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Precise cell elimination within intricate cellular populations is hampered by issues arising from the multifaceted biological properties of cells and the expansive reactivity of chemical agents. Current chemical platforms are often limited by their complexity, toxicity, and poor physical/chemical properties. Here, we report on the synthesis of a structurally versatile library of chemically tunable bisacylphosphane oxides (BAPOs), which harnesses the spatiotemporal precision of light delivery, thereby establishing a universal strategy for on-demand, precise cellular ablation in vitro and in vivo .

Reflecting on Giacomo Ciamician's revolutionary vision of harnessing sunlight to drive photochemical transformations, the field of materials science has evolved significantly, yet it has been constrained by the misconception that the highest reactivity in photochemical systems is achieved at the absorption maxima. Here, we explore this notion further with evidence from photochemical action plots, demonstrating that reactivity can indeed be maximal at wavelengths significantly separated from the absorption peak. By examining the implications of the disparity between absorptivity and photochemical reactivitiy, we explore its impact for the enhanced penetration depth of light in photoresists, the reduction of energy requirements for photochemical reactions, and its transformative potential for volumetric 3D printing. Ultimately, we argue for a renewed appreciation of light's capability to facilitate photochemical reactions across the entire volume of a material.

This report presents a selective synthetic approach towards borazine from ammonia borane using a dinuclear rhodium olefin homogeneous catalyst. The synthesis and spectroscopic characterization of a dirhodium ammonia borane complex as an intermediate provides insight into a possible mode of activation.

A carbon-rich molecule is synthesized, which mainly contains conjugated sp 2 and sp hybridized carbon centers. Alkenyl and alkynyl binding sites are arranged such that this compound serves as ligand to a binuclear metal unit with a Rh I ─Rh I bond. Furthermore, CH units are placed in proximity to the metal centers. The dicationic complex [Rh 2 (bipy) 2 {Ph 2 Ptrop (C≡CCy)2 }] 2+ (OTf - ) 2 allows to study possible responses of the carbon-framework to redox reactions as well as deprotonation reactions. All products are, whenever possible, characterized by X-ray diffraction (XRD) methods, NMR and EPR spectroscopy as well as electrochemical methods. It is shown that the carbon skeleton of the ligand framework undergoes C─C bond rearrangement reactions of remarkable diversity. In combination with DFT (density functional theory) studies, these results allow to gain insight into the electronic structure changes caused by metal sites in a carbon-rich environment, which may be of relevance for the properties of metal particles on carbon support materials when they are exposed to hydrogen, electrons, or protons., (© 2024 The Authors. Advanced Science published by Wiley‐VCH GmbH.)

A tridentate ligand L with a P,NH,N donor motif was synthesized in few steps from commercially available precursors. Upon reaction with [MnBr(CO) 5 ], an octahedral 18-electron complex [Mn(CO) 3 (L)]Br (1) is obtained in which L adopts a facial arrangement. After deprotonation of the NH group in the cationic complex unit, a neutral Mn(I) amido complex [Mn(CO) 2 (L-H)] (2) is formed under loss of CO. Rearrangement of L-H leads to a trigonal bipyramidal structure in which the P and N donor centers are in trans position. Further deprotonation of 2 results in a dep-blue anionic complex fragment [Mn(CO) 2 (L-2H)] - (3). DFT calculations and a QTAIM analysis show that the amido complex 2 contains a Mn-N bond with partial double bond character and 3 an aromatic MnN 2 C 2 ring. The anion [Mn(CO) 2 (L-2H)] - reacts with Ph 2 PH to give a phosphido complex, which serves as phosphide transfer reagent to activated olefins. But the catalytic activity is low. However, the neutral amido complex 2 is an excellent catalyst and with loadings as low as 0.04 mol %, turn over frequencies of >40'000 h -1 can be achieved. Furthermore, secondary and primary alkyl phosphines as well as PH 3 can be added in a catalytic hydrophosphination reaction to a wide range of activated olefins such as α,β-unsaturated aldehydes, ketones, esters, and nitriles. But also, vinyl pyridine and some styrene derivatives are converted into the corresponding phosphanes., (© 2024 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Stereodefined vinylboron compounds are important organic synthons. The synthesis of E-1-vinylboron compounds typically involves the addition of a B-H bond to terminal alkynes. The selective generation of the thermodynamically unfavorable Z-isomers remains challenging, necessitating improved methods. Here, such a proficient and cost-effective catalytic system is introduced, comprising a cobalt salt and a readily accessible air-stable CNC pincer ligand. This system enables the transformation of terminal alkynes, even in the presence of bulky substituents, with excellent Z-selectivity. High turnover numbers (>1,600) and turnover frequencies (>132,000 h -1 ) are achieved at room temperature, and the reaction can be scaled up to 30 mmol smoothly. Kinetic studies reveal a formal second-order dependence on cobalt concentration. Mechanistic investigations indicate that the alkynes exhibit a higher affinity for the catalyst than the alkene products, resulting in exceptional Z-selective performance. Furthermore, a rare time-dependent stereoselectivity is observed, allowing for quantitative conversion of Z-vinylboronate esters to the E-isomers., (© 2024. The Author(s).)

Distonic radical cations (DRCs) with spatially separated charge and radical sites are expected to show both radical and cationic reactivity at different sites within one molecule. However, such "dual" reactivity has rarely been observed in the condensed phase. Herein we report the isolation of crystalline 1λ 2 ,3λ 2 -1-phosphonia-3-phosphinyl-cyclohex-4-enes 2a,b˙ + , which can be considered delocalized DRCs and were completely characterized by crystallographic, spectroscopic, and computational methods. These DRCs contain a radical and cationic site with seven and six valence electrons, respectively, which are both stabilized via conjugation, yet remain spatially separated. They exhibit reactivity that differs from that of conventional radical cations (CRCs); specifically they show sequential radical and cationic reactivity at separated sites within one molecule in solution., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Dehydrogenation of ammonia borane to well-defined products is an important but challenging reaction. A dinuclear ruthenium complex with a Ru-Ru bond bearing a diazadiene (dad) unit and olefins as non-innocent ligands catalyzes the highly selective formation of conjugated polycondensed borazine oligomers (B x N x H y ), predominantly B 21 N 21 H 18 , the BN analogue of superbenzene.

Herein, we present a convenient synthesis for symmetrical and mixed substituted tris(acyl)phosphines (TAPs) starting from red phosphorus. All TAPs exhibit a phosphaalkene-acylphosphine equilibrium, which was investigated in detail by variable-temperature (VT) NMR spectroscopy supported by density-functional theory (DFT) calculations. Depending on the substituents, two phosphaalkene derivatives and ten acylphosphine derivatives could be isolated. NMR spectroscopy and single-crystal X-ray crystallography enabled a clear structural assignment of these compounds. Oxidation of selected TAPs led to the formation of the corresponding tris(acyl)phosphine oxides (TAPOs). Furthermore, their spectroscopic properties as well as their photochemistry was investigated. Especially, the TAPO compounds were evaluated for their suitability as photoinitiators by CIDNP spectroscopy, photobleaching measurements and by storage stability tests., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Invited for the cover of this issue are the groups of M. Haas, G. Gescheidt and H. Grützmacher from the Graz University of Technology and the ETH Zürich. The image depicts a phosphorus mine, where the workers are acid chlorides using their shovels and red phosphorus to provide the chemicals necessary to produce novel reagents. Read the full text of the article at 10.1002/chem.202302535., (© 2023 Wiley-VCH GmbH.)

E , Z -isomers display distinct physical properties and chemical reactivities. However, investigations on heavy main group elements remain limited. In this work, we present the isolation and X-ray crystallographic characterization of N-heterocyclic vinyl (NHV) substituted diphosphenes as both E - and Z -isomers (L[double bond, length as m-dash]CH-P[double bond, length as m-dash]P-CH[double bond, length as m-dash]L, E , Z -2b; L = N-heterocyclic carbene). E -2b is thermodynamically more stable and undergoes reversible photo-stimulated isomerization to Z -2b. The less stable Z -isomer Z -2b can be thermally reverted to E -2b. Theoretical studies support the view that this E ↔ Z isomerization proceeds via P[double bond, length as m-dash]P bond rotation, reminiscent of the isomerization observed in alkenes. Furthermore, both E , Z -2b coordinate to an AuCl fragment affording the complex [AuCl(η 2 - Z -2b)] with the diphosphene ligand in Z -conformation, exclusively. In contrast, E , Z -2b undergo [2 + 4] and [2 + 1] cycloadditions with dienes or diazo compounds, respectively, yielding identical cycloaddition products in which the phosphorus bound NHV groups are in trans -position to each other. DFT calculations provide insight into the E / Z -isomerisation and stereoselective formation of Au(i) complexes and cycloaddition products., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

We review the known chemistry of the cyaphide ion, (C≡P) - . This remarkable diatomic anion has been the subject of study since the late nineteenth century, however its isolation and characterization eluded chemists for almost a hundred years. In this mini-review, we explore the pioneering synthetic experiments that first allowed for its isolation, as well as more recent developments demonstrating that cyaphide transfer is viable in well-established salt-metathesis protocols. The physical properties of the cyaphide ion are also explored in depth, allowing us to compare and contrast the chemistry of this ion with that of its lighter congener cyanide (an archetypal strong field ligand and important organic functional group). Recent studies show that the cyaphide ion has the potential to be used as a versatile chemical regent for the synthesis of novel molecules and materials, hinting at many interesting future avenues of investigation., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

A N-hydroxy succinimide (NHS) ester substituted bis(acyl)phosphane oxide (ACTIVE-BAPO) was prepared by phospha-Michael addition and used for an easy one-step BAPO ligation with substrates containing primary amino groups, such as amino acids, proteins, and poly(amidoamine) (PAMAM) dendrimers. Thereby, a range of new molecular and polymeric photoinitators was obtained. Real-time photo-rheology experiments demonstrated the outstanding efficiency of the PAMAM BAPOs as photoinitiators for free radical polymerization. Remarkably, it is found that PAMAM BAPOs also act as crosslinking agents to convert monofunctional methacrylate monomers into thermosetting networks without any further additives. Depending on the number of the attached BAPOs, thermosets with a different degree of crosslinking and swelling capability in water were obtained., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Decomposition of the environmentally harmful gas nitrous oxide (N 2 O) is usually performed thermally or catalytically. Selective catalytic reduction (SCR) is currently the most promising technology for N 2 O mitigation, a multicomponent heterogeneous catalytic system that employs reducing agents such as ammonia, hydrogen, hydrocarbons, or a combination thereof. This study reports the first homogenous catalyst that performs the reduction of nitrous oxide employing readily available and cheap light alcohols such as methanol, ethanol or ethylene glycol derivatives. During the reaction, these alcohols are transformed in a dehydrogenative coupling reaction to carboxylate derivatives, while N 2 O is converted to N 2 and H 2 O, later entering the reaction as substrate. The reaction is catalysed by the low-valent dinuclear ruthenium complex [Ru 2 H(μ-H)(Me 2 dad)(dbcot) 2 ] that carries a diazabutadiene, Me 2 dad, and two rigid dienes, dbcot, as ligands. The reduction of nitrous oxide proceeds with low catalyst loadings under relatively mild conditions (65-80 °C, 1.4 bar N 2 O) achieving turnover numbers of up to 480 and turnover frequencies of up to 56 h -1 ., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Reaction of the imidazolium-stabilized diphosphete-diide IDP with trityl phosphaalkyne affords a mixture which contains the molecules 1 a and 1 b with a central C 3 P 3 core, which formally carries a two-fold negative charge. In order to avoid the formation of an antiaromatic 8π electron system within a conjugated dianionic six-membered [C 3 P 3 ] 2- ring, 1 a adopts a bicyclic [3.1.0] and 1 b a tricyclic [2.2.0.0] structure which are in a dynamic equilibrium. 1 a, b can be reversibly oxidized to a triphosphinine dication [5] 2+ with a central flat aromatic six-membered C 3 P 3 ring. This two-electron redox reaction occurs in two single-electron transfer steps via the 7π-radical cation [4]⋅ + , which could also be isolated and fully characterized. The profound reversible structural change observed for the two-electron redox couple [5] 2+ /1 a, b is in sharp contrast to the C 6 H 6 /[C 6 H 6 ] 2- couple, which undergoes only a modest structural deformation., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Phosphane, PH 3 -a highly pyrophoric and toxic gas-is frequently contaminated with H 2 and P 2 H 4 , which makes its handling even more dangerous. The inexpensive metal-organic framework (MOF) magnesium formate, α-[Mg(O 2 CH) 2 ], can adsorb up to 10 wt % of PH 3 . The PH 3 -loaded MOF, PH 3 @α-[Mg(O 2 CH) 2 ], is a non-pyrophoric, recoverable material that even allows brief handling in air, thereby minimizing the hazards associated with the handling and transport of phosphane. α-[Mg(O 2 CH) 2 ] further plays a critical role in purifying PH 3 from H 2 and P 2 H 4 : at 25 °C, H 2 passes through the MOF channels without adsorption, whereas PH 3 adsorbs readily and only slowly desorbs under a flow of inert gas (complete desorption time≈6 h). Diphosphane, P 2 H 4 , is strongly adsorbed and trapped within the MOF for at least 4 months. P 2 H 4 @α-[Mg(O 2 CH) 2 ] itself is not pyrophoric and is air- and light-stable at room temperature., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

A number of stable group 6 metal complexes bearing 2,4,6-oxy functionalised 1,3,5-triphosphinines, phosphorus containing heterocyclic ligands with a central C 3 P 3 core, were synthesised such that a complete series of [M{P 3 C 3 (OX) 3 }(CO) 3 ] compounds is obtained [M = Cr(0), Mo(0), W(0); X = H, Si t BuPh 2 , B(ipc) 2 ]. In all complexes, the triphosphinine coordinates in a η 6 -binding mode via the delocalized 6π-system of the ring. The ligand properties can be tuned by changing the substituent on the oxygen centre. The π-electron accepting properties of the ligand increases in the following order: P 3 C 3 (OH) 3 < P 3 C 3 (OSi t BuPh 2 ) 3 < P 3 C 3 (OB(ipc) 2 ) 3 . This trend is reflected in the structures determined by X-ray crystallography, and the ν (CO) stretching frequencies determined by IR spectroscopy. The collected data raise questions with respect to the frequently made assumption that phosphinines act as stronger π-acceptors with respect to arenes and thereby deplete electron density at the metal centres. With P 3 C 3 (OH) 3 as an η 6 -coordinated ligand further molecules can be coordinated in the second coordination sphere via hydrogen bonds, which may be of interest for the construction of coordination polymers.

The reactivity of the bis(acyl)phosphide ion [P(COR) 2 ] - (BAP - , R=Ph, Mes) with silicon halides SiX 4 (X=Cl, Br) and pnictogen chlorides ECl 3 (E=As, Sb and Bi) was investigated. The reaction with SiX 4 leads to the hexacoordinate silanes SiX 2 (BAP) 2 in which BAP - is coordinated in the chelating κ 2 -O,O' mode, analogously to acac - . Unexpectedly, the coordination behaviour of BAP - differs from the one of acac - in the interpnictogen compounds E(BAP) 3 (E=As, Sb) in which the formation of E-P bonds is favoured over κ 2 -O,O' chelation via the oxygen centres. Finally, the reaction of BiCl 3 with three equivalents of Na(BAP) leads to the formation of red, crystalline Bi 2 (BAP) 4 , an air stable dibismuthine, as product of a redox reaction., (© 2023 The Authors. ChemPlusChem published by Wiley-VCH GmbH.)

Addition of the P-H bond in bis(mesitoyl)phosphine, HP(COMes) 2 (BAPH), to a wide variety of activated carbon-carbon double bonds as acceptors was investigated. While this phospha-Michael addition does not proceed in the absence of an additive or catalyst, excellent results were obtained with stoichiometric basic potassium or caesium salts. Simple amine bases can be employed in catalytic amounts, and tetramethylguanidine (TMG) in particular is an outstanding catalyst that allows the preparation of bis(acyl)phosphines, R-P(COMes) 2 , under very mild conditions in excellent yields after only a short time. All phosphines RP(COMes) 2 can subsequently be oxidized to the corresponding bis(acyl)phosphane oxides, RPO(COMes) 2 , a substance class belonging to the most potent photoinitiators for radical polymerizations known to date. Thus, a simple and highly atom economic method has been found that allows the preparation of a broad range of photoinitiators adapted to their specific field of application even on a large scale., (© 2022 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Reaction of the imidazolium-substituted iphosphate-diide, (Ipr) 2 C 2 P 2 (IDP), with GeCl 2  ⋅ dioxane and KBArF 24 [(BarF 24 ) - =tetrakis[(3,5-trifluoromethyl)phenyl]borate)] afforded the dicationic spherical-aromatic nido-cluster [Ge(η 4 -IDP)] 2+ ([1] 2+ ) (Ipr=1,3-bis(2,6-diisopropylphenyl)imidazolium-2-ylidene). This complex is a rare heavy analogue of the elusive pyramidane [C(η 4 -C 4 H 4 )]. [1] 2+ undergoes two reversible one-electron reductions, which yield the radical cation [2]⋅ + and the neutral Ge II species 3. Both [2]⋅ + and 3 rearrange in solution forming the 2D aromatic and planar imidazolium-substituted digermolide [4] 2+ and germole-diide 5, respectively. Both planar species can be oxidized back to [1] 2+ using AgSbF 6 . These redox-isomerizations correspond to the fundamental transformation of a 3D aromatic cluster into a 2D aromatic ring compound upon reduction and vice versa. The mechanism of these reactions was elucidated using DFT calculations and cyclic voltammetry experiments., (© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Reaction of the 6π-electron aromatic four-membered heterocycle (IPr) 2 C 2 P 2 (1) (IPr=1,3-bis(2,6-diisopropylphenyl)-1,3-dihydro-2H-imidazol-2-ylidene) with [Fe 2 CO 9 ] gives the neutral iron tricarbonyl complex [Fe(CO) 3 -η 3 -{(IPr) 2 C 2 P 2 }] (2). Oxidation with two equivalents of the ferrocenium salt, [Fe(Cp) 2 ](BArF 24 ), affords the dicationic tricarbonyl complex [Fe(CO) 3 -η 4 -{(IPr) 2 C 2 P 2 }](BArF 24 ) 2 (4). The one-electron oxidation proceeds under concomitant loss of one CO ligand to give the paramagnetic dicarbonyl radical cation complex [Fe(CO) 2 -η 4 -{(IPr) 2 C 2 P 2 }](BArF 24 ) (5). Reduction of 5 allows the preparation of the neutral dicarbonyl complex [Fe(CO) 2 -η 4 -{(IPr) 2 C 2 P 2 }] (6). An analysis by various spectroscopic techniques ( 57 Fe Mössbauer, EPR) combined with DFT calculations gives insight into differences of the electronic structure within the members of this unique series of iron carbonyl complexes, which can be either described as electron precise or Wade-Mingos clusters., (© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

The synthesis and reactivity of the heavier group 13 phosphaketene complexes (2,6-Mes 2 C 6 H 3 ) 2 EPCO (1, E = Ga; 2, E = In) were reported. The reaction of 1 and 2 with 1,2,3,4-tetramethylimidazolin-2-ylidene, IMe 4 , gave rise to the formation of (2,6-Mes 2 C 6 H 3 ) 2 EP(O)C(IMe 4 ) (3, E = Ga; 4 E = In; Mes = mesityl). Subsequent addition of elemental tellurium proceeded via insertion into the E-P bond and provided (2,6-Mes 2 C 6 H 3 ) 2 ETeP(O)C(IMe 4 ) (5, E = Ga; 6, E = In) comprising five-membered ETePCO-heterocycles. Compounds 1-6 were fully characterized by X-ray crystallography and heteronuclear NMR spectroscopy. The electronic structures of 1-6 were studied by DFT calculations and analyses of a complementary set of real-space bonding indicators (AIM, ELI-D, NCI) derived from the electron and pair densities, with focus on the bond characteristics of the PCO fragment.

The dinuclear Ru diazadiene olefin complex, [Ru 2 (OTf)(μ-H)(Me 2 dad)(dbcot) 2 ], is an active catalyst for hydrogen evolution in a Polymer Exchange Membrane (PEM) water electrolyser. When supported on high surface area carbon black and at 80 °C, [Ru 2 (OTf)(μ-H)(Me 2 dad)(dbcot) 2 ]@C evolves hydrogen at the cathode of a PEM electrolysis cell (400 mA cm -2 , 1.9 V). A remarkable turn over frequency (TOF) of 7800 mol H 2 mol catalyst -1 h -1 is maintained over 7 days of operation. A series of model reactions in homogeneous media and in electrochemical half cells, combined with DFT calculations, are used to rationalize the hydrogen evolution mechanism promoted by [Ru 2 (OTf)(μ-H)(Me 2 dad)(dbcot) 2 ]., Competing Interests: There are no conflicts of interest to declare., (This journal is © The Royal Society of Chemistry.)

A reaction of trisodium phosphide (Na 3 P) with chlorosilanes allows for simple derivatization into silyl- and cyano-substituted phosphanide species which were compared with each other. The recently discovered cyano(triphenylsilyl)phosphanide shows unique coordination properties compared to bis(silyl)phosphides.

Homogeneous ruthenium catalysed methanol dehydrogenation could become a key reaction for hydrogen production in liquid fuel cells. In order to improve existing catalytic systems, mechanistic insight is paramount in directing future studies. Herein, we describe what computational mechanistic research has taught us so far about ruthenium catalysed dehydrogenation reactions. In general, two mechanistic pathways can be operative in these reactions: a metal-centered or a metal-ligand cooperative (Noyori-Morris type) minimum energy reaction pathway (MERP). Discerning between these mechanisms on the basis of computational studies has proven to be highly input dependent, and to circumvent pitfalls it is important to consider several factors, such as solvent effects, metal-ligand cooperativity, alternative geometries, and complex electronic structures of metal centres. This Frontiers article summarizes the reported computational research performed on ruthenium catalyzed dehydrogenation reactions performed in the past decade, and serves as a guide for future research.

The nitrogen oxides NO 2 , NO, and N 2 O are among the most potent air pollutants of the 21 st century. A bimetallic Rh I -Pt II complex containing an especially designed multidentate phosphine olefin ligand is capable of catalytically detoxifying these nitrogen oxides in the presence of hydrogen to form water and dinitrogen as benign products. The catalytic reactions were performed at room temperature and low pressures (3-4 bar for combined nitrogen oxides and hydrogen gases). A turnover number (TON) of 587 for the reduction of nitrous oxide (N 2 O) to water and N 2 was recorded, making these Rh I -Pt II complexes the best homogeneous catalysts for this reaction to date. Lower TONs were achieved in the conversion of nitric oxide (NO, TON=38) or nitrogen dioxide (NO 2 , TON of 8). These unprecedented homogeneously catalyzed hydrogenation reactions of NO x were investigated by a combination of multinuclear NMR techniques and DFT calculations, which provide insight into a possible reaction mechanism. The hydrogenation of NO 2 proceeds stepwise, to first give NO and H 2 O, followed by the generation of N 2 O and H 2 O, which is then further converted to N 2 and H 2 O. The nitrogen-nitrogen bond-forming step takes place in the conversion from NO to N 2 O and involves reductive dimerization of NO at a rhodium center to give a hyponitrite (N 2 O 2 2- ) complex, which was detected as an intermediate., (© 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

The cyano(triphenylsilyl)phosphanide anion was prepared as a sodium salt from 2-phosphaethynolate. The electronic structure of this new cyano(silyl)phosphanide was studied via computational methods and its reactivity investigated using various electrophiles and Lewis acids, demonstrating its P- and N-nucleophilicity. The ambident reactivity is in agreement with computations. The silyl group also shows lability and therefore the cyano(silyl)phosphanide can be considered as a phosphacyanamide synthon, [PCN] 2- , and serves as building block for the transfer of a PCN moiety., (© 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

The vibrational spectra of the simplest phosphaketene HPCO and its isotopologue DPCO in solid Ar-matrices at 12.0 K have been analyzed with the aid of the computations at the CCSD(T)-F12a/cc-pVTZ-F12 level using configuration-selective vibrational configuration interaction (VCI). In addition to the four IR fundamentals, four overtone and ten combination bands have been unambiguously identified. Furthermore, the photochemistry of HPCO in the matrix has been investigated for the first time. Upon UV-light irradiation (365 or 266 nm), CO-elimination occurs by forming the parent phosphinidene HP that can be trapped by ˙NO to yield the elusive phosphinimine- N -oxyl radical HPNO˙. In contrast, an excimer laser (193 nm) irradiation of HPCO causes additional decomposition to H˙ and ˙PCO with concomitant formation of the long-sought phosphaethyne HOCP.

The replacement of carbon in (C─C) n chains of polyolefins by phosphorus leads to polycarbophosphanes (P─C) n , which may possess unique chemical and physical properties. However, macromolecules with a regular (P─C) n chain have never been unambiguously identified. Here, we demonstrate that addition polymerization, a general concept to polymerize olefins, can be extended to P═C double bonds. The polymerization of monomeric 2-phosphanaphthalenes is mediated by copper(I) halides and leads to polycarbophosphanes with an M n of 14 to 34 kDa. Each phosphorus is coordinated to Cu(I), which can be easily removed. Unlike long-term durable polyolefins, the metal-free polymers depolymerize rapidly back to monomers under sunlight or ultraviolet irradiation at λ = 365 nm. The monomers can be recycled for repolymerization, demonstrating a cradle-to-cradle life cycle for polycarbophosphanes., (Copyright © 2021 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).)

An alternative intracranial aneurysm embolic agent is emerging in the form of hydrogels due to their ability to be injected in liquid phase and solidify in situ . Hydrogels have the ability to fill an aneurysm sac more completely compared to solid implants such as those used in coil embolization. Recently, the feasibility to implement photopolymerizable poly(ethylene glycol) dimethacrylate (PEGDMA) hydrogels in vitro has been demonstrated for aneurysm application. Nonetheless, the physical and mechanical properties of such hydrogels require further characterization to evaluate their long-term integrity and stability to avoid implant compaction and aneurysm recurrence over time. To that end, molecular weight and polymer content of the hydrogels were tuned to match the elastic modulus and compliance of aneurysmal tissue while minimizing the swelling volume and pressure. The hydrogel precursor was injected and photopolymerized in an in vitro aneurysm model, designed by casting polydimethylsiloxane (PDMS) around 3D printed water-soluble sacrificial molds. The hydrogels were then exposed to a fatigue test under physiological pulsatile flow, inducing a combination of circumferential and shear stresses. The hydrogels withstood 5.5 million cycles and no significant weight loss of the implant was observed nor did the polymerized hydrogel protrude or migrate into the parent artery. Slight surface erosion defects of 2-10 μm in depth were observed after loading compared to 2 μm maximum for non-loaded hydrogels. These results show that our fine-tuned photopolymerized hydrogel is expected to withstand the physiological conditions of an in vivo implant study., Competing Interests: AS was a shareholder at Lumendo SA to which the intellectual property was licensed. Lumendo SA was not involved in the study design, collection, analysis, interpretation of data, the writing of this article, or the decision to submit it for publication. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Poupart, Conti, Schmocker, Pancaldi, Moser, Nuss, Sakar, Dobrocky, Grützmacher, Mosimann and Pioletti.)

Distonic radical cations (DRCs) with spatially separated charge and radical sites have, so far, largely been observed by gas-phase mass spectrometry and/or matrix isolation spectroscopy work. Herein, we disclose the isolation of a crystalline dicarbondiphosphide-based β-distonic radical cation salt 3 .+ (BARF) (BARF=[B(3,5-(CF 3 ) 2 C 6 H 3 ) 4 )] - ) stable at room temperature and formed by a one-electron-oxidation-induced intramolecular skeletal rearrangement reaction. Such a species has been validated by electron paramagnetic resonance (EPR) spectroscopy, single-crystal X-ray diffraction, UV/Vis spectroscopy and density functional theory (DFT) calculations. Compound 3 .+ (BARF) exhibits a large majority of spin density at a two-coordinate phosphorus atom (0.74 a.u.) and a cationic charge located predominantly at the four-coordinate phosphorus atom (1.53 a.u.), which are separated by one carbon atom. This species represents an isolable entity of a phosphorus radical cation that is the closest to a genuine phosphorus DRC to date., (© 2020 Wiley-VCH GmbH.)

Fluorinated organophosphorus(V) compounds are a very versatile class of compounds, but the synthetic methods available to make them bear the disadvantages of 1) occasional handling of toxic or pyrophoric P III starting materials and 2) a dependence on hazardous fluorinating reagents such as XeF 2 . Herein, we present a simple solution and introduce a deoxygenative fluorination (DOF) approach that utilizes easy-to-handle phosphine oxides as starting materials and effectively replaces harsh fluorinating reagents by a combination of oxalyl chloride and potassium fluoride. The reaction has proven to be general, as R 3 PF 2 , R 2 PF 3 , and RPF 4 compounds (as well as various cations and anions derived from these) are accessible in good yields and on up to a multi-gram scale. DFT calculations were used to bolster our observations. Notably, the discovery of this new method led to a convenient synthesis of 1) new difluorophosphonium ions, 2) hexafluorophosphate salts, and 3) fluorinated antimony- and arsenic- compounds., (© 2020 Wiley-VCH GmbH.)

The synthesis, isolation and full characterization of ion pairs between alkaline metal ions (Li + , Na + , K + ) and mono-anions and dianions obtained from 5H -dibenzo[ a , d ]cycloheptenyl (C 15 H 11 = trop) is reported. According to Nuclear Magnetic Resonance (NMR) spectroscopy, single crystal X-ray analysis and Density Functional Theory (DFT) calculations, the trop ‒ and trop 2-• anions show anti-aromatic properties which are dependent on the counter cation M + and solvent molecules serving as co-ligands. For comparison, the disodium and dipotassium salt of the dianion of dibenzo[ a,e ]cyclooctatetraene (C 16 H 12 = dbcot) were prepared, which show classical aromatic character. A d 8 -Rh(I) complex of trop - was prepared and the structure shows a distortion of the C 15 H 11 ligand into a conjugated 10π -benzo pentadienide unit-to which the Rh(I) center is coordinated-and an aromatic 6π electron benzo group which is non-coordinated. Electron transfer reactions between neutral and anionic trop and dbcot species show that the anti-aromatic compounds obtained from trop are significantly stronger reductants.

We present a computational study on tetrapnictide dianions Pn 4 2- (Pn = P, As, Sb, Bi), using density functional theory (DFT), coupled-cluster [DLPNO-CCSD(T)] and complete active space self-consistent field (CASSCF) methods. Environmental effects such as solvation and coordination of counterions are included. The calculations reveal that out of three isomers (square-planar, butterfly and capped-triangle), the square planar isomers are generally the most stable. The counterion (Li + and Mg 2+ ) used in the calculations have a substantial effect on the relative stabilities. The square planar isomers show considerable biradical character. Calculated reactions toward alkenes indicate that this unusual electronic structure has significant implications on the reactivity of the Pn 4 2- dianions., (© 2020 The Authors published by Wiley‐VCH GmbH.)

The dehydrogenation of organosilanes (R x SiH 4-x ) under the formation of Si-Si bonds is an intensively investigated process leading to oligo- or polysilanes. The reverse reaction is little studied. To date, the hydrogenolysis of Si-Si bonds requires very harsh conditions and is very unselective, leading to multiple side products. Herein, we describe a new catalytic hydrogenation of oligo- and polysilanes that is highly selective and proceeds under mild conditions. New low-valent nickel hydride complexes are used as catalysts and secondary silanes, RR'SiH 2 , are obtained as products in high purity., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Reactive species, such as . PO 2 and HOPO, are considered of upmost importance in flame inhibition and catalytic combustion processes of fuels. However, the underlying chemistry of their formation remains speculative due to the unavailability of suitable analytical techniques that can be used to identify the transient species which lead to their formation. This study elucidates the reaction mechanisms of the formation of phosphoryl species from dimethyl methyl phosphonate (DMMP) and dimethyl methyl phosphoramidate (DMPR) under well-defined oxidative conditions. Photoelectron photoion coincidence techniques that utilized vacuum ultraviolet synchrotron radiation were applied to isomer-selectively detect the elusive key intermediates and stable products. With the help of in situ recorded spectral fingerprints, different transient species, such as PO 2 and triplet O radicals, have been exclusively identified from their isomeric components, which has helped to piece together the formation mechanisms of phosphoryl species under various conditions. It was found that . PO 2 formation required oxidative conditions above 1070 K. The combined presence of O 2 and H 2 led to significant changes in the decomposition chemistry of both model phosphorus compounds, leading to the formation of . PO 2 . The reaction . PO+O 2 → . PO 2 +O: was identified as the key step in the formation of . PO 2 . Interestingly, the presence of O 2 in DMPR thermolysis suppresses the formation of PN-containing species. In a previous study, PN species were identified as the major species formed during the pyrolysis of DMPR. Thus, the findings of this study has shed light onto the decomposition pathways of organophosphorus compounds, which are beneficial for their fuel additive and fire suppressant applications., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Annulated oxy-substituted 1,3,4-azadiphospholides such as the anion in Na[1] are readily accessible phosphorus heterocycles made from the phosphaethynolate anion (OCP)- and 2-chloropyridines. The sodium salt Na[1] reacts with oxophilic element halides such as OPCl3, PhSiCl3, PhBCl2 and CpTiCl3 at room temperature to form exclusively the oxygen bound tris-substituted compounds E(1)3 (with E = OP, PhSi, PhB- or CpTi). Six equivalents of Na[1] with group four metal chlorides MCl4 (M = Ti, Zr, Hf) form cleanly the hexa-substituted dianions (Na2[M(1)6]) which are isolated in excellent yields. The titanium complexes are deeply coloured species due to ligand to metal charge transfer (LMCT) excitations. In all complexes, the phosphorus atoms of the azadiphosphole moieties are able to coordinate to a soft metal center as shown in their reactions with [Mo(CO)3Mes], yielding complexes in which the Mo(CO)3 binds in a fac manner. Functionalization of the oxy group with amino phosphanes allows isolation of tridentate ligands, which have been used as synthons for macrocyclic molybdenum carbonyl complexes.

A new multi-photoactive γ-cyclodextrin substituted bis(acyl)phosphane oxide derivative (BAPO-γ-CyD) was successfully prepared via a convergent synthesis using a phospha-Michael-addition, as confirmed by 1H-, 13C-, 31P-NMR and IR spectroscopy and mass spectrometry. Kinetic studies carried out by photo-DSC and photo-rheology demonstrated its outstanding efficiency as a photoinitiator for free-radical polymerization. Remarkably, it is found that BAPO-γ-CyD also acts as a crosslinking agent to convert monofunctional methacrylate monomers into self-standing thermosetting networks with extensive swelling capability in water.

Intracranial aneurysms are increasingly being treated with endovascular therapy, namely coil embolization. Despite being minimally invasive, partial occlusion and recurrence are more frequent compared to open surgical clipping. Therefore, an alternative treatment is needed, ideally combining minimal invasiveness and long-term efficiency. Herein, we propose such an alternative treatment based on an injectable, radiopaque and photopolymerizable polyethylene glycol dimethacrylate hydrogel. The rheological measurements demonstrated a viscosity of 4.86 ± 1.70 mPa.s, which was significantly lower than contrast agent currently used in endovascular treatment ( p = 0.42), allowing the hydrogel to be injected through 430 μm inner diameter microcatheters. Photorheology revealed fast hydrogel solidification in 8 min due to the use of a new visible photoinitiator. The addition of an iodinated contrast agent in the precursor contributed to the visibility of the precursor injection under fluoroscopy. Using a customized light-conducting microcatheter and illumination module, the hydrogel was implanted in an in vitro silicone aneurysm model. Specifically, in situ fast and controllable injection and photopolymerization of the developed hydrogel is shown to be feasible in this work. Finally, the precursor and the polymerized hydrogel exhibit no toxicity for the endothelial cells. Photopolymerizable hydrogels are expected to be promising candidates for future intracranial aneurysm treatments., (Copyright © 2020 Poupart, Schmocker, Conti, Moser, Nuss, Grützmacher, Mosimann and Pioletti.)

In contrast to cyclic π-conjugated hydrocarbons, the coordination chemistry of inorganic heterocycles is less developed. Dicarbondiphosphides stabilized by N-heterocyclic carbenes (NHCs) NHC→C 2 P 2 ←NHC (1 a,b) (NHC=IPr or SIPr) contain a four-membered C 2 P 2 ring with an aromatic 6π-electron configuration. These heterocycles coordinate to a variety of complex fragments with metals from groups 6, 9, and 10, namely [M 0 (CO) 3 ] (M=Cr, Mo), [Co I (CO) 2 ] + , or [Ni II Br 2 ], through an η 4 -coordination mode, leading to complexes 2 a,b, 3 a,b, 5 a,b, and 6 a,b, respectively. These complexes were characterized by X-ray diffraction methods using single crystals, IR spectroscopy, and DFT calculations. In combination these methods indicate that 1 a,b behave as exceptionally strong 6π-electron donors., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

In the present study, a different approach for the preparation of poly(ethylene glycol) diacrylate-gelatin (PEGDA-gelatin) hydrogels was investigated. Gelatin type A from porcine skin was used as the co-initiator of a radical photo-initiating system instead of the traditional aliphatic or aromatic amines. This became possible because, upon visible-light irradiation, the amine sequences within gelatin generate initiating free-radicals through the intermolecular proton transfer in a Norrish type II reaction with camphorquinone (CQ). PEGDA-gelatin hydrogels were prepared by visible-light-induced photopolymerization. The gelatin content in the precursor formulations was varied. The influence of gelatin on the kinetics of the photocuring reaction was investigated, and it was found that gelatin fastened the rate of polymerization at all concentrations. The covalent attachment of gelatin segments within the cross-linked hydrogels was evaluated by means of attenuated total reflectance-infrared spectroscopy (ATR-FTIR) spectroscopy after solvent extraction. The thermo-mechanical properties, as well as the swelling behavior and gel content, were also investigated.

The facile preparation of alkali salts of phosphanyl cyanophosphides [NHP-PCN] - (NHP=N-heterocyclic phosphenium) is reported. Their formation is achieved by isoelectronic replacement of O for [N] - in the phosphaketenes NHP-PCO using alkaline hexamethyldisilazide M[N(SiMe 3 ) 2 ] (M=Na, K) as reagent. The new anionic entities are versatile PCN building blocks which allow the formation of a diversity of new cyanophosphine derivates including the first example of a PCNB hetero-cumulene and a PCN-ligated transition metal complex., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Supporting two metal binding sites by a tailored polydentate trop-based (trop = 5 H -dibenzo[ a , d ]cyclohepten-5-yl) ligand yields highly unsymmetric homobimetallic rhodium(i) complexes. Their reaction with hydrogen rapidly forms Rh hydrides that undergo an intramolecular semihydrogenation of two C[triple bond, length as m-dash]C bonds of the trop ligand. This reaction is chemoselective and converts C[triple bond, length as m-dash]C bonds to a bridging carbene and an olefinic ligand in the first and the second semihydrogenation steps, respectively. Stabilization by a bridging diphosphine ligand allows characterization of a Rh hydride species by advanced NMR techniques and may provide insight into possible elementary steps of H 2 activation by interfacial sites of heterogeneous Rh/C catalysts., (This journal is © The Royal Society of Chemistry 2019.)

Tailor-made photoinitiators play an important role for efficient radical polymerisations in aqueous media, especially in hydrogel manufacturing. Bis(acyl)phosphane oxides (BAPOs) are among the most active initiators. Herein, we show that they display a remarkable photochemistry in aqueous and alcoholic media: Photolysis of BAPOs in the presence of water or alcohols provides a new delocalized π-radical, which does not participate in the polymerization. It either converts into a monoacylphosphane oxide acting as a secondary photoactive species or it works as a one-electron reducing agent. Upon the electron-transfer process, it again produces a dormant photoinitiator. We have established the structure and the chemistry of this π radical using steady-state and time-resolved (CIDEP) EPR together with ESI-MS, NMR spectroscopy, and DFT calculations. Our results show that bis(acyl)phosphane oxides act as bifunctional reagents when applied in aqueous and alcoholic media., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Phosphaheteroallenes R-P=C=L, with L = N-heterocyclic carbenes (NHCs), can be viewed to a certain extent as phosphaisonitriles stabilized with NHCs, R-P=C:←L. The suitability of these molecules as ligands for coinage-metal ions was investigated and coordination through the central carbon center was observed in most cases. A combination of experiments, spectroscopic methods, and DFT calculations indicates the presence of a hidden electron pair at the carbon center of R-P=C:←L. Remarkably, this lone pair also inserts intramolecularly in C-H bonds showing the carbene-type reactivity which is expected for phosphaisonitriles., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Transmetallation studies with the phosphaethynolate ion, [OCP] - , have largely resulted in coordination according to classical Lewis acid-base theory. That is, for harder early transition metal ions, O-bound coordination has been observed, whereas in the case of softer late transition metal ions, P-bound coordination predominates. Herein, we report the use of a V(iii) complex, namely [(nacnac)VCl(OAr)] (1) (nacnac - = [ArNC(CH 3 )] 2 CH; Ar = 2,6- i Pr 2 C 6 H 3 ), to transmetallate [OCP] - and bind via the P-atom as [(nacnac)V(OAr)(PCO)] (2), the first example of a 3d early transition metal that binds [OCP] - via the P-atom. Full characterization studies of this molecule including HFEPR spectroscopy, SQuID measurements, and theoretical studies are presented.

Bisacylphosphane oxides (BAPOs) are established as photoinitiators for industrial applications. Light irradiation leads to their photolysis, producing radicals. Radical species induce oxidative stress in cells and may cause cell death. Hence, BAPOs may be suitable as photolatent cytotoxic agents, but such applications have not been investigated yet. Herein, we describe for the first time a potential use of BAPOs as drugs for photolatent therapy. We show that treatment of the breast cancer cell lines MCF-7 and MDA-MB-231 and of breast epithelial cells MCF-10A with BAPOs and UV irradiation induces apoptosis. Cells just subjected to BAPOs or UV irradiation alone are not affected. The induction of apoptosis depend on the BAPO and the irradiation dose. We proved that radicals are the active species since cells are rescued by an antioxidant. Finally, an optimized BAPO-derivative was designed which enters the cells more efficiently and thus leads to stronger effects at lower doses.

The first OCP adducts of aluminium and gallium are reported. The complexes are supported by sterically encumbered salen ligands and reveal a selective binding to O and P, respectively. Their reactivity with diazaphosphenium Lewis acids and N-heterocyclic carbene Lewis bases is described, in addition to cycloaddition reactions with s-tetrazines.

The transition metal mediated functionalization of P4 is an approach to develop a more sustainable production of organophosphorus compounds. In this paper a ruthenium complex is presented, in which the P4 unit can be selectively converted into new P4R2 molecules in a two-step synthesis. The unsaturated 16 electron species [RuX(Cp*)(PCy3)] (Cp* = C5Me5, X = Cl, Br) reacts with a half equivalent of P4 affording a bimetallic complex bearing a planar P4X2 moiety as a ligand. The latter eliminates chloride anions under reduction with magnesium. In this process the butadiene-like P4Cl2 ligand is converted into two weakly bound P2 units which bridge the ruthenium centers. In the presence of n-BuLi, the P4Cl2 unit can be selectively alkylated, yielding the planar organophosphorus ligand P4nBu2. A detailed analysis of the electronic properties and solid state structures of the compounds combined with DFT calculations and AIM analyses demonstrate that the P4 unit in all complexes acts as an electronically highly flexible, non-innocent ligand.