Search

Reactivity of (triphosphine)MoIV‐nitrido complex generated by N2 splitting, toward boranes is reported. The simple adduct Mo≡N→BH3 is observed with BH3.SMe2 while 1,2 addition is evidenced with 9‐BBN leading to H−Mo=NBR2. A second addition of BH3.SMe2 is facile and forms an unprecedented complex featuring two bridging H between two B and the Mo centers. Addition of PMe3 or BH3.SMe2 promotes reductive elimination and N−H bond formation. The full sequence of functionalization at Mo≡N obtained after N2 splitting is therefore evidenced in this work. [ABSTRACT FROM AUTHOR]

Numerous synthetic models of the FeMo‐co cluster of nitrogenases have been proposed to find the simplest structure with relevant reactivity. Indeed, such structures are able to perform multi‐electrons reduction processes, such as the conversion of N2 to ammonia, and of CO2 into methane and alkenes. The most challenging parameter to imitate is indeed the central carbide ligand, which is believed to maintain the integrity of iron sulfide assembly during the course of catalytic cycles. The study proposes the use of bis(diphenylthiophosphinoyl)methanediide (SCS)2− as an ideal platform for the synthesis of bi‐ and tetra‐metallic iron complexes, in which the iron‐carbon interaction is maintained upon structural diversification and redox state changes. [ABSTRACT FROM AUTHOR]

A DFT study of several L→Al(ORF)3 (L=Lewis bases) adducts allowed the identification of (iPr2S)→Al(ORF)3 1-SiPr2 as a "stable yet reactive" adduct. 1-SiPr2 was shown to act as a masked Lewis superacid able to release Al(ORF)3 under mild conditions. It could be used to abstract a ORF- ligand from bipyMe2)Ni(ORF)2 (bipyMe2 : 6,6'-dimethyl-2,2'-dipyridyl) and generate the nickel alkoxide complex [(bipyMe2)Ni-(ORF)(iPr2S)]+[(RFO)3Al--F--Al(ORF)3]- 5. Ligand exchange of iPr2S by Ph3P yielded [(bipyMe2)Ni(ORF)(PPh3)]+[(RFO)3Al--F--Al-(ORF)3]-6. [ABSTRACT FROM AUTHOR]

Two different dinitrogen‐derived molybdenum nitrido complexes varying by their geometry, ligand spheres and oxidations states were shown to engage their N ligand in dative bonding with the strong Lewis acid B(C6F5)3. The stable adducts were assessed for frustrated Lewis pair‐type heterolytic E−H bond splitting of hydrosilanes (E=Si) and HB(C6F5)2. Whereas Si−H bond activation was achieved, HB(C6F5)2 was shown to substitute B(C6F5)3 in a quantitative or equilibrated fashion, depending on the nature of the nitrido complex. No B−H bond splitting was observed. Thermodynamics of these reactions, computed by DFT, are in agreement with the experimental outcomes. [ABSTRACT FROM AUTHOR]

Ammonia, NH3, is an essential molecule, being part of fertilizers. It is currently synthesized via the Haber–Bosch process, from the very stable dinitrogen molecule, N2 and dihydrogen, H2. This process requires high temperatures and pressures, thereby generating ca 1.6 % of the global CO2 emissions. Alternative strategies are needed to realize the functionalization of N2 to NH3 under mild conditions. Here, we show that boron‐centered radicals provide a means of activating N2 at room temperature and atmospheric pressure whilst allowing a radical process to occur, leading to the production of borylamines. Subsequent hydrolysis released NH4+, the acidic form of NH3. EPR spectroscopy supported the intermediacy of radicals in the process, corroborated by DFT calculations, which rationalized the mechanism of the N2 functionalization by R2B radicals. [ABSTRACT FROM AUTHOR]

Nitrogen reduction under mild conditions (room T and atmospheric P), using a non‐fossil source of hydrogen remains a challenge. Molecular metal complexes, notably Mo based, have recently been shown to be active for such nitrogen fixation. We report electrochemical N2 splitting with a MoIII triphosphino complex [(PPP)MoI3], at room temperature and a moderately negative potential. A MoIV nitride species was generated, which is confirmed by electrochemistry and NMR studies. The reaction goes through two successive one electron reductions of the starting Mo species, coordination of a N2 molecule, and further splitting to a MoIV nitride complex. Preliminary DFT studies support the formation of a bridging MoIN2MoI dinitrogen dimer evolving to the Mo nitride via a low energy transition state. This example joins a short list of molecular complexes for N2 electrochemical reductive cleavage. It opens a door to electrochemical proton‐coupled electron transfer (PCET) conversion studies of N2 to NH3. [ABSTRACT FROM AUTHOR]

Binary ruthenium‐phosphorus nanoparticles (NPs) with different Ru/P ratio were prepared in mild conditions using white phosphorus (P4) as phosphorus source. Accurate study of both their morphology and structure at the atomic level by TEM and HAADF‐STEM, respectively, showed that Ru2P and RuP have a narrow size distribution (ca. 3.3 nm) and are lacking an ordered ruthenium phosphide lattice. 31P Solid State NMR highlighted the existence of three different phosphorus species consistently with the lack of a metal phosphide lattice and finally XPS revealed that the true nature of these nanoparticles can be better described as a ruthenium‐phosphorus alloy. As a benchmark test, the selective hydrogenation of nitroarenes to primary aromatic amines was studied and evidenced how the P‐alloying imparts a surface modification resulting in a higher catalytic activity and excellent chemoselectivity of Ru2P in comparison to Ru(0) and RuP. [ABSTRACT FROM AUTHOR]

In ample variety of transformations, the presence of silver as an additive or co‐catalyst is believed to be innocuous for the efficiency of the operating metal catalyst. Even though Ag additives are required often as coupling partners, oxidants or halide scavengers, its role as a catalytically competent species is widely neglected in cross‐coupling reactions. Most likely, this is due to the erroneously assumed incapacity of Ag to undergo 2e− redox steps. Definite proof is herein provided for the required elementary steps to accomplish the oxidative trifluoromethylation of arenes through AgI/AgIII redox catalysis (i. e. CEL coupling), namely: i) easy AgI/AgIII 2e− oxidation mediated by air; ii) bpy/phen ligation to AgIII; iii) boron‐to‐AgIII aryl transfer; and iv) ulterior reductive elimination of benzotrifluorides from an [aryl‐AgIII‐CF3] fragment. More precisely, an ultimate entry and full characterization of organosilver(III) compounds [K]+[AgIII(CF3)4]− (K‐1), [(bpy)AgIII(CF3)3] (2) and [(phen)AgIII(CF3)3] (3), is described. The utility of 3 in cross‐coupling has been showcased unambiguously, and a large variety of arylboron compounds was trifluoromethylated via [AgIII(aryl)(CF3)3]− intermediates. This work breaks with old stereotypes and misconceptions regarding the inability of Ag to undergo cross‐coupling by itself. [ABSTRACT FROM AUTHOR]

Catalytic formation of borylamines from atmospheric N2 is achieved for the first time using a series of homogenous (triphosphine)Mo complexes. Stepwise functionalization of the (triphosphine)Mo‐nitrido complex with chloroborane led to the synthesis of the imido complex. Electrochemical characterization of the (PPP)Mo‐nitrido and (PPP)Mo‐borylimido complexes showed that the latter is much more easily reduced. [ABSTRACT FROM AUTHOR]

The direct synthesis of nitrile from N2 under mild conditions is of great importance and has attracted much interest. Herein, we report a direct conversion of N2 into nitrile via a nitrile–alkyne cross‐metathesis (NACM) process involving a N2‐derived Mo nitride. Treatment of the Mo nitride with alkyne in the presence of KOTf afforded an alkyne‐coordinated nitride, which was then transformed into MoV carbyne and the corresponding nitrile upon 1 e− oxidation. Both aryl‐ and alkyl‐substituted alkynes underwent this process smoothly. Experiments and DFT calculations have proved that the oxidation state of the Mo center plays a crucial role. This method does not rely on the nucleophilicity of the N2‐derived metal nitride, offering a novel strategy for N2 fixation chemistry. [ABSTRACT FROM AUTHOR]

Functionalization of nitrido complex [(PPhP2Cy)Mo(N)(I)] by a bis‐silane in concentrated medium generates the hydrido‐imido complex [(PPhP2Cy)Mo(H)(=NSiMe2CH2CH2SiMe2H)(I)]. Abstraction of the iodide by thallium salt TlX (X = PF6, OTf) results in a second N–Si bond formation and forms the bis‐hydride amide complex [(PPhP2Cy)Mo(H)2(NSiMe2CH2CH2SiMe2)]+. An alternative synthesis relies on the abstraction of the iodide from the nitride complex [(PPhP2Cy)Mo(N)(I)] to generate the corresponding cationic complex [(PPhP2Cy)Mo(N)]+ followed by addition of the bis‐silane. Addition of PMe3 to the [(PPhP2Cy)Mo(H)2(NSiMe2CH2CH2SiMe2)]+ complex liberates the silylamine and forms the Mo(II) cationic complex [(PPhP2Cy)Mo(H)(PMe3)]+. DFT calculations rationalizing the observed reactivity are presented. [ABSTRACT FROM AUTHOR]

The [4+2] cycloaddition of 2‐(2′‐pyridyl)‐4,6‐diphenyl‐λ3‐phosphinine with the highly reactive dienophile hexafluoro‐2‐butyne has been studied and the first pyridyl‐functionalized 1‐phosphabarrelene was obtained and structurally characterized. Although monodentate CF3‐1‐phosphabarrelenes show only a poor coordination ability, the chelating nature of the novel P,N‐hybrid ligand gives access to various transition‐metal complexes. Upon irradiation with UV light, the pyridyl‐functionalized 1‐phosphabarrelene undergoes a rather selective di‐π‐methane rearrangement in the coordination sphere of the metal center, leading to the formation of a complex based on a hitherto unknown pyridyl‐functionalized 5‐phosphasemibullvalene derivative. DFT calculations provide first insights into the mechanism of this reaction. [ABSTRACT FROM AUTHOR]

A series of substituted phosphinines, 1‐phosphabarrelenes and 5‐phosphasemibullvalenes were synthesized and evaluated for their potential application as ligands in homogeneous catalytic reactions. While their buried volume (%Vbur) was calculated to get insight into the steric properties, [LNi(CO)3] complexes were prepared in order to determine the corresponding Tolman electronic parameter. ETS‐NOCV (extended‐transition‐state natural orbital for chemical valence) calculations on [LAuCl] complexes further allowed an estimation of the σ‐ and π‐contributions to the L−M interaction. AuI coordination compounds of selected examples were prepared and characterized by single crystal X‐ray diffraction. Finally, the three classes of PIII compounds were successfully used in the AuI‐catalyzed cycloisomerization of N‐2‐propyn‐1‐ylbenzamide, showing very good activities and selectivities, which are comparable with the reported data of cationic phosphorus‐based gold catalysts. [ABSTRACT FROM AUTHOR]

Copyright of Angewandte Chemie is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract: Reduction of the FeII complex [(PhPP2Cy)FeCl2] (2) generated an electron‐rich and unsaturated Fe0 species, which was reacted with white phosphorus. The resulting new complex, [(PhPP2Cy)Fe(η4‐P4)] (3), is the first iron cyclo‐P4 complex and the only known stable end‐deck cyclo‐P4 complex outside Group V. Complex 3 features an FeII center, as shown by Mössbauer spectroscopy, associated to a P42− fragment. The distinct reactivity of complex 3 was rationalized by analysis of the molecular orbitals. Reaction of complex 3 with H+ afforded the unstable complex [(PhPP2Cy)Fe(η4‐P4)(H)]+ (4), whereas with CuCl and BCF, the complexes [(PhPP2Cy)Fe(η4:η1‐P4)(μ‐CuCl)]2 (5) and [(PhPP2Cy)Fe(η4:η1‐P4)B(C6F5)3] (6) were formed. [ABSTRACT FROM AUTHOR]

The robust, high-valent NiIV complex [(Py)2NiIVF2(CF3)2] (Py=pyridine) was synthesized and fully characterized by NMR spectroscopy, X-ray diffraction, and elemental analysis. It reacts with aromatic compounds at 25 °C to form the corresponding benzotrifluorides in nearly quantitative yield. The monomeric and dimeric NiIIICF3 complexes 2⋅Py and 2 were identified as key intermediates, and their structures were unambiguously determined by EPR spectroscopy and X-ray diffraction. Preliminary kinetic studies in combination with the isolation of reaction intermediates confirmed that the C−H bond-breaking/C−CF3 bond-forming sequence can occur both at NiIVCF3 and NiIIICF3 centers. [ABSTRACT FROM AUTHOR]

The first AuIII carbene complex was prepared by reacting a geminal dianion with a (P,C) cyclometalated AuIII precursor. Its structure and bonding situation have been thoroughly investigated by experimental and computational means. The presence of a high-energy highest occupied molecular orbital (HOMO) centered at the carbene center suggests nucleophilic character for the AuIII carbene complex. This unprecedented feature was confirmed by reactions with two electrophiles (PhNCS and CS2), resulting in two types of C=C coupling reactions. [ABSTRACT FROM AUTHOR]

Herein, we present a detailed study of the conversion of a nickel(II) diamide precursor to size-tunable, monodisperse nickel nanoparticles (NPs). The thermal decomposition of nickel(II) dioleylamide, synthesized either independently or in situ, resulted in the formation of Ni NPs without the coproduction of water. Mechanistic studies were conducted on the stability and reduction pathway of the NiII precursor, and on the consequent particle formation. Variations in the ratio of trioctylphosine (TOP) to nickel allowed size tunability, which resulted in nanoparticles that ranged in size from 4 to 11 nm in diameter. The DFT calculations support a mechanistic pathway that involves nickel reduction by imine formation. This water-free method was extended to the synthesis of water-sensitive M0 NPs (M=Fe, Co). [ABSTRACT FROM AUTHOR]

A homogeneous system which is able to yield silylamine from N2 and bis(silane) in one pot is reported. Mechanistically a {(triphosphine)molybdenum(I)} fragment, generated in situ, splits N2 into the corresponding nitrido complex at room temperature. Then, functionalization of the molybdenum nitrido is achieved by double Si−H addition under mild reaction conditions. Moreover, the bis(silyl)amine product is decoordinated from the metal center. [ABSTRACT FROM AUTHOR]

A series of tridentate aryloxy-based ligands were synthesized and characterized for their coordination behaviour towards TiIV. Coordination studies revealed that the nature of the central atom (amine vs. ether) and the type of bridging spacer (aromatic vs. aliphatic) are important aryloxy ligand parameters and influence the ligand coordination mode and the formation of stable titanium complexes. This series of titanium complexes were evaluated in ethylene oligomerization and polymerization after activation with methylaluminoxane (MAO) and showed the preferential formation of polyethylene. In some cases, the formation of a small amount of 1-hexene suggests the existence of several catalytic centres in the reaction mixture. [ABSTRACT FROM AUTHOR]

The use of a strongly donating '(bis-dialkylphosphine)Ni' fragment promotes the catalytic coupling of a large range of ArCl and ArZnCl derivatives under mild conditions. Stoichiometric mechanistic investigations and DFT calculations prove that a Ni0/NiII cycle is operative in this system. [ABSTRACT FROM AUTHOR]

Detailed studies on the reactivity of 2-(2′-pyridyl)-4,6-diphenylphosphinine ( 2) towards CF3SO3H and sulfur have been performed, and the results were compared with those for nonfunctionalized 2,4,6-triphenylphosphinine derivatives. Substantial differences between these heterocycles were observed, and the reaction products could be characterized crystallographically. The reactions of 2,4,6-triarylphosphinine sulfides with methanol led to different products, which could be characterized by NMR spectroscopy and X-ray crystal structure analysis. Interestingly, the outcomes of these transformations strongly depend on the presence of an additional donor functionality within the phosphorus heterocycle as well as the nature of the solvent and the reaction temperature. DFT calculations were performed to rationalize the different reaction pathways. [ABSTRACT FROM AUTHOR]

Stoichiometric reduction of N2 at a Mo center stabilized by a bulky tetradentate phosphine ligand ( ${{\rm PP}{{{\rm Cy}\hfill \atop 3\hfill}}}$) allowed isolation of Mo-imidoamine and Mo-imido complexes. Both complexes as well as the MoII precursor are equally suitable catalysts for the synthesis of NTMS3 (TMS=trimethylsilyl) from N2, TMSCl, and electron sources. Mechanistic studies prove the involvement of a TMS radical at least in one of the catalytic steps. [ABSTRACT FROM AUTHOR]

The synthesis of two novel titanium carbene complexes from the bis(thiophosphinoyl)methanediide geminal dianion 1 (SCS2-) is described. Dianion 1 reacts cleanly with 0.5 equivalents of [TiCl4(thf)2] to afford the bis-carbene complex [(SCS)2Ti] (2) in 86% yield. The mono-carbene complex [(SCS)TiCl2(thf)] (3) can also be obtained by using an excess of [TiCl4(thf)2]. The structures of 2 and 3 are confirmed by Xray crystallography. A strong nucleophilic reactivity towards various electrophiles (ketones and aldehydes) is observed. The reaction of 3 with N,N'-dicyclohexylcarbodiimide (DCC) and phenyl isocyanate leads to the formation of two novel diphosphinoketenimines 8a and 8b. The bis-titanium guanidinate complex 9 is trapped as the by-product of the reaction with DCC. The X-ray crystal structures of 8a and 9 are presented. The mechanism of the reaction between complex 3 and DCC is rationalized by DFT studies. [ABSTRACT FROM AUTHOR]

The platinum(II) complex [(dcpp)Pt(C7H7)H] ( 1) [dcpp = 1,3-bis(dicyclohexylphosphanyl)propane] reacts under 1 atm of CO to form the bis(carbonyl) complex of Pt0, [(dcpp)Pt(CO)2] ( 2). Complex 2 slowly crystallizes in toluene solution to form crystals of the Pt0 dimer [(dcpp)(η1-CO)Pt{μ-C(O)}Pt(dcpp)] ( 3) in which one Pt atom is only three-coordinated with the diphosphane dcpp and one μ-C(O), while the other is coordinated in a tetrahedral arrangement with one μ-C(O) and one η1-CO. Complexes 2 and 3 were characterized in solution by 31P NMR spectroscopy, and complex 3 readily reacts with O2 to form the carbonate complex, [(dcpp)Pt(CO3)] ( 4). The reaction of the dimeric complex 3 with MeI allows the insertion of a methyl group into the carbonyl group to form the PtII complex [(dcpp)Pt(C(O)Me)I] ( 5). Reaction of another equivalent of MeI with complex 5 leads to the formation and elimination of acetone and the bis(iodide) complex [(dcpp)PtI2] ( 6). X-ray crystal structures of complexes 3 and 4 are reported along with DFT calculations and mechanistic studies of the formation of 3, 4, 5, and 6. [ABSTRACT FROM AUTHOR]

Activation of X-H bonds with SCS pincer palladium complexes featuring methanediide and indenediide backbones was studied by DFT calculations. Me2NH, Me2PH, MeOH, MeSH, PhOH, and PhSH were chosen as model substrates. Different products were considered for these addition reactions: simple adduct (X coordination), 1,2-addition across the Pd-C and Pd-S bonds, 1,3-addition (if possible), as well as oxidative addition at Pd. For the methanediide system, 1,2-PdC adducts were predicted to be the most favored activation products. For the indenediide system, 1,3-PdC and 1,2-PdC additions are conceivable. This theoretical study suggests that methanediide and indenediide Pd complexes may be interesting candidates for catalytic transformations involving X-H bond activation, typically hydrofunctionalization reactions. [ABSTRACT FROM AUTHOR]

A new unsymmetrical geminal dianion that contained both a phosphine oxide moiety and a phosphine sulfide moiety has been synthesized. Its reactivity towards RuII was explored, which led to the formation of a highly reactive carbene complex that evolved at room temperature to yield a kinetic orthometalated RuII complex through CH activation of the phenyl group of the phosphine oxide moiety. This insertion was found to be thermally reversible and a second CH insertion occurred at a phenyl group of the phosphine sulfide moiety to form the thermodynamic orthometalated RuII complex in a diastereospecific manner. DFT calculations fully rationalized the experimental findings in terms of the relative energies of the kinetic and thermodynamic products and allowed the mechanism of this process to be fully understood. [ABSTRACT FROM AUTHOR]

The widely used preparation of Ni0 nanoparticles from [Ni(acac)2] (acac=acetylacetonate) and oleylamine, often considered to be a thermolysis or a radical reaction, was analyzed anew by using a combination of DFT modeling and designed mechanistic experiments. Firstly, the reaction was followed up by using TGA to evaluate the energy barrier of the limiting step. Secondly, all the byproducts were identified using NMR spectroscopy, mass spectrometry, FTIR, and X-ray crystallography. These methods allowed us to depict both main and side-reaction pathways. Lastly, DFT modeling was utilized to assess the validity of this new scheme by identifying the limiting steps and evaluating the corresponding energy barriers. The oleylamine was shown to reduce the [Ni(acac)2] complex not through a one-electron radical mechanism, as often stated, but as an hydride donor through a two-electron chemical reduction route. This finding has strong consequences not only for the design of further nanoparticles syntheses that use long-chain amine as a reactant, but also for advanced understanding of catalytic reactions for which these nanoparticles can be employed. [ABSTRACT FROM AUTHOR]

Keywords: AgIII chemistry; cross-coupling; fluorine; high-valent species; trifluoromethylation EN AgIII chemistry cross-coupling fluorine high-valent species trifluoromethylation 15273 15273 1 11/09/21 20211105 NES 211105 B Landing to explore beneath the silvery reflection b of the moon, the unusual air oxidation of silver was investigated, granting access to the homoleptic anion [Ag SP III sp (CF SB 3 sb ) SB 4 sb ] SP - sp ( B 1 b ). The crew compartment of the Lunar Lander illustrates the structure of B 1 b mimicking the heraldic Occitan Cross, symbol of Occitania, where this work was developed. Upon addition of aryl boron derivatives and base, [(phen)Ag SP III sp (CF SB 3 sb ) SB 3 sb ] undergoes aromatic trifluoromethylation. [Extracted from the article]

Keywords: coordination chemistry; DFT calculations; di-pi-methane rearrangement; phosphabarrelene; phosphorus ligands This P,N-hybrid ligand readily forms coordination compounds with Rh SP I sp , W SP 0 sp , and Fe SP 0 sp and undergoes a rather selective photochemical di- -methane rearrangement in the coordination sphere of the metal center to afford a novel 5-phosphasemibullvalene derivative. Coordination chemistry, DFT calculations, di-pi-methane rearrangement, phosphabarrelene, phosphorus ligands. [Extracted from the article]

Highlights from the article: Cover Feature: Phosphinine-Based Ligands in Gold-Catalyzed Reactions (Chem. Eur. J. 37/2019) Keywords: density functional calculations; heterocycles; homogeneous gold catalysis; phosphorus ligands; X-ray diffraction Density functional calculations, heterocycles, homogeneous gold catalysis, phosphorus ligands, X-ray diffraction.

The widely used preparation of Ni0 nanoparticles from [Ni(acac)2] (acac=acetylacetonate) and oleylamine, often considered to be a thermolysis or a radical reaction, was analyzed anew by using a combination of DFT modeling and designed mechanistic experiments. Firstly, the reaction was followed up by using TGA to evaluate the energy barrier of the limiting step. Secondly, all the byproducts were identified using NMR spectroscopy, mass spectrometry, FTIR, and X-ray crystallography. These methods allowed us to depict both main and side-reaction pathways. Lastly, DFT modeling was utilized to assess the validity of this new scheme by identifying the limiting steps and evaluating the corresponding energy barriers. The oleylamine was shown to reduce the [Ni(acac)2] complex not through a one-electron radical mechanism, as often stated, but as an hydride donor through a two-electron chemical reduction route. This finding has strong consequences not only for the design of further nanoparticles syntheses that use long-chain amine as a reactant, but also for advanced understanding of catalytic reactions for which these nanoparticles can be employed. [ABSTRACT FROM AUTHOR]