378784-00-0

Basic information

• Product Name: rhodium
• CAS NO: 378784-00-0
• Molecular Weight: 102.906
• Mol File: 378784-00-0.mol
• Article Data: 170

Chemical Properties

• CAS DataBase Reference: rhodium(CAS DataBase Reference)
• NIST Chemistry Reference: rhodium(378784-00-0)
• EPA Substance Registry System: rhodium(378784-00-0)

Safety Data

• Hazardous Substances Data: 378784-00-0(Hazardous Substances Data)

Usage

Chemical Description

Different sources of media describe the Chemical Description of 378784-00-0 differently. You can refer to the following data:
1. Rhodium is a chemical element with the symbol Rh and atomic number 45.
2. Rhodium is a transition metal that is commonly used as a catalyst in organic reactions.

Upstream product

• 16940-66-2 sodium tetrahydroborate 
• 1333-74-0 hydrogen 
• 16065-89-7 rhodium(III) 
• 7439-95-4 magnesium 
• 10049-07-7 rhodium(III)chloride 
• 7647-01-0 hydrogenchloride 
• 14119-03-0 tris(η3-allyl)rhodium 
• 141-43-5 ethanolamine 
• 483367-28-8 [((C₆H₅)2Si(CH₂N(CH₃)2)2)Rh(norbornadiene)][PF₆] 
• 1095-04-1 triphenyl thiophosphite 

Downstream Products

• 14085-43-9 2-cyclohexyl-1H-imidazole 
• 3796-70-1 trans geranyl acetone 
• 227296-56-2 (R)-1-[3-[[(3,4-dihydro-2H-1-benzopyran-2-yl)-methyl]amino]propyl]tetrahydro-2(1H)-pyrimidinone 
• 145149-55-9 3-{[(tert-butoxycarbonyl)amino]methyl}cyclohexanecarboxylic acid 
• 108-24-7 acetic anhydride 
• 100400-96-2 (S)-2-acetylamino-3-cyclohexylpropionic acid 
• 2949-92-0 methanethiosulfonic acid S-methyl ester 
• 129488-61-5 4-(2-Amino-1,1-dimethylethyl)-N-(4-methoxyphenyl)-benzamide 
• 139-61-7 4-(Cyclohexyloxy)benzoic acid 
• 120-72-9 indole 
• 2163-42-0 2-methyl-1.3-propanediol 
• 15608-29-4 rhodium(III) bromide 
• 10049-07-7 rhodium(III)chloride 
• 12036-35-0 rhodium oxide 

Relevant articles and documents

Abnormal infrared effects of nanostructured rhodium thin films for CO adsorption at solid/gas interfaces

Nanometer-scale thin films of rhodium supported on glassy carbon (nm-Rh/GC) were prepared by electrochemical deposition using cyclic voltammetry. STM studies demonstrated that the Rh film is made of layered crystallites of an average size 230 nm (1) ?? 90 nm (w) ?? 10-30 nm (h). In situ FTIR spectroscopic investigations revealed, for the first time, that the nanostructured film exhibits abnormal infrared effects (AIREs) for CO adsorption at solid/gas interfaces. The AIREs are characterized by the inverting of the direction of IR bands of adsorbed CO (COad), an enhancement of IR absorption intensity, and an increase in the full width at half-maximum (FWHM) of the bands. The inversion of the direction of the absorption bands and the increase in the FWHM are observed in spectra of CO on nm-Rh/GC of different Rh film thicknesses; the enhancement of IR absorption depends strongly on the thickness of the Rh film. The maximum enhancement factor has been determined to be 10.38 for an Rh film thickness of 79 nm. The present study demonstrated that the AIREs are general phenomena exhibited by nanostructured thin-film materials at both solid/liquid and solid/gas interfaces; they are of importance in revealing the intrinsic properties of 2D nanomaterials.

New recovery process for rhodium using metal vapor

Rhodium (Rh) is an essential element as a catalyst in automotive catalytic converters, and the recovery of Rh from scrap is an important issue. However, the chemical inertness of Rh makes it difficult to recover it from scrap. This study focused on a new process for recovering platinum group metals (PGM) from scrap with the purpose of improving Rh dissolution in acid. Reactive metal vapors such as magnesium (Mg) and calcium (Ca) were reacted with powdered Rh in a closed stainless steel reaction vessel at a constant temperature ranging from 873 to 1173 K. Mg and Ca deposited on Rh at temperatures above 973 and 1073 K, respectively. Dissolution experiments of the obtained compounds were conducted at 323-333 K for 1 h using an aqueous HCl solution or aqua regia. After reactive metal treatment 99% of Rh was dissolved by aqua regia leaching. Under the same leaching condition only 8% of the untreated pure Rh powder was dissolved. Rh was recovered from the solution obtained by leaching Mg reacted Rh compound using precipitation or cementation methods, demonstrating the feasibility of such recovery. These results show the possibility of developing a new Rh recovery process utilizing reactive metal vapor treatment.

Synthesis of a Cu-Filled Rh17S15 Framework: Microwave Polyol Process Versus High-Temperature Route

Metal-rich, mixed copper-rhodium sulfide Cu3-δRh34S30 that represents a new Cu-filled variant of the Rh17S15 structure has been synthesized and structurally characterized. Copper content in the [CuRh8] cubic cluster was found to vary notably dependent on the chosen synthetic route. Full site occupancy was achieved only in nanoscaled Cu3Rh34S30 obtained by a rapid, microwave-assisted reaction of CuCl, Rh2(CH3CO2)4 and thiosemicarbazide at 300 °C in just 30 min; whereas merely Cu-deficient Cu3-δRh34S30 (2.0 ≥ δ ≥ 0.9) compositions were realized via conventional high-temperature ceramic synthesis from the elements at 950 °C. Although Cu3-δRh34S30 is metallic just like Rh17S15, the slightly enhanced metal content has a dramatic effect on the electronic properties. Whereas the Rh17S15 host undergoes a superconducting transition at 5.4 K, no signs of the latter were found for the Cu-derivatives at least down to 1.8 K. This finding is corroborated by the strongly reduced density of states at the Fermi level of the ternary sulfide and the disruption of long-range Rh-Rh interactions in favor of Cu-Rh interactions as revealed by quantum-chemical calculations.

Stabilization of decatellurium molecules in isolated and concatenated clusters

Black, shiny crystals of the molecular cluster compounds (Te 10)[M(TeX4)(TeX3)]2 (M/X = Rh/Cl (1), Ir/Br (2)), (Te10)[Ru(TeI4)(TeI2)] 2 (3), (Te10)[M(TeI4)(TeI2)] 2(TeI4)(Te2I2) (M = Rh (4), Ir (5)) as well as the one-dimensional cluster polymer (Te10I 2)[Ir(TeI4)]2(Te4)I2 (6) were synthesized by melting reactions of an electron-rich transition metal M (M = Ru, Rh, Ir) with tellurium and TeX4 (X = Cl, Br, I). X-ray diffraction on single-crystals revealed that the compounds crystallize in the triclinic space group type P1. 4 and 5 show [3+1]-dimensional modulations of their structures. All compounds contain binuclear complexes with central μ-η4:η4-bridging Te10 units and terminal halogenidotellurate(II) groups. Each of the transition metal cations is in a slightly distorted octahedral coordination by six tellurium atoms; the two [MTe6] octahedra share a common edge. With the tellurium atoms acting as electron-pair donors, the 18 electron rule is fulfilled for the electrophilic M atoms. The central tricyclo[5.1.1.13, 5]- decatellurium molecule consists of two ecliptically stacked Te4 rings, which are linked through two tellurium atoms. The symmetric or asymmetric 3c4e bonds along these almost linear bridges are in analogy to polyanionic forms of tellurium, while the tricyclic conformation is stabilized by the strong bonding to the transition-metal cations. Multi-center bonding (3c4e) is also present in the terminal square [Te+IIX4]2- and the T-shaped [Te+IIX3]- groups. The crystal structures of 4 and 5 are organized in layers of (Te10)[M(TeI 4)(TeI2)]2n+ clusters (n ≤ 2) that are quite robust upon oxidation or reduction as shown by molecular calculations. These clusters alternate with incommensurately modulated layers that probably consist of TeI42- anions and a previously unknown Te2I2 molecule. The uncertainty arises primarily from equal scattering powers of I and Te atoms as well as from the known flexibility of the electron count of the Te10 unit. In 6, neutral Te4 rings concatenate (Te10I2)[Ir(TeI 4)]2 clusters into chains, which run parallel to the a axis. Copyright

Subsolidus phase relations in the Gd2O3-Rh 2O3 system

The Gd2O3-Rh2O3 system is studied using the anneal-and-quench technique, X-ray powder diffraction, thermal analysis, and chemical analysis. A schematic subsolidus phase diagram is designed. One double oxide of composition GdRhO3 is found to exist. It was characterized using some physicochemical methods. Pleiades Publishing, Inc., 2006.

Effect of the nature of rhodium catalyst supports on initiation of H 2 production during n-butane oxidative reforming at room temperature

Three rhodium catalysts supported on rare earth oxides with redox properties, Rh/CeO2, Rh/Pr6O11, and Rh/Tb 4O7, were tested for their ability to trigger oxidative reforming of n-butane at room temper

Rh(0) nanoparticles as catalyst precursors for the solventless hydroformylation of olefins

The hydroformylation of 1-alkenes can be performed in solventless conditions using ligand-modified or unmodified Rh(0) nanoparticles prepared in imidazolium ionic liquids as catalyst precursors. There is a strong influence of the nanoparticle size on the hydroformylation reaction. Aldehydes are generated when 5.0 nm Rh(0) nanoparticles are used in the hydroformylation of 1-alkenes and l/b selectivities up to 25 can be achieved by addition of Xantphos (9,9-dimethyl-4,5-bis(diphenylphosphino)xanthene). Although small nanoparticles also generate catalytically active species the chemoselectivity decreases (around 11-17% of olefin isomerization) compared to those performed with the 5.0 nm nanoparticles. In contrast, the large sized nanoparticles (15 nm) produce only small amounts of aldehydes similar to that observed with a classical heterogeneous Rh/C catalyst precursor. TEM, XRD, IR and NMR experiments indicated that these Rh(0) nanoparticles are probably degraded under the reaction conditions into soluble mononuclear Rh-carbonyl catalytically active species.

CoFeRh alloys. Part 1. Electrodeposition of Rh and nonmagnetic CoFeRh alloy

The electrochemical behavior of Rh(III) species in CoFe solution containing RhCl3, NH4Cl, H3BO3, CoSO4, FeSO4, saccharin, and NaLS (Na lauryl sulfate) has been investigated. The electrochemistry of Rh(III) species is influenced by each of the compounds present in CoFe plating solution, but especially by addition of saccharin and H3BO3 to the RhCl3-NH4Cl solution. The nucleation and growth of Rh on GC (glassy carbon), Ru, and Cu electrodes from NH4Cl solution was studied using the potentiostatic current-transient methods. The results support a predominantly progressive nucleation of Rh on all three-electrode surfaces. The nucleation kinetic parameters ANo (steady state nucleation rate) and Ns (saturation nuclear number density) were found to vary with potential and are electrode-dependent in order: GC > Ru～Cu. The electrodeposited Rh films obtained from NH4Cl solution and nonmagnetic CoFeRh film obtained from CoFe solution were characterized in terms of the following properties: morphology, surface roughness, crystal structure and chemical composition. The origin of light elements found in Rh and CoFeRh films (O, Cl, S, C, N) was discussed.

Reduction kinetics of surface rhodium oxide by hydrogen and carbon monoxide at ambient gas pressures as probed by transient surface-enhanced raman spectroscopy

The transient reduction kinetics of surface rhodium oxide (Rh2O3) by gaseous H2 and CO have been probed in situ by surface-enhanced Raman spectroscopy (SERS). The Rh surfaces are ultrathin films electrodeposited onto SERS-active gold, enabling surface vibrational spectroscopic information to be obtained with high temporal resolution (≈1 s) at elevated temperatures (up to 500 °C) and under ambient-pressure flow-reactor conditions. Surface Rh2O3 is formed by heating Rh in flowing O2 at 1 atm and fingerprinted by an intense 530 cm-1 VRH-O feature. The reduction of such oxidized surfaces upon sudden exposure to either H2 or CO over a range of partial pressures (1-760 Torr) was monitored from the decay kinetics of the vRh-o band intensity. Surface oxide is readily reduced by both reductants, although striking differences in the observed kinetic behavior indicate the occurrence of distinct reaction pathways. In the case of H2, at low partial pressures (≤7.6 Torr) below 200 °C a temperature-dependent induction period is observed prior to rapid first-order oxide reduction. Such autocatalytic$ behavior is indicative of a νucleation/growth mechanism, where H2 dissociatively adsorbs to form reaction centers, followed by facile reaction between adsorbed (or lattice) oxygen and (possibly subsurface) hydrogen atoms. Immeasurably fast H2-induced oxide reduction, however, occurs at higher temperatures (≥200 °C) and pressures (≥76 Torr). In contrast, CO-induced oxide reduction was found to be substantially (at least 10-fold) slower than with H2 at similar pressures and temperatures, yet no induction period was detected. At lower temperatures (≤250 °C), the oxide reduction kinetics by CO exhibit fast initial removal followed by a much more sluggish zero-order response. Such autoinhibited kinetic behavior, along with the lack of an appreciable CO pressure dependence, suggests that oxide removal is hindered by the extensive formation of adsorbed CO, which is observed to develop rapidly under these conditions from the characteristic Rh-CO and C-O stretching vibrations. This mechanism is further supported by the first-order kinetic response observed throughout oxide removal at temperatures (≥300 °C) where buildup of adsorbed CO is not detected. The transient kinetics for CO-induced oxide reduction are linked to the well-known poisoning effect that Rh surface oxidation exerts on catalytic CO oxidation by O2. Comparisons are also made between the present results and those recently obtained for methanol-induced oxide removal in order to elucidate which chemisorbed alcohol fragment(s) constitute the reactive oxygen scavenger .

Synthetic route to metal nitrides: High-pressure solid-state metathesis reaction

We report a general synthetic route to well-crystallized metal nitrides through a high-pressure solid-state metathesis reaction (HPSSM) between boron nitride (BN) and ternary metal oxide AxMyOz (A = alkaline or alkaline-earth metal and M = main group or transition metal). On the basis of the synthetic metal nitrides (Fe3N, Re3N, VN, GaN, CrN, and WxN) and elemental products (graphite, rhenium, indium, and cobalt metals), the HPSSM reaction has been systematically investigated with regard to its general chemical equation, reaction scheme, and characteristics, and its thermodynamic considerations have been explored by density functional theory (DFT) calculations. Our results indicate that pressure plays an important role in the synthesis, which involves an ion-exchange process between boron and the metal ion, opening a new pathway for material synthesis.

Complex salts trans-[Rh(β-Pic)4Cl2]X (X = Cl-, ReO4-, and ClO4-): Synthesis, crystal structures, and thermal properties

Three novel complex salts containing the cation trans-[Rh(β-Pic) 4Cl2]+ with the anions Cl- (I), ReO4- (II), and ClO4- (III) were obtained and characterized by elemental analysis, X-ray diffraction, NMR spectroscopy, and IR spectroscopy. The complex trans-[Rh(β-Pic) 4Cl2]ReO4 crystallizes from DMF as a solvate in which solvent molecules fill the channels formed by the cations and anions. The thermal properties of complexes I, II, and II · DMF were examined by DTA. Final and some intermediate products of the thermolysis were isolated and characterized by physicochemical methods. Pleiades Publishing, Ltd., 2010.

On Rhodium Phosphate RhPO4 and Rhodium Arsenic Oxide RhAsO4 with Rutile Structure.

RhPO//4 and RhAsO//4 were synthesized and an X-ray investigation showed that RhPO//4 crystallizes with the orthorhombic structure of high-temperature CrPO//4. The lattice constants are a equals 1039. 1 pm, b equals 1309. 1 pm, and c equals 639. 1 pm. The tetragonal rutile structure was found for RhAsO//4 with a equals 446. 0 pm and c equals 297. 3 pm. This compound represents a double oxide with a statistical distribution of rhodium and arsenic on the metal atom positions. The octahedral coordination of the arsenic is corroborated by the IR spectrum.

Tunable aqueous phase synthesis and shape-dependent electrochemical properties of rhodium nanostructures

Rhodium nanostructures with highly selective morphologies such as cubes, horned particles, dendrites, and network-shaped wires have been achieved through the synergetic effect of sodium lauryl sulfate (SLS) and halogen anions (F -, Cl-, Br-, I-) in a green solvent, water. The effects of SLS and halogen anions were systematically investigated. The electrocatalytic performances of Rh nanostructures toward ethanol oxidation were tested. The results have shown that the rhodium nanostructures displayed shape-dependent properties, and the nanodendrites possessed the maximum catalytic activity.

Catalytic performance and characterization of Rh-CeO2/MgO catalysts for the catalytic partial oxidation of methane at short contact time

The addition of an optimum amount of CeO2 (Ce/Rh = 4) to 1.0 wt% Rh/MgO promoted the catalytic partial oxidation (CPO) of methane with N2 dilution. At the same time, it can suppress the temperature increase at the catalyst bed inlet

Arrangement and dispersion of rh and pt atoms on graphene oxide sheets

Hybrid materials of ultimately minimized metal particles, namely, isolated atoms or subnano-sized particles, on thermally exfoliated graphene oxide sheets were produced using cationexchanged highly oxidized graphite as a precursor. Rh atoms on graphene sheets arrange with a regular spacing of 0.50 or 0.45 nm and form square or rectangular grid patterns, whereas isolated Pt atoms disperse on graphene sheets randomly.

Chiral dendrimer encapsulated Pd and Rh nanoparticles

The synthesis of a series of chiral PAMAM dendrimers and the formation of chiral dendrimer encapsulated metal nanoparticles are described. The Royal Society of Chemistry.

Rhodium(I) complexes of the type [Tp(3R,5R)Rh(LL)] (LL=2 CO, NBD, COD) with trifluoromethyl substituted tris(pyrazolyl)borate ligands and theirdynamic behaviour in solution. The X-ray crystal structure of Tp(CF3,Me)Rh(CO)2

Three series of Rh(I) complexes of the type Tp(3R,5R)Rh(LL), with LL=2 CO (1), norbornadiene (NBD) (2) and 1,5-cyclooctadiene (COD) (3) and thetris(pyrazolyl)borate (Tp) ligands 3R=5R=Me (a), 3R=CF3, 5R=Me (b); and3R=5R=CF3 (c) were synthesized and fully characterized by IR and multinuclear NMR spectroscopy. Three isomeric forms were identified in solutions of these complexes: two square-planar isomers with a κ(2)-Tp(3R,5R) ligand, the uncoordinated pyrazolyl ring occupying either an equatorial position (type A), or an axial position (type B), and a five-coordinated species with a κ(3)-Tp(3R,5R) ligand (type C). In the carbonyl complexes 1 the dynamic equilibria between these isomers are solvent dependent. Interestingly, solutions of complex 1c contained all three isomers simultaneously. (103)Rh and (13)C NMR spectral studies indicate that the NBD compounds, 2, preferentially form square-planar complexes when Tp(CF3,Me) and Tp(CF3,CF3) are present, while for the COD complexes, 3, square-planar complexes are preferred for all three Tp-type ligands. The X-ray structure of Tp(CF3,Me)Rh(CO)2 (1b) was determined (space groupC2/c, a=21.271(9), b=11.004(3), c=21.563(9) ?, β=114.93(3)°, V=4577(3) ?**3, Z=8, R=3.41, R(w)=4.70). Its structure is of type B, with the third pyrazolyl ring axially placed, the N(4) being almost directly above the Rh atom but exerting only a weak Rh-N interaction.

Nitrate and nitrite electrocatalytic reduction on Rh-modified pyrolytic graphite electrodes

The electrochemical reduction of nitrate and nitrite anions was investigated on Rh-modified pyrolytic graphite electrodes prepared by potentiostatic electrodeposition with the use of a double-pulse technique. Several important parameters (pH, temperature and composition of electrolytic medium, electrolysis potential) were varied. Only ammonia and nitrite ions were detected among NO3- reduction products, while NO2- ions are straightforwardly reduced to ammonia. The experimental data (CV measurements and the results of electrolyses) clearly show that Rh/graphite electrodes are much more efficient for NO2- reduction than for that of NO3- at room temperature which was confirmed by the determination of rate constants of corresponding reactions and the activation energy of NO2- reduction. The influence of carboxylate anions and tetraalkylammonium cations on the electrocatalytic activity of Rh/graphite electrodes was investigated and the inhibiting effect of HCOO- anions on hydrogen evolution reaction and nitrate reduction was demonstrated.

Electro-oxidation of methanol on Pt-Rh alloys

Methanol adsorption and electro-oxidation on Pt-Rh alloys have been studied in aqueous 0.5 M H2SO4 for a broad range of alloy surface composition including the pure Pt and Rh metals. Adsorption results have been compared with equivalent data obtained for CO and CO2 adsorption on these alloys. Current densities of continuous methanol oxidation on Pt, Rh and a Pt-Rh alloy with optimum surface molar fraction of Rh have been measured. Although on the pure Pt and Rh metals the methanol adsorption products exhibit similar energetic stability, as judged from the peak potential of electro-desorption, on the Pt-Rh alloys, there is a lowering of the stability. Similar behavior is observed for the CO and CO2 adsorption products, however, the lowering for methanol is much less than for CO and CO2. In the case of methanol, the maximum lowering is obtained for a surface molar fraction of Rh equal to ca. 0.65 and it is the same alloy surface composition that results in maximum lowering of the stability of the CO2 adsorption products, but not of the CO adsorption products (optimal fraction of Rh equal ca. 0.10). Structural similarity of the methanol and the CO2 adsorption products finds support in similar values of the electrons-per-site parameter obtained. Pt-Rh alloys show insufficient electrode potential improvement over Pt in continuous methanol electro-oxidation due to the susceptibility of Rh to strong poisoning by the methanol adsorption products, which switches off the bi-functional mechanism of methanol electro-oxidation on this alloy. The presence of Rh in the alloy with Pt additionally strongly lowers the methanol electro-oxidation turnover rate of the Pt component.

Rhodium(I) complexes of β-diketonates and related ligands as homogeneous hydrogenation catalysts

Rhodium(I) complexes of β-diketonates such as bis(η2-ethene)[1,3-(1-phenyl)-butanedionato-O,O′]rhod ium(I) and related (O...O) ligands are active catalysts for the hydrogenation of unhindered alkenes at 30°C (1 atm H2). Substrates such as α-acylaminocinnamic acid are not hydrogenated under these conditions, a result that can be used as a test for homogeneity in these catalytic systems. The crystal structures of two catalysts are described: bis(η2-ethene)[1,3-(1-ferrocenyl)-butanedionato-O, O′]rhodium(I), orthorhombic, space group P212121, with a = 7.8550(4), b = 9.8400(4), c = 21.5093(7) A, and Z = 4. R = 0.037 and Rw = 0.042 for 2993 reflections with I > 3?(I). (1,5-cyclooctadiene)(2′-acetylphenoxy-O,O′)rhodium(I), triclinic, space group P1ˉ with a = 7.6634(5), b = 9.7831(3), c = 10.1112(6) A, α = 104.763(3), β = 73.668(6), γ = 98.470(4)°, and Z = 2. R = 0.028 and Rw = 0.034 for 5174 reflections with I > 3 ?(I).

Studies of the thermal and photochemical lability of olefin complexes of rhodium(I) to form Rh and Rh2O3

Thermogravimetric analyses of the series of compounds 2, where L2 = 1,5-COD, NBD and (C2H4)2 under air, nitrogen and 7percentH2 in N2 atmospheres reveal that thermal decomposition behavior depends on the nature of the olefin ligand and the composition of the atmosphere.Under a 7percent H2 in N2 atmosphere, the onset of thermal decomposition of these species occurs in the following order: L2 = (C2H4)2, 91 deg C, NBD, 143 deg C; 1,5-COD, 212 deg C.Under a nitrogen atmosphere, 2, L2 = NBD and (C2H4)2, undergo weight loss consistent with loss of one or more olefin ligands, then formation of Rh metal at higher temperatures.In contrast, 2 formed Rh metal directly.In air, thermal decomposition generally resulted in formation of crystalline Rh metal followed by oxidation above 500 deg C to form crystalline Rh2O3, except for 2, which gave Rh2O3 directly.The Rh and Rh2O3 powders were analyzed by powder X-ray diffraction.In some experiments, a weight loss consistent with formation of RhCl was observed.However, as a result of the crystalline Rh present, it is proposed that disproportionation to Rh and RhCl3 may have occurred.The compound 2 * H2O is photolabile and undergoes decomposition on exposure to UV radiation to give crystalline, 2 nm sized Rh metal particles as determined by TEM, EDS and electron diffraction.

Decomposition of rhodium and iridium complexes of tripodal phosphine derivatives studied by thermal analysis

Thermal behaviour of five or six-coordinate rhodium and iridium complexes of two tripodal phosphines, CH3C(CH2PPh2)3 and CH3C{CH2P(m-CF3C6 H4)2}3, and their mixed-ligand complexes containing C1, CO and MeCN was studied by TG, DTA and DTG in dynamic nitrogen atmosphere. The plain complexes exhibit very high thermal stability and degradation of the phosphine ligands follow a complicated process, while the first stage of the mixed-ligand complexes corresponds to removal of CO or MeCN and decomposition of the phosphine ligands occurs in the subsequent stages. All complexes undergo complete decomposition to form the respective metals as the final decomposition product. It was found that iridium complexes showed much higher thermal stability than their rhodium analogues.

Nature of the Short Rh-Li Contact between Lithium and the Rhodium ω-Alkenyl Complex [Rh(CH2CMe2CH2CH═CH2)2]-

We describe the preparation of the cis-bis(η1,η2-2,2-dimethylpent-4-en-1-yl)rhodate(I) anion, cis-[Rh(CH2CMe2CH2CH═CH2)2]-, and the interaction of this species with Li+ both in solution and in the solid state. For the lithium(diethyl ether) salt [Li(Et2O)][Rh(CH2CMe2CH2CH═CH2)2], VT-NMR and 1H{7Li} NOE NMR studies in toluene-d8 show that the Li+ cation is in close proximity to the dz2 orbital of rhodium. In the solid-state structure of the lithium(12-crown-4) salt [Li(12-crown-4)2][Li{Rh(CH2CMe2CH2CH═CH2)2}2], one lithium atom is surrounded by two [Rh(CH2CMe2CH2CH═CH2)2]- anions, and in this assembly there are two unusually short Rh-Li distances of 2.48 ?. DFT calculations, natural energy decomposition, and ETS-NOCV analysis suggest that there is a weak dative interaction between the 4dz2 orbitals on the Rh centers and the 2pz orbital of the Li+ cation. The charge-transfer term between Rh and Li+ contributes only about the 1/5 of the total interaction energy, however, and the principal driving force for the proximity of Rh and Li in compounds 1 and 2 is that Li+ is electrostatically attracted to negative charges on the dialkylrhodiate anions.

Rational Synthesis for a Noble Metal Carbide

Transition metal carbides have attractive physical and chemical properties that are much different from their parent metals. Particularly, noble metal carbides are expected to be promising materials for a variety of applications, particularly as efficient catalysts. However, noble metal carbides have rarely been obtained because carbide phases do not appear in noble metal-carbon phase diagrams and a reasonable synthesis method to make noble metal carbides has not yet been established. Here, we propose a new synthesis method for noble metal carbides and describe the first synthesis of rhodium carbide using tetracyanoethylene (TCNE). The rhodium carbide was synthesized without extreme conditions, such as the very high temperature and/or pressure typically required in conventional carbide syntheses. Moreover, we investigated the electronic structure and catalytic activity for the hydrogen evolution reaction (HER). We found that rhodium carbide has much higher catalytic activity for HER than pure Rh. Our study provides a feasible strategy to create new metal carbides to help advance the field of materials science.

Ice Melting to Release Reactants in Solution Syntheses

Aqueous solution syntheses are mostly based on mixing two solutions with different reactants. It is shown that freezing one solution and melting it in another solution provides a new interesting strategy to mix chemicals and to significantly change the reaction kinetics and thermodynamics. For example, a precursor solution containing a certain concentration of AgNO3 was frozen and dropped into a reductive NaBH4 solution at about 0 °C. The ultra-slow release of reactants was successfully achieved. An ice-melting process can be used to synthesize atomically dispersed metals, including cobalt, nickel, copper, rhodium, ruthenium, palladium, silver, osmium, iridium, platinum, and gold, which can be easily extended to other solution syntheses (such as precipitation, hydrolysis, and displacement reactions) and provide a generalized method to redesign the interphase reaction kinetics and ion diffusion in wet chemistry.