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The introduction of heteroatoms into conjugated organic molecules is an important strategy to tune their reactivity and physical properties. In this realm triazabutadienes (TBDs) of the general from R2C=N-N=NR' are an interesting class of compounds, however, general synthetic protocols for their generation are limited. Based on the serendipitous finding that the sterically encumbered azide Mes*N3 (Mes* = 2,4,6-tBu3C6H2) reacted with PMe3 in the presence of an aromatic aldehyde to form a TBD, we now report on the "Azide-Wittig" reaction. This azide-Wittig reaction is shown to be a versatile tool for the synthesis of a variety of TBDs, tolerating a wide range of aldehydes and organic azides as coupling partners. The preference for azide-Wittig, rather than aza-Wittig reactivity was rationalized using computational methods. This study shows how kinetic control can significantly alter the reaction pathway, thereby switching from an aza-Wittig to an azide-Wittig regime., (© 2024 Wiley‐VCH GmbH.)

Biradicals are important intermediates in the formation and breaking of a chemical bond. Their use as molecular switches is of particular interest. Much less is known about tetraradicals, which can, for example, consist of two biradical(oid) units. Here we report the synthesis of the first persistent phosphorus-centred tetraradical bound to a transition metal fragment. Starting from a zirconocene complex, rac-(ebthi)ZrCl 2 (rac-(ebthi)=1,2-ethylene-1,10-bis(η 5 -tetrahydroindenyl), two cyclo-1,3-diphospha-pentane-1,3-diyls were successfully introduced, which finally led to the isolation of a deep green zirconcene-bridged bis(biradicaloid) complex (5) that can act as a double molecular switch. Under the influence of light (570 nm), this tetraradical forms a transannular bond in each of the two five-membered biradical units, leading to the formation of housane 5 h. Upon irradiation at 415 nm, the reverse reaction is observed, fully recovering tetraradical 5. Through single-crystal-to-single-crystal transformation, both stable species of the molecular switch could be structurally characterised using SCXRD. The switching under the influence of light and the activation of molecular hydrogen were analysed in solution using NMR and UV spectroscopy. It was found that the addition of one or two equivalents of molecular hydrogen can be switched on and off by light., (© 2024 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

On-line reaction monitoring of hydrogenation reactions featuring oxygen-sensitive organometallic complexes is done via a 31 P benchtop NMR spectrometer using the Multi-Resonance Sensitive Homogeneous And Resolved PEaks in Real time (MR-SHARPER) sequence. Signal enhancement generated by MR-SHARPER enables monitoring of reactivity on the order of minutes that could not be followed with traditional 31 P{ 1 H} NMR detection.

The synthesis of group 4 metal 1-metallacyclobuta-2,3-dienes as organometallic analogues of elusive 1,2-cyclobutadiene has so far been limited to SiMe 3 substituted examples. We present the synthesis of two Ph substituted dilithiated ligand precursors for the preparation of four new 1-metallacyclobuta-2,3-dienes [rac-(ebthi)M] (M=Ti, Zr; ebthi=1,2-ethylene-1,10-bis(η 5 -tetrahydroindenyl)). The organolithium compounds [Li 2 (RC 3 Ph)] (1 b: R=Ph, 1 c: R=SiMe 3 ) as well as the metallacycles of the general formula [rac-(ebthi)M(R 1 C 3 R 2 )] (2 b: M=Ti, R 1 =R 2 =Ph, 2 c: M=Ti, R 1 =Ph, R 2 =SiMe 3 ; 3 b: M=Zr, R 1 =R 2 =Ph; 3 c: M=Zr, R 1 =Ph, R 2 =SiMe 3 ) were fully characterised. Single crystal X-ray diffraction and quantum chemical bond analysis of the Ti and Zr complexes reveal ligand influence on the biradicaloid character of the titanocene complexes. X-band EPR spectroscopy of structurally similar Ti complexes [rac-(ebthi)Ti(Me 3 SiC 3 SiMe 3 )] (2 a), 2 b, and 2 c was carried out to evaluate the accessibility of an EPR active triplet state. Cyclic voltammetry shows that introduction of Ph groups renders the complexes easier to reduce. 13 C CPMAS NMR analysis provides insights into the cause of the low field shift of the resonances of metal-bonded carbon atoms and provides evidence of the absence of the β-C-Ti interaction., (© 2024 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Direct coupling of benzotriazole to unsaturated substrates such as allenes represents an atom-efficient method for the construction of biologically and pharmaceutically interesting functional structures. In this work, the mechanism of the N 2 -selective Rh complex-catalyzed coupling of benzotriazoles to allenes was investigated in depth using a combination of experimental and theoretical techniques. Substrate coordination, inhibition, and catalyst deactivation was probed in reactions of the neutral and cationic catalyst precursors [Rh(μ-Cl)(DPEPhos)] 2 and [Rh(DPEPhos)(MeOH) 2 ] + with benzotriazole and allene, giving coordination, or coupling of the substrates. Formation of a rhodacycle, formed by unprecedented 1,2-coupling of allenes, is responsible for catalyst deactivation. Experimental and computational data suggest that cationic species, formed either by abstraction of the chloride ligand or used directly, are relevant for catalysis. Isomerization of benzotriazole and cleavage of its N-H bond are suggested to occur by counteranion-assisted proton shuttling. This contrasts with a previously proposed scenario in which oxidative N-H addition at Rh is one of the key steps. Based on the mechanistic analysis, the catalytic coupling reaction could be optimized, leading to lower reaction temperature and shorter reaction times compared to the literature.

Nickel fluoride complexes of the type [Ni(F)(L) 2 (Ar F )] (L = phosphine, Ar F = fluorinated arene) are well-known to form strong halogen and hydrogen bonds in solution and in the solid state. A comprehensive study of such non-covalent interactions using bis(carbene) complexes as acceptors and suitable halogen and hydrogen bond donors is presented. In solution, the complex [Ni(F)(iPr 2 Im) 2 (C 6 F 5 )] forms halogen and hydrogen bonds with iodopentafluorobenzene and indole, respectively, which have formation constants ( K 300 ) an order of magnitude greater than those of structurally related phosphine supported nickel fluorides. Co-crystallisation of this complex and its backbone-methylated analogue [Ni(F)(iPr 2 Me 2 Im) 2 (C 6 F 5 )] with 1,4-diiodotetrafluorobenzene produces halogen bonding adducts which were characterised by X-ray analysis and 19 F MAS solid state NMR analysis. Differences in the chemical shifts between the nickel fluoride and its halogen bonding adduct are well in line with data that were obtained from titration studies in solution.

The long-term stability of an active-pharmaceutical ingredient and its drug products plays an important role in the licensing process of new pharmaceuticals and for the application of the drug at the patient. It is, however, difficult to predict degradation profiles at early stages of the development of new drugs, making the entire process very time-consuming and costly. Forced mechanochemical degradation under controlled conditions can be used to realistically model long-term degradation processes naturally occurring in drug products, avoiding the use of solvents, thus excluding irrelevant solution-based degradation pathways. We present the forced mechanochemical oxidative degradation of three platelet inhibitor drug products, where the drug products contain thienopyridine. Model studies using clopidogrel hydrogen sulfate ( CLP ) and its drug formulation Plavix show that the controlled addition of excipients does not affect the nature of the main degradants. Experiments using drug products Ticlopidin-neuraxpharm and Efient show that significant degradation occurs after short reaction times of only 15 min. These results highlight the potential of mechanochemistry for the study of degradation processes of small molecules relevant to the prediction of degradation profiles during the development of new drugs. Furthermore, these data provide exciting insights into the role of mechanochemistry for chemical synthesis in general., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

Cationic rhodium(I) diphosphine complexes, referred to as Schrock-Osborn catalysts, are privileged homogeneous catalysts with a wide range of catalytic applications. The coordination of solvent molecules can have a significant influence on reaction mechanisms and kinetic scenarios. Although solvent binding is well documented for these rhodium species, comparative quantifications for structurally related systems are not available to date. We present a method for systematic investigation and quantification of this important parameter, using MeCN which replaces diolefins and forms stable Rh(I) MeCN complexes. Using UV-vis and 31 P{ 1 H} NMR spectroscopy we determine and compare stability constants of different [Rh(PP)(NBD)]BF 4 and [Rh(PP)(COD)]BF 4 complexes (PP = diphosphine; COD = 1,5-cyclooctadiene; NBD = 2,5-norbornadiene) and discuss the influence of PP ligands and reaction temperature. A DFT study reveals the dependence of the stability on the thermodynamics of the exchange reaction. Using variable temperature NMR spectroscopy, the first mixed solvate complex could be verified as an intermediate in the MeCN-MeOH exchange.

The dehydropolymerisation of phenylsilane is investigated using group 4 metallocene amide complexes as catalysts. The dinuclear zirconocene amide complex Cp 2 Zr(NMe 2 )(μ-Me 3 SiC 3 SiMe 3 )Zr(NMe 2 )Cp 2 (2) (Cp = η 5 -cyclopentadienyl) shows high activity in dehydrocoupling reactions, producing polyphenylsilanes with molecular weights ranging from 200 to 3000 g mol -1 and linear-to-cyclic product ratios of up to 80 : 20. Likewise, different ratios of oligomers and polymers with different tacticities could be described. Ansa -zirconocene amide complexes possessing the ebthi (ebthi = 1,2-ethylene-1,1'-bis(η 5 -tetrahydroindenyl)) ligand systems were prepared and evaluated for catalytic dehydropolymerisation in comparison to the dinuclear catalyst system., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The synthesis of P,N-phosphaalkene ligands, py-CH═PMes* ( 1 , py = 2-pyridyl, Mes* = 2,4,6- t Bu-C 6 H 2 ) and the novel quin-CH═PMes* ( 2 , quin = 2-quinolinyl) is described. The reaction with [Rh(μ-Cl)cod] 2 produces Rh(I) bis(phosphaalkene) chlorido complexes 3 and 4 with distorted trigonal bipyramidal coordination environments. Complexes 3 and 4 show a pronounced metal-to-ligand charge transfer (MLCT) from Rh into the ligand P═C π* orbitals. Upon heating, quinoline-based complex 4 undergoes twofold C-H bond activation at the o - t Bu groups of the Mes* substituents to yield the cationic bis(phosphaindane) Rh(I) complex 5 , which could not be observed for the pyridine-based analogue 3 . Using sub- or superstoichiometric amounts of AgOTf the C-H bond activation at an o - t Bu group of one or at both Mes* was detected, respectively. Density functional theory (DFT) studies suggest an oxidative proton shift pathway as an alternative to a previously reported high-barrier oxidative addition at Rh(I). The Rh(I) mono- and bis(phosphaindane) triflate complexes 6 and 7 , respectively, undergo deprotonation at the benzylic CH 2 group of the phosphaindane unit in the presence of KO t Bu to furnish neutral, distorted square-planar Rh(I) complexes 8 and 9 , respectively, with one of the P,N ligands being dearomatized. All complexes were fully characterized, including multinuclear NMR, vibrational, and ultraviolet-visible (UV-vis) spectroscopy, as well as single-crystal X-ray and elemental analysis.

Iridium(III) bis(thiophosphinite) complexes of the type [( R PSCSP R )Ir(H)(Cl)(py)] ( R PSCSP R = κ 3 -(2,6-SPR 2 )C 6 H 3 ) (R = t Bu, iPr, Ph) can be prepared from the ligand precursors 1,3-(SPR 2 )C 6 H 4 by C-H activation at Ir using [Ir(COE) 2 Cl] 2 or [Ir(COD)Cl] 2 . Optimisation of the protocol for complexation showed that direct cyclometallation in the absence or presence of pyridine, as well as C-H activation in the presence of H 2 are viable options that, depending on the phosphine substituent furnish the five-coordinate Ir(III) hydride chloride complexes 2-R or the base stabilised species 3-R in good yields. In case of the Ph PSCSP Ph ligand, P-S activation results in the formation of a thiophosphine stabilised Ir(III) hydride complex [( Ph PSCSP Ph )Ir(H)(Cl)(PPh 2 SH)] (4). Reaction of 2-tBu with H 2 in the presence of base furnishes an Ir(III) dihydride complex (5) via a labile Ir(III) dihydride-dihydrogen complex (6). All complexes are inactive for transfer dehydrogenation of cyclooctane in the presence of NaO t Bu and tert -butylethylene, likely due to decomposition of the Ir complex in the presence of base at higher temperature.

Hard modeling of NMR spectra by Gauss-Lorentz peak models is an effective way for dimensionality reduction. In this manner high-dimensional measured data are reduced to low-dimensional information as peak centers, amplitudes or peak widths. For time series of spectra these parameters can be assumed to be smooth functions in time. We suggest to model these time-dependent parameter functions by cubic spline functions, which makes a stable quantitative analysis of NMR series possible even for crossing, highly overlapping peaks. Applications are presented for the batch distillation of methanol and diethylamine, and the reaction of acetic anhydride with 2-propanol., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Inc. All rights reserved.)

The conversion of CO 2 into multicarbon (C 2+ ) compounds by reductive homocoupling offers the possibility to transform renewable energy into chemical energy carriers and thereby create "carbon-neutral" fuels or other valuable products. Most available studies have employed heterogeneous metallic catalysts, but the use of molecular catalysts is still underexplored. However, several studies have already demonstrated the great potential of the molecular approach, namely, the possibility to gain a deep mechanistic understanding and a more precise control of the product selectivity. This Minireview summarizes recent progress in both the thermo- and electrochemical reductive homocoupling of CO 2 toward C 2+ products mediated by molecular catalysts. In addition, reductive CO homocoupling is discussed as a model for the further conversion of intermediates obtained from CO 2 reduction, which may serve as a source of inspiration for developing novel molecular catalysts in the future., (© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

The structure, bonding, and reactivity of small, highly unsaturated ring systems is of fundamental interest for inorganic and organic chemistry. Four-membered metallacyclobuta-2,3-dienes, also referred to as metallacycloallenes, are among the most exotic examples for ring systems as these represent organometallic analogs of 1,2-cyclobutadiene, the smallest cyclic allene. Herein, the synthesis of the first examples of 1-zirconacyclobuta-2,3-dienes of the type [Cp' 2 Zr(Me 3 SiC 3 SiMe 3 )] (Cp' 2 = rac -(ebthi), (ebthi = 1,2-ethylene-1,1'-bis(η 5 -tetrahydroindenyl)) (2a); rac -Me 2 Si(thi) 2 , thi = (η 5 -tetrahydroindenyl), (2b)) is presented. Both complexes undergo selective thermal C-H activation at the 7-position of the ansa -cyclopentadienyl ligand to produce a new type of "tucked-in" zirconocene system, 3a and 3b, that possesses a η 3 -propargyl/allenyl ligand. Both types of complexes react with carbonyl compounds, producing enynes in the case of 2a and 2b, as well as η 1 -allenyl complexes for 3a and 3b. Computational analysis of the structure and bonding of 2a and 3a reveals significant differences to a previously described related Ti complex. All complexes were fully characterised, including X-ray crystallography and experimental results were supported by DFT analysis., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

A method for forced oxidative mechanochemical degradation of active pharmaceutical ingredients (APIs) using clopidogrel hydrogensulfate as a model compound is presented. Considerable and selective formation of degradants occurs already after very short reaction times of less than 15 minutes and the nature of the products is strongly dependent on the used oxidant.

Phospha-Wittig reagents, RPPMe3 (R = Mes* 2,4,6-tBu3-C6H2; MesTer 2,6-(2,4,6-Me3C6H2)-C6H3; DipTer 2,6-(2,6-iPr2C6H3)-C6H3), can be considered as phosphine-stabilized phosphinidenes. In this study we show that PMe3 can be displaced by NHCs or NHOs. Interestingly, phosphinidene-like reactivity results in a subsequent C(sp2)-H activation of the exocyclic CH2 group in NHOs. This concept was further extended to allyl-apended NHOs, which resulted in phosphine-substituted allyl species.

Dehydropolymerisation of methylamine borane (H 3 B⋅NMeH 2 ) using the well-known iron amido complex [(PNP)Fe(H)(CO)] (PNP=N(CH 2 CH 2 PiPr 2 ) 2 ) (1) gives poly(aminoborane)s by a chain-growth mechanism. In toluene, rapid dehydrogenation of H 3 B⋅NMeH 2 following first-order behaviour as a limiting case of a more general underlying Michaelis-Menten kinetics is observed, forming aminoborane H 2 B=NMeH, which selectively couples to give high-molecular-weight poly(aminoborane)s (H 2 BNMeH) n and only traces of borazine (HBNMe) 3 by depolymerisation after full conversion. Based on a series of comparative experiments using structurally related Fe catalysts and dimethylamine borane (H 3 B⋅NMe 2 H) polymer formation is proposed to occur by nucleophilic chain growth as reported earlier computationally and experimentally. A silyl functionalised primary borane H 3 B⋅N(CH 2 SiMe 3 )H 2 was studied in homo- and co-dehydropolymerisation reactions to give the first examples for Si containing poly(aminoborane)s., (© 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

The thermodynamics of halogen bonding of a series of isostructural Group 10 metal pincer fluoride complexes of the type [(3,5-R 2 - tBu POCOP tBu )MF] (3,5-R 2 - tBu POCOP tBu =κ 3 -C 6 HR 2 -2,6-(OPtBu 2 ) 2 with R=H, tBu, COOMe; M=Ni, Pd, Pt) and iodopentafluorobenzene was investigated. Based on NMR experiments at different temperatures, all complexes 1-tBu (R=tBu, M=Ni), 2-H (R=H, M=Pd), 2-tBu (R=tBu, M=Pd), 2-COOMe (R=COOMe, M=Pd) and 3-tBu (R=tBu, M=Pt) form strong halogen bonds with Pd complexes showing significantly stronger binding to iodopentafluorobenzene. Structural and computational analysis of a model adduct of complex 2-tBu with 1,4-diiodotetrafluorobenzene as well as of structures of iodopentafluorobenzene in toluene solution shows that formation of a type I contact occurs., (© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

Nickel(ii) chloride and thiolate complexes with iPr PE 1 CE 2 P iPr (E = O, S) pincer ligands were investigated as electrocatalysts for the hydrogen evolution reaction in CH 3 CN in the presence of acetic acid and trifluoroacetic acid. The bis(thiophosphinite) (S,S) chloride complex reduced protons at the lowest overpotential in comparison with the bis(phosphinite) (O,O) and mixed phosphinite-thiophosphinite (O,S) complexes. A combination of electrochemical, NMR and UV-vis spectroscopic and mass spectrometric experiments provides mechanistic insights into the catalytic cycle for proton reduction to dihydrogen.

Reactions of the zirconocene alkyne complex [rac-(ebthi)Zr(η2-Me3SiC2SiMe3)] (rac-(ebthi) = rac-1,2-ethylene-1,1'-bis(η5-tetrahydroindenyl)) with tert-butylisocyanide and methylbenzenes were investigated. Depending on the stoichiometry, the solvent and the reaction temperature different products were obtained. Starting with the end-on coordination of the isocyanide to the zirconium centre (2), elevated reaction temperatures and an excess of tert-butylisocyanide resulted after the elimination of the alkyne in the formation of zirconocene η2-iminoacyl cyanide complexes 3a-d. These complexes are formed by coupling with a benzyl fragment through C-H bond activation of a methyl group of methylbenzene. The dimeric cyanide bridged zirconocene complex 4 is formed as a side-product of this process. The unexpected dimer and the heterometallacycles were fully characterised, including X-ray crystallography.

In the crystal structure of the isostructural title compounds, namely {2,6-bis-[(di- tert -butyl-phosphan-yl)-oxy]-4-hy-droxy-phen-yl}chlorido-palladium(II), [Pd(C 22 H 39 O 3 P 2 )Cl], 1 , and {2,6-bis-[(di- tert -butyl-phosphan-yl)-oxy]-4-hy-droxy-phen-yl}chlorido-platinum(II), [Pt(C 22 H 39 O 3 P 2 )Cl], 2 , the metal centres are coordinated in a distorted square-planar fashion by the POCOP pincer fragment and the chloride ligand. Both complexes form strong hydrogen-bonded chain structures through an inter-action of the OH group in the 4-position of the aromatic POCOP backbone with the halide ligand.

The synthesis of an unusual 1-metalla-2,3-cyclobutadiene complex [ rac -(ebthi)Ti(Me 3 SiC 3 SiMe 3 )] ( rac -ebthi = rac -1,2-ethylene-1,1'-bis(η 5 -tetrahydroindenyl)), a formal metallacyclic analogue of a non-existent four-membered 1,2-cyclobutadiene, is described. By variation of the cyclopentadienyl ligand of the titanocene precursor it was possible to stabilise this highly exotic compound which selectively reacts with ketones and aldehydes to yield enynes by oxygen transfer to titanium. Analysis of the bonding and electronic structure of the metallacycle shows that the complex is best described as an unusual antiferromagnetically coupled biradicaloid system, possessing a formal Ti(iii) centre coordinated with a monoanionic radical ligand.

The dinuclear zirconocene chloride complex 1 is a highly active precatalyst for the dehydropolymerisation of methylamine borane. Comparison with mononuclear Zr chlorides and related dinuclear complexes suggests that the nature of the bridging motif is essential for the unique reactivity of 1.

Rhodium(iii) thiophosphinito pincer hydrido complexes were synthesised by C-H activation under exceptionally mild conditions at room temperature without additional base or irradiation and fully characterised by multinuclear NMR spectroscopy and X-ray crystallography. C-H activation under these mild conditions contrasts with the reactivity of related systems with POCOP ligands.

The reaction of the allene precursor Li 2 (Me 3 SiC 3 SiMe 3 ) with [Cp 2 ZrCl 2 ] (Cp=cyclopentadienyl) was examined. The selective formation of hitherto unknown linear, allene-bridged dizirconocene complexes [(Cp 2 ZrCl) 2 {-μ-(Me 3 Si)C 3 (SiMe 3 )-}] and [(Cp 2 Zr) 2 {-μ-(Me 3 Si)C 3 (SiMe 3 )-} 2 ] was observed. Upon σ coordination of the allenediyl unit to {Cp 2 Zr}, pyrophoric Li 2 (Me 3 SiC 3 SiMe 3 ) is tamed stepwise to yield a surprisingly robust 1,5-dizirconacyclooctatetra-2,3,6,7-ene with cumulated double bonds. This complex is unexpectedly inert against moisture, air, water and acetone. Surprisingly, it degrades under MS conditions to give the highly strained 1-zirconacyclobuta-2,3-diene. All compounds isolated have been fully characterised and the molecular structures are discussed. The stability and reactivity of these complexes are rationalised by DFT computations., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The crystal structure of the title zwitterionic zirconocene complex containing a furan-one unit, [AlZr(C 10 H 15 ) 2 (C 4 H 9 ) 3 (C 9 H 18 O 2 Si 2 )], is reported. On reacting a zircona-furan-one with two equivalents of HAl( i -Bu) 2 , disproportionation of the Lewis acid results in the formation of a triiso-butyl-aluminium fragment, Al( i -Bu) 3 , which coordinates to the exocyclic carbonyl O atom of the zircona-furan-one ring. Single-crystal X-ray diffraction reveals that the zircona-furan-one ring remains intact with coordination of the aluminium to the exocyclic O atom. One of the i -butyl groups is disordered over two sets of sites, with an occupancy ratio of 0.731 (3):0.269 (3).

The synthesis and crystal structure of the multidentate PPN ligand 2-[bis(diisopropylphosphanyl)methyl]-6-methylpyridine (L), C 19 H 35 NP 2 , are described. In the isostructural tetrahedral Fe and Co complexes of type LMCl 2 (M = Fe, Co), namely {2-[bis(diisopropylphosphanyl)methyl]-6-methylpyridine-κ 2 P,N}dichloridoiron(II), [FeCl 2 (C 19 H 35 NP 2 )], and {2-[bis(diisopropylphosphanyl)methyl]-6-methylpyridine-κ 2 P,N}dichloridocobalt(II), [CoCl 2 (C 19 H 35 NP 2 )], the ligand adopts a bidentate P,N-coordination, whereas in the case of the octahedral Mn complex {2-[bis(diisopropylphosphanyl)methyl]-6-methylpyridine-κ 2 P,P'}bromidotricarbonylmanganese(I), [MnBr(C 19 H 35 NP 2 )(CO) 3 ], the ligand coordinates via both P atoms to the metal centre.

Coordination of the alkyl-substituted alkynes Me 3 SiC 2 CH 2 R (1: R=SiMe 3 ; 2: R=N(SiMe 3 ) 2 ) to titanocene centres [Cp' 2 Ti] (Cp'=Cp, Cp*) yields stable alkyne complexes of the type Cp' 2 Ti(η 2 -Me 3 SiC 2 CH 2 R) (3: Cp'=Cp, R=SiMe 3 ; 5: Cp'=Cp, R=N(SiMe 3 ) 2 ; 6: Cp'=Cp*, R=SiMe 3 ) that are not prone to alkyne/allene isomerisation. When reacting alkyne 2 with Cp * 2 TiCl 2 and Mg formation of the complex Cp* 2 Ti(III)(η 3 -Me 3 SiC 2 CH 2 ) (7) which displays a propargylic unit coordinated to the Ti III centre takes place. All complexes were fully characterised, the molecular structures for 5, 6, and 7 are discussed., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A mixed decamethyltitanocene(III) isonitrile alkynyl complex (7) was synthesized by the sequential introduction of the isonitrile and alkynyl ligands. Direct synthesis results in the formation of the diamagnetic decamethyltitanocene bis(isonitrile) (2) and bis(alkynyl) (3) complexes. Compound 7 undergoes disproportionation at room temperature to give 2 and 3. All complexes were fully characterized by IR, NMR, and EPR spectroscopy, and mass spectrometry. Molecular structures for complexes 2 and 7 are reported. The stability and reactivity of these complexes are rationalized by DFT computations., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The complex [(PNHP)Fe(H)(CO)(HBH 3 )] (PNHP = HN(CH 2 CH 2 Pi-Pr 2 ) 2 ) serves as a catalyst precursor for the selective dehydrocoupling of methylamine borane at room temperature, tentatively via an off-metal polymerisation pathway.

The synthesis of 3,5-disubstituted cyclometalated iridium(iii) hydrido complexes of the type [3,5-R 2 (POCOP)IrHX] (3,5-R 2 (POCOP) = κ 3 -C 5 HR 2 -2,6-(OPtBu 2 ) 2 with R = t-Bu, COOMe; X = Cl, H) is described. All complexes were investigated in the catalytic dehydrogenation of hydrazine borane and compared with the unsubstituted compounds [(POCOP)IrHX] (X = Cl, H). All catalysts are highly active and recyclable, clearly maintaining hydrogen production activity. The dehydrogenation products were structurally characterised by solid state NMR and FTIR spectroscopy. Experimental observations were complemented by a dispersion-corrected DFT study to rationalise the mechanism of hydrazine borane dehydrogenation.

The crystal structures of two ansa -titanocene tri-fluoro-methane-sulfonate complexes bearing the Me 2 Si(C 5 Me 4 ) 2 ligand are reported, namely [di-methylbis-(η 5 -tetra-methyl-cyclo-penta-dien-yl)silane](tri-fluoro-methane-sulfonato-κ 2 O , O ')titanium(III) toluene monosolvate, [Ti(CF 3 O 3 S)(C 20 H 30 Si)]·C 7 H 8 , 1 , and chlorido-[di-methyl-bis-(η 5 -tetra-methyl-cyclo-penta-dien-yl)silane](tri-fluoro-methane-sulfonato-κ O )titanium(IV), [Ti(CF 3 O 3 S)(C 20 H 30 Si)Cl], 2 . Both complexes display a bent metallocene unit, the metal atom being coordinated in a distorted tetra-hedral geometry, with the tri-fluoro-methane-sulfonate anion acting as a bidentate or monodentate ligand in 1 and 2 , respectively. In 1 , weak π-π stacking inter-actions involving the toluene solvent mol-ecules [centroid-to-centroid distance = 3.9491 (11) Å] are observed.

A series of ansa-titanocene triflate complexes are described as model compounds for the elementary steps of light-driven overall water splitting. Titanocene(III) triflate complexes are readily obtained by reaction of a titanocene source with Yb(OTf)3. Subsequent reactions with water and with/without TEMPO as hydrogen scavenger are studied. The as-obtained titanocene(IV) compounds can be photoreduced to give titanocene(III) triflate complexes, which can undergo further hydrolysis to form a closed catalytic cycle of water splitting. No further degradation of the photoreduced species was observed because of the presence of the OTf group. The stability of the system was evaluated in an experiment with high concentrations of water and TEMPO. X-ray crystallography on all titanocene complexes, EPR and NMR spectroscopy, and DFT were used to support our observations.

In the cation of the title salt, C9H20NO(+)·CF3O3S(-), the six-membered heterocyclic ring displays a chair conformation. In the crystal, centrosymmetric pairs of cations and anions are linked by N-H⋯O and O-H⋯O hydrogen bonds to form rings with a R 4 (4)(14) graph-set motif.

The mol-ecular structure of the title compound, C22H38Si2, features a trans arrangement of the cyclo-penta-dienyl rings to avoid steric strain [C-Si-Si-C torsion angle = -179.0 (5)°]. The Si-Si bond length is 2.3444 (4) Å. The most notable inter-molecular inter-actions in the mol-ecular packing are C-H⋯π contacts that lead to the formation of wave-like supra-molecular chains along the b axis.

A study of visible-light-driven hydrogen production using a multicomponent system consisting of different boron dipyrromethene (BODIPY) dyes, triethylamine and [{Pd(PPh3)Cl2}2] from THF/water mixtures is presented. A trio of meso-mesityl BODIPY dyes display the best activities and long-term stabilities of more than ten days with the 2,6-diiodo derivative showing the best performance., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The association constants and enthalpies for the binding of hydrogen bond donors to group 10 transition metal complexes featuring a single fluoride ligand (trans-[Ni(F)(2-C5NF4)(PR3)2], R = Et 1a, Cy 1b, trans-[Pd(F)(4-C5NF4)(PCy3)2] 2, trans-[Pt(F){2-C5NF2H(CF3)}(PCy3)2] 3 and of group 4 difluorides (Cp2MF2, M = Ti 4a, Zr 5a, Hf 6a; Cp*2MF2, M = Ti 4b, Zr 5b, Hf 6b) are reported. These measurements allow placement of these fluoride ligands on the scales of organic H-bond acceptor strength. The H-bond acceptor capability β (Hunter scale) for the group 10 metal fluorides is far greater (1a 12.1, 1b 9.7, 2 11.6, 3 11.0) than that for group 4 metal fluorides (4a 5.8, 5a 4.7, 6a 4.7, 4b 6.9, 5b 5.6, 6b 5.4), demonstrating that the group 10 fluorides are comparable to the strongest organic H-bond acceptors, such as Me3NO, whereas group 4 fluorides fall in the same range as N-bases aniline through pyridine. Additionally, the measurement of the binding enthalpy of 4-fluorophenol to 1a in carbon tetrachloride (-23.5 ± 0.3 kJ mol(-1)) interlocks our study with Laurence's scale of H-bond basicity of organic molecules. The much greater polarity of group 10 metal fluorides than that of the group 4 metal fluorides is consistent with the importance of pπ-dπ bonding in the latter. The polarity of the group 10 metal fluorides indicates their potential as building blocks for hydrogen-bonded assemblies. The synthesis of trans-[Ni(F){2-C5NF3(NH2)}(PEt3)2], which exhibits an extended chain structure assembled by hydrogen bonds between the amine and metal-fluoride groups, confirms this hypothesis.

A study of the dehydrogenation of dimethylamine borane using different titanocene(III) complexes with 2-phosphinoaryloxide ligands is presented. Complexes Cp2Ti(κ(2)-O, P-O-C6H4-PR2) (3a: R = i-Pr, 3b: R = Ph) (Cp = η(5)-cyclopentadienyl) and Cp*2Ti(κ(1)-O-O-C6H4-PR2) (5a: R = i-Pr, 5b: R = Ph) (Cp* = η(5)-pentamethylcyclopentadienyl) were prepared by reactions of the 2-phosphinophenol ligand with different titanocene sources and fully characterised. Their catalytic activity depends on the steric influence of the cyclopentadienyl ligand, the coordination mode of the 2-phosphinoaryloxide ligand and on the used solvent. Complex 3a showed a turnover number of 43.2 in the neat substrate after 24 hours. EPR investigations were used to elucidate the fate of the Ti(III) catalyst.

Nanocomposites based on molybdenum disulfide (MoS2 ) and different carbon modifications are intensively investigated in several areas of applications due to their intriguing optical and electrical properties. Addition of a third element may enhance the functionality and application areas of such nanocomposites. Herein, we present a facile synthetic approach based on directed thermal decomposition of (Ph4 P)2 MoS4 generating MoS2 nanocomposites containing carbon and phosphorous. Decomposition at 250 °C yields a composite material with significantly enlarged MoS2 interlayer distances caused by in situ formation of Ph3 PS bonded to the MoS2 slabs through MoS bonds and (Ph4 P)2 S molecules in the van der Waals gap, as was evidenced by (31) P solid-state NMR spectroscopy. Visible-light-driven hydrogen generation demonstrates a high catalytic performance of the materials., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Irradiation of a substituted ansa-titanocene(IV) dihydroxido complex with visible light induces Ti-O bond dissociation. In contrast to previous studies on structurally similar unbridged complexes, no side reactions are observed and formation of the Ti(III) species is highly selective. The formation of OH radicals was proved using a biradicaloid species.

The asymmetric unit of the title compound, [Co(C24H30N2P2)(CO)3][Co(CO)4]·0.25C7H8, consists of two crystallographically independent cations with similar conformations, two anions, and one-half of a toluene mol-ecule disordered about an inversion centre. In the cations, a Co/P/N/P four-membered slightly bent metallacycle is the key structural element. The pendant NH group is not coordinated to the Co(I) atom, which displays a distorted trigonal-bipyramidal coordination geometry. Weak inter-ionic hydrogen bonds are observed between the NH groups and a carbonyl group of the tetrahedral [Co(CO)4](-) anions.

A detailed mechanism of hydrogen production by reduction of water with decamethyltitanocene triflate [Cp*2 Ti(III) (OTf)] has been derived for the first time, based on a comprehensive in situ spectroscopic study including EPR and ATR-FTIR spectroscopy supported by DFT calculations. It is demonstrated that two H2 O molecules coordinate to [Cp*2 Ti(III) (OTf)] subsequently forming [Cp2 *Ti(III) (H2 O)(OTf)] and [Cp*Ti(III) (H2 O)2 (OTf)]. Triflate stabilizes the water ligands by hydrogen bonding. Liberation of hydrogen proceeds only from the diaqua complex [Cp*Ti(III) (H2 O)2 (OTf)] and involves, most probably, abstraction and recombination of two H atoms from two molecules of [Cp*Ti(III) (H2 O)2 (OTf)] in close vicinity, which is driven by the formation of a strong covalent TiOH bond in the resulting final product [Cp*2 Ti(IV) (OTf)(OH)]., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A study of the full dehydrogenation of hydrazine borane (H2N-NH2·BH3) to give H2 and N2 as gaseous products catalysed by a variety of group 4 metallocene alkyne complexes of the type CpM(L)(η(2)-Me3SiC2SiMe3) (Cp' = substituted or unsubstituted η(5)-cyclopentadienyl; M = Ti, no L; M = Zr, L = pyridine) and group 4 metallocene hydrides is presented. Volumetric data show that the amount of hydrogen released is strongly dependent on both, the metal and the cyclopentadienyl ligand.

The title compound, [Ti(C5H5)2(C9H11F12NO4P2)], is a four-membered titanacycle obtained from the reaction of Cp2Ti(η(2)-Me3SiC2SiMe3) and CH3N[P(OCH2CF3)2]2 {N,N-bis-[bis-(tri-fluoro-eth-oxy)phosphan-yl]methyl-amine, tfepma}. The Ti(II) atom is coordinated by two cyclo-penta-dienyl (Cp) ligands and the chelating tfepma ligand in a strongly distorted tetra-hedral geometry. The mol-ecule is located on a mirror plane.

The synthesis of a series of ansa-titanocene dichlorides [Cp'2TiCl2] (Cp' = bridged η(5)-tetramethylcyclopentadienyl) and the corresponding titanocene bis(trimethylsilyl)acetylene complexes [Cp'2Ti(η(2)-Me3SiC2SiMe3)] is described. The ethanediyl-bridged complexes [C2H4(C5Me4)2TiCl2] (2-Cl2) and [C2H4(C5Me4)2Ti(η(2)-Me3SiC2SiMe3)] (2-btmsa; btmsa = η(2)-Me3SiC2SiMe3) can be obtained from the hitherto unknown calcocenophane complex [C2H4(C5Me4)2Ca(THF)2] (1). Furthermore, a heterodiatomic bridging unit containing both, a dimethylsilyl and a methylene group was introduced to yield the ansa-titanocene dichloride [Me2SiCH2(C5Me4)2TiCl2] (3-Cl2) and the bis(trimethylsilyl)acetylene complex [Me2SiCH2(C5Me4)2Ti(η(2)-Me3SiC2SiMe3)] (3-btmsa). Besides, tetramethyldisilyl- and dimethylsilyl-bridged metallocene complexes (structural motif 4 and 5, respectively) were prepared. All ansa-titanocene alkyne complexes were reacted with stoichiometric amounts of water; the hydrolysis products were isolated as model complexes for the investigation of the elemental steps of overall water splitting. Compounds 1, 2-btmsa, 2-(OH)2, 3-Cl2, 3-btmsa, 4-(OH)2, 3-alkenyl and 5-alkenyl were characterised by X-ray diffraction analysis., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Carbon containing nano-sized molybdenum sulfide composites (MoS(x)C(y)) obtained by thermal decomposition reactions of (R(4)N)(2)MoS(4) (R = -H (C(0)), -CH(3) (C(1)), -C(3)H(7) (C(3)), and -C(6)H(13) (C(6))) show promising performance in visible-light driven photocatalytic hydrogen generation.