Support Engineering for the Stabilisation of Heterogeneous Pd3 P-Based Catalysts for Heck Coupling Reactions.

Herein we report the use of a supported Pd3 P catalyst for Heck coupling reactions. For the stabilisation of Pd3 P and Pd, as reference system, the silica support material was modified via phosphorus doping (0.5 and 1 wt % P). Through this so-called support engineering approach, the catalytic activity of Pd3 P was clearly enhanced. Whereas an iodobenzene conversion of 79 % was witnessed for Pd3 P@SiO2 in the coupling of styrene and iodobenzene in 1 h, 90 % conversion could be achieved using Pd3 P@1P-SiO2 . This improved catalytic activity probably stems from an electronic modulation of the support surface via the introduction of phosphorus. Simultaneously, the recyclability was boosted and the Pd3 P@1P-SiO2 catalyst has shown to maintain its catalytic activity over several recovery tests. Hereby, metal leaching could almost be suppressed completely to 3 % by the use of a P-modified silica support.

Acute Bite Angle POP- and PSP-Type Ligands and Their Trinuclear Copper(I) Complexes: Synthesis and Photo-Luminescence Properties.

In the current work, the rational synthesis of trinuclear copper complexes, incorporating acute bite angle POP- and PSP-type ligands, is reported. The in situ formation of POP (Ph2P-O-PPh2) or PSP (Ph2P-S-PPh2) ligands in the presence of a copper(I) precursor gave access to various trinuclear copper complexes of the form [Cu3(µ3-Hal)2(µ-PXP)3]PF6 [X = O; Hal = Cl (1), Br (2), I (3) and X = S; Hal = Cl (5), Br (6), I (7)]. Related iodide-containing complexes and clusters, such as [Cu4(µ3-I)4(Ph2PI)4] (4) and [Cu3(µ3-I)2(µ-I)(µ-PSP)2] (8), could also be obtained via the variation of the reaction stoichiometry. The investigation of the photo-optical properties by photo-luminescence spectroscopy has demonstrated that the phosphorescence in the visible region can be switched off through the mere change of the heteroatom in the ligand backbone (POP vs PSP ligand scaffold). Theoretical studies have been conducted to complement the experimental photo-optical data with detailed insights into the occurring electronic transitions. Consequently, this systematic study paves the way for tuning the photo-optical properties of transition metal complexes in a more rational way.

A Supported Palladium Phosphide Catalyst for the Wacker-Tsuji-Oxidation of Styrene.

The substitution of pure metal particles by metal phosphides in catalysis represents a promising opportunity to lower the required metal quantity in the context of a sustainable use of metal resources. Herein we show the synthesis of palladium phosphide, Pd3 P, supported on silica, which is tested as catalyst for the Wacker-Tsuji-oxidation of styrene to acetophenone. The synthesized catalyst is characterized by PXRD, SEM-EDX, FTIR, ICP-AES and XPS measurements. Four different reaction systems are investigated in this study including different co-catalysts and reaction media. Conversions of styrene up to 95 % with a selectivity of 73 % towards acetophenone are observed using Pd3 P/SiO2 as catalyst, CuCl2 as co-catalyst and O2 as oxidant. An enhanced selectivity up to 100 % towards acetophenone is obtained in other reaction systems. The use of Pd3 P/SiO2 leads to an optimized selectivity and conversion in the oxidation reaction in comparison with the purely Pd-based system Pd/SiO2 . These results give an insight on how the incorporation of phosphorus has a great effect on the performance of heterogeneous catalysts.

How Research Data Management Plans Can Help in Harmonizing Open Science and Approaches in the Digital Economy.

Within this perspective article, we intend to summarise definitions and terms that are often used in the context of open science and data-driven R&D and we discuss upcoming European regulations concerning data, data sharing and handling. With this background in hand, we take a closer look at the potential connections and permeable interfaces of open science and digital economy, in which data and resulting immaterial goods can become vital pieces as tradeable items. We believe that both science and the digital economy can profit from a seamless transition and foresee that the scientific outcomes of publicly funded research can be better exploited. To close the gap between open science and the digital economy, and to serve for a balancing of the interests of data producers, data consumers, and an economy around services and the public, we introduce the concept of generic research data management plans (RDMs), which have in part been developed through a community effort and which have been evaluated by academic and industry members of the NFDI4Cat consortium. We are of the opinion that in data-driven research, RDMs do need to become a vital element in publicly funded projects.

Transition metal complexes of the PPO/POP ligand: variable coordination chemistry and photo-luminescence properties.

In the current work the tautomeric equilibrium between tetraphenyldiphosphoxane (Ph2P-O-PPh2, POP) and tetraphenyldiphosphine monoxide (Ph2P-P(O)Ph2, PPO) in the absence and presence of transition metal precursors is investigated. Whereas with hard transition metal ions, such as Fe(II) and Y(III), PPO-type complexes, such as [FeCl2(PPO)2] (1) and [YCl3(THF)2(PPO)] (2), are formed, softer transition metals ions tend to form so-called coordination stabilised tautomers of the POP ligand form, such as [Cu2(MeCN)3(µ2-POP)2](PF6)2 (3), [Au2Cl2(µ2-POP)] (4), and [Au2(µ2-POP)2](OTf)2 (5). The photo-optical properties of the PPO- and POP-type transition metal complexes are investigated experimentally using photo-luminescence spectroscopy, whereby the presence of metallophillic interactions was found to play a crucial role. The dinuclear copper complex [Cu2(MeCN)3(µ2-POP)2](PF6)2 (3) shows a very interesting thermochromic behavior and intense photo-luminescence with remarkable phosphoresence lifetimes at 77 K, which can probably be attributed to short intramolecular Cu-Cu distances.

Synthesis and coordination behaviour of aluminate-based quinolyl ligands.

The effects of moving the donor N-atom from the 2-position in lithium (2-pyridyl)- and (2-quinolyl)aluminates to the more remote position in (8-quinolyl)aluminates have been investigated by solid-state structural and DFT computational studies of the new complexes [{EtAl(2-qy)3}Li(µ-X)Li(THF)3] (X = Cl/Br 62 : 38) [(1)Li(µ-X)Li(THF)3], [{(EtAl(2-qy)3)Li}2(µ-Br)]-Li(THF)4+ [{1Li}2(µ-Br)]-Li(THF)4+, [{EtAl(2-Me-8-qy)3}Li] [(2)Li], [{Me2Al(2-Me-8-qy)2}Li(THF)] [(3a)Li(THF)], [{Me2Al(6-Me-2-py)2}Li(THF)2] [(4)Li(THF)2] and [{{EtAl(2-Me-8-qy)2}2O}(Li2THF)] (5). Increasing the remoteness of the donor N-atom from the bridgehead results in large differences in the coordination of the Li+ cations by the (8-quinolyl)aluminate anions compared to 2-quinolyl or 2-pyridyl counterparts. The results are of potential interest in understanding how the coordination sites of ligands of this type can be tuned for the coordination requirements of specific metal centres.

Facile synthesis of a nickel(0) phosphine complex at ambient temperature.

The reaction of the bis(methoxy)-2-pyridyl-phosphine (MeO)2P(2-py) (1) with [Ni(MeCN)6](BF4)2 leads to the unexpected single-step reduction of NiII and the formation of a tetrahedral nickel(0) complex [{(MeO)2P(2-py-H)}2{(MeO)2P(2-py)}2Ni](BF4)2 (2). The redox activity is probably induced by the decomposition of the tetrafluoroborate anion; NMR spectroscopic studies point towards a fluoride-assisted oxidation of the 2-pyridyl-phosphine ligand, with associated reduction of the metal.

An experimental and theoretical study of the coordination and donor properties of tris-2-pyridyl-phosphine ligands.

The coordination characteristics and donor/acceptor properties of a series of 2-pyridyl substituted phosphine ligands have been investigated using structural, spectroscopic and DFT calculational studies. A range of different coordination modes are observed in Mo and W carbonyl complexes of tris-2-pyridyl-phosphine ligands of the type P(2-py') (2-py' = substituted or unsubstituted 2-pyridyl group), including an unprecedented example exhibiting N,N',µ2-π coordination. DFT calculations were used to assess the relative donor/acceptor properties of a range of related 2-pyridyl-phosphine ligands with respect to PPh3 and PtBu3.

Unusual Racemization of Tertiary P-Chiral Ferrocenyl Phosphines.

Tertiary phosphines are generally known to withstand inversion under moderate conditions. In this work, a remarkable racemization process of three P-chiral ferrocenyl phosphines is reported. Subjected to conventional column chromatography as highly enantioenriched compounds, they greatly experienced racemization when collected at the column outlet within minutes. Initially, attention was drawn to this unusual inversion behavior after observing that the superb enantiomeric excess of these ligands (>95 % ee in all cases) was almost lost in their corresponding ruthenium(II) complexes. Successively excluding possible racemization causes, these P-chiral ferrocenyl phosphines were found to undergo a significant, acid-catalyzed racemization process at room temperature within a few minutes. This process is mainly observed during standard column chromatography by using conventional silica or alumina, but can also be triggered deliberately by addition of certain acids. Therefore, the stereochemical preservation of P-chiral phosphines during their purification may per se not always be guaranteed, since column chromatography is the most frequently used technique for purifying such types of compounds.

Facile Arene Ligand Exchange in p-Cymene Ruthenium(II) Complexes of Tertiary P-Chiral Ferrocenyl Phosphines.

Half-sandwich arene-metal complexes are commonly used for specific applications. Herein, we report facile arene ligand exchange reactions of two ruthenium(II) complexes of tertiary P-stereogenic ferrocenyl phosphines. By mild photochemical activation, the displacement of p-cymene and subsequent tethering by η6-coordination of the terminal phenyl ring of a biphenylyl-substituted ferrocenyl phosphine were enabled. Furthermore, the spontaneous p-cymene displacement in a 2-methoxyphenyl-containing ferrocenyl phosphine and ensuing coordination of the ligand as a P,O chelate were examined. For both reactions, theoretical calculations of the general course of the reaction confirmed the experimental findings. The ease of the controlled arene displacement reported here can offer new pathways for the synthesis and design of novel tailor-made catalysts.

Regioselective 1,4-hydroboration of pyridines catalyzed by an acid-initiated boronium cation.

The reaction of the commercially available ammonium salt NH4BPh4 with a pyridine-activated pinacolborane species generates a boronium cation that facilitates the 1,4-selective hydroboration of pyridines in polar solvents. This catalytic reaction is amenable to a host of reactive functional groups and provides access to sterically bulky hydroboration products, previously inaccessible by metal-free routes. Further, the regioselectivity of this reaction can be altered by reducing the polarity of the reaction solvent, resulting in greater proportions of the 1,2-hydroboration product.

A non-chiral lithium aluminate reagent for the determination of enantiomeric excess of chiral alcohols.

Here we illustrate a new method for the rapid determination of ee's of chiral alcohols using the thermally-stable, non-chiral lithium aluminate reagent [EtAl(6-Me-2-py)3Li] (1). In situ reaction of the alcohols with 1 produces robust dimers in solution, present as diastereomeric pairs (SS/RR and RS) with distinct resonances in their 1H and 7Li NMR spectra. The ee can be calculated simply from integration of the 1H and/or 7Li NMR spectra.

The influence of halides in polyoxotitanate cages; dipole moment, splitting and expansion of d-orbitals and electron-electron repulsion.

Metal-doped polyoxotitanate (M-POT) cages have been shown to be efficient single-source precursors to metal-doped titania [TiO2(M)] (state-of-the-art photocatalytic materials) as well as molecular models for the behaviour of dopant metal ions in bulk titania. Here we report the influence halide ions have on the optical and electronic properties of a series of halide-only, and cobalt halide-'doped' POT cages. In this combined experimental and computational study we show that halide ions can have several effects on the band gaps of halide-containing POT cages, influencing the dipole moment (hole-electron separation) and the structure of the valance band edge. Overall, the band gap behaviour stems from the effects of increasing orbital energy moving from F to I down Group 17, as well as crystal-field splitting of the d-orbitals, the potential effects of the Nephelauxetic influence of the halides and electron-electron repulsion.

Sterically-constrained tripodal phosphorus-bridged tris-pyridyl ligands.

Introducing substituents into the 6-position of the 2-pyridyl rings of neutral tris-pyridyl phosphanes of the type P(2-py')3 (where 2-py' is a substituted 2-pyridyl ring), has a marked impact on their coordination of transition metal ions, as revealed in the current study. Whereas the unsubstituted phosphorus-bridged tris-pyridyl ligand P(2-py)3 (1) forms the sandwich cation [{P(py)3}2Fe](2+) (4) with iron(II), coordinating via all of the donor nitrogen atoms, the reaction of the methyl-substituted counterpart P(6-Me-2-py)3 (2) and FeCl2 results in the half-sandwich arrangement [{P(6-Me-2-py)3}FeCl2]·toluene (5·toluene), in which only two N-atoms of the ligand coordinate to the metal. A similar half-sandwich type complex, [{P(6-Me-2-py)3}FeCl(OTf)]·2THF (6·2THF), is obtained from reaction of 2 with Fe(OTf)2 in the presence of LiCl, only now with all three of the N-atoms of the ligand coordinated to Fe(II). The formation of a half-rather than full-sandwich complex 2 with suggests that steric clashing of the Me groups prevents the formation of sandwich-type arrangements. The reaction of [Cu(MeCN)4]PF6 with P(6-Me-2-py) (2) gives the complex [(MeCN)3Cu{P(6-Me-2-py)3}Cu(MeCN)](PF6)2 (7), in which two Cu(I) atoms are coordinated by the bridgehead P-atom and by the three N-atoms of the tris-pyridyl ligand (a unique coordination mode in this area). Overall, the results indicate that 6-Me substitution results in a promising 6-electron capping ligand for organometallic synthesis and catalysis.