The oxidative addition of hydrogen sulfide to the electron-rich triple bond: The isolation and characterization of compounds that contain the Re2(μ-H)(μ-SH) cluster unit

The reactions of Re₂X₄(-dppm)₂ (X=Cl or Br; dppm=Ph₂PCH₂PPh₂) with H₂S in THF afford the dirhenium (III) complexes Re₂(-H)(-SH)X₄(-dppm)₂, the first examples of the oxidative addition of an S-H unit across an electron-rich metal-metal triple bond. The bromide complex Re₂(-H)(-SH)Br₄(-dppm)₂ (C₂H₅)₂O crystallizes in the space group P2₁/n witha=16.631(2) Å,b=15.967(3) Å,c=19.904(2) Å, =92.698(7)°,V=5279(2) ų, andZ=4. The structure which was refined toR=0.053 (R _w=0.070) for 4903 data withI>3.0(I), shows the presence of an edge-shared bioctahedral geometry with a very short Re-Re distance of 2.4566(7) Å. While the hydrogen atoms of the -H and -SH ligands were not located in the X-ray structure determination, their presence is confirmed by IR and¹H NMR spectroscopy.     

Tetrarhena-heterocycle from the palladium-catalyzed dimerization of Re2(CO)8(μ-SbPh2)(μ-H) exhibits an unusual host-guest behavior

The six-membered heavy atom heterocycles [Re(2)(CO)(8)(μ-SbPh(2))(μ-H)](2), 5, and Pd[Re(2)(CO)(8)(μ-SbPh(2))(μ-H)](2), 7, have been prepared by the palladium-catalyzed ring-opening cyclo-dimerization of the three-membered heterocycle Re(2)(CO)(8)(μ-SbPh(2))(μ-H), 3. The palladium atom that lies in the center of the heterocycle 7 was removed to yield 5. The palladium removal was found to be partially reversible leading to an unusual example of host-guest behavior. A related dipalladium complex Pd(2)Re(4)(CO)(16)(μ(4)-SbPh)(μ(3)-SbPh(2))(μ-Ph)(μ-H)(2), 6, was also formed in these reactions of palladium with 3.     

The effect of structure and phase transformation on the mechanical properties of Re₂N and the stability of Mn₂N

First‐principles calculations were carried out on recently synthesized Re₂ and Re₃ as well as hypothetical Tc and Mn nitrides. It is found that structure and covalent bonds play an important role in determining mechanical properties. Under a large strain along (0001)〈101 0〉direction, Re₂N undergoes a phase transformation with a slight increase in ideal shear strength. On the other hand, it is transformed into a phase with weaker mechanical properties, if the strain is along Re₂〈1 21 0〉 direction. Mn₂N can be synthesized under moderate conditions due to its more negative formation energy. Re₂N, Re₃N, and Mn₂N show structure‐related mechanical property under larger strains to ReB₂ but exhibit much lower ideal strengths, which is attributed to the larger ionicity of cation–anion bond. Three‐dimensional framework of strong covalent bonds is thus highly recommended to design superhard materials. © 2011 Wiley Periodicals, Inc. J Comput Chem, 2011     

Synthesis of the gold-dirhenium ferrocenylacetylide cluster. The crystal structure of Re2(μ-C≡CFc){Au(PPh3)}(CO)8

The thermal reaction of Re₂(CO)₈(NCMe)₂ with Au(CCFc)PPh₃ afforded the cluster Re₂(-CCFc){Au(PPh₃)}(CO)₈, which was characterized by X-ray diffraction analysis.     

The preparation of trichlorotris(hydrogen-salicylato)rhodate(III) and tetra-μ-(hydrogen-salicylato)diaquadirhodium(II)

The preparation of a new example of a salicylato divalent rhodium complex, namely, tetra--(Hsal)diaquadirhodium(II), and a new trivalent complex, the trichlorotris(Hsal)rhodium(III) ion are reported. The complexes were isolated and characterized by spectrochemical methods including FT-Raman and n.m.r. spectroscopies. The trivalent complex has a monodentate Hsal ligand bonded through a carboxyl oxygen with a facial configuration.     

Study of the Structure and Reactions of Bis(μ-Oxalato)tetramminediplatinum(II) in Aqueous Chloride Solutions

A comparison study of the bis(-oxalato)tetramminediplatinum(II) dimer [Pt₂(NH₃)₄(-C₂O₄)₂] and the oxalatodiammineplatinum(II) chelate [Pt(NH₃)₂C₂O₄] is performed. The kinetics and mechanism of substitution of C₂O^2– ₄ for Cl^– in aqueous chloride solutions are studied by photoelectronic spectroscopy, gravimetry, and chemical phase analysis within the 1.0–6.7 pH range at 75°C. The rate constants of substitution and the equilibrium constants for a two-step protonation for the dimeric and chelate complexes are calculated. Their solubility in 1 M KCl at 75°C; is determined. The unit cell parameters for [Pt₂(NH₃)₄(-C₂O₄)₂] are determined: a = 3.858 Å, b = 10.704 Å, c = 6.795 Å, = 94.35°. The IR spectra of [Pt(NH₃)₂C₂O₄], [Pt₂(NH₃)₄(-C₂O₄)₂], and their deuterated analogs are studied.     

The crystal and molecular structures of di-μ-hydroxy-bis(di-2-pyridylamine)dinitratodicopper(II) and aqua-μ-formato-triformato-bis(di-2-pyridylamine)dicopper(II) monohydrate

The preparation, magnetic and spectroscopic properties, crystal and molecular structures of binuclear complexes of formulae [Cu₂(dpyam)₂(OH)₂(ONO₂)₂] (I), [Cu₂(dpyam)₂(O₂CH)₄(OH₂)].H₂O (II) are described. (I) consists of pairs of copper atoms linked by two hydroxo bridges. The co-ordination geometry at each copper atom is distorted square-pyramidal, the basal plane consisting of two hydroxo oxygen atoms and two nitrogen atoms from a dpyam ligand, while the axial co-ordination sites are occupied by nitrate oxygen atoms. The copper(II) ions in (II) are also in a distorted square-pyramidal environment. They are bridged by a formate group in an anti–syn configuration from a basal position to an axial position, while another axial position is occupied by the water oxygen atom. From magnetic susceptibility measurements at room temperature, both complexes are found to exhibit antiferromagnetic interactions and some magneto-structural trends are discussed.     

Hydrido-Carbonyl Rhenium Clusters with a Square Geometry of the Metal Core. Synthesis and X-Ray Characterization of the Novel [Re4(μ-H)3(CO)16]− Anion

Three and tetranuclear ring clusters have been obtained by treatment of [Re₂(CO)₈(THF)₂] with carbonyl-rhenates containing two terminal hydrides. The reaction with [ReH₂(CO)₄]^- provided a selective route to the previously known [Re₃(-H)₂(CO)₁₂]^- triangular cluster anion 1. The reaction with [Re₂H₂(-H)(CO)₈]^- gave the novel [Re₄(-H)₃(CO)₁₆]^- anion 2, containing a rare example of a puckered-square metal cluster. Protonation of 1 is known to afford the neutral [Re₃(-H)₃(CO)₁₂] species 3. Analogously the reaction of 2 with a strong acid afforded the previously known square metal clusters [Re₄(-H)₄(CO)₁₆] 4. The reaction could not be reversed by treatment with bases. Photolysis of 4 gave the unsaturated complex [Re₂(-H)₂(CO)₈] 5: this is the reverse of the dimerization reaction, that in THF at room temperature produces 4 from 5. Thermal treatment (reflux in cyclohexane for 24 h) left 4 almost unchanged. A single crystal X-ray analysis of [NEt₄]2 showed a s/e/s/s (e=eclipsed, s=staggered) conformation of the Re(CO)₄ units, leading to a puckered geometry of the ring, at variance with the square-planar geometry of 4 (all eclipsed). Two of the three hydrides of 2 have been located as bridging the Re–Re edges from inside the metal ring, as previously observed in 4. Density functional computations indicated a puckered conformation as the most stable for both 2 and 4, with very low activation energies for ring inversion (6.6 and 2.2 kcal·mol^-1, respectively), but ruled out solid state fluxionality for 4, whose observed planar geometry must be attributed to packing stabilization.     

Structure of the catena-bis(trimethylamine)cadmium(II)-tetra-μ-cyanonickelate(II) complex and contact self-stabilization of molecules

The [Cd(N(CH₃)₃)₂Ni(CN)₄] complex crystallizes in a tetragonal system, space group 14/mmm with two formula units per unit cell (XRD, Rigaku AFC-6A diffractometer, λ MoK_α, ω/2θ scan mode, θ_max = 38?, 635 observed unique reflections, 53 parameters, R = 0.027). The structure consists of parallel polymer layers made up of coordinated metal atoms and bridging cyanides. The octahedral environment of Cd(II) involves six nitrogen atoms of the four cyanide groups in the layer plane (2.323(4) Å) and the two trimethylamine ligands in the transposition (2.42(1) Å). The square-planar environment of Ni(II) consists of four carbon atoms of the cyanide ligands (1.857(3) Å). The layers are packed according to van der Waals type; the “hollows” near the nickel atoms are filled by the “hills” of the trimethylamino groups from the neighboring layer (the interlayer distance is 7 Å). The spatial complementarity of the layers leads to close packing of the complex and explains the lack of a clathrate-forming ability in the latter. The trimethylamine ligands here play the same role as guest molecules in Hofmann clathrates, stabilizing the planar polymer structure of the complex. This phenomenon is called contact self-stabilization.

     

Mixed Bis(μ-silylene) and (μ-Silylene)/(μ-Germylene) Complexes Involving the Rh/Ir Metal Combination: Nature of the Si···Si Interactions in the Bis(μ-silylene) Species

A series of mixed bis(μ-silylene) complexes of rhodium and iridium [RhIr(CO)(2)(μ-SiHR)(μ-SiR(1)R(2))(dppm)(2)] (R = R(1) = R(2) = Ph (4); R = R(1) = Ph, R(2) = Cl (5); R = R(1) = Ph, R(2) = Me (6); R = 3,5-C(6)H(3)F(2), R(1) = Ph, R(2) = Me (7); R = 3,5-C(6)H(3)F(2), R(1) = 2,4,6-C(6)H(2)Me(3), R(2) = H (8)) have been synthesized by the reaction of the silylene-bridged dihydride complexes, [RhIr(H)(2)(CO)(2)(μ-SiHR)(dppm)(2)] (1, R = Ph; 2, R = C(6)H(3)F(2)), with a number of secondary or primary silanes (Ph(2)SiH(2), PhClSiH(2), PhMeSiH(2), C(6)H(2)Me(3)SiH(3)). The influence of substituents and π-stacking interactions on the Si···Si distance (determined by X-ray crystallography) in this series and the implications regarding the nature of the Si···Si interactions are discussed. A series of novel (μ-silylene)/(μ-germylene) complexes, [RhIr(CO)(2)(μ-SiHPh)(μ-GePh(2))(dppm)(2)] (9) and [RhIr(CO)(2)(μ-SiR(1)R(2))(μ-GeHPh)(dppm)(2)] (R(1) = Ph, R(2) = H (11); R(1) = R(2) = Ph (12); R(1) = Ph, R(2) = Me (13)), have also been synthesized by reaction of the silylene-bridged dihydride complex, [RhIr(H)(2)(CO)(2)(μ-SiHPh)(dppm)(2)] (1), with 1 equiv of diphenylgermane and by reaction of the germylene-bridged dihydride complex, [RhIr(H)(2)(CO)(2)(μ-GeHPh)(dppm)(2)] (3), with 1 equiv of the respective silanes. These complexes have been characterized by multinuclear NMR spectroscopy and X-ray crystallography.     

The X-ray Structure, Electrochemistry and Catalytic Reactivity of Os4Au(μ-H)3(CO)12(PPh3) Towards the Oxidative Carbonylation of Aniline

The reaction of the anion [Os₄(-H)₃(CO)₁₂]^– with one equivalent of Au(PPh₃)Cl affords [Os₄Au(-H)₃(CO)₁₂(PPh₃)] (1), the structure of which was established by single crystal X-ray analysis. Its electrochemical behavior and catalytic properties are also reported. This bimetallic cluster catalyses the oxidative carbonylation of aniline to give methyl phenylcarbamate in methanol with good conversion and selectivity compared to the homometallic [Os₄(-H)₄(CO)₁₂] cluster.     

Selective two-step oxidation of μ2-S ligands in trigonal prismatic unit {Re3(μ6-C)(μ2-S)3Re3} of the bioctahedral cluster anion [Re12CS17(CN)6]6–

An oxidation of cluster anion [Re(12)CS(17)(CN)(6)](6-) by H(2)O(2) in water has been investigated. It was shown that selective two-step oxidation of bridging μ(2)-S-ligands in trigonal prismatic unit {Re(3)(μ(6)-C)(μ(2)-S)(3)Re(3)} takes place. The first stage runs rapidly, whereas the speed of the second stage depends on intensity of ultraviolet irradiation of the reaction mixture. Each stage of the reaction is accompanied by a change in the solution's color. In the first stage of the oxidation, the cluster anion [Re(12)CS(14)(SO(2))(3)(CN)(6)](6-) is produced, in which all bridging S-ligands are turned into bridging SO(2)-ligands. The second stage of the oxidation leads to formation of the anion [Re(12)CS(14)(SO(2))(2)(SO(3))(CN)(6)](6-), in which one of the SO(2)-ligands underwent further oxidation forming the bridging SO(3)-ligand. Seven compounds containing these anions were synthesized and characterized by a set of different methods, elemental analyses, IR and UV/vis spectroscopy, and quantum-chemical calculations. Structures of some compounds based on similar cluster anions, [Cu(NH(3))(5)](3)[Re(12)CS(14)(SO(2))(3)(CN)(6)]·9.5H(2)O, [Ni(NH(3))(6)](3)[Re(12)CS(14)(SO(2))(3)(CN)(6)]·4H(2)O, and [Cu(NH(3))(5)](2.6)[Re(12)CS(14)(SO(2))(3)(CN)(6)](0.6)[{Re(12)CS(14)(SO(2))(2)(SO(3))(CN)(5)(μ-CN)}{Cu(NH(3))(4)}](0.4)·5H(2)O, were investigated by X-ray analysis of single crystals.     

Further studies of the reactions of PtRu5(μ6-C)(CO)16 with alkynes: The preparation and structural characterizations of PtRu5(CO)13(μ-EtC2Et)(μ3-EtC2Et)(μ5-C) and Pt2Ru6(CO)17(μ-η5-Et4C5)(μ3-EtC2Et) (μ6-C)

The reaction of PtRu₅(CO)₁₆(μ₆-C),1 with 3-hexyne in the presence of UV irradiation produced two new electron-rich platinum-ruthenium cluster complexes PtRu₅(CO)₁₃(μ-EtC₂Et)(μ₃-EtC₂Et)(μ₅-C),2 (20% yield) and Pt₂Ru₆(CO)₁₇(μ-η⁵-Et₄C₅)(μ₃-EtC₂Et) (μ₆-C),3 (7% yield). Both compounds were characterized by single-crystal X-ray diffraction analyses. Compound2 contains of a platinum capped square pyramidal cluster of five ruthenium atoms with the carbido ligand located in the center of the square pyramid. A EtC₂Et ligand bridges one of the PtRu₂ triangles and the Ru-Pt bond between the apical ruthenium atom and the platinum cap. The structure of compound3 consists of an octahedral PtRu₅ cluster with an interstitial carbido ligand and a platinum atom capping one of the PtRu₂ triangles. There is an additional Ru(CO)₂ group extending from the platinum atom in the PtRu₅ cluster that contains a metallated tetraethylcyclopentadienyl ligand that bridges to the platinum capping group. There is also a EtC₂Et ligand bridging one of the PtRu₂ triangular faces to the capping platinum atom. Compounds2 and3 both contain two valence electrons more than the number predicted by conventional electron counting theories, and both also possess unusually long metal-metal bonds that may be related to these anomalous electron configurations. Crystal data for2, space group Pna2₁,a=19.951(3) Å,b=9.905(2) Å,c=17.180(2) Å,Z=2, 1844 reflections,R=0.036; for3, space group Pna2₁,α=13.339(1) Å,b=14.671(2) Å,c=11.748(2) Å, α=100.18(1)°, β=95.79(1)°, γ=83.671(9)°,Z=2, 3127 reflections,R=0.026.     

Geometrically specific imino complexes of the [Re6(μ3-Se)8]2+ core-containing clusters

The reactions of nitrile complexes of the [Re(6)(μ(3)-Se)(8)](2+) core-containing clusters, [Re(6)(μ(3)-Se)(8)(PEt(3))(n)(CH(3)CN)(6-n)](2+) [n = 5 (1); n = 4, cis- (2) and trans- (3); n = 0 (4)], with organic azides C(6)H(5)CH(CH(3))N(3) and C(6)H(5)CH(2)N(3) produced the corresponding cationic imino complexes of the general formula [Re(6)(μ(3)-Se)(8)(PEt(3))(n)(L)(6-n)](2+) [L = PhN=CHCH(3): n = 5 (5); n = 4, cis- (6) and trans- (7); n = 0 (8) and L = HN=CHPh: n = 5 (9); n = 4, cis- (10) and trans- (11)]. These novel complexes were characterized by NMR spectroscopy ((1)H and (31)P) and single-crystal X-ray diffraction. A mechanism involving the migration of one of the groups on the azido α-C atom to the α-N atom of the azido complex, concerted with the photo-expulsion of N(2), was invoked to rationalize the formation of the imino complexes. Density functional theory (DFT) calculations indicated that due to the coordination with and activation by the cluster core, the energy of the electronic transition responsible for the photo-decomposition of a cluster-bound azide is much reduced with respect to its pure organic counterpart. The observed geometric specificity was rationalized by using the calculated and optimized preferred ground-state conformation of the cluster-azido intermediates.     

Absolute measurement of the S(0) and S(1) lines in the electric quadrupole fundamental band of D(2) around 3μm

The electric quadrupole fundamental (v=1←0) band of molecular deuterium around 3?μm is accessed by cavity ring-down spectroscopy using a difference-frequency-generation source linked to the Cs-clock primary standard via an optical frequency comb synthesizer. An absolute determination of the line position and strength is reported for the first two transitions (J=2←0 and J=3←1) of the S branch. An accuracy of 6×10(-8) is achieved for the line-center frequencies, which improves by a factor 20 previous experimental results [A. R. W. McKellar and T. Oka, Can. J. Phys. 56, 1315 (1978)]. The line strength values, measured with 1% accuracy, are used to retrieve the quadrupole moment matrix elements which are found in good agreement with previous theoretical calculations [A. Birnbaum and J. D. Poll, J. Atmos. Sci. 26, 943 (1969); J. L. Hunt, J. D. Poll, and L. Wolniewicz, Can. J. Phys. 62, 1719 (1984)].     

The importance of an additional water bridge in making the exchange coupling of bis(μ-phenoxo) dinickel(II) complexes ferromagnetic

Two new nickel(II) complexes [Ni(2)L(2)(PhCOO)(2)(H(2)O)] (1), [Ni(2)L(2)(PhCH(2)COO)(2)(H(2)O)] (2) have been synthesized using a tridentate Schiff base ligand, HL (2-[(3-dimethylamino-propylimino)-methyl]-phenol) and the carboxylate monoanions, benzoate and phenylacetate, respectively. The complexes have been characterized by spectral analysis, variable temperature magnetic susceptibility measurement and crystal structure analysis. The structural analyses reveal that both complexes are dinuclear in which the distorted octahedral Ni(2+) ions share a face, bridged by one water molecule and two μ(2)-phenoxo oxygen atoms. A monodentate benzoate or phenylacetate anion and two nitrogen atoms of the chelating deprotonated Schiff base (L) complete the hexa-coordination around the metal ion. Variable-temperature magnetic susceptibility studies indicate the presence of dominant ferromagnetic exchange coupling in complexes 1 and 2 with J values of 11.1(2) and 10.9(2) cm(-1) respectively. An attempt has been made to rationalize the observed magneto-structural behavior considering the importance of the additional water bridge in the present two complexes and also in other similar species.     

The investigation of the quantitative structure–activity relationships between the structure of hydrazine derivatives and the reduction of Np(VI)

The 3D structure of hydrazine derivatives was optimized and their energy was calculated by density functional theory with B3LYP method and 6-311 + (3d, 3p) basis set. The results show that the reaction relationship between the structure of hydrazine derivatives and Np(VI) could be explained by two quantitative structure–activity relationships equations. In Eq. 1, the lowest unoccupied molecular orbital energy is a major factor affecting the reduction rate, and it is negatively correlated with the reaction rate. In Eq. 2, the molecular dipole moment and hydrophobic parameters are the most important factors affecting the reduction rate. The molecular dipole moment is negatively correlated with the reaction rate, but the hydrophobic parameter is positively correlated with the reaction rate.     

Further Aspects of the Chemistry of the Dirhenium Complexes [(triphos)Re(μ-X)3Re(triphos)]n+ (n=1 or 0), Where triphos=CH3C(CH2PPh2)3 and X=Cl or Br

The dirhenium(II) complexes [Re₂(-X)₃(triphos)₂]O₃SCF₃ (X=Cl or Br) have been prepared by anion exchange reactions. These salts show well defined simple electron-transfer redox chemistry (two reversible one-electron oxidations and two one-electron reductions) but the [Re(-X)₃Re] unit is remarkably stable to reactions with donor molecules such as monodentate tertiary phosphines which can often induce cleavage of M-X-M bridges. The crystallographic characterization of these two salts show that Re–Re bonds are not present, the Re...Re distances being 3.274(1) Å for X=Cl and 3.277(1) Å for X=Br.     

The effects of redox-inactive metal ions on the activation of dioxygen: isolation and characterization of a heterobimetallic complex containing a Mn(III)-(μ-OH)-Ca(II) core

Rate enhancements for the reduction of dioxygen by a Mn(II) complex were observed in the presence of redox-inactive group 2 metal ions. The rate changes were correlated with an increase in the Lewis acidity of the group 2 metal ions. These studies led to the isolation of heterobimetallic complexes containing Mn(III)-(μ-OH)-M(II) cores (M(II) = Ca(II), Ba(II)) in which the hydroxo oxygen atom is derived from O(2). This type of core structure has relevance to the oxygen-evolving complex within photosystem II.     

The shape of the Sc2(μ2-S) unit trapped in C82: crystallographic, computational, and electrochemical studies of the isomers, Sc2(μ2-S)@C(s)(6)-C82 and Sc2(μ2-S)@C(3v)(8)-C82

Single-crystal X-ray diffraction studies of Sc(2)(μ(2)-S)@C(s)(6)-C(82)·Ni(II)(OEP)·2C(6)H(6) and Sc(2)(μ(2)-S)@C(3v)(8)-C(82)·Ni(II)(OEP)·2C(6)H(6) reveal that both contain fully ordered fullerene cages. The crystallographic data for Sc(2)(μ(2)-S)@C(s)(6)-C(82)·Ni(II)(OEP)·2C(6)H(6) show two remarkable features: the presence of two slightly different cage sites and a fully ordered molecule Sc(2)(μ(2)-S)@C(s)(6)-C(82) in one of these sites. The Sc-S-Sc angles in Sc(2)(μ(2)-S)@C(s)(6)-C(82) (113.84(3)°) and Sc(2)(μ(2)-S)@C(3v)(8)-C(82) differ (97.34(13)°). This is the first case where the nature and structure of the fullerene cage isomer exerts a demonstrable effect on the geometry of the cluster contained within. Computational studies have shown that, among the nine isomers that follow the isolated pentagon rule for C(82), the cage stability changes markedly between 0 and 250 K, but the C(s)(6)-C(82) cage is preferred at temperatures ≥250 °C when using the energies obtained with the free encapsulated model (FEM). However, the C(3v)(8)-C(82) cage is preferred at temperatures ≥250 °C using the energies obtained by rigid rotor-harmonic oscillator (RRHO) approximation. These results corroborate the fact that both cages are observed and likely to trap the Sc(2)(μ(2)-S) cluster, whereas earlier FEM and RRHO calculations predicted only the C(s)(6)-C(82) cage is likely to trap the Sc(2)(μ(2)-O) cluster. We also compare the recently published electrochemistry of the sulfide-containing Sc(2)(μ(2)-S)@C(s)(6)-C(82) to that of corresponding oxide-containing Sc(2)(μ(2)-O)@C(s)(6)-C(82).