Theoretical study on the reaction mechanism of the gas-phase H2/CO2/Ni(3D) system

The ground-state potential energy surface (PES) in the gas-phase H2/CO2/Ni(3D) system is investigated at the CCSD(T)//B3LYP/6-311+G(2d,2p) levels in order to explore the possible reaction mechanism of the reverse water gas shift reaction catalyzed by Ni(3D). The calculations predict that the C-O bond cleavage of CO2 assisted by co-interacted H2 is prior to the dissociation of the H2, and the most feasible reaction path for Ni(3D) + H2 + CO2 --> Ni(3D) + H2O + CO is endothermic by 12.5 kJ mol(-1) with an energy barrier of 103.9 kJ mol(-1). The rate-determining step for the overall reaction is predicted to be the hydrogen migration with water formation. The promotion effect of H2 on the cleavage of C-O bond in CO2 is also discussed and compared with the analogous reaction of Ni(3D) + CO2 --> NiO + CO, and the difference between triplet and singlet H2/CO2/Ni systems is also discussed.     

羰基镍簇Ni(CO)n(n=1-4)的结构和Ni-CO键解离性质的密度泛函理论研究

在密度泛函理论框架下, 应用不同泛函计算了配合物Ni(CO)n(n=1~4)的平衡几何构型和振动频率. 考察了泛函和基组重叠误差对预测Ni—CO键解离能的影响. 计算结果表明, 用杂化泛函能得到与实验一致的优化几何构型和较合理的振动频率. 对Ni(CO)n(n=2~4)体系, 用“纯”泛函, 如BP86和BPW91, 可得到与CCSD(T)更符合、 并与实验值接近的解离能. 当解离产物出现单个金属原子或离子(如金属羰基配合物的完全解离)时, BSSE校正项的计算中应保持金属部分的电子结构一致. 只有考虑配体基组和不考虑配体基组两种情况下金属的电子构型与配合物中金属的构型一致时, 才能得到合理的BSSE校正, 从而预测合理的解离能.     

The [1+1] two-photon dissociation spectra of CO2 + via A 2Pi u,12(upsilon1upsilon20)<--X 2Pi g,12(000) transitions

In the wavelength range of 235-354 nm, we have obtained the mass-resolved [1+1] two-photon dissociation spectra of CO(2) (+) via A (2)Pi(u,12)(upsilon(1)upsilon(2)0)<--X (2)Pi(g,12)(000) transitions by preparing CO(2) (+) ions in the X (2)Pi(g,12)(000) state via [3+1] multiphoton ionization of CO(2) molecules at 333.06 nm. The vibronic bands of (upsilon(1)20;upsilon(1)=0-11)micro (2)Pi(12) and (upsilon(1)20;upsilon(1)=0-6)kappa (2)Pi(12) involving the bending mode of CO(2) (+)(A (2)Pi(u,12)) were assigned. The spectroscopic constants of T(e)=27 908.9+/-1.1 cm(-1) [above CO(2) (+)(X (2)Pi(g,12))], nu(1)=1126.00+/-0.36 cm(-1), chi(11)=-1.602+/-0.005 cm(-1), nu(2)(micro (2)Pi(12))=402.5+/-13.3 cm(-1), and nu(2)(kappa (2)Pi(12))=493.1+/-23.6 cm(-1) for CO(2) (+)(A (2)Pi(u,12)) are deduced from the data of the A (2)Pi(u,12)(upsilon(1)upsilon(2)0)<--X (2)Pi(g,12)(000) transitions. The observed intensity reversal between (500) (2)Pi(12) and (420)micro (2)Pi(12) can be attributed to the conformational variation of CO(2) (+)(A (2)Pi(u,12)) from linear to bent, then the conversion potential barrier is estimated to be 5209 cm(-1) above CO(2) (+)(A (2)Pi(u,12)(000)). The wavelength and level dependence of the photofragment branching ratios have been measured and the dissociation dynamics of CO(2) (+) via A (2)Pi(u,12) state is discussed.     

Detection of free nickel monocarbonyl, NiCO: rotational spectrum and structure

Unsaturated transition metal carbonyls are important in processes such as organometallic synthesis, homogeneous catalysis, and photochemical decomposition of organometallics. In particular, a metal monocarbonyl offers a zeroth-order model for interpreting the chemisorption of a CO molecule on a metal surface in catalytic activation processes. Quite large numbers of theoretical papers have appeared which predict spectroscopic and structural properties of transition metal carbonyls. The nickel monocarbonyl NiCO has been one of the metal carbonyls most extensively studied by the theoretical calculations. At least 50 theoretical studies have been published on this simplest transition metal carbonyl up to the present time. However, experimental evidence of NiCO is much more sparse than theoretical predictions, and the actual structure of NiCO has never been determined by any experimental methods. This Communication reports the first preparation of free nickel monocarbonyl and observation of its rotational transitions. The NiCO molecule was generated by the sputtering reaction of a Ni cathode in the presence of CO. The accurate bond lengths of Ni-C and C-O were experimentally determined from isotopic data and were compared with the theoretical predictions for the first time.     

Steric and electronic properties of N-heterocyclic carbenes (NHC): a detailed study on their interaction with Ni(CO)4

N-heterocyclic carbene ligands IMes (1), SIMes (2), IPr (3), SIPr (4), and ICy (5) react with Ni(CO)(4) to give the saturated tricarbonyl complexes Ni(CO)(3)(IMes) (8), Ni(CO)(3)(SIMes) (9), Ni(CO)(3)(IPr) (10), Ni(CO)(3)(SIPr) (11), and Ni(CO)(3)(ICy) (12), respectively. The electronic properties of these complexes have been compared to their phosphine analogues of general formula Ni(CO)(3)(PR(3)) by recording their nu(CO) stretching frequencies. While all of these NHCs are better donors than tertiary phosphines, the differences in donor properties between ligands 1-5 are surprisingly small. Novel, unsaturated Ni(CO)(2)(IAd) (13) and Ni(CO)(2)(I(t)()Bu) (14) compounds are obtained from the reaction of Ni(CO)(4) with IAd (6) and I(t)()Bu (7). Complexes 13 and 14 are highly active toward substitution of the NHC as well as the carbonyl ligands. This has allowed the determination of Ni-C(NHC) bond dissociation energies and the synthesis of various unsaturated Ni(0) and Ni(II) complexes. Computational studies on compounds 8-14 are in line with the experimental findings and show that IAd (6) and I(t)()Bu (7) are more bulky than IMes (1), SIMes (2), IPr (3), SIPr (4), and ICy (5). Furthermore, a method based on %V(bur) values has been developed for the direct comparison of steric requirements of NHCs and tertiary phosphines. Complexes 8-14, as well as NiCl(C(3)H(5))(I(t)()Bu) (16) and NiBr(C(3)H(5))(I(t)()Bu) (17), have been characterized by X-ray crystallography.     

清洁及部分氧化的Ni_3Ti(0001)表面CO吸附的HREELS研究

用离子散射谱（ＩＳＳ）、俄歇电子能谱（ＡＥＳ）及低能电子衍射（ＬＥＥＤ）技术对Ｎｉ３Ｔｉ（０００１）表面结构与组成进行考察后，主要采用高分辨电子能量损失谱（ＨＲＥＥＬＳ），以ＣＯ为探针分子，研究了清洁及部分氧化的Ｎｉ３Ｔｉ（０００１）表面上Ｎｉ，Ｔｉ间的相互作用及对ＣＯ吸附态的影响．结果表明：（１）在最表层几乎完全为Ｎｉ的Ｎｉ３Ｔｉ（０００１）清洁规整表面上，ＣＯ没有发生解离；（２）次表层Ｔｉ原子与最表层Ｎｉ原子间的电子相互作用，使初始吸附的ＣＯ伸缩振动与Ｎｉ（１１１）相比向低频位移约６０ｃｍ－１；（３）适量ＣＯ暴露后，ＣＯ氧端与近邻Ｔｉ原子的成键作用产生了一种新的Ｎｉｘ－Ｃ－Ｏ－Ｔｉｙ物种．Ｎｉ３Ｔｉ（０００１）表面部分氧化后，上述（２）和（３）作用消失     

CO在Ni(100)面吸附模式的研究

本文首次将McGreery的推广LEPS法用于异核双原子分子的吸附势能面.设CO在Ni面上的吸附位置有3种(图1).取Sato参数为0.5,所得典型的势能面示于图2、图3.当C—O键平行于表面并接近Ni面上的3种吸附位置时,各势能面均与图2类似,先进入一势阱,然后越过势垒进入第二势阱.发生解离型C及O的原子吸附时,共有4种模式.各势能面上表征吸附的参数列于表1,吸附模式见图1.在4种吸附模式中最稳定的是C模式,即对角相邻5CN上的解离双原子吸附,R_(c-o)=6.65a.u.,它是R_(c-o)(平衡)=2.17a.u.的三倍多.当CO键与表面垂直且接近Ni面上3种吸附位置时所得势     

Characterization of silicon-carbon clusters by infrared laser spectroscopy: the nu 3(sigma u) band of linear Si2C3

The nu 3(sigma u) fundamental vibration of 1 sigma g+ Si2C3 has been observed using a laser vaporization-supersonic cluster beam-diode laser spectrometer. Forty rovibrational transitions were measured in the range of 1965.8 to 1970.9 cm-1 with a rotational temperature of 10-15 K. A least-squares fit of these transitions yielded the following molecular constants: nu 3(sigma u)=1968.188 31(18) cm-1, B"=0.031 575 1(60) cm-1, and B'=0.031 437 4(57) cm-1. These results are in excellent agreement with recent Fourier transform infrared (FTIR) measurements of Si2C3 trapped in a solid Ar matrix [J. Chem. Phys. 100, 181(1994)] and with ab initio calculations [J. Chem. Phys. 100, 175 (1994)] which suggest cumulenic-like bonding for Si2C3, analogous to the isovalent C5 carbon cluster.     

Structure of Copper（Ⅱ）Bis（piperidyldithiocarbamate）

ＳｔｒｕｃｔｕｒｅｏｆＣｏｐｐｅｒ（Ⅱ）Ｂｉｓ（ｐｉｐｅｒｉｄｙｌｄｉｔｈｉｏｃａｒｂａｍａｔｅ）ＬａｎｇＪｉａｎ－ｐｉｎｇ；ＬｕＪｉａｎ－Ｍｅｉ；ＢｉａｎＧｕｏ－Ｑｉｎｇ（ＤｅｐａｒｔｍｅｎｔｏｆＣｈｅｍｉｓｔｒｙ，ＳｕｚｈｏｕＵｎｉｖｅｒｓｉｔｙ...     

Syntheses and structural analyses of variable-stoichiometric Au-Pt-Ni carbonyl/phosphine clusters, Pt3(Pt(1-x)Ni(x))(AuPPh3)2(mu2-CO)4(CO)(PPh3)3 and Pt2(Pt(2-y)Ni(y))(AuPPh3)2(mu2-CO)4(CO)2(PPh3)2, with ligation-induced site-specific Pt/Ni substitutional disorder within butterfly-based Pt3(Pt(1-x)Ni(x))Au2 and Pt2(Pt(2-y)Ni(y))Au2 core-geometries

In ongoing attempts of directed synthesis of high-nuclearity Au-Pt carbonyl/phosphine clusters with [Ni6(CO)12]2- used as reducing agent and CO source, we have isolated and characterized two new closely related variable-stoichiometric trimetallic clusters, Pt3(Pt(1-x)Ni(x))(AuPPh3)2(mu2-CO)4(CO)(PPh3)3 (1) and Pt2(Pt(2-y)Ni(y))(AuPPh3)2(mu2-CO)4(CO)2(PPh3)2 (2). Their M4Au2 cores may be envisioned as substitutional disordered butterfly-based M4Au2 frameworks (M = Pt/Ni) formed by connections of the two basal M(B) atoms with both (Au-Au)-linked Au(PPh3) moieties. Based upon low-temperature CCD X-ray diffraction studies of eight crystals obtained from different samples, ligation-induced site-specific Pt/Ni substitutional disorder (involving formal insertion of Ni in place of Pt) in a given crystal was found to occur only at the one OC-attached basal M(B) site in 1 or at both OC-attached basal M(B) sites in 2 corresponding to a crystal composite of the Pt3(Pt(1-x)Ni(x))Au2 core in 1 or of the Pt2(Pt(2-y)Ni(y))Au2 core in 2; the Ph3P-attached M(B) site (M(B) = Pt) in 1 and two wingtip M(w) sites (M(w) = Pt) in 1 and 2 were not substitutionally disordered. The resulting variable stoichiometry of the M4Au2 core in 1 may be viewed as a crystal composite of two superimposed individual stereoisomers, Pt4(AuPPh3)2(mu2-CO)4(CO)(PPh3)3 (1a) and Pt3Ni(AuPPh3)2(mu2-CO)4(CO)(PPh3)3 (1b), in the averaged unit cell of a given crystal. Likewise, 2 represents the crystal-averaged composite of three individual stereoisomers, Pt4(AuPPh3)2(mu2-CO)4(CO)2(PPh3)2 (2a), Pt3Ni(AuPPh3)2(mu2-CO)4(CO)2(PPh3)2 (2b), and Pt2Ni2(AuPPh3)2(mu2-CO)4(CO)2(PPh3)2 (2c). Formal Ni substitution for Pt at only the basal M(B) site(s) in the four crystal composites each of 1 and 2 was found to vary widely from 17% to 79% Ni in 1 and from 21% to 95% Ni in 2. Nevertheless, reasonably close Pt/Ni occupancy factors were found within each of the four pairs of composite crystals selected from samples obtained from duplicate syntheses. Both 1 and 2 may be formally derived from the electronically equivalent classic butterfly Pt4(mu2-CO)5(PPh3)4 cluster by replacement of its bridging mu2-CO ligand spanning the basal M(B)-M(B) edge with two one-electron donating (Au-Au)-linked AuPPh3 moieties along with the substitution of a terminal CO in place of one or both M(B)-attached PPh3 ligands in 1 and 2, respectively; site-specific Pt/Ni substitutional disorder occurs only at the CO-attached M(B) sites. The variable-stoichiometric 1 and 2 re also electronically equivalent and geometrically related to the crystal-ordered butterfly-based Pt4(mu2-CO)4(PR3)4(mu3-HgX)2 clusters (R3 = Ph3, MePh2; X = CF3, Br, I).     

SYNTHESES AND CRYSTAL STRUCTURE OF [Et_4N]{Mo(CO)_5L}(L=I~-,SPh~-)

<正> Crystal of [Et4N][Mo(CO)5I](1) (Mr = 493. 15) is tetragonal with space group P4/n, a =b==9. 374(2) ,c=10. 545(2)(?), V=926. 5(?)3, Z = 2, F(000) = 480, Dc=1. 77g/cm3and μ = 23. 6cm-1. R = 0. 040, Rw = 0.043 for 374 observed reflections. Crystal of [Et4N][Mb(CO)5(SPh)] (2) is orthorhombic ith space group Pbam, a= 15. 230(3), b = 18. 389(10), c=8. 172(3)(?), V=2288. 6 (?)3, Z = 4, Dc=1. 38gcm3, μ = 6.7cm-1.R = 0. 043, Rw = 0. 042 for 1621 observed reflections. Complexes 1 and 2 possess the same geometry. The Mo atom is octahe-drally coordinated with obvious trans drrdct, all the Mo -C bond lengths are shorter obviously and the C - O bond are longer than those of Mo(CO)6.     

Rotationally resolved spectra of jet-cooled VMo

The authors report the first gas-phase spectroscopic investigation of diatomic vanadium molybdenum (VMo). The molecules were produced by laser ablation of a VMo alloy disk and cooled in a helium supersonic expansion. The jet-cooled VMo molecules were studied using resonant two-photon ionization spectroscopy. The ground state has been demonstrated to be of (2)Delta(52) symmetry, deriving from the dsigma(2)dpi(4)ddelta(3)ssigma(2) electronic configuration. Rotational analysis has established the ground state bond length and rotational constant as r(0) (")=1.876 57(23) A and B(0) (")=0.142 861(35) cm(-1), respectively, for (51)V(98)Mo (1sigma error limits). Transitions to states with Omega(')=2.5, Omega(')=3.5, and Omega(')=1.5 have been recorded and rotationally analyzed. A band system originating at 15 091 cm(-1) has been found to exhibit a vibrational progression with omega(e) (')=752.7 cm(-1), omega(e) (')x(e) (')=12.8 cm(-1), and r(0) (')=1.90 A for (51)V(98)Mo. The measured bond lengths (r(0)) of V(2), VNb, Nb(2), Cr(2), CrMo, Mo(2), VCr, NbCr, and VMo have been used to derive multiple bonding radii for these elements of r(V)=0.8919 A, r(Nb)=1.0424 A, r(Cr)=0.8440 A, and r(Mo)=0.9725 A. These values reproduce the bond lengths of all nine diatomics to an accuracy of +/-0.012 A or better.     

十二硼十二氢镍乙二胺晶体结构的研究

Ni(en)_3B_(12)H_(12)晶体属于三方晶系,空间群为R_3,晶胞参数为:a=b=12.890(2),c=23.955(20),α=B=90°,Υ=120°,Z=6。在室温下用CAD-4衍射仪收集单晶衍射强度数据(MOK_α);重原子法和差Fourier法解出全部非氢原子坐标,用加氢程序定出全部氢原子的坐标。各原子坐标及热振动参数经全矩阵最小二乘方修正,对于985个独立衍射点[I≥3σ(I)]最后偏离因子R=0.069。结构分析表明,该化合物属于离子型,Ni(en)_-~(2+)离子和B_(12)H_(12)~(-2)离子间相互以正三角双锥方式配位。Ni(en)~(2+)离子具有D_3对称性,Ni-N平均键长为2.138,B_(12)H_(120~(-2)离子呈正二十面体构型,B-B平均键长为1.786。     

Effect of model potential of adsorptive bond on the thermodynamic properties of adsorbed CO molecules on Ni(111) surface

The effect of anharmonicity on the adsorption of CO molecules on the Ni(111) surface has been investigated. The DFT calculations are used to obtain the effective adsorption potential of the CO molecule on the Ni(111) surface. First, using an appropriate slab model, the geometry of adsorption system corresponding to hcp, fcc, bridge, and on-top sites with p(2 x 2) arrangement and coverage of 0.25 ML is optimized by the DFT calculations using a plane wave basis set and ultrasoft pseudopotentials; this gives the hcp site as the most stable site with De = 185 kJ/mol, for which the equilibrium distance of CO from the surface and C-O bond length on the surface are found to be 1.31 and 1.192 A, respectively. Then, the potential function of adsorption versus adsorptive bond distance was plotted, which is significantly different from that of a harmonic oscillator, i.e., the anharmonicity for the adsorptive bond is significant. Also the harmonic and anharmonic shifts of vibrational frequencies of adsorptive and C-O bonds are calculated to be -22.6 and 7.8 cm(-1), respectively. Hence, two potential models are selected for which their Schr?dinger equations are solved analytically, namely the hard repulsion-soft attraction (HS) and Morse potential (MP) models. The adsorption isotherms, internal energy, isochoric heat capacity, and entropy of adsorbed CO molecules have been calculated for the mentioned model potentials and compared with those of the harmonic oscillator (H). As a result, the adsorption isotherms are not considerably sensitive to the model potential. The anharmonicity of CO-Ni bond, which is included in HS and MP models, gives an average deviation in pressure as much as 1.4% for HS and 5.8% for MP, compared to 6.1% for the H model. However, isochoric heat capacity and entropy depend on the model potential significantly, and the differences may be as high as 69% and 55% for isochoric heat capacity and entropy, respectively.     

Microwave spectra and the metal-hydrogen bond lengths for the C5H5Mo(CO)3H and C5H5W(CO)3H complexes

The measurements of rotational spectra and metal-hydrogen bond lengths for molybdenum and tungsten hydride complexes were recently completed in our laboratory. The W-H and Mo-H bond lengths were obtained from high resolution rotational spectra of C5H5Mo(CO)3H, C5H5W(CO)3H, C5H5Mo(CO)3D, and C5H5W(CO)3D. Data for five molybdenum and four tungsten isotopomers were obtained for both the normal and deuterium-substituted species. The asymmetric-top rotational parameters A, B, C, DeltaJ, and deltaJ were determined from the least-squares fits and these results indicate that the structures of these complexes are nearly rigid. The hydrogen bond lengths were determined for both complexes using Kraitchman analyses. The molybdenum-hydrogen bond length for the C5H5Mo(CO)3H complex is rMo-H=1.80(1) A. The tungsten-hydrogen bond length for the C5H5W(CO)3H complex is rW-H=1.79(4) A. Density functional theory (DFT) calculations of the structures were performed to obtain the optimized theoretical structures for C5H5Mo(CO)3H and C5H5W(CO)3H. Results obtained from the DFT calculations are in good agreement with the experimental parameters, and the Mo-H value is in good agreement with previously reported Mo-H bond lengths for similar complexes.     

Reactions of 2,4-hexadiyne-1,6-diol with [H2Os3(CO)9(PR3)] clusters. Cyclization of the diyne and reversible exchange of the phosphine ligands between different positions of the "Os3C3" framework

Reactions between unsaturated [H(2)Os(3)(CO)(9)(PR(3))] clusters (PR(3)= PPh(3), P(4-CF(3)-C(6)H(4))(3), PEt(3)) and 2,4-hexadiyne-1,6-diol have been studied. It was found that the diyne ligand easily reacts with all these complexes to give [HOs(3)(CO)8(PR3)-[mu3, eta1:eta3:eta1)-(CH(3)-C-C=CH-CH=C-O)]] complexes (V, VI and VII, respectively) containing the "Os3C3" pentagonal pyramid cluster framework. This structural pattern is formed through the diyne cyclization, dissociation of a CO ligand and eventual coordination of the cyclized organic moiety to the osmium triangle in the [mu3, eta1:eta3:eta1) manner. In the case of the PEt(3) substituted cluster the second hydride transfer onto the organic fragment occurs to afford the nonhydride [Os(3)(CO)(8)(PR3)[mu3), eta1:eta2:eta1)-(CH(3)-CH-C=CH-CH=C-O)]] cluster, VIII, containing distorted pentagonal pyramid framework with a broken Os-C bond. Heating V, VI of VII and in hexane solutions results in formation of the regioisomers (Va, VIa and VIIa) with the phosphine ligand located at adjacent osmium atoms across the Os-Os bond bridged by the coordinated organic fragment. The most probable mechanism of the isomerization includes reversible phosphine migration between these metal centres. Solid-state structure of V, Va, VI, VIIa and VIII have been established by single crystal X-ray diffraction. A general mechanistic scheme for the diyne ligand cyclization and cluster framework transformations is suggested and discussed.     

Resonant two-photon ionization spectroscopy of jet-cooled OsC

The optical spectrum of diatomic OsC has been investigated for the first time, with transitions recorded in the range from 17 390 to 22 990 cm(-1). Six bands were rotationally resolved and analyzed to obtain ground and excited state rotational constants and bond lengths. Spectra for six OsC isotopomers, 192 Os 12C (40.3% natural abundance), 190 Os 12C(26.0%), 189 Os 12C(16.0%), 188 Os 12C(13.1%), 187 Os 12C(1.9%), and 186 Os 12C(1.6%), were recorded and rotationally analyzed. The ground state was found to be X 3 Delta 3, deriving from the 4 delta 3 16 sigma 1 electronic configuration. Four bands were found to originate from the X 3 Delta 3 ground state, giving B 0"=0.533 492(33) cm(-1) and r 0 "=1.672 67(5) A for the 192 Os 12C isotopomer (1 sigma error limits); two of these, the 0-0[19.1]2<--X 3 Delta 3 and 1-0[19.1]2<--X 3 Delta 3 bands, form a vibrational progression with Delta G' 1/2=953.019 cm(-1). The remaining two bands were identified as originating from an Omega"=0 level that remains populated in the supersonic expansion. This level is assigned as the low-lying A 3 Sigma 0+ (-) state, which derives from the 4 delta 2 16 sigma 2 electronic configuration. The OsC molecule differs from the isovalent RuC molecule in having an X 3 Delta 3 ground state, rather than the X 2 delta 4, 1 Sigma+ ground state found in RuC. This difference in electronic structure is due to the relativistic stabilization of the 6s orbital in Os, an effect which favors occupation of the 6s-like 16 sigma orbital. The relativistic stabilization of the 16 sigma orbital also lowers the energy of the 4 delta 2 16 sigma 2, 3 Sigma(-) term, allowing this term to remain populated in the supersonically cooled molecular beam.     

The role of the bridging group in exchange coupling in dinuclear homo- and heterometallic Ni(ii) and Co(ii) complexes with oxalate, oxamidate and dithiooxamidate bridges

Six homodinuclear and two heteronuclear complexes Tp(Np)Co-C(2)O(4)-CoTp(Np) (1), Tp(Np)Co-C(2)O(4)-NiTp(Cy) (2), Tp(Cy)Ni-C(2)O(4)-NiTp(Cy) (3), Tp(Np)Co-C(2)O(2)(NH)(2)-CoTp(Np) (4), Tp(Cy)Ni-C(2)O(2)(NH)(2)-NiTp(Cy) (5), Tp(Np)Co-C(2)S(2)(NH)(2)-CoTp(Np) (6), Tp(Np)Co-C(2)S(2)(NH)(2)-NiTp(Cy) (7), Tp(Cy)Ni-C(2)S(2)(NH)(2)-NiTp(Cy) (8) (Tp(Np) = tris(3-neopentylpyrazolyl)borate, Tp(Cy) = tris(3-cyclohexylpyrazolyl)borate), were synthesized and characterized by mass spectrometry, electronic spectroscopy and X-ray crystallography. These compounds possess similar molecular structures, with the metal ions linked by bridging oxalate (1-3), oxamidate (4 and 5) or dithiooxamidate (6-8) ions. The heteronuclear nature of compounds 2 and 7 was additionally confirmed by high-resolution mass spectrometry. The magnetic properties of the Co(2+) complexes were modelled taking into account zero-field splitting of this ion, yielding D-values for Co(2+) in the range -17(1) to -50(1) cm(-1). All the metal ion pairs in compounds 1-8 are antiferromagnetically-coupled, with J values between -10.0(1) and -45.0(2) cm(-1) (via the exchange Hamiltonian ?(ex.) = -2J?(1)?(2)) and |J| increasing in the order oxalate < oxamidate < dithiooxamidate. This tendency can be attributed to greater M-S bond covalency compared to M-N or M-O bonds (M = Co(2+) and Ni(2+)). It was found that this antiferromagnetic coupling of Co(2+) and Ni(2+) ions through oxalate is more efficient for these tris(pyrazolyl)borate complexes than for similar oxalate-bridged systems with neutral aliphatic amine ligands.     

Syntheses and Vibrational and (13)C MAS-NMR Spectra of Bis(carbonyl)mercury(II) Undecafluorodiantimonate(V) ([Hg(CO)(2)][Sb(2)F(11)](2)) and of Bis(carbonyl)dimercury(I) Undecafluorodiantimonate ([Hg(2)(CO)(2)][Sb(2)F(11)](2)) and the Molecular Structure of [Hg(CO)(2)][Sb(2)F(11)](2)

The synthesis of bis(carbonyl)mercury(II) undecafluorodiantimonate(V), [Hg(CO)(2)][Sb(2)F(11)](2), and that of the corresponding mercury(I) salt [Hg(2)(CO)(2)][Sb(2)F(11)](2) are accomplished by the solvolyses of Hg(SO(3)F)(2) or of Hg(2)F(2), treated with fluorosulfuric acid, HSO(3)F, in liquid antimony(V) fluoride at 80 or 60 degrees C, respectively, in an atmosphere of CO (500-800 mbar). The resulting white solids are the first examples of metal carbonyl derivatives formed by a post-transition element. Both salts are characterized by FT-IR, FT-Raman, and (13)C-MAS-NMR spectroscopy. For [Hg(CO)(2)][Sb(2)F(11)], unprecedentedly high CO stretching frequencies (nu(av) = 2279.5 cm(-)(1)) and stretching force constant (f(r) = 21.0 +/- 0.1) x 10(2) Nm(-)(1)) are obtained. Equally unprecedented is the (1)J((13)C-(199)Hg) value of 5219 +/- 5 Hz observed in the (13)C MAS-NMR spectrum of the (13)C labeled isotopomers at delta = 168.8 +/- 0.1 ppm. The corresponding values (nu(av) = 2247 cm(-)(1), f(r) = (20.4 +/- 0.1) x 10(2) Nm(-)(1), (1)J((13)C-(199)Hg) = 3350 +/- 50 Hz and (2)J((13)C-(199)Hg) 850 +/- 50 Hz) are found for [Hg(2)(CO)(2)][Sb(2)F(11)](2), which has lower thermal stability (decomposition point in a sealed tube is 140 degrees C vs 160 degrees C for the Hg(II) compound) and a decomposition pressure of 8 Torr at 20 degrees C. The mercury(I) salt is sensitive toward oxidation to [Hg(CO)(2)][Sb(2)F(11)](2) during synthesis. Both linear cations (point group D(infinity)(h)()) are excellent examples of nonclassical (sigma-only) metal-CO bonding. Crystal data for [Hg(CO)(2)][Sb(2)F(11)](2): monoclinic, space group P2(1)/n; Z = 2; a = 7.607(2) ?; b = 14.001(3) ?; c = 9.730(2) ?; beta = 111.05(2) degrees; V = 967.1 ?(3); T = 195 K; R(F) = 0.035 for 1983 data (I(o) >/= 2.5sigma(I(o))) and 143 variables. The Hg atom lies on a crystallographic inversion center. The Hg-C-O angle is 177.7(7) degrees. The length of the mercury-carbon bond is 2.083(10) ? and of the C-O bond 1.104(12) ? respectively. The structure is stabilized in the solid state by a number of significant secondary interionic Hg- - -F and C- - -F contacts.     

Synthesis,structure, and reactions of a three-coordinate nickel-carbene complex, [1,2-Bis(di-tert-butylphosphino)ethane]Ni=CPh(2)

The three-coordinate nickel-carbene complex (dtbpe)Ni=CPh2 (3) was prepared from the thermolysis of the diphenyldiazoalkane complex (dtbpe)Ni(N,N':eta2-N2CPh2) (2) (dtbpe = 1,2-bis(di-tert-butylphosphino)ethane). Complex 3 was structurally characterized by single-crystal X-ray diffraction methods (Ni-C = 1.836(2) A). Complex 3 reacts with 2 equiv of CO2 to afford (dtbpe)Ni{OC(O)CPh2C(O)O} (4), with diphenylketene to give (dtbpe)Ni{OC(=CPh2)CPh2} (5), with excess CO to transfer the carbene fragment and generate diphenylketene and (dtbpe)Ni(CO)2 (6), with sulfur dioxide to give the metallasulfone (dtbpe)Ni{C,S:eta2-S(O)2CPh2} (7), and with the Br?nsted acid [HNMe2Ph][B(C6F5)4] to give the alkyl cation [(dtbpe)Ni(CHPh2)][B(C6F5)4] (8). Complexes 4, 5, and 7 have also been characterized by single-crystal X-ray diffraction methods.