Phosphorus-containing polycarbosilazanes: synthesis dehydrocoupling catalysis and flame-retardant properties.

The barium complex [Ba{N(SiMe)}] has been used to catalyse the dehydropolymerisation of the phosphine-functionalised hydrosilane 4-PhP-CHSiH (A) with the α,ω-diamine 1,4-(CHNHMe)-CH (C), for the production of -[Si(4-CHPPh)H-N(Me)CH-CH-CHN(Me)]- polycarbosilazanes that contain dangling phosphino groups along the polymer backbone. The comonomers A and C, specifically prepared for this purpose and comprehensively characterised, lend themselves well to barium-promoted dehydrocoupling catalysis. They allow for the formation of linear, amine-capped polymers with molecular weights in the range 4000-8000 g mol, as estimated by DOSY and H end-group NMR analyses.

Of perfluorinated aryllead(II) complexes.

The pentafluorophenyl moiety CF was succesfully employed for the first time in lead(II) chemistry. We are reporting on the stable and soluble organolead(II) polymer [Pb(CF)(dx)] (dx = dioxane). An example of a Pb(II) "ate" complex paired with a trimetallic magnesium cation is also presented.

Bis(diiminate)-based boron difluoro complexes: effective synthon for bis(borenium) cations.

A series of boron difluoro bis(diiminate) complexes have been prepared and used to obtain triflate substituted fluoroborane complexes. The corresponding well-defined bis(borenium) cations were subsequently synthesized and structurally authenticated. We are also presenting the first experimental and theoretical study of bis(borenium) cations that are derivative of cationic borinic acid.

C-H bond activation at antimony(III): synthesis and reactivity of Sb(III)-oxyaryl species.

We report on the synthesis, structure and reactivity of [{NCN}Sb(CH-Bu-3,5-O-4)] (3), an organoantimony(III)-oxyaryl species obtained upon C-H bond activation in a phenolate ligand and stabilised by the monoanionic pincer {NCN}. The mechanism leading to the formation of 3 is highly sensitive to steric considerations. It was probed experimentally and by DFT calculations, and a number of intermediates and related complexes were identified.

Barium phosphidoboranes and related calcium complexes.

The attempted synthesis of [{Carb}BaPPh] (1) showed this barium-phosphide and its thf adducts, 1·thf and 1·(thf), to be unstable in solution. Our strategy to circumvent the fragility of these compounds involved the use of phosphinoboranes HPPh·BH and HPPh·B(CF) instead of HPPh. This allowed for the synthesis of [{Carb}Ae{PPh·BH}] (Ae = Ba, 2; Ca, 3), [{Carb}Ca{(HB)PPh}·(thf)] (4), [{Carb}Ba{PPh·B(CF)}] (5), [{Carb}Ba{O(B(CF))CHCHCHCHPPh}·thf] (6), [Ba{O(B(CF))CHCHCHCHPPh}·(thf)] (7) and [Ba{PPh·B(CF)}·(thp)] (8) that were characterised by multinuclear NMR spectroscopy (thp = tetrahydropyran).

Iron(II)-Catalyzed Activation of Si-N and Si-O Bonds Using Hydroboranes.

We report the activation and functionalization of Si-N bonds with pinacol borane catalyzed by a three-coordinate iron(II) β-diketiminate complex. The reactions proceed via the mild activation of silazanes to yield useful hydrosilanes and aminoboranes. The reaction is studied by kinetic analysis, along with a detailed investigation of decomposition pathways using catecholborane as an analogue of the pinacol borane used in catalysis.

Synergy of Turbulent Momentum Drive and Magnetic Braking.

In absence of external torque, plasma rotation in tokamaks results from a balance between collisional magnetic braking and turbulent drive. The outcome of this competition and cooperation is essential to determine the plasma flow. A reduced model, supported by gyrokinetic simulations, is first used to explain and quantify the competition only.

Bonding analysis in ytterbium(II) distannyl and related tetryls.

The syntheses of the ytterbium(II) distannyl [Yb{Sn(SiMe)}·(thf)] (Yb-Sn) and of its digermyl analogue [Yb{Ge(SiMe)}·(thf)] (Yb-Ge) are presented. The compounds were characterised by multinuclear high-resolution solution NMR spectroscopy, including Yb NMR, and by X-ray diffraction crystallography. The bonding and electronic properties of the two complexes, along with those of the known ytterbium(II) disilyl derivative [Yb{Si(SiMe)}·(thf)] (Yb-Si) and those of the congeneric calcium distannyl [Ca{Sn(SiMe)}·(thf)] (Ca-Sn), were investigated in detail by DFT calculations.

Bis(imino)carbazolate lead(II) fluoride and related halides.

The versatility of a bulky bis(imino)carbazolate ligand in lead(ii) chemistry is illustrated by the synthesis of a soluble, heteroleptic lead(ii) fluoride and several halide (Cl, Br and I), amide and hydrocarbyl congeners. All complexes have been structurally authenticated, and a full set of 207Pb NMR data is discussed.

Metal-metal bonded alkaline-earth distannyls.

The first families of alkaline-earth stannylides [Ae(SnPh)·(thf) ] (Ae = Ca, = 3, ; Sr, = 3, ; Ba, = 4, ) and [Ae{Sn(SiMe)}·(thf) ] (Ae = Ca, = 4, ; Sr, = 4, ; Ba, = 4, ), where Ae is a large alkaline earth with direct Ae-Sn bonds, are presented. All complexes have been characterised by high-resolution solution NMR spectroscopy, including Sn NMR, and by X-ray diffraction crystallography. The molecular structures of [Ca(SnPh)·(thf)] (), [Sr(SnPh)·(thf)] (), [Ba(SnPh)·(thf)] (), , and [Ba{Sn(SiMe)}·(thf)] (), most of which crystallised as higher thf solvates than their parents , were established by XRD analysis; the experimentally determined Sn-Ae-Sn' angles lie in the range 158.

Bonding in Barium Boryloxides, Siloxides, Phenoxides and Silazides: A Comparison with the Lighter Alkaline Earths.

Barium complexes ligated by bulky boryloxides [OBR ] (where R=CH(SiMe ) , 2,4,6- Pr -C H or 2,4,6-(CF ) -C H ), siloxide [OSi(SiMe ) ] , and/or phenoxide [O-2,6-Ph -C H ] , have been prepared. A diversity of coordination patterns is observed in the solid state for both homoleptic and heteroleptic complexes, with coordination numbers ranging between 2 and 4. The identity of the bridging ligand in heteroleptic dimers [Ba(μ -X )(X )] depends largely on the given pair of ligands X and X .

Modular Synthesis of 9,10-Dihydroacridines through an -C Alkenylation/Hydroarylation Sequence between Anilines and Aryl Alkynes in Hexafluoroisopropanol.

9,10-Dihydroacridines are frequently encountered as key scaffolds in OLEDs. However, accessing those compounds from feedstock precursors typically requires multiple steps. Herein, a modular one-pot synthesis of 9,10-dihydroacridine frameworks is achieved through a reaction sequence featuring a selective -C alkenylation of diarylamines with aryl alkynes followed by an intramolecular hydroarylation of the olefin formed as an intermediate.

Alkaline-earth complexes with macrocyclic-functionalised bis(phenolate)s and bis(fluoroalkoxide)s.

The synthesis and structural features of several families of unsolvated molecular complexes of the heavy alkaline earths (Ae = calcium, strontium and barium) supported by bis(phenolate)s or bis(fluoroalkoxide)s are described. These dianionic, multidentate ligands are built around diaza-macrocycles that contain either five or six N- and O-heteroatoms. Several of these complexes have been characterised by X-ray diffraction crystallography.

A versatile nitrogen ligand for alkaline-earth chemistry.

The tridentate ligand 1,8-bis-(2,6-diisopropylphenyl)imino-3,6-di-tert-butyl-carbazolate, {Carb}, has been used to prepare a variety of complexes of the large alkaline earths (Ae) calcium, strontium and barium. A complex of their smaller congener, magnesium, has also been synthesised. The range of coligands that have been utilised include alkyls, amides, halides and tetrelides.

Barium-Catalysed Dehydrocoupling of Hydrosilanes and Borinic Acids: A Mechanistic Insight.

Invited for the cover of this issue are the groups of Yann Sarazin at the University of Rennes and Laura Falivene at the King Abdullah University of Science and Technology. The image depicts two barium figures working in tandem to mimic the dinuclear nature of the active species in the catalytic cycle described in the manuscript. Read the full text of the article at 10.

Bis(imino)carbazolate: A Master Key for Barium Chemistry.

Reported here is a readily available bis(imino)carbazole-based proligand that constitutes a convenient entry point into the challenging synthetic molecular chemistry of barium. It enables the preparation of rare or even, up to now, unknown, solution-stable heteroleptic barium complexes. The syntheses and structural features for the first molecular barium fluoride and the first barium stannylide, with an unsupported Ba-Sn bond, are described, along with other carbazolate barium species: an amide (both a remarkably stable starting material and an excellent hydrophosphination precatalyst), iodide, and silanylide.

Barium-Catalysed Dehydrocoupling of Hydrosilanes and Borinic Acids: A Mechanistic Insight.

Two very rare cases of barium boryloxides, the homoleptic [Ba(OB{CH(SiMe ) } ) ⋅C H ] and the heteroleptic [{LO }BaOB{CH(SiMe ) } ] stabilised by the multidentate aminoetherphenolate {LO } , are presented, and their structural properties are discussed. The electron-deficient [Ba(OB{CH(SiMe ) } ) ⋅C H ] shows, in particular, resilient η -coordination of the toluene molecule. Together with its amido parents [Ba{N(SiMe ) } ⋅thf ] and [Ba{N(SiMe ) } ] , this complex catalyses the fast and chemoselective dehydrocoupling of borinic acids R BOH and hydrosilanes HSiR' , yielding borasiloxanes R BOSiR' in a controlled fashion.

Synthesis of Bridged Tetrahydrobenzo[b]azepines and Derivatives through an Aza-Piancatelli Cyclization/Michael Addition Sequence.

Herein, we report the preparation of bridged tetrahydrobenzo[b]azepines, which was accomplished through an aza-Piancatelli cyclization/Michael addition sequence in a one-pot fashion from readily available precursors. It is noteworthy that a general method to access these scaffolds was hitherto unprecedented. Additionally, the multifaceted aspects of this process have been exemplified through its application to the synthesis of 2-azabicyclo[3.

Lead(II) Siloxides.

Although Pb -siloxides have been known until now to decompose to oxoclusters, here [{RO }PbOSi(SiMe ) ] (RO =fluoroalkoxide) and, most importantly, [Pb {OSi(SiMe ) }{μ -OSi(SiMe ) } ], are presented. The unusual bonding pattern in the latter thermally stable dinuclear complex was investigated by crystallographic and computational methods. Its stability is much higher than that of the simple, yet elusive "[Pb(OSiPh ) ]", for which decomposition pathways towards [Pb (μ -O)(μ -OSiPh ) ] have been clearly established.

Barium Siloxides and Catalysed Formation of Si-O-Si' Motifs.

The first unsupported barium siloxide, the homoleptic dimer [Ba {μ -OSi(SiMe ) } {OSi(SiMe ) }], is presented, and its structural features are discussed in the light of DFT computations. This complex, together with the related [Ba{μ -OSi(SiMe ) }{N(SiMe ) }] and their parent [Ba{N(SiMe ) } ] , mediates the formation of asymmetric siloxanes R Si-O-SiR' through the first case of main group metal-mediated dehydrocoupling of silanols and hydrosilanes. Early kinetic analysis highlights an unusual catalytic manifold.

Aminofluoroalkoxide amido and boryloxo lead(ii) complexes.

We report here on the utilisation of a readily available bidentate aminofluoroalkoxide in lead(ii) chemistry. Stable heteroleptic three-coordinate complexes can be produced in high yields, including a convenient amido synthetic precursor and a rare case of Pb-boryloxide.

Barium complexes with crown-ether-functionalised amidinate and iminoanilide ligands for the hydrophosphination of vinylarenes.

The detailed multistep syntheses of two nitrogen-based sterically congested iminoanilidine and amidine proligands bearing a tethered 15-member aza-ether-crown macrocycle, namely {I^Acrown}H and {Amcrown}H, are reported. These proligands react with [Ba{N(SiMe2H)2}2·(thf)n] to generate the heteroleptic barium complexes [{I^Acrown}BaN(SiMe2H)2] (5) and [{Amcrown}BaN(SiMe2H)2] (6) in high yields. These complexes exhibit high coordination numbers (resp.

Metal⋅⋅⋅F-C Bonding in Low-Coordinate Alkaline Earth Fluoroarylamides.

A set of calcium and barium complexes containing the fluoroarylamide N(C F ) is presented. These compounds illustrate the key role of stabilising M⋅⋅⋅F-C secondary interactions in the construction of low-coordinate alkaline earth complexes. The nature of Ca⋅⋅⋅F-C bonding in calcium complexes is examined in the light of structural data, bond valence sum (BVS) analysis and DFT computations.

Heterobimetallic Ba/Li and Ca/Li amides and diphenylmethanide.

The structures of the heterobimetallic Ca/Li and Ba/Li amides [CaLi2{μ2-N(SiMe2H)2}4]∞ and [Ba2Li2{μ2-N(SiMe2H)2}6]∞, stabilised by metalH-Si interactions, and that of a diphenylmethanide calcium salt, [Li(tmeda)2+·Ca(CHPh2)3(thf)-], are presented. These well-defined, storable compounds are inert towards Et2O and thf.

Low-Coordinate Barium Boryloxides: Synthesis and Dehydrocoupling Catalysis for the Production of Borasiloxanes.

The first soluble barium boryloxides [Ba]- OB{CH(SiMe ) } are presented. These mono- or dinuclear complexes feature low coordination numbers, as low as two for [Ba(OB{CH(SiMe ) } ) ], which is further stabilized by intra- and intermolecular Ba⋅⋅⋅H C agostic interactions. Barium boryloxides and the parent [Ba{N(SiMe ) } ⋅(thf) ] catalyze the dehydrocoupling of borinic acids with hydrosilanes, providing borasiloxanes under mild conditions.