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In this article, the catalytic performance of acylenolato cobalt(III) hydrides [CoIII(O∩CO)(PMe3)3H] (O∩CO = acylenolato ligand) 1–3 for alkene hydrosilylation was studied. The experimental results indicate that the three cobalt(III) hydrides exhibit excellent catalytic activity for the hydrosilylation of alkenes. The catalytic effect of hydride 1 is superior to that of complex 2 or 3. This catalytic system has good substrate universality and high selectivity. The catalytic conditions (1 h, 50 °C) are mild. Aromatic alkenes and alkyl alkenes generate respectively Markovnikov products and anti-Markovnikov products with 99% selectivity. In the study of the catalytic mechanism, the silyl cobalt(III) intermediate generated by the reaction between cobalt(III) hydride and silane is considered as the real catalyst. A catalytic mechanism is proposed on the basis of the experimental information and literature reports. [ABSTRACT FROM AUTHOR]

The nature of coinage–metal bonds between AuX (X = F, Cl, Br, CN, NO2, CH3) and aromatic moieties with different electronic properties (benzene, 1,3,5-trifluorobenzene and hexafluorobenzene) has been characterized within the framework of energy decomposition analysis, natural bond orbital analysis, quantum theory of atoms in molecules, and the electron localization function method. The strength and covalency of π⋯AuX interactions depend on the nature of the aromatic moiety and coin metal substituents. The binding energy varies from −6.6 to −34.8 kcal mol−1, and becomes more negative in the order of π = C6F6 < C6H3F3 < C6H6 and X = CH3 < NO2 < CN < Br < Cl < F. Most of the coinage–metal bonds have partially covalent characters, and the degree of covalency is larger in electron-deficient π-systems than in electron-rich π-systems. For the same aromatic moiety, the coinage–metal bond is more covalent when the substituent is a halogen, and the degree of covalency increases with the sequence of CH3 < CN < NO2 < Br < Cl < F. Appreciable tuning of the coinage–metal bond would be possible by varying the substituents on the coinage–metal and aromatic ring. The polarization effect plays an important role in the π⋯AuX interactions, and there is significant charge transfer from the occupied π(C–C) orbital to the empty Au orbital or antibonding Au–X orbital in the formation of coinage–metal bonds. [ABSTRACT FROM AUTHOR]

Asymmetric structures have attracted much attention owing to their potential application in drug delivery, optoelectronics and catalysis. However, current reported works for the preparation of asymmetric particles rely mainly on emulsion, seeding, hydrothermal and templating approaches, but facile strategies are seldom developed. Herein, we first utilize low-cost monomers of thiourea and formaldehyde to fabricate a peculiar V-notched half-open polymer architecture via a facile precipitation polymerization method in a mixed solvent of water/ethanol (1 : 1 v/v) at room temperature, where the volume ratio between water and ethanol can adjust the open angle of the microspheres. Impressively, this method is readily carried out, and no templates, surfactants, hydrothermal devices, complex procedures or toxic solvents are utilized. This synthetic strategy provides a facile approach to prepare V-notched half-open polymer microspheres with potential for materials engineering. [ABSTRACT FROM AUTHOR]

The nature of π-hole spodium bonds in the HgLCl2⋯ZH3/CH2Y complexes (L = pyrrole 1, pyrazole 2, imidazole 3, pyridine 4, pyridazine 5, and pyrimidine 6; Z = N, P, As, and Sb; Y = O, S, Se, and Te) has been studied using theoretical calculations. The electrophilicity of the π-hole in the tri-coordinated HgII complexes varies with the type of N-heterocyclic ligand. The strength and nature of the π-hole spodium bond is closely related to the properties of the Lewis bases. In the case of HgLCl2⋯ZH3, the strength of the π-hole spodium bond weakens as the nucleophilicity of the base decreases, following the sequence HgLCl2⋯NH3 > HgLCl2⋯PH3 > HgLCl2⋯AsH3 > HgLCl2⋯SbH3. The Hg⋯Z spodium bonds change from a partially covalent interaction to a close-shelled noncovalent interaction. The nucleophilic ability of CH2Y decreases in the order CH2O > CH2S > CH2Se > CH2Te, while the strength of the π-hole spodium bond follows the order HgLCl2⋯OCH2 < HgLCl2⋯SCH2 < HgLCl2⋯SeCH2 < HgLCl2⋯TeCH2. The Hg⋯Y spodium bond undergoes a transition from a close-shelled noncovalent to a partially covalent interaction, resulting in an incremental increase in the degree of covalence. The Hg⋯Te spodium bond exhibits certain characteristics resembling those of a coordinate covalent bond. The inter-orbital interactions observed in the formation of the HgLCl2⋯YCH2 complexes appear to be significantly stronger compared to those observed in the HgLCl2⋯ZH3 complexation. [ABSTRACT FROM AUTHOR]

The metal–metal and metal–ligand bonds in the bimetallic sandwich compounds Pn*2M2 (Pn* = C8Me6; M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu) have been investigated using the atoms in molecules (AIM) theory, electron location function (ELF), and electron decomposition analysis (EDA). The calculated results indicate that the strength of the metal–metal (M–M) bond and the coordination mode of the Pn* ligands to a pair of metal atoms depend on the d electron configuration of the transition metal. The more unpaired d electrons, the higher the coordination number of the metal to the ligands, which increases from η1 to η5. The stronger the metal–ligand interaction, the weaker the contribution of the electrostatic interaction to the metal–ligand interaction. The strength of the M–M bonds increases in the sequence M = Sc ＜ Ti ＜ V, and decreases in the sequence V ＞ Cr ＞ Mn ＞ Fe ＞ Co ＞ Ni ＞ Cu. The V–V bond is the strongest of the studied dinuclear first-row transition metal–(C8Me6)2 complexes. The studied M–M bonds are metallic bonds and have a partially covalent character, except for Sc–Sc which is a covalent bond and Cu–Cu which is an electrostatic interaction. [ABSTRACT FROM AUTHOR]

Factors affecting the Cu…Cu distance in copper(i) complexes with the N-heterocyclic carbene (NHC), bis-NHC and N-phosphinomethyl-functionalized NHC (NHCP) ligands have been investigated by quantum chemistry and topological analysis of electron density. The calculated results show that the ligands, ring size and shape, substitution pattern of NHC and NHCP, and overall charge of the system are factors that affect the Cu…Cu distance. The NHC ligand and an overall positive charge of the system lead to a short Cu…Cu distance. Topological analysis shows that there are attractions between the two Cu atoms. And the Cu…Cu attractions in the eight-membered systems and in the 10-membered cation systems are moderately strong and belong to the closed-shell type, which have partially covalent shared-closed interactions. Whereas the same interactions in the 12-membered cation system and in the neutral system with Br are weak and belong to closed-closed interactions. [ABSTRACT FROM AUTHOR]

The nature of the E–E bonds in heavier ditetrel alkyne analogues ArEEAr (Ar = C6H3-2,6(C6H3-2,6-Pri2)2; E = Si, Ge, Sn, Pb) have been studied by topological analysis of the electron localization function (ELF), the delocalization index from the atoms in molecules (AIM) theory and bond orbital analysis. Both the topological and the orbital analysis show that the nature of the E–E bonds in ArEEAr are different to that of the classical covalent triple C≡C bond of ArC≡CAr. In ArEEAr, all of the E–E bonds display charge-shift character; the ELF valence basin centroids of the E–E (E = Ge, Sn) bond do not occupy the central region between the two atoms, but have, in effect, fled that region and split into two kinds of basins. In addition, more and more electrons are transferred from the bond basins of the E–E bond to the lone pair basin of the E atoms, which means that a great portion of the bonding components comes from the lp (lone-pair) orbitals of the E atom rather than the electron-sharing bond, as in acetylene. Furthermore, the strength of the E–E bond decreases in the sequence of E = Si, Ge, Sn, and Pb. [ABSTRACT FROM AUTHOR]

Three silyl [PSiP] pincer cobalt(II) chlorides 1–3 [(2-Ph2PC6H4)2MeSiCo(Cl)(PMe3)] (1), [(2-iPr2PC6H4)2MeSiCo(Cl)(PMe3)] (2) and [(2-Ph2PC6H4)2MeSiCo(Cl)(LSi:)] (LSi: = {PhC(NtBu)2}SiCl) (3) were synthesized and used as catalysts and their catalytic activity for dinitrogen silylation was studied. Among the three complexes complex 3 was new and was synthesized via the reaction of [PSiP] pincer preligand L1 with CoCl2 in the presence of chlorosilylene via Si–H bond cleavage. The molecular structure of 3 was determined by single crystal X-ray diffraction analysis. Compared to complex 1, complex 2 is the more effective catalyst for dinitrogen silylation and 363 equiv. of N(SiMe3)3 could be reached per Co atom. Further study indicates that using the silylene ligand in complex 3 instead of the PMe3 ligand in complex 1, the catalytic activity of 3 is lower than that of 1. The catalytic mechanism for this catalytic system is proposed with the support of experimental evidence. The [PSiP] pincer cobalt(I) dinitrogen complex was proposed as the active catalyst for dinitrogen silylation. [ABSTRACT FROM AUTHOR]

The similarities and differences of pnicogen and tetrel bonds formed by CX2 carbenes (X = F, Cl, Br, OH, OMe, NH2, and NMe2) with σ-holes of H3AsO and H3SiCN were investigated by carrying out ab initio calculations in association with topological analysis of electron density and energy decomposition analysis. The strength of the σ-hole interactions was found to be essentially related to the nature of the group IV/V atom and the substituent of the carbene. The interaction energies of the tetrel-bonded complexes were calculated to be more negative than those of the corresponding pnicogen-bonded complexes except for H3SiCN⋯CF2. In the formation of the complexes, the geometries of the H3AsO⋯CX2 systems did not change much, while greater deformations occurred for the H3SiCN⋯CX2 systems. Our analyses also show a large contribution made by the deformation energy to the tetrel bond and all of the pnicogen bonds displaying the closed shell characteristics of the weak interactions, as well as most of the tetrel bonds having partially covalent character, consistent with the remarkable induced dipole interaction between the two monomers. For the tetrel-bonded complexes, the polarization energies were found to exhibit a polynomial dependence on the change of the dihedral angle of the SiH3 fragment and the increase of integral charge in the Si⋯C internuclear region. [ABSTRACT FROM AUTHOR]

Eight [CNN] pincer nickel NHC chlorides, [RCcarbeneNamidoR′2Namine–Ni–Cl] (R/R′2 = quinolinyl/nBu (3a), quinolinyl/Me (3b), quinolinyl/PhCH2 (3c), (CH2)4/nBu (5a), (CH2)4/iPr (5b), Me2/nBu (5c), Me2/iPr (5d), and Me2/PhCH2 (5e)), were prepared by the reactions of related asymmetric [CNN] NHC preligands with Ni(DME)Cl2via N–H bond activation. The molecular structures of complexes 3a, 3b and 5a were investigated using single crystal XRD. The catalytic experiments showed that the nickel complexes could catalyze the hydrosilylation of unsaturated compounds like aldehydes and ketones, and complex 3b was found to exhibit the best catalytic activity at 30 °C. Using NaBHEt3 as an additive, the catalytic activity of 3b was greatly improved. Furthermore, it was found that good to complete conversion of aldehydes could be achieved within 1.5 h at 30 °C after pre-reacting 3b and NaBHEt3 with silane for 0.5 h. The substrate ketones could be converted to alcohols in good yields by prolonging the reaction time to 2.5 h at 30 °C. It is worth mentioning that all eight [CNN] pincer nickel NHC chlorides are stable in air, and this is rare in nickel catalysts for hydrosilylation of aldehydes and ketones. Moreover, the substrate universality of the catalytic system is also very good, with good functional group tolerance. The molecular structures of complexes 3a, 3b and 5a were investigated using single crystal XRD and a possible reaction mechanism was proposed. [ABSTRACT FROM AUTHOR]

The transition metal-catalyzed alkyne functionalization reaction can produce useful organic reagents and is the most atom-economical, green and sustainable process for combining triple bonds in functional molecules. In this work, the mechanism of the alkyne hydrogermylation reaction catalyzed by ˙Mn(CO)5 and factors influencing reactivity have been investigated based on DFT calculations. The calculated results show that the whole reaction involves three processes: the first hydrogen atom transfer (HAT) process, the radical transformation process, and the second HAT process. The radical transformation process is the rate-determining step. The title reactions have good selectivities and the Z-Pro are the main products. The mechanisms of hydrosilylation and hydrogermylation of alkynes are similar, except that the energy barrier of hydrogermylation is lower than that of hydrosilylation. The period of E (E = C, Si, Ge and Sn) atoms in HEPhMe2, the substituents on alkynes and HEPhMe2, and the nature of solvents are related to the reactivity of the title reaction. The greater positive charge on the E atom and more aromatic substituents on alkynes lead to greater reactivity. The more negative Vs,min of the solvent leads to the lower yield of the reaction. Our results provide a detailed explanation of the experimental results and shed light on the further development of the alkyne-functionalization reaction. [ABSTRACT FROM AUTHOR]

A novel pyridyl-substituted indenyl trinuclear ruthenium complex, {μ2-η5:η1-(C5H3N-6-Br)(C9H5)}Ru3(CO)9 (1), was synthesized by thermal treatment of 1-(6-bromo-2-pyridyl)indene with Ru3(CO)12 (1 : 1 mol ratio) in refluxing heptane and its reactivity with pyridine derivatives, toluene, indene, fluorene, phenylethylene and divinylbenzene was studied. The reaction of 1 with 5-fold excess of 1-(6-bromo-2-pyridyl)indene gave two products, complex {η5-(C5H3N-6-Br)(C9H5)}{η1-(C5H3N)(C9H6)}Ru2(CO)4 (2) and substituted dibenzfulvalene (3). Reaction of 1 in refluxing toluene afforded an unexpected complex {μ3-η6:η3:η1-(C5H3N-6-Br)(C9H5)}Ru3(CO)7 (4), via the loss of two CO groups. Reaction of 1 with indene in refluxing heptane afforded a known complex [{(η5-C9H7)Ru(CO)2}2] (5). The reaction of 1 with fluorene in refluxing heptane afforded complex {μ3-η6:η3:η1-(C5H3N-6-Br)(C9H5)}Ru3(CO)7 (4), fluorene was not involved in the reaction, indicating that the reactivity of fluorene is low. The reactions of 1 with phenylethylene or divinylbenzene in refluxing toluene gave the dinuclear ruthenium complexes {η5-(C5H3N-6-Br)(C9H5CHCH2Ph)}Ru2(CO)5 (6) and {η5-(C5H3N-6-Br)(C9H5CHCH2PhCHCH2)}Ru2(CO)5 (7), respectively. These complexes have been characterized by elemental analysis, IR, and 1H NMR spectroscopy. The molecular structures of 1–6 were determined by X-ray diffraction. The density functional theoretical calculations on the electronic structure of complex 1 give an illustration to its high reactivity. [ABSTRACT FROM AUTHOR]

In this study, two [PCP] pincer silylene cobalt(I) complexes [((Ph2POCH2)2CH)Co(PMe3)(SiCl((NtBu)2CAr))] (Ar = Ph (2) and 4-MePh (3)) were synthesized through the substitution reaction of the [PCP] pincer cobalt(I) complex [((Ph2POCH2)2CH)Co(PMe3)2] (1) with silylene ligands: SiCl((NtBu)2CAr) (Ar = Ph (L1) and 4-MePh (L2)). The reaction of complex 2 with CO afforded the carbonyl silylene cobalt(I) complex [((Ph2POCH2)2CH)Co(CO)(SiCl((NtBu)2CPh))] (4), while complex 2 reacted with CH3I to give rise to cobalt(II) iodide [((Ph2POCH2)2CH)Co(I)(PMe3)] (6). With a catalyst loading of 2 mol%, complex 6 displayed efficient catalytic activity for hydrosilylation of alkenes by using Ph2SiH2 as the hydrogen source under mild conditions. The molecular structures of complexes 2, 3, 4 and 6 were determined by single crystal X-ray diffraction analysis. [ABSTRACT FROM AUTHOR]

Titanium dioxide nanospheres with visible light photocatalytic activity were synthesized via a sol–gel approach using an amphiphilic diblock copolymer, polystyrene-block-polyacrylic acid (PS-b-PAA), as template at room temperature in toluene. The morphology and crystal structure of synthesized TiO2 nanospheres were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The XRD pattern of TiO2 nanospheres revealed the crystal transformation, resulting in the change of photocatalytic activity. The XPS pattern revealed the formation of Ti–O–C bonds upon carbonization, as a result of visible light absorption. The TiO2 nanospheres had diameters ranging from 200 to 500 nm. The photodegradation experiments showed that such TiO2 nanospheres had pronounced visible-light photocatalytic activity. [ABSTRACT FROM AUTHOR]

Transition metal π-diborene species exhibit fascinating photophysical properties, and their unique properties reflect their particular electronic structure. In this work, the nature of π(B≡B)⋯M interactions in coinage metal π-diborene complexes, B2IDip2⋯nMCl (n = 1, 2, 3; M = Cu, Au, Ag), was characterized within the framework of energy decomposition analysis, natural bond orbital analysis, atoms in molecule theory, and the electron localization function method. The calculated results show that the M atom of MCl interacts with two boron atoms of B2IDip2 to form an η2-coordinated structure. The π(B≡B)⋯M interactions belong to the Dewar–Chatt–Duncanson model, the charge transfers from IDip to π(B≡B) bonds first and then from π(B≡B) bonds to the MCl. In π(B≡B)⋯M interactions, electrostatic interactions are dominant, and orbital interactions are important. The strengths of π(B≡B)⋯M interactions increase in the sequence of M = Ag, Cu, and Au for the same n. The formation of π(B≡B)⋯M interactions weakens the B≡B and B-C bonds in B2IDip2. In particular, the B≡B bonds become increasingly weaker with an increasing number of MCl, followed by M = Ag, Cu, and Au. [ABSTRACT FROM AUTHOR]

A new synthetic strategy for the novel diphosphine-phosphine oxide ligand (1) (Ph2P-(C6H4))2P(O)H was designed. A series of [PPP]-pincer Fe, Ni, and Co complexes were prepared. All of them were formed by chelate-assisted P–H activation. Two metal hydrides [(Ph2P-(C6H4))2P(O)]Fe(H)(PMe3)2 (2) and [(Ph2P-(C6H4))2P(O)]Ni(H)(PMe3) (3) were obtained at room temperature. The combination of ligand 1 with Co(PMe3)4Me or Co(PMe3)4 afforded the same Co(i) complex [(Ph2P-(C6H4))2P(O)]Co(PMe3)2 (4) via P–H bond activation. The catalytic performance of the Fe, Ni, and Co complexes for the hydrosilylation of aldehydes and ketones was explored. At a catalyst loading of 2 mol%, complex 2 displayed the best catalytic activity for the hydrosilylation by using (EtO)3SiH as the hydrogen source under mild conditions. Complexes 2, 3, and 4 were characterized by spectroscopic methods and X-ray diffraction analysis. [ABSTRACT FROM AUTHOR]

Polyfluorinated aryl imines 2,4,5-R1,R2,R3-C6H2-HC=N-1-C10H7 (R1 = F, R2 = F, R3 = H (1); R1 = F, R2 = H, R3 = F (2) and R1 = F, R2 = F, R3 = F (3)) and F5C6-HC=N-1-C10H7 (7) reacted with CoMe(PMe3)4 to give rise to hydrido [CNC]-pincer cobalt(iii) complexes (2,4,5-R1,R2,R3-C6H-HC=N-1-C10H6)Co(H)(PMe3)2 (R1 = F, R2 = F, R3 = H (4); R1 = F, R2 = H, R3 = F (5); R1 = F, R2 = F, R3 = F (6)) and (F4C6-HC=N-1-C10H6)Co(H)(PMe3)2 (8) via selective C–F/C–H bond activation. Penta-coordinate dicarbonyl cobalt(i) complexes (2,4,5-R1,R2,R3-C6H-HC=N-1-C10H7)Co(CO)2(PMe3) (R1 = F, R2 = H, R3 = F (9); R1 = F, R2 = F, R3 = F (10)) were obtained from reactions of hexa-coordinate cobalt(iii) complexes 5 and 6 with carbon monoxide through reductive elimination. Cobalt(iii) halides (2,4,5-R1,R2,R3-C6H-HC=N-1-C10H6)Co(i)(PMe3)2 (R1 = F, R2 = F, R3 = H (11); R1 = F, R2 = H, R3 = F (12); R1 = F, R2 = F, R3 = F (13)) and (2,4,5-R1,R2,R3-C6H-HC=N-1-C10H6)Co(Br)(PMe3)2 (R1 = F, R2 = F, R3 = H (14); R1 = F, R2 = H, R3 = F (15); R1 = F, R2 = F, R3 = F (16)) were prepared by the interaction between hydrido cobalt(iii) complexes 4–6 and MeI or EtBr. The molecular configurations of complexes 4, 8, and 11 were determined by single crystal X-ray diffraction. We then confirmed that the four hydrido cobalt(iii) complexes 4–6 and 8 could be used as catalysts for reduction of aldehydes and ketones. Complex 8 is the best catalyst among the four complexes and can selectively catalyze the carbonyl groups of α,β-unsaturated aldehydes and ketones. [ABSTRACT FROM AUTHOR]

C(carbene)N(amido)N(amine)-pincer nickel(ii) complexes [iPrCNN-Ni-Br] (6), [nBuCNN-Ni-Br] (7) and [BnCNN-Ni-Cl] (8) were synthesized. The catalytic performance of complexes 6–8 for Sonogashira cross-coupling reactions was explored. In a combination of 5 mol% catalyst loading of 6 and CuI/Cs2CO3/NaI/DMSO at different temperatures for the coupling reactions between alkyl iodides, bromides, chlorides and terminal alkynes, the corresponding coupling products were obtained in moderate to excellent yields. The mechanism of these catalytic reactions was discussed and partially supported by experiments. The phenylethynyl CNN pincer nickel complex 9 as a catalytically active complex was isolated and structurally characterized using X-ray diffraction. [ABSTRACT FROM AUTHOR]

Two novel cobalt Schiff base complexes 3 and 4, ((2-PPh2)C6H4)C=N(C10H7)Co(PMe3)2 (3) and ((2-PPh2)C6H4)CH=N(C6H5)Co(PMe3)2 (4) with η2(C–H) coordination, were synthesized by the reactions of Schiff base preligands ((2-PPh2)C6H4)CH=N(C10H7) (1) and ((2-PPh2)C6H4)CH=N(C6H5) (2) with CoMe(PMe3)4via sp2 C–H bond activation. Under similar reaction conditions, the reactions of Co(PMe3)4 with 1 and 2 gave rise to the simple π-(C=N)-coordinated cobalt(0) complexes ((2-PPh2)C6H4)CH=N(C10H7)Co(PMe3)2 (5) and ((2-PPh2)C6H4)CH=N(C6H5)Co(PMe3)2 (6). Complex ((2-PPh2)C6H4)C=N(C10H6)CoI(PMe3)2 (7) was obtained through the reaction of 3 with iodomethane via the activation of the second C–H bond in 1. The substitution reaction of complex 3 with carbon monoxide afforded the dicarbonyl cobalt(i) complex ((2-PPh2)C6H4)C=N(C10H7)Co(CO)2(PMe3) (8). The molecular structures of 4, 5, 7 and 8 were determined by single-crystal X-ray diffraction. [ABSTRACT FROM AUTHOR]

The structure, nature of chemical bonds and aromatic properties of Cp2(ME)2 (M = Ni, Pd, Pt; E = O, S, Se, Te) compounds have been studied using density functional theory. The charge transfer from the ground state (GS) to the vertically excited state (VES) as well as the differences in the structure and nature between the GS and the adiabatically excited state (AES) are discussed in this work. The results show that the HOMO (highest occupied molecular orbital)–LUMO (lowest unoccupied molecular orbital) gaps of the studied compounds are small. Hence, the electron in the HOMO is easily excited. The electron transition from the HOMO to the LUMO, the strength and nature of the M–E bond along with the M–Cp and E…E interactions and the aromaticity of the (ME)2 (M = Ni, Pd, Pt; E = O, S, Se, Te) rings are correlated with the periods of the M and E atoms. In addition, electronic excitation enhances the chemical bond strength in the (ME)2 ring. [ABSTRACT FROM AUTHOR]