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The contrasting geometrical features between organic and inorganic counterparts of amines and oxanes are explained in terms of an offset between attractive (donor-acceptor) and repulsive (donor-donor) interactions. Natural bond orbital (NBO) calculations carried out at the density functional theory level of theory reveal that hyperconjugative effects in the organic amines and ethers are overcome by repulsive interactions occurring between the lone pair on the nitrogen/oxygen atom and the adjacent σ(C-R) bond orbitals. Although displaying lower energies than in the corresponding organic derivatives, the LP(X) → σ*(E-R) (X = N, O; E = Si, Ge, Sn) interactions in heavier counterparts overcome the LP(X)···σ(E-R) repulsions, impacting thus their structural behavior. In addition, NBO deletion optimizations emphasize that among hyperconjugations, back-bonding effects of the LP(X) → d(E) type dictate to a lesser extent the anomalous structures of the inorganic amines and oxanes.

Two new stable 3,1-phosphagermapropenes have been synthesized and completely characterized in solution, solid state and by computational methods. The newly obtained compounds contain the germanium atom included into a fluorenylic cycle and their high stability towards air and moisture could be attributed to an extended aromaticity of the germafluorenyl moiety.

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A computational study at several DFT levels of theory was performed for the mono- and diphosphaalkenyl germylene systems in order to understand the Lewis acid-base behaviour of these species towards a few electron-donor systems like tetrahydrofuran, diethyl ether and 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene or/and electron-acceptor ones, as PdCl2 and PtCl2. The ability of these species to concurrently act as a Lewis acid and base was confirmed by the experimental study (synthesis and structural characterization of a new platinum(diphosphaalkenyl)germylene) that aimed to emphasize the theoretical data obtained.

The reactivity of 9-chloro-9-phosphaalkenylchloro-9-germafluorene stabilized by the introduction of the germanium atom into a fluorenyl system, was tested in reaction with lithium derivatives as methyllithium, normal-, sec- and tert-butyllithium. The reactions underwent, depending on the used organolithium derivative, either with the alkylation of the germanium atom or through a lithiation of the carbon atom of the phosphaalkenyl unit, and the successive formation of a carbanion through elimination of LiCl followed by the dimerization of this intermediate species.

A new mononuclear cobalt hybrid material (C6H9N2)2[CoCl4] was prepared using slow evaporation technique at room temperature. The X-ray diffraction analysis revealed that the compound crystallizes in the centrosymmetric space group P-1 of the triclinic system. In the crystal structure, the atomic arrangement is described as an alternation of 0-Dimensional organic and inorganic stacks; these stacks are connected via hydrogen bonds. The supramolecular architecture is stabilized by intermolecular interactions such as π···π stacks and halogen···halogen interactions. Hirshfeld surfaces and the breakdown of the fingerprint plots were determined to quantify the intermolecular contacts present in the crystal lattice. The thermal decomposition was studied by DSC and TGA techniques. The optical band gap energy suggests the semiconductor nature of the complex. The in-vitro biological activities show that the compound is a promising antioxidant agent.

International audience; Pincer ligands have an important role in stabilizing group 14 metallylenes. The particular structure of the aryl pin-6 cer ligands makes them a unique ligand platform. This review is focused on presenting monoanionic metallylenes stabilized by aryl pincer-type ligands, described so far in the literature, with focus on their synthesis, structural features, and reactivity.Throughout this work, the close correlation between structure11and reactivity is highlighted, as well as the manner in which thisinfluences the stability of the compounds and their potentialapplications.

New stable functionalized bis(fluorenyl)stannane derivatives with the general formula (9-SiMe3-CR2)(9-R′-CR2)SnX2 (CR2 = 9-fluorenyl, R′ = H, SiMe3, X = Br, Cl, OCOCH3) were obtained starting from the corresponding tetraorgano-tin compounds of Ph2(9-SiMe3-CR2)(9-R′-CR2)Sn type. All new compounds were completely characterized in solution by multinuclear NMR spectroscopy and mass spectrometry. The structure in solid state for derivatives 2 (R′ = H, X = Ph), 3 (R′ = SiMe3, X = Ph), 4 (R′ = H, X = Br) and 6 (R′ = H, X = Cl), has been elucidated by single crystal X-ray diffraction. The influence of the functional groups X and of the intramolecular C⋯π interactions on the adopted molecular geometry has been analyzed.

Two polymorphs of the new complex (C13H22N)2[CoBr4] have been prepared. The crystal structures of the polymorphs were determined by X-ray crystallography. Polymorph I belongs to the triclinic system, space group P-1 (No 2), while polymorph II adopts the monoclinic space group P21/c (No 14). The crystal packing is guided by C H···Br hydrogen bonds; these interactions contribute to the overall stabilization of the structures as they connect anions and cations together into a three-dimensional network. The polymorphs present different structure-properties relationships. Hirshfeld surfaces analysis contributes to the identification of the primary intermolecular contacts that guide the packing diagram. The thermal decomposition was studied by DSC, VT-PXRD, TDA and TGA techniques. The optical band gap energy suggests the semiconductor nature of the polymorphs. Temperature dependent magnetic susceptibility measurements in the temperature range of 1.8–310 K reveal that the polymorphs exhibit very weak antiferromagnetic interactions or contributions from single ion anisotropy.

New chiral heteroleptic germanium(ii) and tin(ii) metallylenes were obtained using 1-(para-tolylsulfinyl)-3-tosyl-5-tert-butyl-benzene as a non-symmetric O,C,O-chelating pincer ligand. Crystallographic analysis and DFT calculations indicate that the non-symmetric sulfinyl-sulfonyl pincer ligand acts as an O,C,O-coordinating pincer-type-ligand with predominant sulfinyl intramolecular S[double bond, length as m-dash]O coordination to germanium(ii) and tin(ii) centers.

The synthesis and characterization of an E2 CE2 bis-sulfonyl aryl pincer ligand and its efficiency for the stabilization of compounds containing low-valent Group 14 elements (Ge and Sn) are reported. Complexation reaction of these metallylenes with iron or tungsten complexes resulted in the modulation of the oxygen atoms of the sulfonyl groups implicated in the stabilization of the Group 14 elements, demonstrating the original adjustable character of the bis-sulfonyl O2 S-C-SO2 aryl pincer.

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Explaining the nature of the E-O chemical bond (E = Si, Ge, Sn) has been a great challenge for theoretical chemists during the last decades. Among the large number of models used for this purpose, the one based on hyperconjugative interactions sheds more light on the nature of chemical bonding in siloxanes. Starting from this concept, this study aimed to evaluate the impact of siloxane type hyperconjugative effects on the structural features of germoxanic and stannoxanic species and in addition to assess if p-d-like back-bonding interactions can also play important roles in determining the particular structures of these heavier analogues of ethers. Natural bond orbital deletion (NBO DEL) optimizations, carried out at the DFT level of theory, revealed that hyperconjugative effects dictate to a large extent the structural behavior of these species. Furthermore, this study points out that p-d back-bonding interactions also influence the equilibrium geometry of these species, although acting as a secondary electronic effect within the E-O-E moieties (E = Si, Ge, Sn).

New oxathiacrown macrocycles with exocyclic double bond 1 and 2 were synthesized and characterized. Their coordination behavior with soft transition metals is investigated. Reaction of 1 with PdCl2 afforded exo-coordinated complex 3 with the two S-donor atoms. With RuCl2(PPh3)3, the macrocyclic ligand 1 is bonded through three donor atoms (two sulfur and one oxygen) to the ruthenium center in a facial coordination mode. By contrast, double and single-stranded one dimensional (1D) coordination polymers were obtained by reaction of CuBr with macrocycles 1 and 2. All complexes were spectroscopically characterized and their structure was secured by X-ray diffraction analysis.

International audience; Phosphagermaallene 1, Tip(t-Bu)GeCPMes* (Tip = 2,4,6-triisopropylphenyl, Mes* = 2,4,6-tri-tert-butylphenyl), reacts with diphenylsulfoniumylide (Ph2SCH2) leading to adduct 2, through a nucleophilic attack of the negatively charged carbon atom of the ylide on the positively charged germanium atom followed by a migration of one of the phenyl groups. By contrast, dimethyloxosulfoniummethylide (Me2S(O)CH2) appears much less reactive towards 1: it preferentially undergoes an in-situ oxidation of THF leading to a γ-butyrolactone intermediate which gives a [2+2] cycloaddition by the CO group with the GeC double bond to form 3. The new compounds 2 and 3 were completely characterized by multinuclear NMR spectroscopy and by single crystal X-ray structural analysis.

The new phosphaalkenyl(chloro)tin(II) compound NHC-Sn(Cl)[C(SiMe3)=PMes*] was isolated and fully characterized including molecular structure determination by a single crystal X-ray diffraction analysis. Its reaction with Me2SAuCl led to the formation of an unprecedented P=C-bridged trinuclear gold complex [AuC(SiMe3)=PMes*]3 through the transfer of the phosphaalkenyl substituent to the gold atom.

A computational study at different levels of theory was performed for the not yet synthesized phosphastannaallenes >Sn C P– in order to evaluate the strength of the Sn C bond, the main postulated factor to stabilize such species, and the geometry in R 2 Sn C PR derivatives. The influence of the substituents with various electronic effects (H, Me, Ph, F, Cl, OMe, SiMe 3 ) at the Sn or P atoms of the Sn C P unit on the Sn C bond order was evaluated in the quest for a substituent that would stabilize the phosphastannaallenic unit. P C bond orders have also been calculated.

The first diphosphaalkenylstannylene stabilized through complexation with a carbene NHC-Sn[C(Cl)═PMes*](2)1 (Mes* = 2,4,6-tri-tert-butylphenyl; NHC = :C{N(iPr)C(Me)}(2)) was isolated and fully characterized including single crystal X-ray diffraction analysis. Its reaction with elemental sulfur rapidly gives the cyclic Sn(2)S(2) (dithiadistannetanne) derivative 3, presumably formed by dimerization of a stannathione intermediate. By contrast, its germanium analogue NHC-Ge[C(Cl)═PMes*](2)7 leads to the corresponding monomeric germathione 4 and germaselenone 5. The germaselenone was more stable than the germathione and could be structurally characterized. An unusual thermal cyclization reaction of the last one occurs with an excess of selenium to give the Ge(2)Se(3) (triselenadigermolane) ring derivative 6.

The thermal behaviour of three ester derivatives of p-tert-butyl calix[n]arene (n = 4, 6 and 8) in comparison with the parent calixarene was investigated by means of the thermogravimetric (TG) and differential thermogravimetic (DTG) analysis and differential scanning calorimetry (DSC). The thermal stability domains, the composition of the pyrolysis products and the thermal effects, were determined on the basis of TG, DTG and DSC plots registered in nitrogen flow. Attempts to analyse the evolved gases by TG-FTIR coupling were also performed. It was demonstrated that the stability of the calix[n]arene derivatives depends on both the size of the hydrophobic cavity and number of the substituting groups grafted on the calix[n]arene skeleton.

Density functional theory calculations on phosphavinylidene(oxo)phosphorane RP˭C˭P(˭O)R′ I are reported, where the R and R′ groups represent substituents with various electron-donor or electron-acceptor properties and different steric hindrance: H, F, Cl, OMe, SiH3, SiMe3, Me, Ph, Mes (2,4,6-trimethylphenyl), and Mes* (2,4,6-tri-tert-butylphenyl) and RF 2,4,6-tris(trifluoromethyl)-phenyl. The investigations provide information about the groups that seem to be the best choice for the stabilization of such systems. The influence of the substituents’ nature on the geometrical parameters and Wiberg bond orders for the P‒C bonds are discussed. Two isomers of I with a PCPO linkage (P≡C‒P(˭O)RR′ II and O˭P‒C≡PRR′ III) have also been studied. GRAPHICAL ABSTRACT

Phosphasilaallene Tip(Ph)Si = C = PMes* (Tip = 2,4,6-triisopropylphenyl, Mes* = 2,4,6-tri-tert-butylphenyl) and phosphagermaallene Mes2Ge = C = PMes* (Mes = 2,4,6-trimethylphenyl) have been obtained by dehalogenation of their corresponding dihalophosphametallapropenes > E(X)-C(X′) = P− by tert-butyllithium. They dimerize above −40 °C by a cycloaddition involving two E = C double bonds or the E = C and the P = C double bonds but can be characterized at low temperature by trapping reactions and by low field shifts in 31P, 29Si and particularly 13C NMR for the sp carbon atom. Owing to a small increase in the steric hindrance, phosphagermaallene Tip(t-Bu)Ge = C = PMes* can be stabilized and isolated. The Ge = C double bond undergoes nearly quantitative [2 + 1] cycloadditions with chalcogens and [2 + 2] cycloadditions with aldehydes or ketones. The surprisingly stable lithiochlorosilane R(Cl2)Si-C(Li) = PMes* (R = 9-methylfluorenyl) behaves as a synthetic equivalent of the phosphasilaallene R(Cl)Si = C = PMes*. With two alkyl groups (t-Bu) on the germanium atom, the phosphagermaallene t-Bu2Ge = C = PMes* is not obtained but its formal dimers 1,3-digermacyclobutanes have been isolated.

The geometries of all possible isomers of the model compound H2Ge=C=PH were optimized at the B3LYP/6-31G(d,p) level of the theory. The calculation were repeated at higher correlated methods with similar results and for the the isomers of the methyl-substituted phosphagermaallene MeP=C=GeMe2. As another way to stabilise the P=C=Ge unit consists in the use electronic effects, a NBO study was carried out in order to identify the influence that the nature (electropositive or electronegative) of several substituents would have on the strength of the C=Ge bond. Model compounds HP=C=GeR2 and HP=C=GeRR′ were investigated (R = BH2, CH3, SiH3, NH2, OMe, F; R′ = H). It was found that the main interaction contributing to the weakening of the C=Ge bond is a transfer of electron density from the lone pair of the phosphorus atom to the molecular antibonding orbital localized on the Ge–C bond.

New substituted 2,3-dichloro-1-λ3σ2-P,3-λ3σ3-P-diphosphapropenes Mes*P=C(Cl)-P(Cl)tBu (1) (Mes* = 2,4,6-tri-tert-butylphenyl) and the oxidation compounds Mes*P=C(Cl)–P(=E)(Cl)R [R = tBu, E = S (2), O (3); R = Mes, E = O (4)] are reported. From the reaction of 2 with W(CO)5(thf) the chelate compound W(CO)4[Mes*P=C(Cl)–P(S)(Cl)tBu] (5) was obtained. Reaction of 1 or 2 with PdCl2(cod) led to PdCl2[cyMes*PC(H)(Cl)–P(Cl)tBu] (cyMes*P = 5,7-di-tert-butyl-3,3-dimethyl-1-phosphaindane) (6) or PdCl2[cyMes*PC(H)(Cl)–P(S)(Cl)tBu] (7), in which the coordination to the Pd atoms is accompanied by intramolecular addition of CH(tBu) of Mes* to the P=C bond of the dichlorodiphosphapropene. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Bis(2,4,6-tri-tert-butylphenyl)phosphavinylidene(oxo)phosphorane (1) (Mes* = 2,4,6-tri-tert-butylphenyl), the first 1λ5σ3,3λ3σ2-diphosphaallene, has been synthesised by addition of the phosphaalkenyllithium Mes*P=C(Li)Cl to dichlorophosphane oxide Mes*P(O)Cl2. Compound 1 is stable in the solid-state but undergoes a slow intramolecular cyclisation in solution by addition of a C–H bond of an ortho-tert-butyl group to the σ3-P=C double bond. Water adds chemoselectively and regioselectively to the λ5σ3-P=C bond, which appears to be more reactive than the λ3σ2-P=C bond. This leads to the hydrolysis compound 8 which has been structurally characterised. The new bis(phosphane oxide)methylene 9 formed from the successive cyclisation of anortho-tert-butyl group to the λ5σ3-P=C bond and addition of water to the λ3σ2-P=C bond has also been structurally characterised. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

New, yet unprecedented molecular structures with parallel fluorene units were found by X-ray diffraction in (9,9'-disubstituted difluorenyl)(dimethyl) derivatives of group 14 elements Me 2 E(CR'R 2 )(CR"R 2 ) (E = Si, R' = Me, R" = SiMe 3 , 6a; E = Ge, R' = Me, R" = SiMe 3 , 6b; and E = Sn, R' = R" = SiMe 3 , 5c; CR 2 = fluorene units). This is in sharp contrast with the structure of monosubstituted Me 2 Ge(CHR 2 )(CR 2 -SiMe 3 ) (3b) and disubstituted Me 2 E(CMeR 2 ) 2 (E = Ge, 4b; E = Sn, 4c) derivatives where the two fluorene units are almost perpendicular. Intramolecular C-H...π interactions are revealed by solution 1 H NMR spectroscopy and supported by the AM1 molecular orbital calculations. Intermolecular (aryl, alkyl)C-H...π interactions leading to supramolecular associations are shown by the crystal structures of 3b, 4b, 4c, 5c, and 6a. In 4b and 5c rather unusual CH...HC distances resembling the "dihydrogen" bonds are noticed. Synthesis, NMR spectra, and gas phase conformations predicted on the basis of AM1 semiempirical molecular orbital calculations are discussed for Me 2 E(CR"R 2 )(CR"R 2 ) (E = Si, R' = R" = SiMe 3 , 5a; E = Ge, R' = R" = SiMe 3 , 5b; E = Sn, R' = H, R" = Me, 2c; R' = H, R" = SiMe 3 , 3c; R' = Me, R" = SiMe 3 , 6c; CR 2 = fluorene units).

Dechlorofluorination of ArSb(F)–C(Cl) CR 2 (CR 2 = fluorenylidene, Ar = 2,4,6-tri- tert -butylphenyl) by tert -butyllithium afforded a 3,4-bis(fluorenylidene)-1,2-distibacyclobutane. The formation of the latter probably involves the transient stibaallene ArSb C CR 2 followed by a head-to-head dimerization via two Sb C double bonds. Molecular orbital calculations at the ab initio and DFT levels support the head-to-head dimerization of ArSb C CR 2 with the formation of a 1,2-distibacyclobutane.

International audience; Phosphastannapropenes containing the -P=C-Sn < moiety are very scarcely reported in the literature, but their structure suggests that they can be of interest as precursors of inorganic materials, and their potential catalitic activity is worth investigating. Several new phosphastannapropenes were synthesized starting from the dichlorophosphaalkene Mes*P=CCl2 (Mes* = 2,4,6-tri-tertbutyl-phenyl) and dichlorotin derivatives following the synthetic route similar to that described in the literature for phosphasilaand phosphagermapropenes. The tin atom is either substituted by organic groups with low sterical hindrance, or incorporated in a cyclic system. The compounds were characterized by multinuclear NMR spectroscopy and, in some cases, single-crystal X-ray diffraction.

International audience; New oxathioethers macrocycles have been synthesized and characterized. Each macrocycle consists in structurally defined ether and thioether moieties and an exocyclic double-bond (2a-c) or a hydroxymethyl group (3a-c). Macrocycles (2a-c) have been synthesized by reaction of dianions of thioethers dials (1a-c) with 3-chloro-2-chloromethylprop-1-ene. Their hydroboration/oxidation led to corresponding primary alcohols (3a-c). Structures of compounds (2b) and (3a) have been determined by X-ray diffraction. The reactivity of the hydroxyl group allowed the preparation of oxathioethers macrocycles bearing a polyether chain or a benzyl group (4a,b) and the synthesis of new bicyclic sandwich-type compounds (5a,b). The ability of these functionalized macrocycles to coordinate to palladium has been investigated.

Three new silyl-substituted phosphaalkenes Mes*P C(Cl)–Si(Cl)PhR (R = chlorine, 1 ; R = 9-methylfluoren-9-yl, 2 ; R = 9-trimethylsilylfluoren-9-yl, 3 ) were obtained and completely characterized. The coordination compounds 4 and 5 , resulting from the reaction between Au(SMe 2 )Cl and 1 and 3 , respectively, are also described. All these compounds are potential precursors of phosphasilaallenes, not stabilized until now and new ligands in transition metal chemistry.

The new bis(phosphaalkenyl) germanium(II) compound (NHC)Ge(CCl=PMes*)(2) reacts with L(2)M(CO)(4) (M = Mo, W) to give bidentate complexes with an unexpected coordinating behaviour involving the Ge(II) centre and one phosphorus atom, and with AuI or Me(2)SAuCl to afford the monodentate complexes coordinated at the germanium(II) atom.

Phosphasilaallene Tip(Ph)Si = C = PMes* (Tip = 2,4,6-triisopropylphenyl, Mes* = 2,4,6-tri-tert-butylphenyl) and phosphagermaallene Mes2Ge = C = PMes* (Mes = 2,4,6-trimethylphenyl) have been obtained by dehalogenation of their corresponding dihalophosphametallapropenes > E(X)-C(X′) = P− by tert-butyllithium. They dimerize above −40 °C by a cycloaddition involving two E = C double bonds or the E = C and the P = C double bonds but can be characterized at low temperature by trapping reactions and by low field shifts in 31P, 29Si and particularly 13C NMR for the sp carbon atom. Owing to a small increase in the steric hindrance, phosphagermaallene Tip(t-Bu)Ge = C = PMes* can be stabilized and isolated. The Ge = C double bond undergoes nearly quantitative [2 + 1] cycloadditions with chalcogens and [2 + 2] cycloadditions with aldehydes or ketones. The surprisingly stable lithiochlorosilane R(Cl2)Si-C(Li) = PMes* (R = 9-methylfluorenyl) behaves as a synthetic equivalent of the phosphasilaallene R(Cl)Si = C = PMes*. With two alkyl groups (t-Bu) on the germanium atom, the phosphagermaallene t-Bu2Ge = C = PMes* is not obtained but its formal dimers 1,3-digermacyclobutanes have been isolated.

Computational data on homonuclear multiple bonding between elements of group 13 and heavier elements of group 14 are reviewed. For RnEERn, there is an increased tendency of bending the RER planes (n = 2) or the RE bonds (n = 1) toward the EE axis upon descending a group. This is related to the mixing of the valence σ–π orbitals reflecting the tendency of the heavier elements to retain nonbonding character for their ns2 orbital. As a result, the bond orders are also reduced and the EE interaction weakened. Keywords: group 13 double bonding; group 13 triple bonding; group 14 double bonding; group 14 triple bonding

Dimesitylfluoro(trichloromethyl)germane (1) has been synthesized from difluorodimesitylgermane, chloroform, and n-butyllithium. Addition of n-butyllithium to compound 1 gave the lithium carbenoid M...

New 1,3-digermacyclobutanes, with two exocyclic C=PMes* bonds, and the corresponding first bis(methylenethioxo)phosphoranes with C=P(S)Mes* moieties have been synthesized.