Mo Rh Research Articles

Ethanol Synthesis from Syngas on Transition Metal-Doped Rh(111) Surfaces: A Density Functional Kinetic Monte Carlo Study

Advances in methodology, software and power of supercomputers make computational approaches, specifically, density functional theory (DFT), capable of providing qualitative, and in many cases quantitative, insights into catalysis. In this article we adopted a multiscale modeling paradigm in combination of DFT calculations and kinetic Monte Carlo (KMC) methods to provide better understanding of the promoting effect of doping metals (Fe, Mo, Mn) in ethanol synthesis from syngas on Rh(111). Our calculations show that metal-doping and the position of doped metals can have significant effects on the yield and selectivity of ethanol synthesis on Rh(111). Depending on the reaction conditions, Mo and Mn may stay either on the surface or in the subsurface region, while Fe prefers to stay at the surface and participate in the reaction directly. In term of the overall yield and ethanol yield, Mo–Rh(111) with Mo at the surface layer exhibits the highest activity, followed by Mn–Rh(111) with Mn at the subsurface > Fe–Rh(111) > Mo–Rh(111) with Mo at the subsurface, Mn–Rh(111) with Mn at the surface and Rh(111) in a decreasing sequence. In term of the ethanol selectivity, Fe–Rh(111) displays the highest to ethanol, followed by Mo–Rh(111) with Mo at the surface layer, Mn–Rh(111) with Mn at the subsurface > Mo–Rh(111) with Mo at the subsurface, Mn–Rh(111) with Mn at the surface and Rh(111) in a decreasing sequence. As long as Mo stays at the surface layer, Mo is the only dopant we studied here, being able to enhance both yield and selectivity of ethanol synthesis from syngas on Rh(111). Our results suggest that the design of alloy catalyst should be very careful and controlling the position of dopants is essential to the overall catalytic performance.

EFFECTS OF 4D TRANSITION METALS ON NIAL BONDS CHARACTERS FROM FIRST PRINCIPLES

We study systematically the site occupancy and effects of alloying element on NiAl bonds character of 4d transition metals by first-principles method based on density functional theory. The impurity formation energies of 4d TM of NiAl in Al -site and Ni -site are calculated. Y , Zr , Nb , Cd prefer to occupy the Al -site, whereas Mo , Tc , Ru , Rh , Pd , Ag prefers to occupy Ni - si te. Crystal distortion and the overlap population between the alloying element and its first-neighboring atoms and are also calculated. The result shows that the substituting Al -site the elements Y , Zr , Nb , Cd interact with its first-neighboring Ni atom by anti-bonding. The total covalent ratio is decreased by theses elements which may improve ductility of NiAl . For Ni -site elements, the interaction between the alloying element Mo ( Tc , Ru , Rh , Pd , and Ag ) with its first-neighboring atoms Al also shows decrease in covalent. Site occupation of 4d transition metals are also discussed by the reaction energy for formation Ni 2 TiX and X bulk phase.

SU-GG-I-82: Performance Assessment of X-Ray QA Instruments Used in Mammography

Purpose: To establish the calibration standard of dose and kVp meter for performance assessment of mammography X‐ray QA instrumentation and to evaluate the uncertainty and the impact of X‐ray spectrum variation in different beam qualities. Method and Materials: The accuracy of instruments calibration forms the first step to determine the quality control trains in national survey. The primary standard for dose and kVp meter for X‐ray beams was obtained from a free air ionization chamber and high voltage divider. The uncertainty analysis followed the method recommended by the ISO Guide. The beams qualities were at 23–35kVp produced by Mo target X‐ray sets with 30 μm Mo filtration and Rh target X‐ray with 29 μm Rh filtration. Dose verification was conducted by mammographyionization chambers which were previously calibrated by the NIST. Three different techniques were compared: spectrum end‐point direct measurements, calibrated non‐invasive kVp devices and the calibrated voltage divider technique. Results: Acceptable agreement (difference within 1%) was obtained in the mammography X‐ray range. Agreement among these methods was good with a difference less than 1% for all beam qualities. The uncertainty estimates results of the dose and voltage values calculated respectively from the measured spectra and voltage divider technique are less than 3% for voltage range of 23–35 kV. Conclusions: This technique is capable of providing quality services required by quality assurance standards in mammography, namely, the indicated values should be within 5% of the delivered values. The low uncertainties associated with the obtained results in this work pointed out that the method employed can be accurately used for calibration of instrument in mammography. The performance characteristics of dosimeters and non‐invasive kVp meters were determined for annual calibration in an attempt to ascertain the likely performance of instruments in routine use.

Formation and characterization of Rh–Mo bimetallic layers on the TiO 2(1 1 0) surface

The investigation of Rh, Mo and Rh–Mo nanosized clusters formed by physical vapor deposition on TiO 2(1 1 0) single crystal was performed by X-ray Photoelectron Spectroscopy (XPS), Low Energy Ion Scattering (LEIS) and Auger Electron Spectroscopy (AES). There was no sign for site-exchange between Mo and Rh atoms during deposition of Mo onto Rh particles at 330 K. Mixing between Ti and Mo ions was facilitated at the Mo particle–titania interface due to reaction at 550–700 K. The redox process between titania and Mo deposit was hindered at 330 K by forming predeposited rhodium layer ( Θ Rh = 2.0 ML), but reached nearly the same extent as without Rh after moderate heating to 600 K. The encapsulation of Rh by titania was complete by about 700 K in the presence of 1.2 ML Mo, in case of Mo-predeposition and Mo-postdeposition as well. Elevating the temperature of TiO 2/Rh–Mo layers above 700 K, these metals form alloy at the Mo–Rh interface irrespective of deposition sequences.

Physical characteristics of five clinical systems for digital mammography

The purpose of this study was to evaluate and compare the physical characteristics of five clinical systems for digital mammography (GE Senographe 2000D, Lorad Selenia M-IV, Fischer Senoscan, Agfa DM 1000, and IMS Giotto) currently in clinical use. The basic performances of the mammography systems tested were assessed on the basis of response curve, modulation transfer function (MTF), noise power spectrum, noise equivalent quanta (NEQ), and detective quantum efficiency (DQE) in an experimental setting closely resembling the clinical one. As expected, all the full field digital mammography systems show a linear response curve over a dynamic range from 3.5 to 500 microGy (0.998<R2< 1). The presampling MTFs at 2, 3, and 5 lp/mm were found to be respectively 0.78, 0.64, and 0.37 for GE Senographe 2000D; 0.92, 0.85, and 0.69 for Lorad Selenia and Agfa DM1000; 0.75, 0.63, and 0.42 for Fischer Senoscan; and 0.91, 0.82, and 0.61 for the IMS Giotto. According to the pixel size of each digital system, the presampling MTF was calculated within a range up to the Nyquist frequency (5 lp/mm for GE Senographe 2000D, 7.1 lp/mm for Lorad Selenia, 9.3 lp/mm for Fischer Senoscan, and 5.88 lp/mm for IMS Giotto detector). The NEQ becomes related to the exposure in a linear behavior starting from about 40.3 microGy for GE Senographe 2000D, 42.9 microGy for Lorad Selenia, 41.2 microGy for Agfa DM1000, <87.6 microGy for Fischer Senoscan, and 61.3 microGy for the IMS Giotto. Above those values, the systems can be considered "quantum noise limited," that is the electronic noise is negligible if compared to the quantum noise. The DQE, for several emitted x-ray spectra for each system, i.e., 28 kV p Mo-Mo, Mo-Rh, Rh-Rh, W-Al anode-filter combination, hardened by 40 mm poly(methylmethacrylate) (PMMA) was evaluated. For the five different systems, the DQE at close to zero spatial frequency ranges between 0.25 and 0.63 at 131 microGy entrance surface air kerma to the detectors. The results of our quantitative analysis demonstrated a higher DQE for direct conversion technology when compared to that of the indirect conversion. The NEQ behavior of each system can be exploited to select the optimum exposure level set in clinical practice to ensure minimum patient dose though adequate image quality. The detailed results of the physical characterization of the digital systems reported in this work allow the quantitative comparison of different technologies as well as the definition of reference values for subsequent quality control tests. The method developed in this work is suitable to be reproduced in any medical physics department for the previously described goals.

Hydrogen storage properties of modified fumed-Fe-dust generated from a revolving furnace at a steel industry

Pure hydrogen can be chemically stored and supplied directly to PEFC via the redox of modified fumed-Fe-dust obtained from steel company: storage of H 2 : Fe 3 O 4 + 4 H 2 → 3 Fe + 4 H 2 O or Fe 2 O 3 ( initial state ) + 3 H 2 → 2 Fe + 3 H 2 O ; recovery of H 2 : 3 Fe + 4 H 2 O → Fe 3 O 4 + 4 H 2 . Modified fumed-Fe-dust with various metal additives has been prepared by impregnating metal cations of Cr, Al, Zr, Mo, Mo–Al, Mo–Ti, Mo–Zr, Mo–Ce, Mo–Rh, Mo–Ni or Mo–Cu. The reduction of the oxidized fumed-Fe-dust (denoted as FeO x ) with and without additives and the performances of formation H 2 of the reduced FeO x -dust have been mainly investigated. The results show that: (1) among the metal additives tested, Mo was the most effective element to enhance the rate of H 2 produced in the oxidation with H 2O as well as cyclic stability in repeated redox cycles for oxidized fumed-Fe-dust at low temperature 354 °C; (2) the state of additive Mo in oxidized FeO x was suggested to be the chemical composition of 2 FeO · MoO 2 based on the result of XRD spectra; (3) the sintering of the particles was one of the factors effecting on the catalytic activity and cycling stability of the modified FeO x , but what kinds of metal additives to be added in FeO x must be much more important for the sample to promote catalytic activity and keep cyclic stability effective.

Syntheses and reactivities of hydrosulfido- or sulfido-bridged heterobimetallic complexes containing Group 6 and Group 9 metals

Reactions of [Cp2M(SH)2] (M = Mo 1, W 2) with one equiv of [IrH2(PPh3)2(Me2CO)2][PF6] in acetone at room temperature under 1 atm of H2 afforded the hydrosulfido–hydrido complexes [Cp2M(μ-SH)2IrH2(PPh3)2][PF6] (M = Mo 4, W 5), whereas those of 1 and 2 with [RhH2(PPh3)2(Me2CO)(EtOH)][PF6] 6 resulted in the formation of [Cp2Mo(μ-SH)2Rh(PPh3)2][PF6] 7 and [Cp2W(μ-S)2Rh(PPh3)2][PF6] 8. X-Ray analyses have been undertaken to clarify the detailed structure of [Cp2Mo(μ-SH)2IrH2(PPh3)2][BPh4] derived from 4 along with 7 and 8. Bimetallic complexes 4, 5, 7, and 8 catalysed the hydrogenation of alkynes such as 1-octyne and tert-butyl propiolate at room temperature under 1 atm of H2, yielding 1-octene and tert-butyl acrylate as the major products, respectively. In both reactions, the Mo–Rh complex 7 showed the highest catalytic activity, although even the reactions using 7 are much slower than those catalyzed by the mononuclear Rh complex 6.

Synthesis and chemistry of heterobimetallic fulvalene complexes containing W, Mo, and Rh

The photo- and thermal chemistry of the heterobimetallic fulvalene (Fv) complex Fv[W(CO) 3Me][Rh(CO) 2] ( 1) was investigated, and compounds Fv(CO) 2MeWRh(CO)[μ-CO] ( 2), Fv(CO) 3WRh(CO)Me ( 3), and Fv(CO) 3WRh(CO)C(O)Me ( 4) were characterized. Reaction mechanisms were studied by labeling experiments using 13CO and by analogy to the MoRh system. The complexes Fv(CO) 3MoRh(CO)C(O) Me ( 7) and Fv(CO) 3MoRh(CO)Me ( 8) were characterized. Reaction of 3 and 4 with PMe 3 gave the zwitterionic species Fv[W (CO) 3][Rh(PMe 3) 2Me] ( 16) and Fv[W(CO) 3][Rh(PMe 3) 2C(O)Me] ( 17), respectively. An excess of PMe 3, led to the mononuclear compounds FvRh(PMe 3) 2Me ( 18) and FvRh(PMe 3) 2C(O)Me ( 19). The latter was reacted with Mo(CO) 3(EtCN) 3 to give zwitterionic Fv[Mo(CO) 3]Rh(PMe 3) 2C(O)Me] ( 20). The X-ray structures of the acyl complexes 4 and 17 were obtained. X-ray data of 4: P 1 , a = 13.529(3) Å, b = 15.813(3) Å, c = 16.164(3) Å, α = 62.72(1)°, β = 87.24(1)°, gg = 86.32(1)°, V = 3065.9(11) Å 3, Z = 8, R w = 0.045. X-ray data of 17: P2 1/ n, a = 15.412(4) Å, b = 9.745(2) Å, c = 18.209(6) Å, α = 90.0°, β = 93.46(2)°, γ = 90.0°, V = 2730.0(22) Å 3, Z = 4, R w = 0.0303.

A computer calculation of the ternary MoPdRh phase diagram

Thermodynamic coefficients for the phases in the binary MoPd, PdRh and MoRh systems were derived by the assessment of the available experimental data using the binary Lukas optimization program. The resulting coefficients were first successfully utilised in reestablishing the binaries. The coefficients thus obtained in the binary computation were combined with ternary descriptions to compute ternary isothermal sections. Although no ternary interaction term was involved in the construction of the isotherms, the section calculated at 1373 K is found to be consistent with the experimentally established isothermal section at the same temperature. The location of three-phase field ( bcc+hcp+fcc) and phase boundaries in both isotherms are matching reasonably well. Combining only binary coefficients of these phases, it is possible to construct reasonable isothermal sections at different temperatures. Following this conclusion, isothermal sections ranging from 1373 to 2673 K of the ternary MoPdRh system were calculated.

Heterobimetallic group 6 rhodium complexes: I. Formation of tribridges derivatives [(OC) 3M(μ-Cl)(μ-CO)(μ-dppm)Rh(NBD)] (M = Mo, W) by ring opening of [(OC) 4M(dppm-PP)]. Crystal structure of [(OC) 3Mo(μ-Cl)(μ-CO)(μ-dppm)Rh(NBD)

Heterobimetallic complexes of the type [(OC) 3M(μCl)(μCO)(μdppm)Rh(NBD)] (M = Mo, W, dppm = Ph 2PCH 2PPh 2) have been prepared in high yield by ring opening of the coordinatively saturated compound [(OC) 4M(dppm-PP)] with the dimeric complex [RhCl(NBD)] 2 in dichloromethane, and an X-ray diffraction study of the molybdenum derivative has been carried out. The MoRh bond length, 2.945 Å, is consistent with the presence of a single MoRh bond. Additionally, the two metal centres are asymmetrically bridged by dppm, carbonyl and chloride ligands. Different behaviour in solution is proposed for the compounds. The new compounds were characterized by elemental analysis, and infrared and 1H-, 31P- and 13CNMR spectroscopy.

Synthesis and characterization of LMo(CO)3M(PPh3)x (where L = tridentate pyrazolyl-gallate or -borate ligand; M = Rh, x = 2; M = Cu, x = 1). X-ray crystal structures of [MeGapz3]Mo(CO)3Rh(PPh3)2 and [MeGapz3]Mo(CO)3Cu(PPh3) (where pz = pyrazolyl, N2C3H3)

The reactions of the LMo(CO)3− ions (L = MeGapz3, HBpz3, Me2Gapz(OCH2CH2NMe2)) with [Cu(PPh3)Cl]4 and Rh(PPh3)3Cl have yielded complexes with Mo—Cu and Mo—Rh bonds. The X-ray crystal structures of two such complexes have been determined. Crystals of [MeGapz3]Mo(CO)3Cu(PPh3) are monoclinic, a = 17.071(2), b = 16.738(1), c = 23.641(3) Å, β = 104.899(6)°, Z = 8, space group P21/n, and those of [MeGapz3]Mo(CO)3Rh(PPh3)2, are triclinic, a = 12.519(3), b = 17.182(4), c = 12.071(2) Å, α = 105.02(1), β = 109.87(1), γ = 97.10(2)°, Z = 2, space group [Formula: see text]. Both structures were solved by conventional heavy atom methods and were refined by full-matrix least-squares procedures to R = 0.040 and Rw = 0.035 for 6296 reflections with I ≥ 2σ(I) and R = 0.036 and Rw = 0.037 for 5642 reflections with I ≥ 3σ(I), respectively. The former complex provides a rare example of a 3:3:1, or capped octahedral structure, with a short (mean) Mo—Cu distance of 2.513(9) Å. The latter compound displays one terminal and two bridging CO ligands and a Mo—Rh distance of 2.6066(5) Å.

The synthesis of some bi- and tri-metallic clusters containing rhodium; X-ray crystal structures of [MoRh3(µ3-CO)3(CO)3(PPh3)3(η-C5H5)]·CH2Cl2and [MoRhPt(µ-CO)2(µ-PPh2)(µ-1-σ:1–2-η-C6H5)-(PPh3)2(η-C5H5)

Treatment of the complexes [MRh(µ-CO)2(CO)(PPh3)2(η-C5H5)](M = Mo or W) with [Fe2(CO)9] in tetrahydrofuran at room temperature affords the tetranuclear 56 valence-electron cluster compounds [MRh3(µ3-CO)3(CO)3(PPh3)3(η-C5H5)]. The structure of the molybdenumtrirhodium species, which crystallises with a molecule of CH2Cl2, has been established by a single-crystal X-ray diffraction study. The metal-atom core approximates to a regular tetrahedron, with Rh–Rh separations 2.710(1)–2.729(1)A, and Mo–Rh distances 2.764(1)–2.778(1)A. The molybdenum atom carries the η-C5H5 ligand, and a CO and a PPh3 group are attached to each rhodium atom. These terminal carbonyl ligands are directed below the Rh3 triangle, and the three ligated phosphorus atoms lie above. In addition, a CO group triply bridges each of the MoRh2 faces of the cluster. The reaction between [MoRh(µ-CO)2(CO)(PPh3)2(η-C5H5)] and [Pt(C2H4)(PPh3)2] in tetrahydrofuran at 50 °C yields the complexes [MoPt(µ-PPh2)(CO)2(PPh3)2(η-C5H5)] and [MoRhPt(µ-CO)2(µ-PPh2)(µ-1-σ:1–2-η-C6H5)(PPh3)2(η-C5H5)]. The structure of the 44 valence-electron trimetal compound has been determined by X-ray diffraction. The three metal atoms form a triangle [Mo–Pt 2.958(1), Mo–Rh 2.619(1), and Pt–Rh 2.662(1)A], the molybdenum atom carries the η-C5H5 ligand, and the platinum and rhodium atoms are co-ordinated by PPh3 groups. The three edges of the metal triangle are bridged; the Mo–Rh edge by two CO ligands, the Mo–Pt by PPh2, and the Rh–Pt by a C6H5 group. One carbon of the phenyl group is σ bonded to platinum and together with an adjacent carbon is η2-co-ordinated to the rhodium. The n.m.r. data (1H, 13C-{1H}, and 31P-{1H}) for the new compounds are reported and discussed.

Preparation, structural studies, and some reactions of new heterobinuclear complexes containing molybdenum, tungsten, or manganese and rhodium or copper; X-ray crystal structures of [MoRh(CO)(µ-CO)2(PPh3)2(η-C5H5)] and two isomers of [CuW(CO)3(PPh3)2(η-C5H5)

Reaction of the anions [M(CO)3(η-C5H5)]– or [Mn(CO)5]– with [RhCl(PPh3)3] in tetrahydrofuran produces the formally unsaturated bimetallic complexes [MRh(CO)(µ-CO)2(PPh3)2(η-C5H5)][M = Mo (1) or W (2)] or [MnRh(CO)2(µ-CO)2(PPh3)3](3) respectively. An X-ray diffraction study of (1) has established its molecular structure: monoclinic, space group P21/c, a= 18.102(2), b= 10.407(1), c= 20.736(2)A, β= 104.99(1)°, and Z= 4. The structure, determined from 5 233 independent intensities, was refined to R= 0.036 (R1= 0.074). It comprises a Mo(CO)(η-C5H5) group bonded to Rh(PPh3)2 with a short Mo–Rh separation 2.588(1)A and two asymmetric (µ-CO) ligands with Mo–C 1.980(6) and 2.026(5)A and Rh–C 2.182(6) and 2.092(5)A; the Mo(µ-CO)2Rh framework has a dihedral angle (Mo–Rh–C/Mo–Rh–C) of 161°. I.r., 1H and 31P-{1H} n.m.r. spectra of complexes (1)–(3) are presented and discussed in relation to their structures: formal metal–metal multiple bonds, Rh[grahpic omitted]M, are proposed. Complex (1) acts as a catalyst in hydrogenation of cyclohexene and reactions involving the cleavage of M–Rh bonds are described for complexes (1) and (3). Reactions of [M(CO)3(η-C5H5)]– with [{CuCl(PPh3)}4] give the bimetallic products [CuM(CO)3-(PPh3)2(η-C5H5)][M = Mo (4) or W (5)] in relatively low yields. Complex (5) has been obtained in two isomeric crystalline forms, (5a) and (5b), for which X-ray crystal structure determinations have been undertaken: (5a), triclinic, space group P(no. 2), a= 12.404(4), b= 11.756(3), c= 14.208(3)A, α= 101.4(2), β= 79.5(2), γ= 110.3(2)°, and Z= 2; (5b), monoclinic, space group P21/c(no. 14), a= 17.991 (3), b= 10.098(2), c= 21.608(2)A, β= 105.66(1)°, with Z= 4. The structures of (5a) and (5b) have been refined to residuals R= 0.058 and 0.034 from 3 997 and 4 009 unique reflections, respectively. Both isomers contain W(CO)3(η-C5H5) groups bonded to Cu(PPh3)2 units. The carbonyl ligands are essentially terminally bound to W but two CO groups show some semibridging interactions with Cu, especially in structure (5b); Cu–C 2.309(13) and 2.405(13)A in (5a), 2.260(8) and 2.197(9)A in (5b). In (5a) the Cu(PPh3)2 unit occupies the position typical of a ligand to W in a complex with ‘four-legged piano stool’ geometry [W–Cu 2.721(1)A; dihedral angle (W–Cu–C/W–Cu–C′) 139.8°]. In (5b) the W(µ-CO)2Cu fragment is almost planar (W–Cu–C/W–Cu–C′ 170.9°) and W–Cu [2.771 (1)A] is longer. The structures and bonding of complexes (4) and (5) are discussed in relation to i.r. and n.m.r. spectral data; in solution,13C-{1H} n.m.r. spectra support a non-rigid structure for complex (5).

The analogy between alkenes and the dinuclear species [MRh(µ-CO)2(η-C5Me5)2](M = Co or Rh); dynamic nuclear magnetic resonance, X-ray crystallographic, and extended-Hückel molecular-orbital studies of the bonding between unsaturated CoRh and Rh2fragments and the pentacarbonylmolybdenum group

Treatment of [Mo(CO)5(thf)](thf = tetrahydrofuran) with [CoRh(µ-CO)2(η-C5Me5)2] affords the heterotrimetallic complex [MoCoRh(µ-CO)2(CO)5(η-C5Me5)2]. Variable-temperature 13C-{1H} n.m.r. studies on this species revealed that in solution rotation of the CoRh(µ-CO)2(η-C5Me5)2 fragment occurs about an axis through the Mo and the midpoint of the Co–Rh vector, and that the preferred orientation of the Co–Rh vector with respect to the four equatorial carbonyl ligands of the square-pyramidal Mo(CO)5 moiety is staggered. The estimated barrier to rotation (ΔG‡258= 52.3 ± 1.3 kJ mol –1) is in the range observed and calculated for the hindered rotation of alkenes in related d6 ML5 alkene complexes where, however, the orientational preference of the alkene is to lie so as to eclipse an LML vector. The structure of the analogous trinuclear compound [MoRh2(µ-CO)2(CO)5(η-C5Me5)2] has been determined by a single-crystal X-ray diffraction study. The core of the molecule consists of an MoRh2 isosceles triangle [Mo–Rh (mean) 3.009(1), Rh–Rh 2.623(1)A]. The molybdenum atom carries five carbonyl groups, the rhodium atoms are each ligated by an η-C5Me5 group, and the Rh–Rh vector, staggered with respect to the four equatorial carbonyl groups of the Mo(CO)5 fragment, is symmetrically bridged by two CO ligands. Relatively short non-bonded contacts between the oxygen atoms of the equatorial CO ligands and the hydrogen atoms of the η-C5Me5 groups suggest a significant steric barrier to the ‘alkene-like’ rotation of the Rh2(µ-CO)2(η-C5Me5)2 fragment. Extended-Huckel molecular-orbital calculations on the model species [MoRh2(µ-CO)2(CO)5(η-C5H5)2] indicate that the dirhodium fragment and an alkene bond to an Mo(CO)5 moiety in a similar fashion. However, whereas the barrier to alkene rotation in d6 ML5 alkene complexes derives from electronic effects, no significant electronic contribution to the barrier of rotation of the trinuclear metal complex is indicated.

Unsaturated heterobinuclear complexes of rhodium with molybdenum, tungsten, and manganese. X-Ray crystal structure of [MoRh(µ-CO)2(CO)(PPh3)(η-C5H5)

The new, related bimetallic complexes [MRh(µ-CO)2(CO)(PPh3)(η-C5H5)](M = Mo and W) and [MnRh(µ-CO)2(CO)(PPh3)3] have been characterized and some chemical properties examined; the crystal structure of the molybdenum–rhdium complex, determined by X-ray crystallography, reveals a short multiple Mo–Rh bond.

Superconductivity of MoRh metallic glasses

Type-II superconducting transition metal/metalloid metallic glasses TM 1−x M x (TM: Mo, MoRe, MoRh, MoNb; M: B, P, C) are produced by the melt spinning method. Superconducting transition temperatures T c can be as large as 8.5 K and vary with metalloid content C M . Generally T c decreases with C M ; however, for Mo 0.6 Rh 0.4 alloys it increases with the metalloid concentration. The critical current density of these metglasses is small.