Aryne Complexes of Zerovalent Metals of the Nickel Triad

The chemistry of dihapto-aryne complexes of the zerovalent Group 10 metals of general formula [M(η2-aryne)L2] (M = Ni, Pd, Pt; L = various tertiary phosphines) is reviewed, with emphasis on the highly reactive nickel(0) compounds (aryne = benzyne, C6H4; 4,5-difluorobenzyne, 4,5-C6H2F2; 2,3-naphthalyne, 2,3-C10H6; L2 = 2 PEt3, 2 PiPr3, 2 PCy3, dcpe). These can be generated by alkali metal reduction of the appropriate (2-halogenoaryl)nickel(ii) halide precursors, such as [NiX(2-XC6H4)L2], which in turn are accessible by oxidative addition of the 1,2-dihaloarene to nickel(0) precursors such as [Ni(1,5-COD)2]. The X-ray structure of [Ni(η2-C6H4)(dcpe)] shows that this compound is a typical 16-electron Ni(0) (3d10) species in which benzyne acts as a 2π-electron donor. Several unusual organonickel compounds derived from [Ni(η2-4,5-C6H2F2)(PEt3)2] have been isolated recently, including [Ni2(μ-η2:η2-4,5-C6H2F2)(PEt3)4], in which a 4π-electron donor 4,5-difluorobenzyne is located at right-angles to a pair of nickel atoms. Free benzyne can be intercepted by both [Ni(η2-C2H4)(dcpe)] and [Pt(η2-C2H4)(PPh3)2], but the resulting benzyne complexes rapidly insert benzyne to give the appropriate η1:η1-2,2′-biphenylyl complexes. [Pt(η2-C6H4)(PPh3)2] also undergoes rapid ortho-metallation to give [PtPh(2-C6H4PPh2)(PPh3)]. However, a trapping reaction has been used to make the first 1,4-benzdiyne complex, [{Ni(dcpe)2}2(μ-η2:η2-1,4-C6H2)] by treatment of the 4-fluorobenzyne complex [Ni(η2-4-FC6H3)(dcpe)] with LiTMP. The use of alkali metals in the preparation of the η2-benzyne complexes is avoided in a more recently developed procedure, which starts from (2-bromophenyl)boronic acid, and is based on Suzuki–Miyaura coupling. This procedure has made accessible for the first time an aryne complex of palladium(0), [Pd(η2-C6H4)(PCy3)2], and the labile nickel(0) complex [Ni(η2-C6H4)(PPh3)2]. The aryne-nickel(0) complexes Ni(η2-aryne)L2 (L2 = 2 PEt3, dcpe) undergo sequential insertions into the aryne-metal bond with unsaturated molecules, such as CO, C2F4, substituted alkynes, substituted diynes, alkynylphosphines, and alkynyl thioethers, often with considerable regioselectivity. After the reductive elimination of two nickel-carbon σ-bonds, a variety of interesting polycyclic compounds can be obtained.

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Room Temperature Alkali Metal Reduction of Carbon Dioxide

10.26434/chemrxiv.12665336 ◽

2020 ◽

Author(s):

Lucas A. Freeman ◽

Akachukwu D. Obi ◽

Haleigh R. Machost ◽

Andrew Molino ◽

Asa W. Nichols ◽

...

Keyword(s):

Alkali Metal ◽

Alkali Metals ◽

Room Temperature ◽

Chemical Reduction ◽

Bond Cleavage ◽

Open Shell ◽

Metal Reduction ◽

One Pot ◽

Earth Abundant ◽

Electron Reduction

The reduction of the relatively inert carbon–oxygen bonds of CO2 to access useful CO2-derived organic products is one of the most important fundamental challenges in synthetic chemistry. Facilitating this bond-cleavage using earth-abundant, non-toxic main group elements (MGEs) is especially arduous because of the difficulty in achieving strong inner-sphere interactions between CO2 and the MGE. Herein we report the first successful chemical reduction of CO2 at room temperature by alkali metals, promoted by a cyclic(alkyl)(amino) carbene (CAAC). One-electron reduction of CAAC-CO2 adduct (1) with lithium, sodium or potassium metal yields stable monoanionic radicals clusters [M(CAAC–CO2)]n(M = Li, Na, K, 2-4) and two-electron alkali metal reduction affords open-shell, dianionic clusters of the general formula [M2(CAAC–CO2)]n (5-8). It is notable that these crystalline clusters of reduced CO2 may also be isolated via the “one-pot” reaction of free CO2 with free CAAC followed by the addition of alkali metals – a reductive process which does not occur in the absence of carbene. Each of the products 2-8 were investigated using a combination of experimental and theoretical methods.

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Diphosphinoazine Rhodium(I) and Iridium(I) Complexes

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc20060197 ◽

2006 ◽

Vol 71 (2) ◽

pp. 197-206 ◽

Cited By ~ 1

Author(s):

Martin Pošta ◽

Jan Čermák ◽

Pavel Vojtíšek ◽

Ivana Císařová

Keyword(s):

Rhodium Complexes ◽

Iridium Complexes ◽

X Ray ◽

First Time

The first rhodium complexes of diphosphinoazines [{RhCl(1,2-η:5,6-η-CH=CHCH2CH2CH=CHCH2CH2)}2 {μ-R2PCH2C(But)=NN=C(But)CH2PR2] (R = Ph, Cy, Pri) were prepared by cleavage of the bridge in chloro(cycloocta-1,5-diene)rhodium(I) dimer, the analogous iridium(I) complexes were also prepared for the first time. The X-ray structures of isostructural rhodium and iridium complexes with bis(dicyclohexylphosphino)pinacoloneazine were determined. Diphosphinoazine ligands in the complexes remained in (Z,Z) configuration bridging two RhCl(C8H12) units.

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Quartz Crystallite Size and Moganite Content as Indicators of the Mineralogical Maturity of the Carboniferous Chert: The Case of Cherts from Eastern Asturias (Spain)

Minerals ◽

10.3390/min11060611 ◽

2021 ◽

Vol 11 (6) ◽

pp. 611

Author(s):

Celia Marcos ◽

María de Uribe-Zorita ◽

Pedro Álvarez-Lloret ◽

Alaa Adawy ◽

Patricia Fernández ◽

...

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Crystallite Size ◽

Archaeological Sites ◽

X Ray Diffraction ◽

X Ray ◽

Transmission Electron ◽

Infrared And Raman Spectroscopy ◽

First Time ◽

Geological Formations

Chert samples from different coastal and inland outcrops in the Eastern Asturias (Spain) were mineralogically investigated for the first time for archaeological purposes. X-ray diffraction, X-ray fluorescence, transmission electron microscopy, infrared and Raman spectroscopy and total organic carbon techniques were used. The low content of moganite, since its detection by X-ray diffraction is practically imperceptible, and the crystallite size (over 1000 Å) of the quartz in these cherts would be indicative of its maturity and could potentially be used for dating chert-tools recovered from archaeological sites. Also, this information can constitute essential data to differentiate the cherts and compare them with those used in archaeological tools. However, neither composition nor crystallite size would allow distinguishing between coastal and inland chert outcrops belonging to the same geological formations.

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First Report on the Geologic Occurrence of Natural Na–A Zeolite and Associated Minerals in Cretaceous Mudstones of the Paja Formation of Vélez (Santander), Colombia

Crystals ◽

10.3390/cryst11020218 ◽

2021 ◽

Vol 11 (2) ◽

pp. 218

Author(s):

Carlos Alberto Ríos-Reyes ◽

German Alfonso Reyes-Mendoza ◽

José Antonio Henao-Martínez ◽

Craig Williams ◽

Alan Dyer

Keyword(s):

Natural Zeolite ◽

Scanning Electron Micrographs ◽

Total Sulfur ◽

Zeolite A ◽

X Ray Diffraction ◽

X Ray ◽

Mineral Phases ◽

The World ◽

Porosity And Permeability ◽

First Time

This study reports for the first time the geologic occurrence of natural zeolite A and associated minerals in mudstones from the Cretaceous Paja Formation in the urban area of the municipality of Vélez (Santander), Colombia. These rocks are mainly composed of quartz, muscovite, pyrophyllite, kaolinite and chlorite group minerals, framboidal and cubic pyrite, as well as marcasite, with minor feldspar, sulphates, and phosphates. Total organic carbon (TOC), total sulfur (TS), and millimeter fragments of algae are high, whereas few centimeters and not biodiverse small ammonite fossils, and other allochemical components are subordinated. Na–A zeolite and associated mineral phases as sodalite occur just beside the interparticle micropores (honeycomb from framboidal, cube molds, and amorphous cavities). It is facilitated by petrophysical properties alterations, due to processes of high diagenesis, temperatures up to 80–100 °C, with weathering contributions, which increase the porosity and permeability, as well as the transmissivity (fluid flow), allowing the geochemistry remobilization and/or recrystallization of pre-existing silica, muscovite, kaolinite minerals group, salts, carbonates, oxides and peroxides. X-ray diffraction analyses reveal the mineral composition of the mudstones and scanning electron micrographs show the typical cubic morphology of Na–A zeolite of approximately 0.45 mμ in particle size. Our data show that the sequence of the transformation of phases is: Poorly crystalline aluminosilicate → sodalite → Na–A zeolite. A literature review shows that this is an unusual example of the occurrence of natural zeolites in sedimentary marine rocks recognized around the world.

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The Effect of Surfactant-Modified Montmorillonite on the Cross-Linking Efficiency of Polysiloxanes

Materials ◽

10.3390/ma14102623 ◽

2021 ◽

Vol 14 (10) ◽

pp. 2623

Author(s):

Monika Wójcik-Bania ◽

Jakub Matusik

Keyword(s):

Total Pore Volume ◽

Cross Linking ◽

X Ray Diffraction ◽

X Ray ◽

Transmission Electron ◽

The Cross ◽

Chain Lengths ◽

First Time ◽

Substituent Influence ◽

Benzyl Substituent

Polymer–clay mineral composites are an important class of materials with various applications in the industry. Despite interesting properties of polysiloxanes, such matrices were rarely used in combination with clay minerals. Thus, for the first time, a systematic study was designed to investigate the cross-linking efficiency of polysiloxane networks in the presence of 2 wt % of organo-montmorillonite. Montmorillonite (Mt) was intercalated with six quaternary ammonium salts of the cation structure [(CH3)2R’NR]+, where R = C12, C14, C16, and R’ = methyl or benzyl substituent. The intercalation efficiency was examined by X-ray diffraction, CHN elemental analysis, and Fourier transform infrared (FTIR) spectroscopy. Textural studies have shown that the application of freezing in liquid nitrogen and freeze-drying after the intercalation increases the specific surface area and the total pore volume of organo-Mt. The polymer matrix was a poly(methylhydrosiloxane) cross-linked with two linear vinylsiloxanes of different siloxane chain lengths between end functional groups. X-ray diffraction and transmission electron microscopy studies have shown that the increase in d-spacing of organo-Mt and the benzyl substituent influence the degree of nanofillers’ exfoliation in the nanocomposites. The increase in the degree of organo-Mt exfoliation reduces the efficiency of hydrosilylation reaction monitored by FTIR. This was due to physical hindrance induced by exfoliated Mt particles.

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Homopiperazine (Hexahydro-1,4-diazepine)

Molbank ◽

10.3390/m1200 ◽

2021 ◽

Vol 2021 (2) ◽

pp. M1200

Author(s):

R. Alan Aitken ◽

Dheirya K. Sonecha ◽

Alexandra M. Z. Slawin

Keyword(s):

13C Nmr ◽

Title Compound ◽

Coupling Constants ◽

15N Nmr ◽

Time Data ◽

Nmr Spectrum ◽

X Ray ◽

First Time

The X-ray structure of the title compound has been determined for the first time. Data on its 1H–13C-NMR coupling constants and 15N-NMR spectrum are also given.

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A novel and potentially scalable CVD-based route towards SnO2:Mo thin films as transparent conducting oxides

Journal of Materials Science ◽

10.1007/s10853-021-06269-3 ◽

2021 ◽

Author(s):

Tianlei Ma ◽

Marek Nikiel ◽

Andrew G. Thomas ◽

Mohamed Missous ◽

David J. Lewis

Keyword(s):

Thin Films ◽

Photoelectron Spectroscopy ◽

Mixed Valence ◽

Chemical Vapour ◽

X Ray Diffraction ◽

X Ray ◽

Conducting Oxides ◽

Valence States ◽

3 Omega ◽

First Time

AbstractIn this report, we prepared transparent and conducting undoped and molybdenum-doped tin oxide (Mo–SnO2) thin films by aerosol-assisted chemical vapour deposition (AACVD). The relationship between the precursor concentration in the feed and in the resulting films was studied by energy-dispersive X-ray spectroscopy, suggesting that the efficiency of doping is quantitative and that this method could potentially impart exquisite control over dopant levels. All SnO2 films were in tetragonal structure as confirmed by powder X-ray diffraction measurements. X-ray photoelectron spectroscopy characterisation indicated for the first time that Mo ions were in mixed valence states of Mo(VI) and Mo(V) on the surface. Incorporation of Mo6+ resulted in the lowest resistivity of $$7.3 \times 10^{{ - 3}} \Omega \,{\text{cm}}$$ 7.3 × 10 - 3 Ω cm , compared to pure SnO2 films with resistivities of $$4.3\left( 0 \right) \times 10^{{ - 2}} \Omega \,{\text{cm}}$$ 4.3 0 × 10 - 2 Ω cm . Meanwhile, a high transmittance of 83% in the visible light range was also acquired. This work presents a comprehensive investigation into impact of Mo doping on SnO2 films synthesised by AACVD for the first time and establishes the potential for scalable deposition of SnO2:Mo thin films in TCO manufacturing. Graphical abstract

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Reactive Dual Magnetron Sputtering: A Fast Method for Preparing Stoichiometric Microcrystalline ZnWO4 Thin Films

Surfaces ◽

10.3390/surfaces4020013 ◽

2021 ◽

Vol 4 (2) ◽

pp. 106-114

Author(s):

Yannick Hermans ◽

Faraz Mehmood ◽

Kerstin Lakus-Wollny ◽

Jan P. Hofmann ◽

Thomas Mayer ◽

...

Keyword(s):

Thin Films ◽

Magnetron Sputtering ◽

Photoelectron Spectroscopy ◽

Fast Method ◽

X Ray Diffraction ◽

X Ray ◽

Glass Substrates ◽

Post Annealing ◽

Rf Signal ◽

First Time

Thin films of ZnWO4, a promising photocatalytic and scintillator material, were deposited for the first time using a reactive dual magnetron sputtering procedure. A ZnO target was operated using an RF signal, and a W target was operated using a DC signal. The power on the ZnO target was changed so that it would match the sputtering rate of the W target operated at 25 W. The effects of the process parameters were characterized using optical spectroscopy, X-ray diffraction, and scanning electron microscopy, including energy dispersive X-ray spectroscopy as well as X-ray photoelectron spectroscopy. It was found that stoichiometric microcrystalline ZnWO4 thin films could be obtained, by operating the ZnO target during the sputtering procedure at a power of 55 W and by post-annealing the resulting thin films for at least 10 h at 600 °C. As FTO coated glass substrates were used, annealing led as well to the incorporation of Na, resulting in n+ doped ZnWO4 thin films.

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Revealing noncollinear magnetic ordering at the atomic scale via XMCD

Scientific Reports ◽

10.1038/s41598-021-82518-4 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Fridtjof Kielgast ◽

Ivan Baev ◽

Torben Beeck ◽

Federico Pressacco ◽

Michael Martins

Keyword(s):

Ground State ◽

Magnetic Circular Dichroism ◽

Magnetic Moments ◽

Magnetic Ordering ◽

Atomic Scale ◽

Angle Of Incidence ◽

X Ray ◽

First Time ◽

X Ray Absorption ◽

Magnetic Sublattices

AbstractMass-selected V and Fe monomers, as well as the heterodimer $${\text{Fe}}_1{\text{V}}_1$$ Fe 1 V 1 , were deposited on a Cu(001) surface. Their electronic and magnetic properties were investigated via X-ray absorption (XAS) and X-ray magnetic circular dichroism (XMCD) spectroscopy. Anisotropies in the magnetic moments of the deposited species could be examined by means of angle resolving XMCD, i.e. changing the X-ray angle of incidence. A weak adatom-substrate-coupling was found for both elements and, using group theoretical arguments, the ground state symmetries of the adatoms were determined. For the dimer, a switching from antiparallel to parallel orientation of the respective magnetic moments was observed. We show that this is due to the existence of a noncollinear spin-flop phase in the deposited dimers, which could be observed for the first time in such a small system. Making use of the two magnetic sublattices model, we were able to find the relative orientations for the dimer magnetic moments for different incidence angles.

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Tris(dimethylphenylphosphine)ruthenium(0) Complexes of n4-Coordinated Polycyclic Aromatic Hydrocarbons

Australian Journal of Chemistry ◽

10.1071/ch00068 ◽

2000 ◽

Vol 53 (6) ◽

pp. 507 ◽

Cited By ~ 10

Author(s):

Martin A. Bennett ◽

Mark Bown ◽

David C. R. Hockless

Keyword(s):

Coordination Geometry ◽

Crystal Data ◽

Asymmetric Unit ◽

X Ray Diffraction ◽

Tertiary Phosphine ◽

X Ray ◽

Tertiary Phosphines ◽

Polycyclic Aromatic ◽

R Value ◽

Axial Site

From the reaction of [Ru2Cl3(PMe2Ph)6] Cl with the appropriate radical anions, yellow complexes of general formula [Ru(PMe2Ph)3(η4-arene)] [arene = naphthalene (C10H8) (1), anthracene (C14H10) (2), and triphenylene (C18H12) (3)] have been isolated in poor yield and characterized by elemental analysis, n.m.r. (1H, 13C, 31P) spectroscopy and single-crystal X-ray diffraction. Crystal data: (1), monoclinic, C2/c, a 31.096(8), b 12.012(4), c 17.078(8) Å, β 104.41(3)˚, V 6178(4) Å3, ? 8, refined to final R value of 0.032 with use of 3641 reflections [I > 3σ(I)]; (2), monoclinic, C2/c, a 55.909(4), b 14.348(5), c 17.573(5) Å, β 105.41(1)˚, V 13590(6) Å3, Z 16 (two molecules per asymmetric unit), refined to final R value of 0.049 with use of 7770 reflections [I > 3σ(I)]; (3), mono-clinic, Pn, a 9.377(3), b 12.229(3), c 15.975(3) Å, β 103.51(2)˚, V 1781.2 (7) Å3, Z 2, refined to final R value of 0.026 with use of 2830 reflections [I > 3σ(I)]. In each case, coordination of the zerovalent metal fragment Ru(PMe2Ph)3 to the diene section of one of the terminal rings causes the aromatic molecule to be folded by c. 40˚ at the outer carbon atoms of the diene. The coordination geometry about ruthenium is approximately square pyramidal, with the diene and two tertiary phosphines in the equatorial plane and the remaining tertiary phosphine in the axial site.

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