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The article cites a study that reports on the facile and nonreductive C—N activation and cleavage of pyridine by a transient titanium alkylidyne. Activation of the C—N bond in pyridine involves a unique process, a ring-opening metathesis step invoking the cycloadition of the aromatic C=N bond across a reactive TiΞC'Bu linkage. The combination of synthesis, isotopic labeling and theoretical studies allowed for understanding this rare transformation.

Reaction of PNPCo, where PNP is (tBu2PCH2SiMe2)2N-, with the persistent radical galvinoxyl, G, gives PNPCoIIG, a nonplanar S = 3/2 species. Reaction with PhCH2Cl or with 0.5 mol I2 gives PNPCoX (X = Cl or I, respectively), but additional I2, seeking CoIII, gives instead oxidation at phosphorus: (tBu2P(I)CH2-SiMe2NSiMe2CH2PtBu2)CoI2. Hydrogen-atom transfer reagents fail to give PNPCoH, but H2 gives instead PNPCo(H)2, a result rationalized thermodynamically based on DFT calculations. Multiple equiv of PhSiH3 give a product of Co(V), where N/SiPh and P/Si bonds have formed. N2CH(SiMe3) gives a 1:1 adduct of PNPCo, whose metric parameters suggest partial oxidation above CoI; N2CHPh gives a 1:1 adduct but with very different spectroscopic features. PhN3 reacts fast, via several intermediates detected below 0 °C, to finally release N2 and form a CoI product where one phosphorus has been oxidized, PN(PNPh)Co. Whereas PNPCo(N3) resists loss of N2 on heating, one electron oxidation gives a rapid loss of N2, and the remaining nitride nitrogen is quickly incorporated into the chelate ligand, giving [tBu2PCH2SiMe2NSiMe2-NP(tBu2)CH2Co]. O2 or PhlO generally gives products where one or both phosphorus centers are converted to its oxide, bonded to cobalt. [ABSTRACT FROM AUTHOR]

Reactions of LAI with ethyne, mono- and disubstituted alkynes, and diyne to aluminacyclopropene LAl[η²-C2(R¹)(R²)] ((L = HC((CMe)(NAr)]2, Ar = 2,6-/Pr2C6H3); R¹ = R² = H, (1); R¹ = H, R² = Ph, (2); R¹ = R² = Me, (3); R¹ = SiMe3, R² = C≡CSiMe3, (4)) are reported. Compounds 1 and 2 were obtained in equimolar quantities of the starting materials at low temperature. The amount of C2H2 was controlled by removing an excess of C2H2 in the range from -78 to -50 °C. Compound 4 can be alternatively prepared by the substitution reaction of LAl[η²-C2(SiMe3)2] with Me3SiC≡CC≡CSiMe3 or by the reductive coupling reaction of LAII2 with potassium in the presence of Me3SiC≡CC≡CSiMe3. The reaction of LAI with excess C2H2 and PhC≡CH (<1:2) afforded the respective alkenylalkynylaluminum compounds LAl(CH = CH2)(C≡CH) (5) and LAl(CH = CHPh)(C ≡ CPh) (6). The reaction of LAl(η²-C2Ph2) with C2H2 and PhC ≡ CH yielded LAl(CPh = CHPh)(C ≡ CH) (7) and LAl(CPh = CHPh)(C ≡ CPh) (8), respectively. Rationally, the formation of 5 (or 6) may proceed through the corresponding precursor 1 (or 2). The theoretical studies based on DFT calculations show that an interaction between the Al(l) center and the C ≡ C unit needs almost no activation energy. Within the AlC2 ring the computational Al-C bond order of ca. 1 suggests an Al-C σ bond and therefore less π electron delocalization over the AlC2 ring. The computed Al-η²-C2 bond dissociation energies (155-82.6 kJ/mol) indicate a remarkable reactivity of aluminacyclopropene species. Finally, the ¹H NMR spectroscopy monitored reaction of LAl(η²-C2Ph2) and PhC ≡ CH in toluene-da may reveal an acetylenic hydrogen migration process. [ABSTRACT FROM AUTHOR]

The heteronuclear metal carbonyl anions MNi(CO)3- (M = Mg, Ca, Al) have been investigated using photoelectron velocity-map imaging spectroscopy. Electron affinities of neutral MNi(CO)3 (M = Mg, Ca, Al) are measured from the photoelectron spectra to be 1.064 ± 0.063, 1.050 ± 0.064, and 1.541 ± 0.040 eV, respectively. The C-O stretching mode in these three clusters is observed and the vibrational frequency is determined to be 2049, 2000, and 2041 cm-1 for MgNi(CO)3, CaNi(CO)3, and AlNi(CO)3, respectively. Density functional theory calculations are carried out to elucidate the geometric and electronic structures and to aid the experimental assignments. It has been found that three terminal carbonyls are preferentially bonded to the nickel atom in these heterobinuclear nickel carbonyls MNi(CO)3-1/0, resulting in the formation of the Ni(CO)3 motif. Ni remains the 18-electron configuration for MgNi(CO)3 and CaNi(CO)3 neutrals, but not for AlNi(CO)3. This is different from the homobinuclear nickel carbonyl Ni-Ni(CO)3 with the involvement of three bridging ligands. Present findings would be helpful for understanding CO adsorption on alloy surfaces. [ABSTRACT FROM AUTHOR]

Low-energy photoelectron imaging spectra of HCS2- are reported for the first time. Vibrationally resolved photodetachment transitions from the ground state of HCS2- to the ground state and low-lying excited states of HCS2 are observed. Combined with the ab intio calculations and Franck-Condon simulations, well-resolved vibrational spectra demonstrate definitive evidence for the resolution of the ground-state and excited states of HCS2 radical in the gaseous phase. The ground state and two low-lying excited states of HCS2 radical are assigned as ²B2, ²A2, and ²A1 states, respectively. The adiabatic electron affinity is determined to be 2.910 ± 0.007 eV. And the term energies of the excited states, T0 = 0.451 ± 0.009 eV and 0.553 ± 0.009 eV, are directly measured from the experimental data, respectively. Angular filtering photoelectron spectra are carried out to assist in the spectral band assignment. [ABSTRACT FROM AUTHOR]

We have reported a combined photoelectron imaging and theoretical study on gaseous mixed-ligand M(I) complexes of [HMSH]- (M = Cu, Ag, and Au). With the aid of Franck-Condon simulations, vibrationally resolved photoelectron spectra yield accurate electron affinities of 3.269(6), 3.669(10), and 3.591(6) eV for [HCuSH], [HAgSH], and [HAuSH], respectively. And low-frequency modes are observed: 368(12) cm-1 for [HCuSH], 286(12) cm-1 for [HAgSH], and 327(12) cm-1 for [HAuSH], respectively. Extensive theoretical calculations are performed to aid in the spectral assignments and the calculated values agree well with the experimental observations. Although the S and H atoms have little discrepancy in electronegativity (2.20 for H and 2.54 for S), distinct bonding properties are demonstrated between H-M and M-S bond. It is revealed that there exists significant ionic bonding between M-S in [HMSH]- (M = Cu, Ag, and Au), while a gradual transition from ionic behavior between H-Cu in [HCuSH]- to quite strong covalent bonding between H-Au in [HAuSH]-, supported by a variety of chemical bonding analyses. [ABSTRACT FROM AUTHOR]

We report a combined photoelectron velocity-map imaging spectroscopy and density functional theory investigation on lutetium monoxide anion. Transition between the X ¹σ+ anion electronic ground state and the neutral X ²σ+ electronic ground state is observed. Vibrationally resolved spectra were obtained at four different photon energies, providing a wealth of spectroscopic information for the electronic ground states of the anionic lutetium monoxide and corresponding neutral species. Franck- Condon simulations of the ground-state transition are performed to assign vibrational structure in the spectra and to assist in identifying the observed spectral bands. The electronic ground state of LuO- is found to have a vibrational frequency of 743 ± 10 cm-1 and an equilibrium bond length of 1.841 Å. The electron affinity of LuO is measured to be 1.624 ± 0.002 eV. The fundamental frequency of ground-state LuO is estimated to be 839 ± 10 cm-1. [ABSTRACT FROM AUTHOR]

Photoelectron spectra and angular distributions in photodetachment of gold hydride anions AuH- and Au2H- have been obtained using photoelectron velocity-map imaging. Both the images exhibit vibrationally resolved ground state transitions. The adiabatic electron affinities of AuH and Au2H are measured to be 0.758(20) and 3.437(3) eV, respectively. Franck–Condon analyses of the AuH spectra determined that the equilibrium bond length of the ground state of AuH- is 1.597(6) Å. The photoelectron images of Au2H- show a vibrational progression of 148(4) cm-1 assigned to the Au–Au stretching mode at the ground state. Ab initio calculation results are in excellent agreement with the experimental results. For the ground state of Au2H, a new bent Au–Au–H structure with the angle of 131° is suggested. Moreover, energy-dependent photoelectron anisotropy parameters are also reported and discussed. [ABSTRACT FROM AUTHOR]

The article attempts to examine the early stages of the synthesis of Periodic Mesoporous Silicas (PMS) by molecular dynamics simulation through the use of realistic atomistic models. Two solutions have been compared in order to evaluate the effects of silica on surfactant self-assembly including the aqueous solutions of DeTAB without silica and a solution of DeTA and silicic acid monomers. The findings of the study have been discussed.

The efficient use of natural gas will require catalysts that can activate the first C-H bond of methane while suppressing complete dehydrogenation and avoiding overoxidation. We report that single iron sites embedded in a silica matrix enable direct, nonoxidative conversion of methane, exclusively to ethylene and aromatics. The reaction is initiated by catalytic generation of methyl radicals, followed by a series of gas-phase reactions. The absence of adjacent iron sites prevents catalytic C-C coupling, further oligomerization, and hence, coke deposition. At 1363 kelvin, methane conversion reached a maximum at 48.1% and ethylene selectivity peaked at 48.4%, whereas the total hydrocarbon selectivity exceeded 99%, representing an atom-economical transformation process of methane. The lattice-confined single iron sites delivered stable performance, with no deactivation observed during a 60-hour test. [ABSTRACT FROM AUTHOR]

The reaction of (PNP)NiH, where PNP is (tBu2PCH2SiMe2)2-N-1, with CO2 occurs over a period of hours at 25 °C to form (POP)NiH(NCO), which involves transposition of the initial amide nitrogen and one oxygen of CO2. [ABSTRACT FROM AUTHOR]

The article describes a study which examines the reaction of nitrogen oxide with an operationally unsaturated metal complex. The hydrogenation of nitrogen oxide is observed. The role of single and multiple metals in promoting electron transfer to the structural rearrangement of nitrogen oxide is emphasized.

This article reports that nitrogen provides insight into the mechanism of hydrogen to carbon (H-C) bond cleavage. It is informed in this article that execution of a reaction like (H-C) bond activation is facilitated by effecting substrate pre-coordination using a donor functionality in the substrate. It can be observed in several reports where a transition metal species cleaves C-H bonds of its own ancillary ligand. It is further reported that nitrogen is critical to sing pairing of the two unpaired electrons, which have been suggested as the reason behind agostic interactions and attractive species on the path to C-H cleavage.