Thermal decomposition mechanism of Ba(DPM)2

We have investigated the thermal decomposition behavior of Ba(DPM)₂ using thermogravimetry (TG), mass spectrometry (MS), ultraviolet (UV) absorption and in-situ Fourier transform infrared (FTIR) spectroscopy. FTIR has been used particularly for direct monitoring of the bond dissociation order in the metal complex by thermal treatment in either N₂ or O₂. TG analysis shows that the ambient gas has a significant effect on the weight loss patterns of Ba(DPM)₂. The chemical bonds of Ba(DPM)₂ begin to decompose at low temperatures below 50 °C and are sequentially dissociated when the temperature is raised. The C-C(CH₃)₃ and the Ba-O bonds are decomposed most easily at low temperatures, followed by the C-H bond, but the stable C-C and C-O bonds do not dissociate until the total complex is gasified. The decomposition sequence of the chemical bonds in Ba(DPM)₂ is similar to that of Sr(DPM)₂ but differs from that of Ti(O-iPr)₂(DPM)₂ which is decomposed in the sequence of C(CH₃)₃ > C-H and C-O > Ti-O. The major difference in the decomposition sequence between Ba and Ti complexes can be seen to derive from the intrinsic character of the individual metal-oxygen bond as observed by UV spectroscopy.     

Synthesis, Reactivity, and Structural Characterization of the Nonclassical [MTe(7)](n)()(-) Anions (M = Ag, Au, n = 3; M = Hg, n = 2)

Several tellurometalates of the general formula [MTe(7)](n)()(-) (n = 2, 3) have been isolated as salts of organic cations by reaction of suitable metal sources with polytelluride solutions in DMF. The [HgTe(7)](2)(-) anion has the same structure in both the NEt(4)(+) and the PPh(4)(+) salts except for a minor change in the ligand conformation. The [AgTe(7)](3)(-) and [HgTe(7)](2)(-) anions contain metal atoms coordinated in trigonal-planar fashion to eta(3)-Te(7)(4)(-) ligands. The central Te atom of an eta(3)-Te(7)(4)(-) ligand is coordinated to the metal atom and to two Te atoms in a "T"-shaped geometry consistent with a hypervalent 10 e(-) center. The planar [AuTe(7)](3)(-) anion may best be described as possessing a square-planar Au(III) atom coordinated to an eta(3)-Te(5)(4)(-) ligand and to an eta(1)-Te(2)(2)(-) ligand. The reaction of [NEt(4)](n)()[MTe(7)] (M = Hg, n = 2; M = Au, n = 3) with the activated acetylene dimethyl acetylenedicarboxylate (DMAD) has yielded the products [NEt(4)](n)()[M(Te(2)C(2)(COOCH(3))(2))(2)] (M = Hg, n = 2; M = Au, n = 1). The metal atoms are coordinated to two Te(COOCH(3))C=C(COOCH(3))Te(2)(-) ligands, for M = Hg in a distorted tetrahedral fashion and for M = Au in a square-planar fashion.     

Transition metal-boron complexes BnM: from bowls (n = 8-14) to tires (n = 14)

Transition metal-boron complexes BnM have been predicted at density functional theory level to be molecular bowls (n = 8-14) hosting a transition metal atom (M) inside or molecular tires (n = 14) centered with a transition metal atom. Small Bn clusters prove to be effective inorganic ligands to all the VB-VIIIB transition metal elements in the periodic table. Density functional evidences obtained in this work strongly suggest that bowl-shaped fullerene analogues of Bn units exist in small BnM complexes and the bowl-to-tire structural transition occur to the first-row transition metal complexes BnM (M = Mn, Fe, Co) at n = 14, a size obviously smaller than n = 20 where the 2D-3D structural transition occurs to bare Bn. The half-sandwich-type B12Cr (C3v), full sandwich-type (B12)2Cr (D3d), bowl-shaped B14Fe (C2), and tire-shaped B14Fe (D7d) and B14Fe- (C7v) are the most interesting prototypes to be targeted in future experiments. These BnM complexes may serve as building blocks to form extended boron-rich BnMm tubes or cages (m > or = 2) or as structural units to be placed inside carbon nanotubes with suitable diameters.     

Synthesis and structures of M[N(TePPri2)2-Te,Te']n (n = 2, M = Zn, Cd, Hg; n = 3, M = Sb, Bi): the first ditelluroimidodiphosphinato p- and d-block metal complexes

Reactions of Na[N(TePPri2)2] with the appropriate metal halide produce the air-stable complexes M[N(TePPri2)2-Te,Te']n (n = 2, M = Zn, Cd, Hg; n = 3, M = Sb, Bi), which adopt distorted tetrahedral (M = Zn, Cd, Hg) and octahedral (M = Sb, Bi) structures, respectively.     

Bonding of seven carbonyl groups to a single metal atom: theoretical study of M(CO)n (M = Ti, Zr, Hf; n = 7, 6, 5, 4)

The equilibrium geometries, thermochemistry, and vibrational frequencies of the homoleptic metal-carbonyls of the group 4 elements, M(CO)n (M = Ti, Zr, Hf; n = 7, 6, 5, 4) were predicted using density functional theory. Analogous M(CO)n structures were found for all three metals. The global minima for the 18-electron M(CO)7 molecules are all singlet C(3v) capped octahedra. The global minima for the 16-electron M(CO)6 species are triplet M(CO)6 structures distorted from O(h) symmetry to D(3d) symmetry. However, the corresponding singlet M(CO)6 structures lie within 5 kcal/mol of the triplet global minima. The global minima for M(CO)n (n = 5, 4) are triplet structures derived from the D(3d) distorted octahedral structures of M(CO)6 by removal of one or two CO groups, respectively. Quintet D(3h) trigonal bipyramidal structures for M(CO)5 and singlet T(d) tetrahedral structures for M(CO)4 are also found, as well as higher energy structures for M(CO)6 and M(CO)7 containing a unique CO group bonded to the metal atom through both M-C and M-O bonds. The dissociation energies M(CO)7 --> M(CO)6 + CO are substantial, indicating no fundamental problem in bonding seven CO groups to a single metal atom.     

Ternary alkali metal transition metal acetylides A2MC2 (A = Na, K; M = Pd, Pt)

Ternary transition metal acetylides A2MC2 (A = Na, K; M = Pd, Pt) can be synthesised by reaction of the respective alkali metal acetylide A2C2 with palladium or platinum in an inert atmosphere at about 350 degrees C. The crystal structures are characterised by (infinity)1[M(C2)(2/2)2-] chains, which are separated by the alkali metals (P3m1, Z = 1). The refinement of neutron powder diffraction data gave C-C = 1.263(3) A for Na2PdC2 (Na2PtC2: 1.289(4) A), which is distinctively longer than the expected value for a C-C triple bond (1.20 A). On the basis of band-structure calculations this can be attributed to a strong back-bonding from the metal into the anti-bonding orbitals of the C2 unit. This was further confirmed by Raman spectroscopic investigations, which showed that the wavenumbers of the C-C stretching vibrations in Na2PdC2 and Na2PtC2 are about 100 cm(-1) smaller than in acetylene. 13C MAS-NMR spectra demonstrated that the acetylenic C2 units in the title compounds are very different from those in acetylene. Electrical conductivity measurements and band-structure calculations showed that the black title compounds are semiconductors with a small indirect band gap (approximately 0.2 eV).     

异核过渡金属类立方烷原子簇化合物M_3S_4L_9M'X~(n+)的电子结构

本文利用定性价键理论、半经验分子轨道法和分子轨道碎片法,讨论了通式为M_3S_4L_9M′X~(n+)(M=Cr,Mo,W;M′=Fe,Co,Ni,Cu;n=0,4,5)的异核过渡金属簇合物Cr_3S_4Cp_3FeOOCCMe_3(1),Cr_3S_4Cp_3CoCO(2),Mo_3S_4(NH_3)_9FeOH_2~(4+)(3)和Mo_3S_4(OH_2)_9NiOH_2~(4+)(4)的电子结构,成键性质,以及活性元件(碎片)L_9M_3S_4~(n+)和M′X组装的合理性。指出了由于碎片组装成类立方烷后,电子从M′原子转移到M原子,使得过渡金属原子M的氧化态低于不完整类立方烷中的M原子。此外,本文还根据价键理论和分子轨道法的集居数分析,给出簇合物骨架的相对稳定性顺序是Mo_3S_4FC~(4+)>Cr_3S_4Fe~(4+)>Cr_3S_4Co~(4+)>Mo_3S_4Ni~(4+)。     

Anion photoelectron spectroscopy of germanium and tin clusters containing a transition- or lanthanide-metal atom; MGe(n)- (n = 8-20) and MSn(n)- (n = 15-17) (M = Sc-V, Y-Nb, and Lu-Ta)

The electronic properties of germanium and tin clusters containing a transition- or lanthanide-metal atom from group 3, 4, or 5, MGe(n) (M = Sc, Ti, V, Y, Zr, Nb, Lu, Hf, and Ta) and MSn(n) (M = Sc, Ti, Y. Zr, and Hf), were investigated by anion photoelectron spectroscopy at 213 nm. In the case of the group 3 elements Sc, Y, and Lu, the threshold energy of electron detachment of MGe(n)(-) exhibits local maxima at n = 10 and 16, while in the case of the group 4 elements Ti, Zr, and Hf, it exhibits a local minimum only at n = 16, associated with the presence of a small bump in the spectrum. A similar behavior is observed for MSn(n)(-) around n = 16, and these electronic characteristics of MGe(n) and MSn(n) are closely related to those of MSi(n). Compared to MSi(n), however, the larger cavity size of a Ge(n) cage allows metal atom encapsulation at a smaller size n. A cooperative effect between the electronic and geometric structures of clusters with a large cavity of Ge(16) or Sn(16) is discussed together with the results of experiments that probe their geometric stability via their reactivity to H(2)O adsorption.     

Redox energetics of hypercloso boron hydrides B(n)H(n) (n = 6-13) and B12X12 (X = F, Cl, OH, and CH3)

The reduction potentials (E°(Red) versus SHE) of hypercloso boron hydrides B(n)H(n) (n = 6-13) and B(12)X(12) (X = F, Cl, OH, and CH(3)) in water have been computed using the Conductor-like Polarizable Continuum Model (CPCM) and the Solvation Model Density (SMD) method for solvation modeling. The B3LYP/aug-cc-pvtz and M06-2X/aug-cc-pvtz as well as G4 level of theory were applied to determine the free energies of the first and second electron attachment (ΔG(E.A.)) to boron clusters. The solvation free energies (ΔG(solv)) greatly depend on the choice of the cavity set (UAKS, Pauling, or SMD) while the dependence on the choice of exchange/correlation functional is modest. The SMD cavity set gives the largest ΔΔG(solv) for B(n)H(n)(0/-) and B(n)H(n)(-/2-) while the UAKS cavity set gives the smallest ΔΔG(solv) value. The E°(Red) of B(n)H(n)(-/2-) (n = 6-12) with the G4/M06-2X(Pauling) (energy/solvation(cavity)) combination agrees within 0.2 V of experimental values. The experimental oxidative stability (E(1/2)) of B(n)X(n)(2-) (X = F, Cl, OH, and CH(3)) is usually located between the values predicted using the B3LYP and M06-2X functionals. The disproportionation free energies (ΔG(dpro)) of 2B(n)H(n)(-) → B(n)H(n) + B(n)H(n)(2-) reveal that the stabilities of B(n)H(n)(-) (n = 6-13) to disproportionation decrease in the order B(8)H(8)(-) > B(9)H(9)(-) > B(11)H(11)(-) > B(10)H(10)(-). The spin densities in B(12)X(12)(-) (X = F, Cl, OH, and CH(3)) tend to delocalize on the boron atoms rather than on the exterior functional groups. The partitioning of ΔG(solv)(B(n)H(n)(2-)) over spheres allows a rationalization of the nonlinear correlation between ΔG(E.A.) and E°(Red) for B(6)H(6)(-/2-), B(11)H(11)(-/2-), and B(13)H(13)(-/2-).     

The redox series [M(bpy)2(q)]n+, M = Ru or Os, Q = 3,5-di-tert-butyl-n-phenyl-1,2-benzoquinonemonoimine. Isolation and a complete X and W band EPR study of the semiquinone states (n = 1)

The complexes [M(bpy)(2)(Q)](PF(6)) (bpy = 2,2'-bipyridyl; M = Ru, Os; Q = 3,5-di-tert-butyl-N-phenyl-1,2-benzoquinonemonoimine) were isolated and studied by X and W band EPR in a dichloromethane solution at ambient temperatures and at 4 K. For M = Ru, the (14)N hyperfine splitting confirms the Ru(II)/semiquinone formulation, although at a > 1 mT, the (99,101)Ru satellite coupling is unusually high. W band EPR allowed us to determine the relatively small g anisotropy Delta g = g(1) - g(3) = 0.0665 for the ruthenium complex. The osmium analogue exhibits a much higher difference Delta g = 0.370, which is attributed not only to the larger spin-orbit coupling constant of Os versus that of Ru but also to a higher extent of metal contribution to the singly occupied molecular orbital. The difference Delta E between the oxidation and reduction potentials of the radical complexes is larger for the ruthenium compound (Delta E = 0.87 V) than for the osmium analogue (Delta E = 0.72), confirming the difference in metal/ligand interaction. The electrochemically generated states [M(bpy)(2)(Q)](n+), n = 0, 1, 2, and 3, were also characterized using UV-vis-near-infrared spectroelectrochemistry.     

Structure and bonding in coinage metal halide clusters M(n)X(n), M = Cu, Ag, Au; X = Br, I; n = 1-6

Ab initio calculations in the framework of density functional theory (DFT) were performed to study the lowest-energy isomers of noble metal halide clusters M(n)Br(n) and M(n)I(n), for M = Cu, Ag, or Au and n = 1-6. For all species, the most stable structures were found to be cyclic arrangements. Calculated bond lengths and infrared frequencies were compared with the available experimental data. The nature of the ionocovalent bonding was characterized. The stability and fragmentation were also investigated. The present work confirms previous observations on the particular stability of the trimer.     

Density functional theoretical study of a series of binary azides M(N3)n (n = 3, 4)

Geometrical structures of a series of binary azides M(N3)n (M = elements in groups 3 and 13 (n = 3) and in groups 4 and 14 (n = 4)) were investigated at the B3LYP/6-311+G level of theory. Our calculations found that binary group 3 triazides M(N3)3 (M = Sc, Y, La) and binary group 4 tetraazides M(N3)4 (M = Ti, Zr, Hf) turn out to be stable with all frequencies real having a similar linear M-N-NN structural feature, as previously reported for M(N3)4 (M = Ti, Zr, Hf). However, binary azides of group 13 M(N3)3 (M = B, Al, Ga, In, Tl) and group 14 elements M(N3)4 (C, Si, Ge, Sn, Pb) with bent M-N-NN bond angles differ obviously from binary group 3 and 4 azides in geometrical structure. These facts are mainly explained by the difference in electronic density overlap between the central atom and the alpha-N atoms of the azido groups. Two lone-pair electrons on the sp hybridization alpha-N atoms in the binary group 3 and 4 azides donate electron density into two empty d orbitals of the central transition metal atom and a pair of valence bonding electrons, resulting in the alpha-N atoms acting as a tridentate ligand. The sp2 hybridization alpha-N atoms of the binary group 13 and 14 azides only give one valence electron to form one valence bonding electron pair acting virtually as monodentate donors.     

六聚同多酸阴离子M_6O_(19)~(n-)(M=Mo,W,n=2;M=Nb,Ta,n=8)电子结构和化学性质的密度泛函理论研究

采用B3LYP方法在LanL2DZ水平上计算了六聚同多阴离子 (M6On-19,M =Mo和W ,n =2 ;M =Nb和Ta ,n =8)的电子结构 ,分析了它们的前线轨道、分子静电势 (MEP) .计算结果表明 ,Nb6O8-19和Ta6O8-19是电子给体 ,而Mo6O2 -19和W6O2 -19则是电子受体 ,这与它们在溶液中具有不同的化学性质是一致的     

Bingel-Hirsch reactions on non-IPR Gd3N@C2n (2n = 82 and 84)

The Bingel-Hirsch reactions on non-isolated pentagon rule (non-IPR) Gd(3)N@C(2n) (2n = 82, 84) are studied. Computational results show that the two metallofullerenes display similar reactivity according to their related topologies. Long C-C bonds with large pyramidalization angles lead to the most stable adducts, the [5,6] bonds in the adjacent pentagon pair being especially favored. The lesser regioselectivity observed for Gd(3)N@C(82) is probably due to the activation of some C-C bonds by means of the metal cluster.     

Separating innocence and non-innocence of ligands and metals in complexes [(L)Ru(acac)2](n) (n = -1, 0, +1; L = o-iminoquinone or o-iminothioquinone)

The diamagnetic title complexes were obtained from Ru(acac)(2)(CH(3)CN)(2) and 2-aminophenol or 2-aminothiophenol. X-ray structure analysis of (L(1))Ru(acac)(2) (L(1) = o-iminoquinone) revealed C-C intra-ring, C-O, and C-N distances which suggest a Ru(III)-iminosemiquinone oxidation state distribution with antiparallel spin-spin coupling. One-electron oxidation and reduction of both title compounds to paramagnetic monocations [(L)Ru(acac)(2)](+) or monoanions [(L)Ru(acac)(2)](-) occurs reversibly at widely separated potentials (deltaE > 1.3 V) and leads to low-energy shifted charge transfer bands. In comparison with clearly established Ru(II)-semiquinone or Ru(III)-catecholate systems the g tensor components 2.23 > g(1) > 2.09, 2.16 > g(2) > 2.07, and 1.97 > g(3) > 1.88 point to considerable metal contributions to the singly occupied MO, corresponding to Ru(III) complexes with either o-quinonoid (--> cations) or catecholate-type ligands (--> anions) and only minor inclusion of Ru(IV)- or Ru(II)-iminosemiquinone formulations, respectively. The preference for the Ru(III) oxidation state for all accessible species is partially attributed to the monoanionic 2,4-pentanedionate (acac) co-ligands which favor a higher metal oxidation state than, e.g., neutral 2,2'-bipyridine (bpy).     

Di-tert-butyl phosphate as synthon for metal phosphate materials via single-source coordination polymers [M(dtbp)(2)](n) (M = Mn,Cu) and [Cd(dtbp)(2)(H2O)](n) (dtbp-H = (tBuO)(2)P(O)OH)

Reaction of M(OAc)(2).xH(2)O (M = Mn, Cu, or Cd) with di-tert-butyl phosphate (dtbp-H) in a 1:2 molar ratio in methanol followed by slow crystallization of the resultant solid in MeOH/THF medium results in the formation of three new polymeric metal phosphates [M(dtbp)(2)](n)() [M = Mn, 1 (beige); M = Cu, 2 (blue)] and [Cd(dtbp)(2)(H(2)O)](n)(), 3 (colorless)] in good yields. The formation of [Mn(dtbp)(2)](n) (1) proceeds via tetrameric manganese phosphate [Mn(4)(O)(dtbp)(6)] (4), which has been isolated in an analytically pure form. Perfectly air- and moisture-stable compounds 1-4 were characterized with the aid of analytical, thermoanalytical, and spectroscopic techniques. The molecular structures of 1-3 were further established by single-crystal X-ray diffraction studies. Crystal data for 1: C(32)H(72)Mn(2)O(16)P(4), monoclinic, P2(1)/c, a = 19.957(4) A, b = 13.419(1) A, c = 18.083(2) A, beta = 91.25(2) degrees, Z = 4. Crystal data for 2: C(16)H(36)CuO(8)P(2), orthorhombic, Pccn, a = 23.777(2) A, b = 10.074(1) A, c = 10.090(1) A, Z = 4. Crystal data for 3: C(48)H(114)Cd(3)O(27)P(6), triclinic, P1, a = 12.689(3) A, b = 14.364(3) A, c = 22.491(5) A, alpha = 84.54(3) degrees, beta = 79.43(3) degrees, gamma = 70.03(3) degrees, Z = 2. The diffraction studies reveal three different structural forms for the three compounds investigated, each possessing a one-dimensional coordination polymeric structure. While alternating triple and single dtbp bridges are found between the adjacent Mn(2+) ions in 1, uniform double dtbp bridges across the adjacent Cu(2+) ions are present in 2. The cadmium ions in the structure of 3 are pentacoordinated. Thermal analysis (TGA and DSC) indicates that compounds 1-3 convert to the corresponding crystalline metaphosphate materials M(PO(3))(2), in each case at temperatures below 500 degrees C. Similarly, the thermal decomposition of 4 results in the formation of Mn(PO(3))(3) and Mn(2)P(2)O(7). The final materials obtained by independent thermal decomposition of bulk samples have been characterized using IR spectroscopic, powder diffraction, and N(2) adsorption studies.     

A close look at short C-CH3...potassium contacts: synthetic and theoretical investigations of [M2Co2(mu3-OtBu)2(mu2-OtBu)4(thf)n] (M = Na, K, Rb, thf = tetrahydrofuran)

Agostic interactions of the type Si-CH3M+ (M = alkali metal) are frequently mentioned in discussions of solid-state structures of trimethylsilyl compounds and the purpose of this work was to elucidate if they also exist in the related tert-butyl species by using density functional theory. The compounds [M2Co2(mu3-OtBu)2(mu2-OtBu)4(thf)n] (M = Na, n = 2; M = K, n = 0; M = Rb, n = 1) have been synthesised and their crystal structures determined. Close contacts of methyl groups with K atoms are observed in the solid-state structure of [K2Co2(mu3-OtBu)2(mu2-OtBu)4], and calculations of the rotational barrier of a tert-butoxy group about the axis through the C-O bond were performed. It was shown that apparent short C-CH3K distances are in this case a consequence of the packing in the extended solid-state structure.     

Structure and infrared spectroscopy of group 6 transition-metal carbonyls in the gas phase: DFT studies on M(CO)n (M = Cr, Mo, and W; n = 6, 5, 4, and 3)

B3LYP-based density functional theory (DFT) calculations with effective core potentials (ECPs) (LANL2DZ) on M and 6-311+G(2d) all-electron basis function sets on C and O are used to interpret the symmetry characteristic vibrational absorption patterns of CO ligands in the "naked" coordinatively unsaturated transition-metal carbonyls M(CO)n-1 (M = Cr, Mo, and W; n = 4-6) observed by a time-resolved infrared absorption spectroscopy after the UV pulse laser photolysis of M(CO)6 in the gas phase. The UV photolysis results can be reasonably explained by the trends in the calculated bond dissociation enthalpies of M(CO)n-1-CO for group 6 metal carbonyls. M(CO)n-1 produced through one CO elimination from M(CO)n is found out to keep its parent skeleton, resulting in the structure with symmetry of C4v for M(CO)5, C2v for M(CO)4, and C3v for M(CO)3.     

Synthesis, structures and reactions of cyclometallated gold complexes containing (2-diphenylarsino-n-methyl)phenyl (n = 5, 6)

Reaction of (C6H3-2-AsPh2-n-Me)Li (n = 5 or 6) with [AuBr(AsPh3)] at -78 degrees C gives the corresponding cyclometallated gold(I) complexes [Au2[(mu-C6H3-n-Me)AsPh2]2] [n = 5, (1); n = 6, (9)]. 1 undergoes oxidative addition with halogens and with dibenzoyl peroxide to give digold(II) complexes [Au2X2[(mu-C6H3-5-Me)AsPh2]2] [X = Cl (2a), Br (2b), I (2c) and O2CPh (3)] containing a metal-metal bond between the 5d9 metal centres. Reaction of 2a with AgO2CMe or of 3 with C6F5Li gives the corresponding digold(II) complexes in which X = O2CMe (4) and C6F5 (6), respectively. The Au-Au distances increase in the order 4 < 2a < 2b < 2c < 6, following the covalent binding tendency of the axial ligand. Like the analogous phosphine complexes, 2a-2c and 6 in solution rearrange to form C-C coupled digold(I) complexes [Au2X2[mu-2,2-Ph2As(5,5-Me2C6H3C6H3)AsPh2]] [X = Cl (5a), X = Br (5b), X = I (5c) and C6F5 (7)] in which the gold atoms are linearly coordinated by As and X. In contrast, the products of oxidative additions to 9 depend markedly on the halogens. Reaction of 9 with chlorine gives the gold(I)-gold(III) complex, [ClAu[mu-2-Ph2As(C6H3-6-Me)]AuCl[(6-MeC6H3)-2-AsPh2]-kappa2As,C] (10), which contains a four-membered chelate ring, Ph2As(C6H3-6-Me), in the coordination sphere of the gold(III) atom. When 10 is heated, the ring is cleaved, the product being the digold(I) complex [ClAu[mu-2-Ph2As(C6H3-6-Me)]Au[AsPh2(2-Cl-3-Me-C6H3)]] (11). Reaction of 9 with bromine at 50 degrees C gives a monobromo digold(I) complex (12), which is similar to 11 except that the 2-position of the substituted aromatic ring bears hydrogen instead halogen. Reaction of 9 with iodine gives a mixture of a free tertiary arsine, (2-I-3-MeC6H3)AsPh2 (13), a digold diiodo compound (14) analogous to 11, and a gold(I)-gold(III) zwitterionic complex [I2Au(III)[(mu-C6H3-2-AsPh2-6-Me)]2Au(I)] (15) in which the bridging units are arranged head-to-head between the metal atoms. The structures of 2a-2c and 4-15 have been determined by single-crystal X-ray diffraction analysis. The different behaviour of 1 and 9 toward halogens mirrors that of their phosphine analogues; the 6-methyl substituent blocks C-C coupling of the aryl residues in the initially formed oxidative addition product. In the case of 9, the greater lability of the Au-As bond in the initial oxidative addition product may account for the more complex behaviour of this system compared with that of its phosphine analogue.     

双帽Keggin型杂多阴离子[PM12O40(VO)2]n-(M=Mo,n=5; M=V, n=9)的离散变分方法研究

使用密度泛函理论的离散变分方法(DFT-DVM)研究了双帽Keggin型杂多阴离子[PM12O40(VO)2]n-(M=Mo, n=5; M=V, n=9),即[PMo12O40(VO)2]5- (a)和[PV12O40(VO)2]9- (b)的电子结构,讨论了双帽的形成对Keggin型杂多阴离子的电子结构和催化性质的影响,并与其Keggin型杂多阴离子(PM12O40)n-(M=Mo, n=3; M=V, n=15)的计算结果进行了对比分析,计算结果表明,双帽的形成对Keggin型杂多阴离子的电子结构产生了很大的影响,因而它们在催化活性上可能会表现出较大的差异.