Systematic Access of Ternary Organotetrel-Copper Chalcogenide Clusters by [PhTE3]3− Anions (T=Si,Sn; E=S,Se)

Fragmentation reactions of organotetrel chalcogenide heteroadamantane-type clusters [(PhT)₄E₆] (T/E=Si/S ( 1 ); Si/Se; Sn/S, and Sn/Se) by addition of the corresponding sodium chalcogenide gave salts of the general formula Na₃[PhTE₃], with T/E=Si/S ( 2 ); Si/Se ( 3 ); Sn/S ( A ); Sn/Se ( 4 ). Reaction of these salts with [Cu(PPh₃)₃Cl] gave a series of organotetrel–copper chalcogenide clusters [(CuPPh₃)₆(PhTE₃)₂] with T/E=Si/S; ( 5 ), Si/Se ( 6 ), Sn/S ( 7 ) and Sn/Se ( 8 ). Compounds 5 – 8 share a common structural motif with two intact {PhTE₃} units coordinating a Cu₆ moiety, which was previously reported with other ligands, and for the Sn and Ge congeners only. If the Sn/Se reaction system was allowed to crystallize more slowly, single crystals of compound [(CuPPh₃)₆(PhSnSe₃)₃Cu₃SnSe] ( 9 ) were obtained, which are based on a larger cluster structure. Hence, 9 might form from 8 through incorporation of additional cluster fragments. The experimentally and quantum chemically determined optical properties were compared to related clusters.     

Addition of organic and inorganic moieties to Fe2(CO)6(μ-EE′) and Fe3(CO)9(μ3-E)(μ3-E′) [E=Se,Te;E′=S,Se, Te]

Reaction of the iron chalcogen carbonyl clusters Fe₂(CO)₆(-EE) and Fe₃(CO)₉(₃-E)(₃-E), [E=Se, Te;E=S, Se, Te] with various inorganic and organic moieties produce a number of higher nuclearity clusters. The reactivity pattern of these iron chalcogen carbonyl compounds and the structure of the products formed are discussed.     

The photo-induced decarbonylation of Cp′M(NO)(CO)2 (M = Cr,Mo, W) with diorgano dichalcogenides (R2E2; E = S,Se; R = Me,Ph)

The photo-induced decarbonylation of CpCr(NO)(CO)₂ (1a) in MeCN solution in the presence of R₂E₂ (E = S, Se; R = Me, Ph) leads to the formation of chalcogenolato-bridged binuclear complexes Cp₂Cr₂(NO)₂(-ER)₂ [E = S; R = Me (2a), Ph (3a); E = Se, R = Me (4a), Ph (5a)] while reactions between CpM(NO)(CO)₂ [M = Mo (1b), W (1c)] and Ph₂E₂ (E = S, Se) result in mononuclear complexes CpM(NO)(EPh)₂ [M = Mo; E = S (9b), Se (10b); M = W, E = S (11c), Se (12c)]. The corresponding reactions of (1b) with Me₂E₂ (E = S, Se) yielded both mono and binuclear complexes: CpMo(NO)(SeMe)₂ (8b), Cp₂Mo₂(NO)₂(-EMe)₂ [E = S (6b), Se (7b)]. The new complexes have been characterized by i.r., ¹H-, ¹³C-n.m.r. spectra and by electron-impact mass spectrometry.     

Structures and properties of π Br‐bond in complexes C2H4−nFn?BrF (n = 0–2)

Using the counterpoise‐corrected potential energy surface method, the stationary structures of the π Br‐bond complexes C₂H_4‐nF_n? BrF (n = 0–2) with all real frequencies have been obtained at MP2/aug‐cc‐pVDZ level. The order of the π Br‐bond length is 2.625 Å (C₂H₄? BrF) < 2.714 Å (C₂H₃F? BrF) < 2.751 Å (g‐C₂H₂F₂? BrF) < 2.771 Å (trans‐C₂H₂F₂? BrF) < 2.778 Å (cis‐C₂H₂F₂? BrF). The interaction energies (E_int) are, respectively,‐5.9 (C₂H₄? BrF),‐4.4 (C₂H₃F? BrF),‐3.7 (g‐C₂H₂F₂? BrF),‐3.1 (cis‐C₂H₂F₂? BrF),‐2.8 kcal/mol (trans‐C₂H₂F₂? BrF), at the CCSD (T)/aug‐cc‐pVDZ level, which include larger electron correlation contributions (E_corre). The order of E_corre is‐3.40 (C₂H₄? BrF),‐3.60 (C₂H₃F? BrF),‐3.85 (g‐C₂H₂F₂? BrF),‐3.86 (cis‐C₂H₂F₂? BrF),‐3.88 kcal/mol (trans‐C₂H₂F₂? BrF). The earlier results show above that the F substituent effect elongates the π Br‐bond, reduces the E_int, and increases the E_corre contribution of the interaction energy. Interestingly, the interaction energy of the cis‐C₂H₂F₂? BrF structure with longer interaction distance is larger than that of the corresponding trans‐C₂H₂F₂? BrF structure with shorter interaction distance. This reason comes from a special secondary interaction between lone pairs of Br atom with positive charge and some atoms (H, C) with positive charges of C₂H₂F₂ in the cis‐C₂H₂F₂? BrF structure. Comparing with corresponding C₂H_4‐nF_n? ClF and C₂H_4‐nF_n? HF, the C₂H_4‐nF_n? BrF system has the larger E_int in which main contribution comes from the larger E_corre, representing the larger dispersion interaction. The larger E_corre contribution of the E_int of π Br‐bond can be used to understand that the π Br‐bond is shorter and stronger than corresponding π Cl‐bond. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008     

Theoretical studies of (d-p)ρ bonding,electronic spectra,and reactivities in homo- and heterometallic clusters: [Mo3- n W n X4(H2O)9]4+ ( X = O,S, Se,Te;n= 0-3)

Ab initio calculations with relativistic effective potentials have been carried out on 12 trinuclear molybdenum/tungsten cluster aqua ions [M₃X₄(H₂O)₉]^4– (M₃= Mo₃, W₃ for X = O, S, Se, Te; M₃=Mo₂W, MoW₂ for X = O, S). The electronic structures and bonding pictures of l-12 are discussed in terms of the delocalized and localized molecular orbitals as well as the Mulliken populations, natural populations, and Mayer bond orders. It is shown that the (d-p) bonding in the puckered six-membered ring of the [M₃(µ-X)₃] core arises from a closed continuous ring of three mutually adjacent localized (d-p-d) bonds with strong interactions. It is these three-centered two-electron (d-p-d) bonds that account for the unusual physicochemical properties and reactivities of these cluster compounds. The wavelengths and the assignment of electronic spectra have been given, and the relation between the wavelength shili and the (d-p) bonding is discussed, The reactivities of the ligand substitution reactions and two kinds of addition reactions as weil as some kinetic and redox properties of these compounds are briefly discussed by taking advantage of this Iocalization (d-p-d) a bonding picture.     

DFT Studies on the Stoichiometric Thorium Oxide Clusters(ThO_2)_n(n = 1～5): Electronic and Structural Properties

Density functional theory(DFT) calculations are performed to investigate the electronic and structural properties of the stoichiometric thorium oxide clusters(ThO_2)_n-/0(n = 1～5). Generalized Koopmans' theorem is applied to predict the vertical detachment energies(VDEs)which are used to simulate the anionic photoelectron spectra(PES). Molecular orbital analyses are performed as well to analyze the chemical bonding in these thorium oxide clusters. The results show that the ground states of(ThO_2)_n-/0(n = 1～5) clusters prefer the low-spin structures. With increasing of the cluster size(n), the structure parameters of(ThO_2)_n-/0(n = 1～5) gradually evolve toward bulk thorium oxide species. It shows that both the coordination number and the average bond length increase gradually in(ThO_2)_n-/0(n = 1～5) to approach that of ThO2 bulk. What's more, the vibration frequencies of Th=O double bonds are found to be decreasing along with the increased cluster size.     

M4(CH2)4 Cubane‐Type Rare‐Earth Methylidene Complexes: Unique Reactivity toward Unsaturated C?O,C?N,and C?S Bonds

The reactivity of the cubane‐type rare‐earth methylidene complex [Cp′Lu(μ₃‐CH₂)]₄ ( 1 , Cp′=C₅Me₄SiMe₃) with various unsaturated electrophiles was investigated. The reaction of 1 with CO (1 atm) at room temperature gave the bis(ketene dianion)/dimethylidene complex [Cp′₄Lu₄(μ₃‐CH₂)₂(μ₃,η²‐O‐C?CH₂)₂] ( 2 ) in 86 % yield through the insertion of two molecules of CO into two of the four lutetium–methylidene units. In the reaction with the sterically demanding N,N‐diisopropylcarbodiimide at 60 °C, only one of the four methylidene units in 1 reacted with one molecule of the carbodiimide substrate to give the mono(ethylene diamido)/trimethylidene complex [Cp′₄Lu₄(μ₃‐CH₂)₃{iPrNC(=CH₂)NiPr}] ( 3 ) in 83 % yield. Similarly, the reaction of 1 with phenyl isothiocyanate gave the ethylene amido thiolate/trimethylidene complex [Cp′₄Lu₄(μ₃‐CH₂)₃{PhNC(S)=CH₂}] ( 4 ). In the case of phenyl isocyanate, two of the four methylidene units in 1 reacted with four molecules of the substrate at ambient temperature to give the malonodiimidate/dimethylidene complex [Cp′₄Lu₄(μ₃‐CH₂)₂{PhN=C(O)CH₂(O)C?NPh}₂] ( 5 ) in 87 % yield. In this reaction, each of the two lutetium–methylidene bonds per methylidene unit inserted one molecule of phenyl isocyanate. All the products have been fully characterized by NMR spectroscopy, X‐ray diffraction, and microelemental analyses.     

新颖蝶状Fe/E/μ-CO(E=S,Se,Te)簇盐的化学研究进展

介绍了一系列含μ-CO配体的蝶状Fe/E(E=S,Se,Te)簇盐的化学研究进展.这些簇盐包括11种新颖簇阴离子,它们是单蝶状单μ-CO阴离子[(μ-RE)(μ-CO)Fe2(CO)6]-(A,E=S,Se,Te),双蝶状双μ-CO阴离子{[(μ-CO)Fe2(CO)6]2(μ-EZE-μ)}2-(B,E=S;C,E=Se),三蝶状三μ-CO阴离子{[(μ-CO)Fe2(CO)6]3[(μ-SCH2CH2)3-N]}3-(D),{[(μ-CO)Fe2(CO)6]3[1,3,5-(μ-SCH2)3C6H3]}3-(E),{[(μ-CO)Fe2(CO)6]3[(μ-SCH2)3CMe]}3-(F)及由F转化的双蝶状单μ-CO阴离子{[(μ-CO)Fe2(CO)6][Fe2-(CO)6][(μ-SCH2)3CMe]}-(G),四蝶状四μ-CO阴离子{[(μ-CO)Fe2(CO)6]4[1,2,4,5-(μ-SCH2)4C6H2]}4-(H)及由它转化的三蝶状双μ-CO阴离子{[(μ-CO)Fe2(CO)6]2[Fe2-(CO)6][1,2,4,5-(μ-SCH2)4C6H2]}2-(I),四蝶状四μ-CO阴离子{[(μ-CO)Fe2(CO)6]4[(μ-SCH2)4C]}4-(J)及由它转化的三蝶状双μ-CO阴离子{[(μ-CO)Fe2(CO)6]2[Fe2(CO)6]-[(μ-SCH2)4C]}2-(K).文中不仅描述了这十一种阴离子簇盐的形成方法,而且阐述了它们所发生的新颖反应以及由这些反应所生成的多种新型蝶状Fe/E簇合物,具有重要理论和应用价值.     

Can Aromaticity Coexist with Diradical Character? An Ab Initio Valence Bond Study of S2N2 and Related 6π‐Electron Four‐Membered Rings E2N2 and E42+ (E=S,Se, Te)

A series of 6π‐electron 4‐center species, E₂N₂ and E₄²⁺ (E=S, Se, Te) is studied by means of ab initio valence bond methods with the aims of settling some controversies on 1) the diradical character of these molecules and 2) the radical sites, E or N, of the preferred diradical structure. It was found that for all molecules, the cumulated weights of the two possible diradical structures are always important and close to 50 %, making these molecules comparable to ozone in terms of diradical character. While the two diradical structures are degenerate in the E₄²⁺ dications, they have on the contrary strongly unequal weights in the E₂N₂ neutral molecules. In these three molecules, the electronic structure is dominated by one diradical structure, in which the radical sites are the two nitrogen atoms, while the other diradical structure is much less important. The ordering of the various VB structures in terms of their calculated weights is confirmed by the relative energies of individual VB structures. In all cases, the major diradical structure (or both diradical structures when they are degenerate) is (are) the lowest one(s), while the covalent VB structures lie higher in energy. The vertical resonance energies are considerable in S₂N₂ and S₄²⁺, about 80 % of the estimated value for benzene, and diminish as one goes down the periodic table (S→Se→Te). This confirms the aromatic character of these species, as already demonstrated for S₂N₂ on the basis of magnetic criteria. This and the high weights and stabilities of one or both diradical structures in all systems indicates that aromaticity and diradical character do not exclude each other, contrary to what is usually claimed. Furthermore, it is shown that the diradical structures find their place in a collective electron flow responsible for the ring currents in the π system of these species.     

Redox‐Neutral Rhodium‐Catalyzed C?H Functionalization of Arylamine N‐Oxides with Diazo Compounds: Primary C(sp3)?H/C(sp2)?H Activation and Oxygen‐Atom Transfer

An unprecedented rhodium(III)‐catalyzed regioselective redox‐neutral annulation reaction of 1‐naphthylamine N‐oxides with diazo compounds was developed to afford various biologically important 1H‐benzo[g]indolines. This coupling reaction proceeds under mild reaction conditions and does not require external oxidants. The only by‐products are dinitrogen and water. More significantly, this reaction represents the first example of dual functiaonalization of unactivated a primary C(sp³) H bond and C(sp²) H bond with diazocarbonyl compounds. DFT calculations revealed that an intermediate iminium is most likely involved in the catalytic cycle. Moreover, a rhodium(III)‐catalyzed coupling of readily available tertiary aniline N‐oxides with α‐diazomalonates was also developed under external oxidant‐free conditions to access various aminomandelic acid derivatives by an O‐atom‐transfer reaction.     

Copper‐Catalyzed Intramolecular C(sp3)?H and C(sp2)?H Amidation by Oxidative Cyclization

The first copper‐catalyzed intramolecular C(sp³) H and C(sp²) H oxidative amidation has been developed. Using a Cu(OAc)₂ catalyst and an Ag₂CO₃ oxidant in dichloroethane solvent, C(sp³) H amidation proceeded at a terminal methyl group, as well as at the internal benzylic position of an alkyl chain. This reaction has a broad substrate scope, and various β‐lactams were obtained in excellent yield, even on gram scale. Use of CuCl₂ and Ag₂CO₃ under an O₂ atmosphere in dimethyl sulfoxide, however, leads to 2‐indolinone selectively by C(sp²) H amidation. Kinetic isotope effect (KIE) studies indicated that C H bond activation is the rate‐determining step. The 5‐methoxyquinolyl directing group could be removed by oxidation.     

Synthesis and Characterisation of New Metallacycles Containing [Ph2P(E)NP(E)Ph2]− (E = S OR Se) Ligands

Abstract

Reaction of [Ph₂P(E)NP(E)Ph₂]^? (E = S or Se) with a series of late transition-metal dimers, in thf or MeOH, leads to facile bridge cleavage and formation of new mononuclear compounds.     

Studies on the Stability of On-top Al13Inm (n = 1～12,m =-1,0,+1) Clusters

Energetic and electronic structures of the on-top Al13Inm (n = 1 ～12,m = -1,0,+1)clusters have been investigated by employing a first-principles pseudo-potential plane wave method.Several parameters such as binding energies,second differences of energy and vertical-electron detachment energies have been adopted to characterize and evaluate the structure stability of Al13In (n = 1 ～ 12) clusters.The optimized models show that the Al13 moieties in the clusters can not retain the original regular icosahedron structure.Results from binding energy and second difference of energy show that Al13In and Al13In- clusters with even n are more stable than those with odd n in contrast with Al13In+ clusters.The calculation of vertical-electron detachment energies (VDE) of Al13In clusters indicates that Al13In and Al13In- clusters with even n are closer to the closed shell of the Jellium model.Further analysis of electron density of states and electron density differences reveals that the enhanced stability of Al13In- clusters is not only associated with the closed shell of valence electrons but also with the bonding type between I and associated Al atoms.     

Cobalt‐Catalyzed C(sp2)?H Alkoxylation of Aromatic and Olefinic Carboxamides

The cobalt‐catalyzed alkoxylation of C(sp²) H bonds in aromatic and olefinic carboxamides has been developed. The reaction proceeded under mild conditions in the presence of Co(OAc)₂⋅4H₂O as the catalyst and tolerates a wide range of both alcohols and benzamide substrates, including even olefinic carboxamides. In addition, this reaction is the first example of the direct alkoxylation of alkenes through C H bond activation.     

New Insights into Factors Influencing B?N Bonding in X:BH3−nFn and X:BH3−nCln for X=N2, HCN,LiCN, H2CNH,NF3, NH3 and n=0–3: The Importance of Deformation

Understanding the bonding in complexes X:BH_3?nF_n and X:BH_3?nCl_n, for X=N₂, HCN, LiCN, H₂CNH, NF₃, NH₃ with n=0–3, is a challenging task. The trends in calculated binding energies cannot be explained in terms of any of the usual indexes, including π donation from the halogen lone pairs to the p(π) empty orbital on B, deformation energies, charge capacities, or LUMO energies, which are normally invoked to explain the higher Lewis acidity of BCl₃ relative to BF₃. The results of the high‐level G3B3 ab initio calculations reported in this study suggest that the interaction energies of these complexes are determined by a combination of at least three factors. These include the decrease in the electron‐accepting ability of B as a result of π donation by the halogen atom, the increase in the electron‐acceptor capacity of B due to deformation of the acid, and the large increase in the deformation energy of the acid with increasing halogen substitution. The dominant effects are those derived from the electronic effects of acid deformation. Deformation not only has direct energetic consequences, which are reflected in the large differences between dissociation (D₀) and interaction (E_int) energies, but also leads to an enhancement of the intrinsic acidities of BH_3?nF_n and BH_3?nCl_n moieties by lowering the LUMO energies to very different extents, consistent with the frontier orbital model of chemical reactivity. Although this lowering depends on both the number and the nature of the halogen substituents, binding energies do not systematically increase or decrease as the number of halogen atoms increases.