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We review the known chemistry of the cyaphide ion, (C≡P)−. This remarkable diatomic anion has been the subject of study since the late nineteenth century, however its isolation and characterization eluded chemists for almost a hundred years. In this mini‐review, we explore the pioneering synthetic experiments that first allowed for its isolation, as well as more recent developments demonstrating that cyaphide transfer is viable in well‐established salt‐metathesis protocols. The physical properties of the cyaphide ion are also explored in depth, allowing us to compare and contrast the chemistry of this ion with that of its lighter congener cyanide (an archetypal strong field ligand and important organic functional group). Recent studies show that the cyaphide ion has the potential to be used as a versatile chemical regent for the synthesis of novel molecules and materials, hinting at many interesting future avenues of investigation. [ABSTRACT FROM AUTHOR]

Gold(III) π‐complexes have been authenticated recently with alkenes, alkynes, and arenes. The key importance of PdII π‐allyl complexes in organometallic chemistry (Tsuji–Trost reaction) prompted us to explore gold(III) π‐allyl complexes, which have remained elusive so far. The (P,C)AuIII(allyl) and (methallyl) complexes 3 and 3′ were readily prepared and isolated as thermally and air‐stable solids. Spectroscopic and crystallographic analyses combined with detailed DFT calculations support tight quasi‐symmetric η3‐coordination of the allyl moiety. The π‐allyl gold(III) complexes are activated towards nucleophilic additions, as substantiated with β‐diketo enolates. [ABSTRACT FROM AUTHOR]

Four copper(I) π-complexes: [Cu(Hapn)NO3]NO3 (1), [Cu(Hapn)(H2O)2]SiF6 (2), [Cu(Hapn)(H2O)BF4]BF4·H2O (3) and [Cu(Hapn)(NH2SO3)2] (4) were prepared using alternating-current electrochemical technique, starting from alcohol solutions of 3-(prop-2-en-1-ylamino)propanenitrile (apn) titrated with appropriate acid and copper(II) salts (Cu(NO3)2∙3H2O, CuSiF6∙4H2O, Cu(BF4)2∙6H2O or Cu(NH2SO3)2∙xH2O, respectively). Obtained compounds were characterized by single-crystal X-ray diffraction and partially by IR spectroscopy. In the structures of complexes 1, 2 and 4 Cu(I) cation possesses a tetrahedral environment formed by the C=C bond of one organic cation Hapn, the N atom of ciano group from another Hapnmoiety, and two O atoms (from NO3– anions in 1, from H2O molecules in 2) or N atoms (NH2SO3– anions in 4). In compound 3 strongly pronounced trigonal-pyramidal coordination environment of Cu(I) is formed by a mid-point of C=C-bond of one Hapncation, nitrogen atom (of cyano group) of another Hapn unit, O atom of H2O molecule in the basal plane, and F atom of BF4– anion at the apical position.

It is well known that alkynes act as π‐acids in the formation of complexes with metals. We found unprecedented attractive Au–π interactions in diacetylene‐modified [core+exo]‐type [Au8]4+ clusters. The 4‐phenyl‐1,3‐butadiynyl‐modified cluster has unusually short Au–Cα distances in the crystal structure, revealing the presence of attractive interactions between the coordinating C≡C moieties and the neighboring bitetrahedral Au6 core, which is further supported by IR and NMR spectra. Such weak interactions are not found in mono‐acetylene‐modified clusters, which indicates that they are specific for diacetylenic ligands. The attractive Au–π interactions are likely associated with the low energy of the π* orbital in the diacetylenic moieties, into which the valence electrons of the gold core may be back donated. The [Au8]4+ clusters show clear red‐shifts of >10 nm with respect to the corresponding mono‐acetylenic clusters in UV/Vis absorption bands, which indicates substantial electronic perturbation effects of the Au–π interactions. A golden π‐crust: Unprecedented attractive Au–π interactions were found between a σ‐coordinating C≡C moiety and neighboring gold atoms of diacetylene‐modified Au8 clusters. The interaction was observed specifically for the diacetylenic ligands, and not found in the mono‐acetylenic analogues, indicating the uniqueness of the diacetylenic ligands. [ABSTRACT FROM AUTHOR]

A large number of cationic Au(I) π-complexes have been reported in the literature. However, a single X-ray structure of genuine [Au(PPh 3 )(hydrocarbon)] + π-complex without any additional stabilization has not been published so far. We present herein isolation and X-ray characterization of several complexes of this type. Also, we show that these π-complexes are more stable than previously reported and we investigate different modes of activation of the [Au(PPh 3 )]Cl precatalyst on their stability in solution. [ABSTRACT FROM AUTHOR]

The intrinsic features of (hetero-arene)-metal interactions have been elusive mainly because the systematic structure analysis of non-anchored hetero-arene-metal complexes has been hampered by their labile nature. We report successful isolation and systematic structure analysis of a series of non-anchored indole-palladium(II) complexes. It was revealed that there is a σ-π continuum for the indole-metal interaction, while it has been thought that the dominant coordination mode of indole to a metal center is the Wheland-intermediate-type σ-mode in light of the seemingly strong electron-donating ability of indole. Several factors which affect the σ- or π-character of indole-metal interactions are discussed. [ABSTRACT FROM AUTHOR]

A perfect hybrid complex C60(FeCp)12 is predicted using density functional theory method. This fullerene derivative could be view as a C60 cage of which each C5 ring coordinates a (FeCp) ligand. Theoretical calculation reveals that it has a large lowest unoccupied molecular orbital-highest unoccupied molecular orbital gap (2.53 eV) and keeps the Ih symmetry of C60. But the CC bond length of its inner C60 cage trends to be uniform, which is quite different from the bonding character of C60 fullerene. Further investigation reveals that the chemical bonding, TDOS and the aromaticity of the (C5FeCp) unit in C60(FeCp)12 are similar as those of ferrocene molecule, which indicates the similarity of their electronic properties. So, this compound could be viewed as the combination of ferrocene molecules. Thus, its unconventional formation process from 12 Fe(Cp)2 is proposed and the reaction energy is calculated. As the C60(FeCp)12 compound has the geometry framework as C60 and the electronic characters as ferrocene, it would inherit the outstanding properties from both two molecules and have wild potential applications in nanochemistry. We hope our study could give some references for the further investigation and experimental synthesis research of the C60(FeCp)12 compound. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Metal-organics bond dissociation energies in compounds modeling different metal-containing structures in oil have been calculated using ab initio quantum-chemical methods. It has been found that bond energies calculated by the cbs-qb3, b3lyp/dgdzvp, and b3lyp/cc-pVDZ methods for diatomic molecules are arranged in the order: E > E, E > E, where M = V, Ni, or Co. Vanadium oxide VO in the vanadyl porphyrin molecule has been shown to possess the strongest bond (277.4 kcal/mol). Sandwiched structures are also stable: by using the ub3lyp/6-31g(d,p) method, the decomposition energy of the sandwich (CH)M = M + 2CH has been estimated and equals at 260.2 kcal/mol for M = Fe or 141.0 kcal/mol for M = Ni. The electronic structure of transition metal (M = V, Ni, Fe) complexes with π-conjugated bonds of benzene, pyrrole, and pyridine molecules has been calculated using the ub3lyp/6-31g(d) method. The thermal stability of the complexes has been discussed in terms of bond energy. [ABSTRACT FROM AUTHOR]

A series of iridium-stabilized selenocyclohexadienyls of general formula [Cp*Ir(η5-C6H5-nMenSe)][BF4] {Cp* = η5-C5Me5, n = 0, n = 1, and n = 3} is described, with the selenocyclohexadienyl unit being isolated for the first time by π-coordination to a Cp*Ir moiety. The solidstate structure of one of [Cp*Ir(η5-C6H2Me3Se)][BF4] was determined by single-crystal X-ray diffraction analysis. These compounds are obtained in good yields as orange-red microcrystalline solids by halogen displacement from the related π-bonded arene-chlorinated starting materials using Na2Se as the selenium source. Furthermore, these new compounds display relevant cytotoxic properties towards human ovarian cancer cells. [ABSTRACT FROM AUTHOR]

Highlights: [•] NICS are introduced as a means to evaluate the ligand properties of polycyclic Cp-anions. [•] Synthetic methods to access various benzannulated Cp-derivatives are discussed. [•] Transition metals complexes of benzannulated Cp-derivatives are reviewed. [ABSTRACT FROM AUTHOR]

N,N,N′,N′-tetramethylethylenediamine is obtained by the reaction of ethylenediamine with formaldehyde and formic acid (the Eschweiler-Clarke reaction) and then alkylated with allyl chloride (or bromide) in a ratio of 1:1 or 1:2 to obtain N-allyl-N,N,N′,N′-tetramethylethylenediaminium and N,N′-diallyl-N,N,N′,N′-tetramethylethylenediaminium bromide respectively. [{CHN(H)(CH)(CH)}CuCl] ( 1) and [{CHN(CH)(CH)2}CuClBr] ( 2) π-complexes are obtained from alcohol solutions containing an ethylenediamine derivative and copper(II) chloride by ac-electrochemical synthesis on copper wire electrodes. An XRD study of the complexes is carried out. The crystals are monoclinic; 1: P2/ n space group, a = 9.0081(6) Å, b = 12.5608(7) Å, c = 16.8610(10) Å, β = 102.061(3)°, V = 1865.7(2) Å, Z = 4; 2: C2/ c space group, a = 14.462(2) Å, b = 12.519(1) Å, c = 12.762(2) Å, β = 107.861(5)°, V = 2199.1(4) Å, Z = 8. The structure of 1 consists of infinite copper halide networks with four crystallographically independent copper atoms, one of which coordinates the double bond of the allyl group of the ligand. The [CHN(H)(CH)(CH)] cations are attached above and below the plane of the network. The individual fragments are bonded via an extensive system of (N)H...Cl and (C)H...Cl hydrogen bonds. The structure of 2 contains a three-dimensional copper halide framework whose cavities contain the [CHN(CH)(CH)] cations that are π-coordinated with copper(I) atoms. In both structures, the Cu(I) atom that coordinates the C=C bond has a trigonal-pyramidal coordination environment consisting of the double C=C bond of the corresponding ligand and three halogen atoms. The other Cu(I) atoms have a tetrahedral environment consisting solely of halogen atoms. The Cu-(C=C) distance is 1.958(1) Å, (1) and 1.974(1) Å (2). [ABSTRACT FROM AUTHOR]

For 12 acetylacetonates of the composition M(acac) ( n = 2, 3, or 4) and M(acac)(CH) (M is a metal) the total area ( S) of the faces of Voronoi-Dirichlet polyhedra (VDP) corresponding to all intermolecular contacts of one molecule in the crystal structure and the total volume of pyramids ( V), whose bases are formed of such faces and the vertices are occupied by the nuclei of atoms participating in intermolecular contacts, are determined. The key features of non-bonded interactions are considered. The existence of a linear dependence of the sublimation enthalpy of acetylacetonates on the S or V parameters of their molecular VDP is revealed. It is shown that the sublimation enthalpy of Ga(acac) requires the refinement and theoretically should be 124 kJ/mol. [ABSTRACT FROM AUTHOR]

In the MCl-CuCl-HOCHC≡CCHOH (M = Ca, CHNH) system, the crystals of two anionic Ca[CuCl(HOCHC≡CCHOH)]-4HO (1) and (BimH)[CuCl(HOCHC≡CCHOH)] (2) (BimH is cation of benzimidazole-CHNH) π-complexes are obtained and studied by single crystal X-ray diffraction Crystals of 1 are monoclinic: C2/c space group, a = 8.323(3) Å, b = 13.283(4) Å, c = 16.741(5) Å, β = 92.35(3)°, V = 1849.3(10) Å, Z = 4; crystals of 2 are triclinic: P1 space group, a = 6.901(3) Å, b = 9.898(4)Å, c = 9.987(4) Å, α = 94.91(3)°, β = 93.91(3)°, γ = 107.59(4)°, V = 644.7(5) Å, Z = 2. Complex 1 consists of infinite bimetallic chains [Ca(HO)CuCl(HOCHC≡CCHOH)] forming a three-dimensional framework through (Ow)HCl and (C)O-HCl hydrogen bonds. Compound 2 is built from discrete anions [CuCl(HOCHC≡CCHOH)] paired by edge-to-edge packing in the [100] direction and large BimH cations with face-to-face packing. In both structures, the π-coordinated Cu(I) atom has the trigonal environment involving two Cl anions and C≡C 2-butyne-1,4-diol bond (Cu-(C≡C) distance is 1.918(2) Å and 1.910(4) Å for 1 and 2 respectively). [ABSTRACT FROM AUTHOR]

Abstract: 2,4,6-Tri-tert-butyl-1,3,5-triphosphinine (7) was combined with 1,5-COD or 2,4-di-tert-butyl-1,3-diphosphete to form iron π-complexes. The ligands of highly reactive [(2,4-di-tert-butyl-1,3-diphosphete)(2,4,6-tri-tert-butyl-1,3,5-triphosphinine)Fe] (8) are formed by cyclooligomerization of tert-butylphosphaalkyne (3) under the influence of the iron atom. 8 rearranges spontaneously to yield penta-tert-butyl-pentaphosphaferrocene (9) as the isolable product. An intramolecular electron transfer product [(1,5-COD)(η6-1,3,5-triphosphacyclohexa-2,5-dine-1,4-diyl)Fe(2+)] (12) is obtained with 1,5-COD. Addition of [(CO)5Cr(THF)] initiates an interligand hydrogen transfer to form [(η5-trihydropentalenyl)Fe(μ,1-3-η-4,5,6-trihydro-1,3,5-triphosphinine)Cr(CO)5] (13) Extensive DFT calculations of isolated and reactive species, and several possible intermediates agree with the experimental observations and revealed for the first time a possible reaction sequence, which allows a low-activated exchange of ring elements between the ligands of sandwich complex 8 to form 9. The process is based on the specific combination of the metal and its heterocyclic π-ligands. Both, singlet and triplet spin states play an important role in the process. [Copyright &y& Elsevier]

Modeling of structure of bowl-shaped derivatives C21H12R6 (R = —, H, F, Cl, Br, CN) of sumanene C21H12 (R = -) and their complexes with moieties Cr(C6H6), Cr(CO)3, Mo(C6H6) and Mo(CO)3 was carried out by the DFT-PBE method. These molecules can be considered as bowl-shaped precursors of derivatives R6C60 of fullerene C60.. Groups R in molecules C21H12R6 (R = H, F, Cl, Br, CN) were added to carbon atoms of sumanene placed in the α-positions relative to central hexagon. Stability of complexes M(C6H6)C21H12R6 и M(CO)3C21H12R6 (M = Cr, Mo) was estimated. It was found that the addition M(C6H6) and M(CO)3 to sumanene with formation of η6-π-bonds is less profitable than in the case of molecules C21H12R6 (R = H, F, Cl, Br, CN). The most stable complexes were recommended for synthesis. [ABSTRACT FROM AUTHOR]

Abstract: Protonation of norborn-5-en-2-one gives 6-oxo-2-norbornyl cation (2) as most stable C7H9O+ cation. Quantum calculations at B3LYP/6-31G(d) level (gas phase, 1atm, 25°C) predict a C S-structure for 2 that can be represented as an intramolecular π-complex (Dewar π-complex model) of an acetylium ion with an alkene (cyclopent-3-enyl moiety). Isomeric 5-oxo-2-norbornyl (1) cation is calculated to be 16.7kcal/mol less stable than 2. Part of the relatively high stability of 2 arises from the electron-releasing carbonyl group through n(C sp="0.25" />↔ σ ↔2p(C+) hyperconjugation. This effect is also present in more stable 6-oxo-3-oxa (14) and 6-oxo-3-aza-2-norbornyl cation (19) as these ions are calculated to be 7.4 and 3.3kcal/mol, respectively, more stable than their 5-oxo isomers. [Copyright &y& Elsevier]

Abstract: Two trichloroplatinum π-complexes and a diammonium tetrachloroplatinate (II) salt have been unexpectedly isolated during the attempt to synthesize the corresponding cisplatinum square-planar complexes of tertiary cyclohexane 1,4-diamines. All three compounds have been physically and spectroscopically characterized, including X-ray diffraction analysis in two of the three compounds. The formation of the π-complexes instead of the diamino cis-platinum complexes could be explained as due to the steric hindrance exerted by methyl groups on the tertiary amines. So, the π-electrons of the Cbond are more available than the electron lone pair of nitrogen atom from the amino groups. When the π-electrons of the Ce molecule of ligand were made unavailable by transforming the cyclohexene subunit into a benzene aromatic ring, no cis-diamino dichloro platinum(II) complex nor trichloroplatinum-complexes were isolated but the corresponding tetrachloroplatinate(II) diammonium salt of the 1,4-diamino ligand. [Copyright &y& Elsevier]

The results of X-ray diffraction analysis of novel triethylallylammonium chloride compounds with copper(I) chloride, copper(I) bromide, and copper(II) chloride are reported. The [(CH3CH2)3(CH2=CHCH2xN]CuCl4 and [(CH3CH2)3(CH2=CHCH2CuBr3.86)Cl0.14 p-complexes are isostructural: space groupP21/a;a= 17.58(1) Å,b= 12.059(8)Å,c= 7.184(4) Å,ß= 98.37(5)° anda= 17.972(9) Å,b=12.479(8) Å,c= 7.290(5) Å, ß = 98.81(5)°, respectively. ?2-Coordination of the copper atom by the olefinic bond plays a key role in the structural ordering of the tetraalkylammonium cation. In contrast, the structure of {(CH3CH2)3x(CH2=CHCH2)N}2CuIICl4 (P42/nmc;a= 8.839(3) Å,c=15.660(9) Å) follows the ionic salt pattern. [ABSTRACT FROM AUTHOR]

The results of X-ray diffraction analysis of novel triethylallylammonium chloride compounds with copper(I) chloride, copper(I) bromide, and copper(II) chloride are reported. The [(CH3CH2)3(CH2=CHCH2xN]CuCl4 and [(CH3CH2)3(CH2=CHCH2CuBr3.86)Cl0.14 p-complexes are isostructural: space groupP21/a;a= 17.58(1) Å,b= 12.059(8)Å,c= 7.184(4) Å,ß= 98.37(5)° anda= 17.972(9) Å,b=12.479(8) Å,c= 7.290(5) Å, ß = 98.81(5)°, respectively. ?2-Coordination of the copper atom by the olefinic bond plays a key role in the structural ordering of the tetraalkylammonium cation. In contrast, the structure of {(CH3CH2)3x(CH2=CHCH2)N}2CuIICl4 (P42/nmc;a= 8.839(3) Å,c=15.660(9) Å) follows the ionic salt pattern. [ABSTRACT FROM AUTHOR]

Two new $\backslash pi$-complexes of copper(I) halides with the 1,3-diallylbenzimidazolium cation, [C7H5N2(C3H5)2]+[Cu2$\{\backslash rm\; Cl\}\_\{1.40\}\; \{\backslash rm\; Br\}\_\{1.60\}\; ]^-$ and [C7H5N2(C3H5)2]+[Cu2$\{\backslash rm\; Br\}\_3\; ]^-$, have been synthesized and structurally defined (space group $P2\_1/c$ for both; $a=22.094(6)$, $b=9.272(8)$, $c=9.22(1)$ Å, $\backslash beta\; =118.26(4)$° and $a=22.267(5)$, $b=\; 9.311(3)$, $c=9.263(2)$ Å, $\backslash beta\; =117.51(2)$°). The mutual effects of chlorine–bromine substitution and the efficiency of $\backslash pi$-interactions are discussed based on XRD data for these two compounds and for the compounds [C7H5N2(C3H5)2]+[Cu2$\{\backslash rm\; Cl\}\_\{3\}]^-$ and [C7H5N2(C3H5)2]+[Cu2$\{\backslash rm\; Cl\}\_\{0.67\}\; \{\backslash rm\; Br\}\_\{2.33\}\; ]^-$ studied previously. [ABSTRACT FROM AUTHOR]

The ab initio MP2 method is used with the LANL2DZ basis to calculate the mercury chloride $\backslash pi,\backslash pi$-complex with two acetylene molecules (1) and various isomeric forms of mercury di($\backslash beta$)-vinyl chloride $\backslash sigma$-complexes (2): cis-cis (2A), cis-trans (2B), and trans-trans (2C). The $\backslash pi,\backslash pi$-complex is the most stable form of all those considered; the difference between 1 and 2A is 24.9 kcal/mole. A relation between the total energies (kcal/mole) for isomeric forms 2 is established to be $2A\backslash ,\; (0)\; \backslash textless\; 2B\backslash ,\; (0.98)\; \backslash textless\; 2C\backslash ,\; (1.58)$. Complex 1 is shown to be transformed into $2A$ via the intermediate formation of 3, which is a hybrid form of the complex ($\backslash pi,\backslash sigma$-complex of mercury chloride with two acetylene molecules). The structures of the transition states for the transformations of 1 into 3 (structure 4) and of 3 into $2A$ (structure 5) and the corresponding transition activation energies are determined. The interaction of $2A$, $2B$, and $2C$ with the $\{\backslash rm\; Cl\}^-$ anion as a model nucleophile is considered. It is shown that the resulting anions ($6A,\backslash ,\; 6B,\backslash ,\; 6C$) have a planar structure with the relative stability increasing in the series $6A\backslash textless6B\backslash textless6C$. [ABSTRACT FROM AUTHOR]

The ab initio MP2 method is used with the LANL2DZ basis to calculate the mercury chloride $\backslash pi,\backslash pi$-complex with two acetylene molecules (1) and various isomeric forms of mercury di($\backslash beta$)-vinyl chloride $\backslash sigma$-complexes (2): cis-cis (2A), cis-trans (2B), and trans-trans (2C). The $\backslash pi,\backslash pi$-complex is the most stable form of all those considered; the difference between 1 and 2A is 24.9 kcal/mole. A relation between the total energies (kcal/mole) for isomeric forms 2 is established to be $2A\backslash ,\; (0)\; \backslash textless\; 2B\backslash ,\; (0.98)\; \backslash textless\; 2C\backslash ,\; (1.58)$. Complex 1 is shown to be transformed into $2A$ via the intermediate formation of 3, which is a hybrid form of the complex ($\backslash pi,\backslash sigma$-complex of mercury chloride with two acetylene molecules). The structures of the transition states for the transformations of 1 into 3 (structure 4) and of 3 into $2A$ (structure 5) and the corresponding transition activation energies are determined. The interaction of $2A$, $2B$, and $2C$ with the $\{\backslash rm\; Cl\}^-$ anion as a model nucleophile is considered. It is shown that the resulting anions ($6A,\backslash ,\; 6B,\backslash ,\; 6C$) have a planar structure with the relative stability increasing in the series $6A\backslash textless6B\backslash textless6C$. [ABSTRACT FROM AUTHOR]

The vibrational frequencies and force constants for naphthalene (C10H8), 1,4,5,8- and 2,3,6,7-tetradeuterionaphthalenes (C10H4D4), octadeuterionaphthalene (C10D8), and chromium (η6-naphthalene)tricarbonyl were calculated by the DFT method using the PBE approximation in extended and split bases. The results calculated without the use of scaling factors are in good agreement with the IR and Raman experimental data. All vibrational frequencies for the free ligand and π-complex molecules were assigned. The influence of coordination to the transition metal on the frequencies and force field of the naphthalene molecule (both for the free ring and the ring coordinated to the transition metal) was discussed. [ABSTRACT FROM AUTHOR]

The problem of stabilization of polyhedral carbon clusters, which do not obey the isolated pentagon rule, is discussed taking a dodecahedral fullerene C20 as an example. Ab initio MO LCAO calculations in the HF/3-21G approximation showed that fullerene C20 as well as its C20H5 hydrides with C5v symmetry can form stable 2η5-π-complexes of the CpFeC20FeCp and H5C20FeC20H5 types. The energies of the η5-Fe--C20 π-bonds in these complexes were compared with those of the Fe--Cp bond in ferrocene and the Fe--C60 bond in the η5-π-C60H5FeCp complex. [ABSTRACT FROM AUTHOR]

The reaction of maleic anhydride with 2-methylimidazole in acetonitrile and DMF is accompanied by the appearance of strong absorption bands in the visible part of the spectrum due to the formation of molecular complexes. In acetonitrile the reaction proceeds by two routes via the formation of an amide and the molecular complex. Phthalic anhydride reacts with 2-methylimidazole to give amide but not to form molecular complexes. [ABSTRACT FROM AUTHOR]

The effects of the solvent and the ligand chirality on the regioselectivity of oxidative esterification of propylene and cyclohexene by PdII carboxylates were studied using achiral (MeCO2 −, Me2CHCH2CO2 −), racemic ((±)-CF3CF2CF2OC*F(CF3)CO2 −), and chiral (( S)−(+)−MeC*H(Et)CO2 −, (+)−CF3CF2CF2OC*F(CF3)CO2 −) carboxylate ligands. The oxidation of alkenes in aprotic media (CHCl3, CH2Cl2, CO2, THF) affords mainly allylic esters (in the case of cyclohexene also homoallylic esters) and the oxidative esterification at the vinylic position is absent. In weakly solvating media (CHCl3, CH2Cl2) the regioselectivity of cyclohexene oxidation (the allyl to homoallyl ratio) increases substantially on going from achiral or racemic acido ligands to chiral acido ligands. In a more donor medium (THF) the ligand chirality effect almost vanishes. The effects of the ligand chirality and the nature of the solvent on the mechanism of alkene oxidation by PdII complexes are discussed. [ABSTRACT FROM AUTHOR]

The problem of existence of η5-π-complexes of unsubstituted fullerene I h -C60 and its cyclopentadienyl type derivative C60H5 . is discussed. Ab initio MO LCAO SCF calculations of hypothetical sandwich systems η5-π-C60H5XCp (X=Fe ( 1a), Si ( 1b)), the cationic complex C60FeCp+ of unsubstituted C60, and the C60H5 . radical were performed in the STO-3G and 3-21G basis sets. In the 1a, 1b, and C60H5 . systems, hydrogen atoms are attached to carbon atoms of fullerene i h -C60 at α-positions relative to the same pentagonal face ( pent *). In η5-complexes, XCp species are also coordinated to this face. According to calculations in the 3-21G basis set, the Fe- pent * bond energy in complex 1a is much higher than those of similar bonds in 1b and in the η5-π-C60FECp+ cation (117 kcal mol−1 vs. 37 and 64 kcal mol−1, respectively) and is 7 kcal mol−1 higher than the Fe−Cp bond energy in the classical sandwich system FeCp2. The Fe...C pent* and Fe...CCp distances in complex 1a are slightly shorter than the Fe...C distance in the ferrocene molecule. The spin populations in the C60-π-complexes of this radical. [ABSTRACT FROM AUTHOR]5 . radical are almost completely localized on the atoms of the pent * face, which must favor the formation of η5-π-complexes of this radical. [ABSTRACT FROM AUTHOR]

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Hypothetical derivatives of corannulene C20H10 (Cor), namely, CorX5 • radicals, CorX5-π-complexes with SiCp, were calculated by the MNDO/PM3 method. The possibilities of using the results of these calculations for modeling the electronic structure and geometry of fragments of the analogous complexes of the fullerene derivatives C− anions (X=H, Cl, or Br), and their η5-π-complexes with SiCp, were calculated by the MNDO/PM3 method. The possibilities of using the results of these calculations for modeling the electronic structure and geometry of fragments of the analogous complexes of the fullerene derivatives C60X5 are discussed. Calculations of C60X5 • radicals and C60X5 − anions were also carried out. In all the compounds under study, the X atoms are attached to carbon atoms in α positions with respect to the same five-membered ring. [ABSTRACT FROM AUTHOR]

Qualitative estimates of possibility of the formation of fullerene η-π-complexes have been carried out by the MNDO/PM3 method. It was shown, as exemplified by the C cluster, that the introduction of five univalent functional groups R (R = H, Cl, Br) to α-positions of a separate pentagon of C with the formation of [RC] anions results in a pronounced increase in the π-electron density on the atoms of this five-membered cycle and more favorable conditions for the formation of π-bonds with the η-ligand. The nature of the interaction between the atoms of the separate cycle in [RC] anion and η-ligand was analyzed by the example of hypothetical sandwich systems RCSiCp. Half-sandwich complexes RCSiX (X = H, Cl) were also investigated. The local energy minima were found on the potential energy surfaces (PES) of systems RCSiCp and RCSiX with C symmetry. These systems transform barrirlessly into q5-7E-complexes with the angular structure if the symmetry restrictions are removed. The most favorable conditions for η-π-complexes of RC to form are realized for R = H. The results obtained were compared to those of semiempirical and nonempirical calculations of bis (cyclopentadienyl) silicon. [ABSTRACT FROM AUTHOR]

Regioselectivity and diastereoselectivity of the addition of BrCCl to ( R)-3-( E)-cinnamoyl-4-phenyloxazolidin-2-one ( 1) and ( R)-3-( E)-acryloyl-4-phenyloxazolidin-2-one ( 2) catalyzed by Fe(CO) or initiated with benzoyl peroxide were investigated. Stereochemistry of the reaction of BrCCl with the a-complexes (4 R,α S,β S)-ν-(3-( E)-cinnamoyl-4-phenyl-oxazolidin-2-one)irontetracarbonyl ( 3a) and (4 R,α R)-η-(3-acryloyl-4-phenyloxazolidin-2-one)irontetracarbonyl ( 4b) was also studied. The results obtained allow the following conclusions to be drawn: (1) the thermal Kharasch reaction catalyzed by Fe(CO) proceeds by a redox catalysis mechanism; (2) iron (in any of its oxidation states) is not coordinated to olefins in the transition state of the reaction; (3) the transfer of the halogen atom on the radical adduct probably occurs inside a radical-iron cation pair. [ABSTRACT FROM AUTHOR]

The stability constants of some bi- and trivalent metal complexes with methyl-, trifluoromethyl-, and phenyl-substituted 6-heptene-1,3-diones have been determined by pH-metric titration at 20 °C and an ionic strength μ = 0.1. It is proposed that vinyl groups of ligands are involved in complexation. [ABSTRACT FROM AUTHOR]

FTIR spectra have been studied for 'staircase' cyclopentadienyl complexes containing two or three metal carbonyl fragments bound by the metal-carbon bond Cp(CO)Fe-CpmMn(CO) ( 1), Cp(CO)Fe-CpmFe(CO)CHPh ( 2), Cp(CO)Fe-Cpm(CO)Fe-CpmMn(CO) ( 3), Cp(CO)Mo-Cpm(CO)Fe-CpmMn(CO) ( 4), Cp(CO)W-Cpm(CO)Fe-CpmMn(CO) ( 5), Cp(CO)Fe-Cpm(CO)Fe-BmCr(CO) ( 6), Cr(CO)Bm-CpmFe(CO)CHPh ( 7), where Cp = η-CH, Cpm = η∶η-CH, Bm = η∶η-CH. Temperature-dependent FTIR spectra were measured in n-pentane solutions over a wide temperature range and in the low-temperature solid matrices of argon and nitrogen. Rotamers, formed due to rotation about the metal-carbon σ-bond, were found in solutions and matrices. A molecular mechanics calculation of 1 proved the possibility of such rotation. [ABSTRACT FROM AUTHOR]

The molecular and electronic structures of some hypothetical sandwich-type π-complexes of transition metals with fullerene C were modeled. The M-C bonds in η-CMCp complexes (M = Fe, Ru, Os) are less strong than the M-Cp bonds in ferrocene, ruthenocene, and osmocene, respectively. The η-CMCH complexes (M = Cr, Mo, W) should be less stable than their classical analogs (CH)M(CH). The coordination of a metal atom with the fullerene at its pentagonal face is more energetically favorable than at a hexagonal face. [ABSTRACT FROM AUTHOR]

New cationic complexes [(η-CH)Fe(η-Cp)]PF and [(η-9-CH-CH)Fe(η-Cp)]PF were obtained by the reaction of CpFe(CO)Br with fluorene and 9-methylfluorene, respectively. Deprotonation of these complexes by t-BuOK in THF affords zwitter-ionic compounds (η-CH)Fe(η-Cp) and (η-9-CH-CH)Fe(η-Cp) ( A). When A is heated in nonane at 150 °C it undergoes η⇌η inter-ring rearrangement with the formation of hexamethyldibenzoferrocene ( B). The electrochemical behavior of A and B was studied by cyclic voltammetry. One-electron reduction of A and B to the corresponding radical anions induces inter-ring haptotropic rearrangement A⇌η B. The equilibrium in the 19ē state is shifted to the η-isomeric radical anion A, while in the 18ē precursors, it shifts to the η-isomer B. [ABSTRACT FROM AUTHOR]

The isotope effects of deuterium, manifested in theC NMR spectra of complexes of deuterated hexamethylbenzenes C(CD)·(CH) with the nitrosonium cation, have been studied. The small values observed for the isotopic perturbation are evidence of π-bonding of the NO group the hexamethylbenzene molecule. The applicability of an additive scheme of calculation of isotope effects for the ring carbon atoms of the complexes, based on the increments of replacement of the CH group by CD in hexamethylbenzene, has been demonstrated. [ABSTRACT FROM AUTHOR]

The article discusses research on the x-ray crystal structure of a cuprate-carbonyl π-complex. It states that rapid-injection techniques were applied in the study to evaluate aldehydes and ketones. It also offers information on tetrahedral lithium atom, tetrahydrofuran (THF) ligands, and cuprated carbonyl group.