reaction with LiNMe2 produced a P-chloro-diazaphospha[3]ferrocenophane. Condensation of diaminoferrocenes and aminodichlorophosphines were mostly unselective, but afforded in one case a 3-amino[3]ferrocenophane. All reaction products were characterised by spectroscopic and single-crystal XRD studies. DFT studies indicate that the product selectivity in the reactions studied depends on a combination of kinetic and thermodynamic effects, which correlate subtly with the steric bulk of the N-substituents. Cyclic voltammetry measurements revealed that the ferrocenophanes can undergo multiple oxidation events, the first of which may according to DFT studies be located in both the ferrocene and aminophosphine units. The quantum chemical studies provided also insight into stereochemical aspects like ring strain in the ferrocenophane units.

International audience; A series of complexes including sigma3,lambda3-P-modified PAH as a ligand have been prepared showing that the ligand possesses a classical “phosphine like” reactivity. The use of different metals (Pd(II), Cu(I), Re(I), Au(I)) having different coordination number allows to tune the optical properties of the complexes, which is dominated basically by the electronic transitions of the ligand itself. The study of the solid state properties by mean of X-ray diffraction also shows that the combination of coordination chemistry and pi-stacking interactions between the PAH ligand allows to obtain a great diversity of solid state structures.

The substituent effect on the hydrolysis of chlorosilanes was studied computationally. Sixteen practically important compounds with SiCl bond were considered, and the stationary points along their reaction pathway with different-sized water clusters (monomer and tetramer) were investigated using density functional theory. While in the case of a single reactant water molecule the reactions are endothermic for most of the substituents, with the larger reactant water cluster the reactions are mainly exothermic. In the case of the reactant cluster consisting of four water molecules both an inversion and a retention pathway are located. The reaction barrier for both pathways is about 50% that with a single water molecule, and the inversion pathway is somewhat more preferred over retention for most substituents except for cage-like chlorosilanes. Strong correlations were indentified between several factors of substituted chlorosilanes and their activation energy of hydrolysis. Cl-Si-O bond angle in the transition state as an indirect descriptor of steric effect, electrophilicity and partial charge at silicon of the reactant chlorosilane, and the opportunity of extra H-bond formation have influence on the reaction barrier. Quantitative structure-property relationship (QSPR) analysis showed that the hydrolysis activation energy can be well described by using these factors.

The organocatalytic activity of the recently synthesized diamino[3]ferrocenophanes and the related thioamino[3]ferrocenophane was investigated in the benzoin condensation computationally. The nucleophilicity of these compounds is slightly increased compared to the imidazolidin-2-ylidene, as a consequence of the increased bond angle at the carbene center. Among the possible isomers of the carbene–aldehyde adducts, we have located a hitherto unexplored structure with an oxirane moiety. The isomers of the related carbene–aldehyde adducts including the Breslow intermediates have similar stability in comparison with the imidazolidin-2-ylidene and thiazolidin-2-ylidene, respectively; moreover, the barriers of the interconversion of these adducts are also similar; however, the oxirane-type compound formed from benzaldehyde and the diamino[3]ferrocenophane is significantly stabilized with respect to its isomers. The barrier of the addition of the second aldehyde to the Breslow intermediate increased by 9–15 kcal/mol in case of the [3]ferrocenophanes compared to the 5-membered analogues, which could partly be explained by the higher stabilization of the van der Waals adduct of the Breslow intermediate and the second aldehyde. Since the addition of the second aldehyde is blocked, these carbenes could be suitable for the experimental investigation of the carbene–aldehyde adducts.

International audience; In this letter, we present the synthesis of a new family of pi-extended dithieno[b,f]phosphepines. The Pd-catalyzed direct-arylation allows the introduction of various substituents, which tune the absorption/emission in the visible range as well as the redox properties. All those modifications were rationalized through DFT calculations. The physical properties of ambipolar phos-phepine with diphenylamino substituents conduct us to use it as a semiconductor in a p-type organic field-effect transistors (OFETs).

International audience; A new synthetic route toward the synthesis of benzo[b]phospholes-and benzo[b]siloles-fused pyrenes using a transition metal-catalyzed C-H bond activation is described. The compounds were fully characterized including X-ray dif-fraction. A combined experimental and theoretical study shows that both the heteroa-tom and the substitution pattern impact the optical and redox properties.

A new sulfur-enriched tricyclic 1,4-diphosphinine (2) was synthesized and novel reactivity studies on the phosphorus heterocycle were performed: a weak anionic nucleophile (KHMDS) adds selectively thus forming a stable anionic 1,4-diphosphinine derivative (3b) which was fully characterized. The substitution potential of 3b was demonstrated using Ph2PCl to give 4b, while oxidation of 3b using elemental iodine furnished cleanly the P–P coupling product 5.

A bisphosphanylsilylene with [3]ferrocenophane backbone and its heavier analogues are described in the form of donor adducts. These heterocarbenes can be formed by dehydrochlorination (Si) or cycloreversion (Sn, Pb) using NHC (N-heterocyclic carbene) tetramethylimidazol-2-ylidene. The structures of the bisphosphanyl-silylene, -stannylene and -plumbylene NHC adducts are presented, and the bonding and stability of these compounds were elucidated using DFT calculations. Reactivity studies confirm the stability of the silylene adduct, where the electrophilic character of the silylene center is comparable to a borane.

The reaction of 1-chlorosilols (12, 13) and K[Fe(CO)2Cp] in THF yielded two new η1-silolyl-FeCp(CO)2 complexes (15, 16) in good yield. These complexes are the first covalent Fe–Si bonded silolyl complexes reported in the literature, which were structurally proven by single crystal X-ray diffraction and multinuclear NMR spectroscopy. By temperature dependent NMR spectroscopy a rotational barrier of 14.4 kcal/mol was revealed, in agreement with the calculated 14.9 kcal/mol barrier of the phenyl rotation. The attempted transformation of these complexes to the corresponding silaferrocene by CO elimination failed. DFT calculations revealed that the rather high stability of the Si–Fe comparing to the C–Fe bond might be responsible for the stability of the complexes.

N-Heterocyclic phosphanes react under UV irradiation in a highly selective dehydrocoupling reaction to diphosphanes and H2. Computational studies suggest that the product formation is initiated by the formation of dimeric molecular associates whose electronic excitation yields H2 and a diphosphane. Combining the dehydrocoupling of sterically demanding phosphanes with Mg-reduction of the formed diphosphanes allows constructing a reaction cycle for the photocatalytic reductive generation of H2 from Et3NH(+).

Detailed computational studies have been carried out to explain the unexpected differing reactions that occur between dimethylamine and the difluorophosphines, CX3PF2 (X = F, Cl). The reaction affords the thermodynamically controlled product chloroform in the case of X = Cl, whereas when X = F the analogous reaction pathway leading to fluoroform is hindered by a substantial reaction barrier in the gas phase, where the reaction should take place due to the volatility of the reactant. While the gas-phase reaction energy gap is somewhat reduced when X = Cl, due to the stability of the migrating CCl3− moiety, the still substantial barrier does not account for the chloroform formation. Polarizable continuum model (PCM) calculations indicate a reduction of the barrier, facilitating the liquid-phase reaction. The alternative gas-phase reaction path, resulting in the aminolysis of a P—F bond is reversible and is shifted toward the product by capturing HF as the dimethylamino salt of the [CF3PF4H]− anion.

The reaction of 1-neopentyl-1,3-benzazaphosphole 1 with CuCl, CuBr, or Cu(SMe2)Br in THF at room temperature provides sparingly soluble [Cu7(μ(2)-L6)(μ(2)-X7)](+)[CuX2](-) cluster complexes 2a,b (L indicates coordinated 1, a X = Cl, b X = Br), with loosely bound THF, in high yields. The conversions proceed via transient THF-soluble labile [(L2CuX)2] complexes. Separation before complete conversion, combined with suitable conditions for crystallization, allowed these intermediates to be trapped. Depending on the reactant ratios, crystals of the clusters or of dimeric L2CuX complexes were formed. The crystal structure analyses of 2a·4THF and the dimers 3b [{Cu(η(1)-L)2(μ(2)-Br)}2], 4b [{Cu(μ(2)-L)(η(1)-L)(κBr)}2], 5a·2MeOH, and 5b·2MeOH [{Cu(μ(2)-L)(η(1)-L)(κX···HOMe)}2] generally display μ(2)-P- and/or tilted η(1)-P-coordination, contrasting with the preference for the η(1)-P in-plane coordination mode of phosphinine ligands in their copper(I) halide complexes. DFT studies of geometry-optimized monomers LCuBr, L(CuBr)2, L2CuBr, and the dimers 3b and 4b, calculated at the ωB97xD/cc-PVDZ level, suggest that weak competing interactions with the solvent THF and the entropy factor of the dimerization result in lability and a subtle balance between the different complexes in solution, whereas the particular coordination observed in the crystals is attributable to conservation of the delocalized π-system in the ligand. The HOMO of 4b is composed of Cu d orbitals and the π-type HOMO of the bridging ligand. Interestingly, despite the rather short Cu···Cu interatomic separation (2.726 Ǻ), no bond critical point could be located in 4b, indicating the absence of weak cuprophilic interactions in this compound.

The –PCH–NR-heterocycle 1-neopentyl-1,3-benzazaphosphole (npBAP) reacts in THF with copper(I) acetate via labile soluble complexes (npBAP)xCuOAc preferably to form the insoluble tetranuclear (npBAP)2(CuOAc)4 complex 1. The crystal structure analysis of 1·2CH2Cl2, grown from CH2Cl2–hexane, reveals two μ2-P coordinated ligands, folding the Cu4 ring with each two short distances of the cyclic copper(I) acetate tetramer to a butterfly arrangement. AIM analysis of the ωB97-D/6-31+G* electron density, obtained at the crystal structure geometry, shows bond critical points between the copper atoms indicating covalent bonding interactions between the neighboring Cu atoms.