Synthesis and crystal structures of the first germanium-containing alkylidene complexes of molybdenum R3Ge-CHMo(NAr)(OR′)2 (R = Me, Ph) with direct germanium-carbene carbon bond

The novel germanium-containing alkylidene complexes of molybdenum R₃Ge-CHMo(NAr)(OCMe₂CF₃)₂ (Ar = 2,6-i-Pr₂C₆H₃; R = Me, Ph) have been prepared by the reaction of organogermanium vinyl reagents R₃ GeCHCH₂ with known alkylidene compounds Alkyl-CHMo(NAr)(OCMe₂CF₃)₂ (Alkyl = Bu^t, PhMe₂C). The titled compounds were isolated as crystalline solids and characterized by elemental analysis, ¹H NMR, ¹³C NMR spectroscopy and X-ray diffraction studies. The geometry of the Mo atoms in the compounds can be described as a distorted tetrahedron.     

The structure of the H3O+ hydronium ion in benzene

Infrared, X-ray structural, 1H NMR, and computational evidence for pi-solvation of H3O+ by benzene molecules is presented. A salt with a discrete [H3O.3benzene]+ cation can be isolated using a very weakly interacting carborane counterion, CHB11Cl11-. pi-Arene solvation of H3O+ explains the solubility of this salt in benzene solution. Similar results are indicated for the "Zundel-type" H5O2+ ion. These findings suggest structures for the active protonating species when strong acids are used as catalysts in arene solvents containing trace water. They are also relevant to structures that may be present in biological proton transport.     

Kinetics and mechanism of the proton transfer to CpFe(dppe)H: absence of a direct protonation at the metal site

The reaction between CpFe(dppe)H and a number of different proton donors (2-fluoroethanol, MFE; 2,2,2-trifluoroethanol, TFE; hexafluoro-2-propanol, HFIP; perfluoro-tert-butyl alcohol, PFTB; and trifluoroacetic acid, TFA) has been investigated spectroscopically by variable-temperature infrared, UV-visible, and NMR spectroscopy, and has been measured kinetically by the stopped-flow technique with UV-visible detection. The low-temperature IR study shows the establishment of hydrogen-bonding interactions which involve the hydride ligand as the proton accepting site. This investigation quantifies the thermodynamics of the hydrogen-bonding interaction and the basicity factor (E(j)) of the hydride complex. All techniques agree in indicating an equilibration process, after the immediate hydrogen-bond formation, between the hydride complex and an intermediate dihydrogen complex, [CpFe(dppe)(H(2))](+). The equilibrium is shifted toward the dihydrogen complex to a greater extent for the stronger alcohols and for higher alcohol/Fe ratios. The observed equilibration rate constant is linearly dependent on the alcohol concentration, in agreement with the involvement of two alcohol molecules and the formation of a homoconjugate pair. The rate constant increases with the acidity of the proton donor (TFE < HFIP < PFTB < TFA). The rate of the subsequent irreversible isomerization leading to the classical dihydride complex, [CpFe(dppe)H(2)](+), is first order, and the rate constant does not depend on the proton donor nature. The reaction continues, if conducted in CH(2)Cl(2), with a third, slower step leading to the paramagnetic [CpFe(dppe)Cl](+) product. The kinetic data are in accord with an isomerization mechanism consisting of an intramolecular reorganization, leading in one step from the dihydrogen complex to the classical dihydride species, and disagree with the occurrence of a proton-transfer process at the metal site.     

Influence of silver nanoparticles on the phase behavior of side-chain liquid crystalline polymers

The synthetic approach to the new class of mesomorphous nanocomposite polymer systems was developed. It is based on the in situ reduction of silver ions in the liquid crystalline (LC) polymer matrix leading to the formation of nanoparticles with typical sizes in the range of 5-30 nm. The influence of silver nanoparticles on the phase state of the LC composites, i.e., type and temperature interval of the mesophase, was studied. Regardless of chemical structure of the LC polymer matrix, an increase in the metal concentration is accompanied by a decrease of clearing temperature due to adsorption of macromolecules on the nanoparticle's surface. In the case of an LC copolymer with cyanobiphenyl side mesogenic fragments, the complete disruption of mesophase is observed below 2 wt% content of silver. This phenomenon is, most likely, a result of chemosorption of terminal cyano groups on the nanoparticles with the formation of sigma complexes that disturb packing of the mesogenic units.     

Molecular structure of the solvated proton in isolated salts. Short,strong, low barrier (SSLB) H-bonds

Large, inert, weakly basic carborane anions of the icosahedral type CHB(11)R(5)X(6)(-) (R = H, Me; X = Cl, Br) allow ready isolation and structural characterization of discrete salts of the solvated proton, [H(solvent)(x)][CHB(11)R(5)X(6)], (solvent = common O-atom donor). These oxonium ion Br?nsted acids are convenient reagents for the tuned delivery of protons to organic solvents with a specified number of donor solvent molecules and with acidities leveled to those of the chosen donor solvent. They have greater thermal stability than the popular [H(OEt(2))(2)][BAr(F)] acids based on fluorinated tetraphenylborate counterions because carborane anions can sustain much higher levels of acidity. When organic O-atom donors such as diethyl ether, tetrahydrofuran, benzophenone, and nitrobenzene are involved, the coordination number of the proton (x) in [H(solvent)(x)()](+) is two. A mixed species involving the [H(H(2)O)(diethyl ether)](+) ion has also been isolated. These solid-state structures provide expectations for the predominant molecular structures of solvated protons in solution and take into account that water is an inevitable impurity in organic solvents. The O.O distances are all short, lying within the range from 2.35 to 2.48 A. They are consistent with strong, linear O.H.O hydrogen bonding. Density functional theory calculations indicate that all H(solvent)(2)(+) cations have low barriers to movement of the proton within an interval along the O.H.O trajectory, i.e., they are examples of so-called SSLB H-bonds (short, strong, low-barrier). Unusually broadened IR bands, diagnostic of SSLB H-bonds, are observed in these H(solvent)(2)(+) cations.     

Prediction of Fluorooxoborates with Colossal Second Harmonic Generation (SHG) Coefficients and Extremely Wide Band Gaps: Towards Modulating Properties by Tuning the BO3/BO3F Ratio in Layers

Fluorooxoborates have inspired investigations of deep‐ultraviolet (DUV) nonlinear optical (NLO) materials that can meet the multiple criteria. Herein, five stable structures with the composition of BaB₂O₃F₂ (I–V) are discovered using the ab initio evolutionary algorithm. Among them, BaB₂O₃F₂‐I has been synthesized experimentally and confirms the reliability of the method. All of the predicted structures possess extremely wide band gaps (8.1–9.0 eV). Moreover, four new structures exhibit giant second harmonic generation (SHG) coefficients (>3×KDP, d₃₆=0.39 pm V^?1). A novel type of the [BOF] layer with BO₃:BO₃F ratio of [1:1] is found in BaB₂O₃F₂‐II and BaB₂O₃F₂‐III. While BaB₂O₃F₂‐IV and BaB₂O₃F₂‐V are solely composed of the BO₃F group and have colossal SHG coefficients (ca. 4×KDP). It gives the direct evidence that the BO₃F group could generate strong SHG effect. Most importantly, the influences of BO₃:BO₃F ratio and their number density on band gap, birefringence and SHG effects are investigated.     

Intermolecular hydrogen bonding between neutral transition metal hydrides (eta(5)-C5H5)M(CO)3H (M = Mo, W) and bases

The interaction of CpM(CO)3H (M = Mo, W) hydrides as proton donors with different bases (B = pyridine, (n-Oc)3PO, ((CH3)2N)3PO, H3BNEt3) was studied by variable temperature IR spectroscopy and theoretically by DFT/B3LYP calculations. The data obtained show for the first time the formation of intermolecular hydrogen bonds between the neutral transition metal hydrides and bases in solutions of low polarity. These M-H...B hydrogen bonds are shown to precede the hydrides' deprotonation.     

Asymmetric synthesis of (R,S)- and (R,R)-4-hydroxy-5-(α-substituted)-hydroxymethyl[2.2]paracyclophane and derivatives by stereoselective addition to (R)-4-hydroxy-5-formyl[2.2]paracyclophane and derivatives

Highly diastereoselective nucleophilic addition reactions of organometallic reagents to formyl[2.2]paracyclophane derivatives which were ortho-substituted by hydroxy-, alkoxy- and trimethylsilyloxy-groups are reported. The absolute configuration of the newly formed secondary alcohols is assigned on the basis of the X-ray diffraction study as well as chemical correlation. The magnitude of the asymmetric induction and even the sense of chirality of the forming asymmetric carbon atoms of the alcohols depended on the nature of the ortho-substituents.     

Some problems on narrow operators on function spaces

It is known that if a rearrangement invariant (r.i.) space E on [0, 1] has an unconditional basis then every linear bounded operator on E is a sum of two narrow operators. On the other hand, for the classical space E = L ₁[0, 1] having no unconditional basis the sum of two narrow operators is a narrow operator. We show that a Köthe space on [0, 1] having “lots” of nonnarrow operators that are sum of two narrow operators need not have an unconditional basis. However, we do not know if such an r.i. space exists. Another result establishes sufficient conditions on an r.i. space E under which the orthogonal projection onto the closed linear span of the Rademacher system is a hereditarily narrow operator. This, in particular, answers a question of the first named author and Randrianantoanina (Problem 11.9 in [Popov M., Randrianantoanina B., Narrow Operators on Function Spaces and Vector Lattices, de Gruyter Stud. Math., 45, Walter de Gruyter, Berlin, 2013]).