Phosphanylphosphaalkenes as precursors for metallaphosphaalkene complexes.

We synthesized phosphanylphosphaalkenes (biph)CP-P(Bu) (2), PhCP-P(NEt) (3), and (biph)CP-P(NEt) (4). The diaminophosphanyl derivatives reversibly dimerize head-to-head and react with a ruthenium complex, leading to P-P bond activation and the formation of a bridging phospaalkene complex under mild conditions.

Gold(III) complexes with chloride and cyanopyridines: Facilitated hydrolysis of nitrile ligand to amide and antibacterial activity.

A range of novel simple gold(III) compounds has been synthesized in their monocrystalline form, including two previously unknown chloro-complexes of Au with 2-cyanopyridine or 3-cyanopyridine, respectively. Our investigations have revealed the intricate nature of the reaction between 2-cyanopyridine and tetrachloroauric acid, yielding at least three distinct products. The main product, obtained in high yield, is a salt featuring a tetrachloroauric anion and a pyridinium cation stabilized by a hydrogen bond to a further 2-cyanopyridine molecule.

Chromium Complexes with Benzanellated N-Heterocyclic Phosphenium Ligands-Synthesis, Reactivity and Application in Catalytic CO Reduction.

A chromium complex carrying two benzanellated N-heterocyclic phosphenium (bzNHP) ligands was prepared by a salt metathesis approach. Spectroscopic studies suggest that the anellation enhances the π-acceptor ability of the NHP-units, which is confirmed by the facile electrochemical reduction of the complex to a spectroscopically characterized radical anion. Co-photolysis with H allowed extensive conversion into a σ-H-complex, which shows a diverse reactivity towards donors and isomerizes under H-H bond fission and shift of a hydride to a P-ligand.

The Noble Addendum of a Phosphenium Ligand to a Base Metal: Coordination, Activation, and Hydrogenation of Alkenes and Alkynes on a Chromium Complex.

The synthesis of a new bis-NHP complex (NHP=N-heterocyclic phosphenium) of chromium via salt metathesis and studies of its reactivity are reported. Photochemical reactions with H and selected olefins give rise to non-isolable H- and π-alkene complexes identified spectroscopically, while internal alkynes react via activation of the triple bond to yield isolable metalla-phospha-cyclobutenes characterized by spectroscopic and XRD data. DFT studies give a preliminary account of the bonding in H- and alkene-complexes and explain the different reactivity towards alkenes and alkynes as the consequence of kinetic effects.

Reversible Binding of Hydrogen and Styrene Coordination on a Manganese Phosphenium Complex.

The reactions of two complexes [( NHP)Mn(CO) ] ( NHP=N-arylated N-heterocyclic phosphenium) with H at elevated pressure (≈4 bar) were studied by NMR spectroscopy. Irradiation with UV light initialized in one case (5 a, R=Dipp) the unselective formation of ( NHP-H)MnH(CO) ] (6 a) via cooperative addition of H across the Mn=P double bond. In the other case (5 b, R=Mes), addition of H was unobservable and the reaction proceeded via decarbonylation to a dimeric species [( NHP) Mn (CO) ] (7 b) that was isolated and identified spectroscopically.

Annellated 1,3,4,2-Triazaphospholenes-Simple Modular Synthesis and a First Exploration of Ligand Properties.

The successful use of 1,3,4,2-triazaphospholenes (TAPs) as organo-catalysts stresses the need for efficient synthetic routes to these molecules. In this study, we establish the [1 + 4]-cycloaddition of PBr to azo-pyridines as a new approach to preparing pyrido-annellated TAPs in a single step from easily available precursors. The modular assembly of the azo-component via condensation of primary amines and nitroso compounds along with the feasibility of post-functionalization at the P-Br bond under conservation of the heterocyclic structure allows, in principle, to address a wide range of target molecules, which is illustrated by prototypical examples.

A neutral analogue of a phosphamethine cyanine.

Reaction of an imidazolio-phosphide with an N-heterocyclic bromo-borane and NaH afforded a neutral analogue of a phosphamethine cyanine cation. DFT studies were used to analyse the dative bonding across P-C/B bonds and the conformational preferences and imply that the observed conformation is imposed by sterics.

A PH-functionalized dicationic bis(imidazolio)diphosphine.

Reaction of the iodide salt of a secondary imidazolio-iodophosphine [(L)PHI]I (L = 1,3-diarylimidazolium-yl) with an imidazolio-phosphide (L)PH in the presence of GaI afforded the isolable salt of a dicationic, bis(imidazolio)-substituted dihydro-diphosphine [(L)PH][GaI]. Non-preparative formation of the cationic diphosphines was also observed upon spontaneous "dehalo-coupling" of [(L)PHI], or in reactions of [(L)PHI]I and (L)PH in the absence of GaI. Further reaction of [(L)PH] with (L)PH produced an iodide salt of a known (bis)imidazolio-diphosphide monocation [(L)PH].

Reversible cooperative dihydrogen binding and transfer with a bis-phosphenium complex of chromium.

The reversible reaction of H with a bis-phosphenium complex of chromium provides a rare example of 3d transition metal/phosphenium cooperativity. Photolysis induces the activation of H and yields a spectroscopically detectable phosphenium-stabilized (σ-H)-complex, readily showing exchange with gaseous H and D. Further reaction of this complex affords a phosphine-functionalized metal hydride, representing a unique example of reversible H cleavage across a 3d M[double bond, length as m-dash]P bond.

Synthesis and Ambiphilic Reactivity of Metalated Diorgano-Phosphonite Boranes.

Unprecedented metalated phosphonite boranes were prepared from PH-substituted precursors and silyl amides. Although potassium derivatives were thermally stable and could even be isolated and structurally characterised, lithiated analogues proved to be unstable towards self-condensation under cleavage of LiOR at ambient temperature. Reaction studies revealed that the metalated phosphonite boranes exhibit ambiphilic character.

Proton transfer vs. oligophosphine formation by P-C/P-H σ-bond metathesis: decoding the competing Brønsted and Lewis type reactivities of imidazolio-phosphines.

Studies of the protonation and alkylation of imidazolio-phosphides and deprotonation of imidazolio-phosphines reveal a complex behaviour that can be traced back to an interplay of Brønsted-type proton transfers and Lewis-type P-P bond formation reactions. As a consequence, the expected (de)protonation and (de)alkylation processes compete with reactions producing cyclic or linear oligophosphines. A careful adjustment of the conditions allows us to selectively address each reaction channel and devise specific synthesis methods for primary, secondary and tertiary imidazolio-phosphines, imidazolio-alkylphosphides, and cyclic oligophosphines, respectively.

Formation and properties of inorganic Si-contaminant compounds.

Soil contamination with inorganic contaminants such as lead (Pb), copper (Cu) and cadmium (Cd) is a major environmental issue. Silicon (Si) may reduce the mobility of the contaminants in the environment so that we studied the extent and the mechanisms of the interactions between Pb, Cd and Cu and silicic acid during its polymerization. We used tetraethyl orthosilicate as Si source and separately Pb(NO), Cd(NO) or Cu(NO).

Isolable Diaminophosphide Boranes.

Metalation of secondary diaminophosphine boranes by alkali metal amides provides a robust and selective access route to a range of metal diaminophosphide boranes M[(R N) P(BH )] (M=Li, Na, K; R=alkyl, aryl) with acyclic or heterocyclic molecular backbones, whereas reduction of a chlorodiaminophosphine borane gave less satisfactory results. The metalated species were characterized in situ by NMR spectroscopy and in two cases isolated as crystalline solids. Single-crystal XRD studies revealed the presence of salt-like structures with strongly interacting ions.

Approaching Dissolved Species in Ammonoacidic GaN Crystal Growth: A Combined Solution NMR and Computational Study.

Solutions of gallium trihalides GaX (X=F, Cl, Br, I) and their ammoniates in liquid ammonia were studied at ambient temperature under autogenous pressure by multinuclear ( Ga, Cl, Br) NMR spectroscopy. To unravel the role of pH, the analyses were done both in absence and in presence of ammonium halides, which are employed as mineralizers during ammonoacidic gallium nitride crystal growth. While gallium trifluoride and its ammoniate were found to be too sparingly soluble to give rise to a NMR signal, the spectra of solutions of the heavier halides reveal the presence of a single gallium-containing species in all cases.

Bis-[3]Ferrocenophanes with Central >E-E'< Bonds (E, E'=P, SiH): Preparation, Properties, and Thermal Activation.

A series of bis-[3]ferrocenophanes of the general type Fe(CHE')E-E(E'CH)Fe (E=P, SiH and E'=PBu, NPentyl, NSi(CH)) with an isolobal molecular framework have been prepared and characterized by heteronuclear NMR spectroscopy and X-ray crystallography. The thermal dissociation behavior with respect to homolytic fission of the central bond generating phosphorus centered radicals was investigated using EPR spectroscopy and quantum chemical calculations.

Bis-[3]Ferrocenophanes with Central >E-E'< Bonds (E, E'=P, SiH): Preparation, Properties, and Thermal Activation.

Invited for this month's cover picture are the groups of Professors Rudolf Pietschnig at the University of Kassel, Professor Dietrich Gudat at the University of Stuttgart and Professor László Nyulászi at the Budapest University of Technology and Economics. The cover picture shows the thermally induced homolytic cleavage of the central P-P bond in a phosphorus-rich bis-ferrocenophane furnishing P-centered radicals (as evidenced by the computed spin-density highlighted in blue). The central P unit in the title compound is a structural analog of the connecting unit in Hittorf's violet phosphorus, which links the orthogonally arranged tubular entities.

Comparing the Ligand Behavior of N-Heterocyclic Phosphenium and Nitrosyl Units in Iron and Chromium Complexes.

N-Heterocyclic phosphenium (NHP) and nitrosonium (NO) ligands are often viewed as isolobal analogues that share the capability to switch between different charge states and thus display redox "noninnocent" behavior. We report here on mixed complexes [(NHP)M(CO) (NO)] (M = Fe, Cr; n = 2, 3), which permit evaluating the donor/acceptor properties of both types of ligands and their interplay in a single complex. The crystalline target compounds were obtained from reactions of N-heterocyclic phosphenium triflates with PPN[Fe(CO)(NO)] or PPN[Cr(CO)(NO)], respectively, and fully characterized (PPN = nitride-bistriphenylphosphonium cation).

Controllable access to P-functional [3]ferrocenophane and [4]ferrocenophane frameworks.

Condensation of secondary 1,1'-diaminoferrocenes with phosphorus trihalides (PCl3 or PBr3) yielded either P-halo-1,3-diaza-2-phospha[3]ferrocenophanes or 1,1'-diaminoferrocenediyl-bis(dichlorophosphines), respectively. The latter provide controlled access to both [3]- and [4]ferrocene frameworks. Thus, reductive coupling with magnesium gave diaza-diphospha[4]ferrocenophane-annelated tetraphosphetanes, while a reaction with LiNMe2 produced a P-chloro-diazaphospha[3]ferrocenophane.

Variable Reactivity of a N-Heterocyclic Phosphenium Complex: P-C Bond Activation or "Abnormal" Deprotonation.

The reaction of an N-heterocyclic phosphenium complex of manganese with MeLi/Et NHCl under formal addition of CH to the Mn=P double bond can be reversed upon UV photolysis, providing a rare example for selective P-C(alkyl) bond activation. Action of LDA on the phosphenium complex does not proceed via attack at phosphorus but rather via C4-deprotonation to yield a unique P-analogue of an "abnormal" carbene. A transmetalation product of the original complex was fully characterized.

N-Heterocyclic Phosphenium Complex of Manganese: Synthesis and Catalytic Activity in Ammonia Borane Dehydrogenation.

A neutral N-heterocyclic phosphenium complex of manganese was synthesised by a metathesis approach and characterised by IR, NMR, and XRD studies. The short P-Mn distance suggests a substantial metal-ligand double bond character. Reaction with a hydride produced an anionic phosphine complex, which was also characterised by IR and NMR spectroscopy and, after anion exchange, a single-crystal XRD study.

Visible light assisted hydrogen generation from complete decomposition of hydrous hydrazine using rhodium modified TiO photocatalysts.

Hydrogen is considered to be an ideal energy carrier, which produces only water when combined with oxygen and thus has no detrimental effect on the environment. While the catalytic decomposition of hydrous hydrazine for the production of hydrogen is well explored, little is known about its photocatalytic decomposition. The present paper describes a highly efficient photochemical methodology for the production of hydrogen through the decomposition of aqueous hydrazine using titanium dioxide nanoparticles modified with a Rh(i) coordinated catechol phosphane ligand (TiO-Rh) as a photocatalyst under visible light irradiation.

Phosphenium Hydride Reduction of [(cod)MX] (M = Pd, Pt; X = Cl, Br): Snapshots on the Way to Phosphenium Metal(0) Halides and Synthesis of Metal Nanoparticles.

The outcome of the reduction of [(cod)PtX] (X = Cl, Br; cod = 1,5-cyclooctadiene) with N-heterocyclic phosphenium hydrides NHP-H depends strongly on the steric demand of the N-aryl group R and the nature of X. Reaction of [(cod)PtCl] with NHP-H featuring bulky N-Dipp groups produced an unprecedented monomeric phosphenium metal(0) halide [(NHP)(NHP-H)PtCl] stabilized by a single phosphine ligand. The phosphenium unit exhibits a pyramidal coordination geometry at the phosphorus atom and may according to DFT calculations be classified as a Z-type ligand.

New Selective Synthesis of Dithiaboroles as a Viable Pathway to Functionalized Benzenedithiolenes and Their Complexes.

A synthetic protocol to synthesize 2-bromobenzo-1,3,2-dithiaboroles in one step from easily accessible benzene bis(isopropyl thioether)s has been developed. The reaction is remarkably specific in converting substrates with two adjacent (i)PrS moieties while leaving isolated thioether functions and other functional groups intact. On the basis of the spectroscopic detection or isolation of reaction intermediates, a mechanistic explanation involving a neighbor-group-assisted dealkylation as a key step is proposed.

Bismuth Undecahydro-closo-dodecaborane: A Retainable Intermediate of B-H Bond Activation by Bismuth(III) Cations.

The [B12 H12](2-) anion shows an extensive substitutional chemistry based on its three-dimensional aromaticity. The replacement of functional groups can be attained by electrophilically induced substitution caused by Brønsted or Lewis acidic electrophiles (e.g.