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Abstract The synthesis of heteroleptic monomeric cationic Rh(I) bis-diphosphine complex [Rh(dppe)(dppp)]Cl (dppe = 1,2-bis-(diphenylphosphino)ethane and dppp = 1,3-bis-(diphenylphosphino)propane) was achieved by reaction between the neutral dimeric complex [Rh 2 (dppe) 2 (μ 2 -Cl) 2 ] and the dppp ligand. The corresponding complex [Rh(dppe)(dppp)]BF 4 was instead obtained from reaction between [Rh(dppe)(nbd)]BF 4 (nbd = bicyclo-[2.2.1]-hepta-2,5-diene) and the dppp ligand. Previous protocols had extended to the synthesis of the analogous homoleptic complexes containing two dppe or two dppp ligands. The structural analysis of such complexes conducted in the solid state by single-crystal x-ray crystallography and in solution by 31P and 1H NMR revealed a distorted square planar geometry where the anion and the cation are not bonded each other. Nevertheless, important differences in reactivity can be found if same complexes with different anions are compared, as in the case of the phosphine exchange reaction between [Rh(dppp) 2 ]X (X = Cl−, BF 4 −) and the dppe ligand or in the case of the employment of such complexes as catalytic precursors for the transfer hydrogenation reaction from 2-propanol to acetophenone. Graphical abstract Image 1 Highlights • The reactivity of cationic Rh(I) bis-diphosphine complexes [Rh(dppe)(dppp)]X (X = Cl−, BF4−) can be affected by the type of anion. • Heteroleptic [Rh(dppe)(dppp)]X complexes (X = Cl−, BF 4 −) can be prepared by reaction between [Rh 2 (dppe) 2 (μ 2 -Cl) 2 ] and dppp. • Rh(I) bis-diphosphine complexes catalyze hydrogen transfer from 2-propanol to acetophenone. • BF 4 − can inhibit the hydrogen transfer reaction catalyzed by Rh(I) bis-diphosphine complexes. [ABSTRACT FROM AUTHOR]

Graphical abstract A new rhodium(III) triphenylphosphine complex having the general formula [Rh(PPh 3) 2 (L)Cl] (1) was synthesized by C S bond cleavage of an ONS donor azo-thioether ligand (L-CH 2 Ph). The complex was thoroughly characterized by various spectroscopic techniques. Its single crystal X-ray structure exhibits an octahedral geometry around the rhodium(III) center. A cyclic voltammogram of the complex exhibits ligand based quasi-irreversible oxidative and reductive responses. The electronic structure, redox properties and electronic excitations in the complex were interpreted by DFT and TDDFT calculations. The complex effectively catalyzed the transfer hydrogenation reaction of ketones with high yields. Abstract A new rhodium(III) triphenylphosphine complex having the general formula [Rh(PPh 3) 2 (L)Cl] (1) was synthesized by C S bond cleavage of an ONS donor azo-thioether ligand (L-CH 2 Ph). The complex was thoroughly characterized by various spectroscopic techniques. Its single crystal X-ray structure exhibits an octahedral geometry around the rhodium(III) center. A cyclic voltammogram of the complex exhibits ligand based quasi-irreversible oxidative and reductive responses. The electronic structure, redox properties and electronic excitations in the complex were interpreted by DFT and TDDFT calculations. The complex effectively catalyzed the transfer hydrogenation reaction of ketones with high yields in i -PrOH in the presence of a base. [ABSTRACT FROM AUTHOR]

During the reaction of [{Rh(μ‐Cl)(coe)2}2] (1) (coe = cis‐cyclooctene) with the tertiary phosphane tBu2PPh in a nitrogen atmosphere the square planar rhodium(II) complex trans‐[RhCl2(tBu2PPh)2] (2) was identified as a side product in moderate yield. 2 was synthesized in a defined manner in higher yields using a known procedure starting from [{Rh(μ‐Cl)(coe)2}2], tBu2PPh (molar ratio Rh:P of 1:2), and N‐chlorosuccinimide as the oxidizing agent in THF at room temperature. The molecular structure of 2 was determined by X‐ray crystallography. Additionally, to further confirm the molecular structure of trans‐[RhCl2(tBu2PPh)2], extensive DFT calculations were undertaken, which gave further evidence for its molecular structure. In contrast to the remarkable stability of 2 in the solid state, the investigation of solutions of this compound afforded hints at a dynamic equilibrium, which renders more difficult the collection of adequate NMR spectroscopic data for the title complex. [ABSTRACT FROM AUTHOR]

A new diarylmido-based pincer proto ligand (iPrPNHSbPh) with one –PPri2 and one –SbPh2 side donor has been synthesized. Three complexes of its amido form were prepared using standard metalation techniques: (iPrPNSbPh)PdCl, (iPrPNSbPh)RhCO, and (iPrPNSbPh)Ir(COE), where COE = cis-cyclooctene. These complexes were compared with their previously reported analogs incorporating a –PPh2 side donor in place of –SbPh2. The –SbPh2 donor arm is less donating towards the metal and is less strongly trans-influencing, based on the structural and IR spectroscopic analysis of the Rh complexes. The redox potential of the Pd complexes is only marginally affected by the change from –PPh2 to –SbPh2. (iPrPNSbPh)Ir(COE) proved to be a slower and less selective catalyst in the dehydrogenative borylation of terminal alkynes (DHBTA) than its –PPh2 analog. [ABSTRACT FROM AUTHOR]

A series of mono- and multivalent phosphorus-based ligands was synthesised by the lower-rim benzylation of the water-soluble ligand, 1,3,5-triaza-7-phosphaadamantane (PTA). These ligands were used to prepare mono-, bi- and trinuclear Rh(I) complexes whose catalytic activity, product selectivity and recyclability were evaluated in the aqueous biphasic hydroformylation of 1-octene. [ABSTRACT FROM AUTHOR]

The synthesis and characterisation of a new anionic flexible scorpionate ligand, methyl(bis-7-azaindolyl)borohydride [MeBai]− is reported herein. The ligand was coordinated to a series of group nine transition metal centres forming the complexes, [Ir(MeBai)(COD)] (1), [Rh(MeBai)(COD)] (2), [Rh(MeBai)(CODMe)] (2-Me) and [Rh(MeBai)(NBD)] (3), where COD = 1,5-cyclooctadiene, CODMe = 3-methyl-1,5-cyclooctadiene and NBD = 2,5-norbornadiene. In all cases, the boron based ligand was found to bind to the metal centres via a κ3-N,N,H coordination mode. The ligand and complexes were fully characterised by spectroscopic and analytical methods. The structures of the ligand and three of the complexes were confirmed by X-ray crystallography. The potential for migration of the “hydride” or “methyl” units from boron to the metal centre was also explored. During these studies an unusual transformation, involving the oxidation of the rhodium centre, was observed in complex 2. In this case, the η4-COD unit transformed into a η1,η3-C8H12 unit where the ring was bound via one sigma bond and one allyl unit. This is the first time such a transformation has been observed at a rhodium centre. [ABSTRACT FROM AUTHOR]

The thermal and photochemical pathway of compound 1 [6-( η 5 -C 5 Me 5 )- nido -6-RhB 9 H 13 ] is reported. Under thermal conditions, compound 1 was converted to [ hypercloso -( η 5 -C 5 Me 5 )RhB 9 H 9 ] ( 2 ) through the loss of two dihydrogen molecules in toluene. In contrast, under UV irradiation, compound 1 undergoes reactions in benzene to give the previously known compound [ nido -5-( η 5 -C 5 Me 5 )RhB 9 H 13 ] ( 3 ). The hypercloso compound 2 is the first Rhodium containing hypercloso -metalladecaborane, while the photochemically induced isomerization is unprecedented. The compounds were identified using spectroscopic methods. [ABSTRACT FROM AUTHOR]

Abstract: Rhodium nanoparticles (Rh NPs) were prepared according to a green method based on the reduction of (acetylacetonato)dicarbonylrhodium(I), Rh(acac)(CO)2, in water at 80 °C. The nanoparticles, which were obtained without the addition of a reducing agent, were stabilized by polyvinylpyrrolidone (PVP) or polyvinyl alcohol (PVA) polymers and characterized by TEM (transmission electron microscopy), XPS (X‐ray photoelectron spectroscopy), and XRD (X‐ray powder diffraction) methods. The excellent catalytic activity of these Rh NPs was evidenced in the hydrogenation of benzene to cyclohexane. In the presence of PPh3, Rh NPs formed a highly active system in the hydroformylation of 1‐hexene. In this system, they acted as a source of soluble rhodium species. Rh NPs were also synthesized in water using rhodium(II) acetate, Rh2(OAc)4, and rhodium(III) chloride, RhCl3, as rhodium sources, and their catalytic activity was compared with that of the rhodium precursors. [ABSTRACT FROM AUTHOR]

A procedure to synthesize (μ-hydroxo)bis-pentaaquarhodium(III) nitrate tetrahydrate [Rh2(H2O)8(μ-OH)2](NO3)4·4H2O from potassium hexachlororhodiate(III) is elaborated. The compound is isolated into the solid phase and structurally characterized. The crystallographic data are as follows: a = 5.8763(2) Å, b = 9.4749(4) Å, c = 9.6249(3) Å, α = 79.905(1)°, β = 84.324(1)°, γ = 82.922(1)°, space group P-1, Z = 1, ρcalc = 2.240 g/cm3. The compound is soluble in water, ethanol, and acetone. Hydrolysis takes place in concentrated nitric acid with the formation of mononuclear aqua- and aquanitrate complexes. Thermal decomposition of the salt at a temperature above 580 °C leads to the formation of a single product-rhodium(III) oxide. [ABSTRACT FROM AUTHOR]

A RhCp* (Cp* = pentamethylcyclopentadienyl) complex bearing an NAD+/NADH-functionalized ligand, [RhCp*(pbn)Cl]Cl ([1]Cl, pbn = (2-(2-pyridyl)benzo[b]-1,5-naphthyridine)), was synthesized. The cyclic voltammogram of [1]Cl in CH3CN shows two reversible redox waves at E1/2 = −0.58 and −1.53 V (vs. the saturated calomel electrode (SCE)), which correspond to the RhIII/RhI and pbn/pbnṖ− redox couples, respectively. The addition of acetic acid to the solution afforded the proton-coupled two-electron reduction of [1]Cl at −0.62 V, from which [RhCp*(pbnHH)Cl]+ was selectively generated, probably via a hydride transfer from a RhIII–hydride intermediate to the pbn ligand. Complex [1]Cl is stable under acidic conditions, whereas a methyl proton of the Cp* moiety dissociates under basic conditions. The resulting anionic methylene group attacks the para carbon of the free pyridine of pbn, accompanied by protonation of the nitrogen atom of the ligand. As a result, treatment of [1]Cl with a base produces selectively the cyclic complex [1CH]Cl, which bears a reduced pbn framework (pbnCH). [1CH]Cl forms 1 : 1 adducts with PhCOO−via hydrogen bonding. A similar adduct, formed by a Ru–pbnHH scaffold and RCOO− (R = CH3, C6H5), has been reported to react with CO2 to produce HCOO− under concomitant regeneration of Ru–pbn. The adduct of [1CH]Cl with PhCOO−, however, lacks such hydride-donor ability, due to a steric barrier in the molecular structure of [1CH]Cl, which hampers the hydride transfer. [ABSTRACT FROM AUTHOR]

The reaction of the dimeric cyclometalated complexes [{M(µ-Cl)(ptpy) 2 } 2 ] with symmetrical di alkyl-substituted bipyridines followed by metathesis with KPF 6 yields the complex salts [M(ptpy) 2 (6,6′-dimethyl-bipyridine)]PF 6 and [M(ptpy) 2 (4,4′-dialkyl-bipyridine)]PF 6 , (M = Rh, Ir; alkyl = methyl, n -Propyl, t -Butyl or n -nonyl, ptpy = 2-( p -tolyl)pyridinato). All compounds were characterized by elemental analyses, mass spectra and 1 H and 13 C NMR spectra. The compounds 1, 6, 7, 8, 10 were also examined by X-ray crystallography and their proposed octahedral tris-chelate structure with trans configuration of the cyclometalating tolylpyridinato N atoms was proven. All compounds display significant cytotoxicity against human cancer cell lines MCF-7 and HT-29. The most active compounds in this study display IC 50 values down to 120 nM, making them two orders of magnitude more active than the established anticancer drug cisplatin. [ABSTRACT FROM AUTHOR]

Although both Pd and Rh fall into the Pd-group Pt-group elements (PPGEs), the electrocatalytic property of Rh nanocrystals for the methanol oxidation reaction (MOR) in alkaline media is rarely explored till now. In this work, we develop a surfactant-free co-precipitation/co-reduction method to synthesize the carbon ball supported RhCo alloy nanocrystals (RhCo/CB) nanohybrids with different Rh/Co atomic ratios and investigate their electrocatalytic acitvity for the MOR in alkaline media. Cyclic voltammetry and chronoamperometry measurements show Rh 3 Co 1 /CB nanohybrids have exceptional electrocatalytic activity and long-term stability for the MOR in alkaline media, much higher than commercial Pd/C and Pt/C electrocatalysts, demonstrating that Rh-based alloy nanocrystals may be highly promising Pt-alternative electrocatalyst for the MOR in alkaline media. [ABSTRACT FROM AUTHOR]

Aluminabenzene-rhodium and -iridium complexes were synthesized, in which the aluminum atom played as a proximal Lewis acidic site. Based on their structural analysis, aluminabenzene ligand could coordinate to Rh and Ir as a η5-pentadienyl ligand. The Lewis acidic character of aluminum atom in aluminabenzene ligand was confirmed by treatment with 4-dimethylaminopyridine to form the corresponding Lewis acid-base complexes. In addition, the α-selective C-H borylation of triethylamine with the aluminabenzene-ligated iridium catalyst was demonstrated. [ABSTRACT FROM AUTHOR]

A flexible and efficient rhodium(iii)-catalyzed intramolecular annulation of benzamides bearing tethered alkynes for the synthesis of indolizinones and quinolizinones is reported. This reaction shows a broad substrate scope and excellent functional-group tolerance, including different kinds of heterocyclic substrates, such as furan, thiophene, pyrrole, benzofuran, benzothiophene, indole and isonicotinamide substrates. This method also provides a practical and efficient approach for the synthesis of rosettacin and oxypalmatime. [ABSTRACT FROM AUTHOR]

The first filled Bi95+ polycation was isolated in the form of [RhBi9](AlCl4)4 crystals by dissolution of the solid precursor Bi12- xRh X13- x in the Lewis-acidic ionic liquid [BMIm]Cl·3.6AlCl3 (BMIm = 1-butyl-3-methylimidazolium) at 140 °C. In the monoclinic crystal structure [ P21/ n, a = 1217.5(2) pm, b = 1741.6(3) pm, c = 5085.7(7) pm, β = 90.117(8)°], the almost spherical [RhBi9]4+ polycations (approximate D3 h symmetry; Rh-Bi 276 ± 3 pm) show pronounced orientational disorder. Shiny black needles of Bi7RhI8 were obtained from the reaction of rhodium, bismuth, and BiI3 in the ionic liquid [BMIm]Cl ·1.3AlCl3 at 200 °C. Bi7RhI8 [ P21/ n, a = 943.10(1) pm, b = 1582.40(1) pm, c = 1645.40(1) pm, β = 95.48(1)°] is isostructural to Bi7RhBr8 and consists of molecular clusters [(RhBi7)I8]. The rhodium atom centers a pentagonal bipyramid of bismuth atoms, and the two apical bismuth atoms are in square-planar coordination of iodide ions. DFT-based calculations indicate strong bismuth-rhodium bonding with predominantly covalent character for both clusters. The electronic structure of the Bi95+ cage is notably modified by this interaction, but the characteristic bonding features of the host cluster with the D3 h configuration are still maintained. In Bi7RhI8, on the other hand, bonding is dictated by the spatial distribution of mutually repelling iodine atoms, and the Bi-Rh bonding is highly polar. [ABSTRACT FROM AUTHOR]

The first filled Bi95+ polycation was isolated in the form of [RhBi9](AlCl4)4 crystals by dissolution of the solid precursor Bi12- xRh X13- x in the Lewis-acidic ionic liquid [BMIm]Cl·3.6AlCl3 (BMIm = 1-butyl-3-methylimidazolium) at 140 °C. In the monoclinic crystal structure [ P21/ n, a = 1217.5(2) pm, b = 1741.6(3) pm, c = 5085.7(7) pm, β = 90.117(8)°], the almost spherical [RhBi9]4+ polycations (approximate D3 h symmetry; Rh-Bi 276 ± 3 pm) show pronounced orientational disorder. Shiny black needles of Bi7RhI8 were obtained from the reaction of rhodium, bismuth, and BiI3 in the ionic liquid [BMIm]Cl ·1.3AlCl3 at 200 °C. Bi7RhI8 [ P21/ n, a = 943.10(1) pm, b = 1582.40(1) pm, c = 1645.40(1) pm, β = 95.48(1)°] is isostructural to Bi7RhBr8 and consists of molecular clusters [(RhBi7)I8]. The rhodium atom centers a pentagonal bipyramid of bismuth atoms, and the two apical bismuth atoms are in square-planar coordination of iodide ions. DFT-based calculations indicate strong bismuth-rhodium bonding with predominantly covalent character for both clusters. The electronic structure of the Bi95+ cage is notably modified by this interaction, but the characteristic bonding features of the host cluster with the D3 h configuration are still maintained. In Bi7RhI8, on the other hand, bonding is dictated by the spatial distribution of mutually repelling iodine atoms, and the Bi-Rh bonding is highly polar. [ABSTRACT FROM AUTHOR]

Reaction of bis( p -tolyl-propargyl)-tosylamide with [(cod)RhCl] 2 in the presence of CO gives the cyclopentadienone complex [(Cpd’)Rh(CO)Cl] n (Cpd’ = TsN(CH 2 ) 2 C 4 (Tol) 2 CO). Its dissolution in DMSO or pyridine leads to decarbonylation and formation of the adducts (Cpd’)Rh(DMSO) 2 Cl and (Cpd’)Rh(Py) 2 Cl. The reaction of [(Cpd’)Rh(CO)Cl] n with AgPF 6 and p -xylene produces the sandwich arene complex [(Cpd’)Rh( p -xylene)]PF 6 , in which the arene can be substituted by t BuNC ligand to give [(Cpd’)Rh( t BuNC) 3 ]PF 6 . The arene complex acts as an efficient catalyst for the reductive amination of carbonyl compounds in the presence of CO as deoxygenation agent, producing various amines in 75–85% yields. [ABSTRACT FROM AUTHOR]

Rhodium phosphide (RhP) is utilized as a novel cocatalyst for CdS photocatalyst. The RhP cocatalyst greatly improves the photocatalytic performance, reusability and lifetime of CdS for H 2 generation from splitting water under visible light illumination (λ > 420 nm). The optimal compound, 20 wt% RhP/CdS, produces the highest hydrogen amount of 325.4 μmol/mg after 10 h, which is about 196,024 times that of pure CdS. The apparent quantum yield of H 2 evolution over the 20 wt% RhP/CdS after 100 h reaches 34.3%. Ultraviolet photoelectron spectrometer, fluorescence spectroscopy and photocurrent show that the RhP with strong electron attraction ability can accelerate the separation of photo-excited electron-hole pairs, which is responsible for the enhanced hydrogen evolution ability of CdS. [ABSTRACT FROM AUTHOR]

[RhIII(*Cp)Cl(X,Y)] n+ complexes {X, Y = Cl, PTA, n = 0 ( 2); X, Y = en, n = 1 ( 3, Cl- salt; 4, PF6- salt); X, Y = acac, n = 0 ( 5); X, Y = cur, n = 0 ( 6), where *Cp = pentamethylcyclopentadienato, curH = curcumin; PTA = 1,3,5-triaza-7-phosphatricyclo[3.3.1.1]decane; en = 1,2-ethanediamine; acac = acetylacetonato = 2,4-pentanedionato(1-)} were synthesized from [Rh(*Cp)(µ-Cl)Cl]2 ( 1). While 2- 5 were inactive against human epithelial A549 lung-cancer cells in assays of cytotoxicity, and antimetastatic and proapoptotic behaviors, 6 had a cytotoxic activity similar to that of curH over 72 h, but at 24 h in real-time cell migration assays, it was less active, showing slow release of curH. All complexes underwent ligand-exchange reactions with biomolecules and cells within the timeframes of the assays (X-ray absorption spectroscopy). Intracellular elemental distributions (X-ray fluorescence microscopy) showed that 6 effectively delivered curH to cells, where it was released. Other elemental distributions and caspase activities were consistent with preapoptotic activities. As such, 6 is a promising delivery agent for bioactive ligands, such as curH. However, pure curcumin itself showed a previously unrecognized ability to promote migration of A549 cells at subtoxic concentrations in the presence of endothelial growth factor, which may be a concern for its widespread use as a nutritional supplement and as a potential drug. This aspect warrants further research. [ABSTRACT FROM AUTHOR]

A new mononuclear rhodium(III) complex, [Rh(bzimpy)Cl 3 ] (bzimpy = 2,6-bis(2-benzimidazolyl)pyridine), was synthesized and characterized by elemental analysis and spectroscopic methods. The molecular structure of the complex was confirmed by single-crystal X-ray crystallography. The interaction of the complex with fish sperm DNA (FS-DNA) was investigated by UV spectroscopy, emission titration, and viscosity measurement in order to evaluate the possible DNA-binding mode and to calculate the corresponding DNA-binding constant. The results reveal that the Rh(III) complex interacts with DNA through groove binding mode with a binding affinity on the order of 10 4 . In addition, the binding of the Rh(III) complex to bovine serum albumin (BSA) was monitored by UV–Vis and fluorescence emission spectroscopy at different temperatures. The mechanism of the complex interaction was found to be static quenching. The thermodynamic parameters ( ΔH , ΔS , and ΔG ) obtained from the fluorescence spectroscopy data show that van der Waals interactions and hydrogen bonds play a major role in the binding of the Rh(III) complex to BSA. For the comparison of the DNA- and BSA-binding affinities of the free bzimpy ligand with its Rh(III) complex, the absorbance titration and fluorescence quenching experiments of the free bzimpy ligand with DNA and BSA were carried out. Competitive experiments using eosin Y and ibuprofen as site markers indicated that the complex was mainly located in the hydrophobic cavity of site I of the protein. These experimental results were confirmed by the results of molecular docking. Finally, the in vitro cytotoxicity properties of the Rh(III) complex against the MCF-7, K562, and HT-29 cell lines were evaluated and compared with those of the free ligand (bzimpy). It was found that the complexation process improved the anticancer activity significantly. [ABSTRACT FROM AUTHOR]

Treatment of the germyl complex [Rh(GePh3)(PEt3)3] ( 1) with CS2 afforded the rhodium thiocarbonyl complex trans-[Rh(SGePh3)(CS)(PEt3)2] ( 2) by phosphine dissociation and C-S bond activation. The analogous reaction with COS gave the structurally related carbonyl complex trans-[Rh(SGePh3)(CO)(PEt3)2] ( 3). Low-temperature NMR measurements revealed initial formation of the intermediates mer-[Rh(GePh3)(η2-CS2)(PEt3)3] ( 4) and mer-[Rh(GePh3)(η2-COS)(PEt3)3] ( 5). Reactions of 2 towards CO and HCl led to the replacement of the thiocarbonyl or germylthiolato ligand yielding complex 3 and trans-[Rh(Cl)(CS)(PEt3)2] ( 6), respectively. The germylthiolato complex trans-[Rh(SGePh3)(CS)(PEt3)2] ( 2) reacted with the boryl complex [Rh(Bpin)(PEt3)3] ( 7; pin = pinacolato) to afford the rhodium µ-carbido complex trans, trans-[{Rh(SBpin)(PEt3)2}(µ-C){Rh(SGePh3)(PEt3)2}] ( 8). Complex 8 is not stable in solution and rearranges to form the symmetrical µ-carbido complexes trans, trans-[Rh2(µ-C)(SGePh3)2(PEt3)4] ( 9) and trans, trans-[Rh2(µ-C)(SBpin)2(PEt3)4] ( 10). The molecular structures of 2 and 9 were determined by X-ray crystallography. [ABSTRACT FROM AUTHOR]

[RhCl(NCO)(nbyl)(PR3)] (nbyl = σ-norbornenyl; NCO = quinoline-8-acyl; R = p-F-C6H4) (1) has been synthesized by the reaction of [Rh(nbd)Cl]2 (nbd = norbornadiene) with 2 equivalents of NCHO (quinoline-8-carbaldehyde) and 2 equivalents of PR3. Compound 1 has been fully characterized in solution and also in the solid state by X-ray diffraction. Compound 1 shows low stability in solution and undergoes slow ring closure isomerization to [RhCl(NCO)(ntyl)(PR3)] (ntyl = σ-nortricyclyl) (2) after 12 hours. Reaction of 1 with an extra equivalent of aldehyde (NCHO) and PR3 led to the formation of [RhCl(H)(NCO)(PR3)2] (3) and an equivalent of ketone, which is a hydroacylation product. The catalytic activity of 3 in the hydroacylation of nbd with NCHO is reported as well as the catalytic activity of compound 1. Compounds 1 and 3 are proposed as intermediate species in the catalytic hydroacylation of norbornadiene with NCHO. [ABSTRACT FROM AUTHOR]

In recent years, α-imino rhodium carbene complexes derived by ring-opening of N-sulfonyl-1,2,3-triazoles have attracted much attention from organic chemists. Many transformations of these species have been reported that involve, in most cases, nucleophilic attack at the carbene center of the α-imino rhodium carbene, facilitating the synthesis of a wide range of novel and useful compounds, particularly heterocycles. This Minireview mainly focuses on advances in the transformation of N-sulfonyl-1,2,3-triazoles during the past two years. [ABSTRACT FROM AUTHOR]

RhGe synthesized at high pressure crystallizes in the noncentrosymmetric B20 cubic structure. Measurements of electrical resistivity and magnetization demonstrate a superconducting state below T c ∼ 4.3 K and weak ferromagnetism below T m ∼ 140 K. Specific heat data confirm the bulk nature of superconductivity in this ferromagnetic superconductor. Point contact spectra in the superconducting state exhibit the complex Andreev reflection signal which may indicate a mixed singlet-triplet order parameter. The superconducting region forms a dome on the P-T diagram with a maximum of T c near 4 GPa. It was also found that the superconductivity of RhGe 4 is suppressed at high pressure in contrast with RhGe. Ab initio simulations suggest that the observed weak magnetization emerges from the pronounced toroidal-like spin polarization with magnetic quadrupole and toroidal moments located at Rh and Ge sites. [ABSTRACT FROM AUTHOR]

A novel rhodium(iii) complex [RhIII(H2LtBu)Cl3] (1) (H2LtBu = 2,6-bis(5-tert-butyl-1H-pyrazol-3-yl)pyridine) containing a pincer type, tridentate nitrogen-donor chelate system was synthesized. Single crystal X-ray structure analysis revealed that 1 crystallizes in the orthorhombic space group Pbcn with a = 20.7982(6), b = 10.8952(4), c = 10.9832(4) Å, V = 2488.80(15) Å3, and eight molecules in the unit cell. The rhodium center in the complex [RhIII(H2LtBu)Cl3] (1) is coordinated in a slightly distorted octahedral geometry by the tridentate N,N,N-donor and three chloro ligands, adopting a mer arrangement with an essentially planar ligand skeleton. Due to the tridentate coordination of the N,N,N-donor, the central nitrogen atom N1 is located closer to the RhIII center. The reactivity of the synthesized complex toward small biomolecules (l-methionine (l-Met), guanosine-5′-monophosphate (5′-GMP), l-histidine (l-His) and glutathione (GSH)) and to a series of duplex DNAs and RNA was investigated. The order of reactivity of the studied small biomolecules is: 5′-GMP ＞ GSH ＞ l-Met ＞ l-His. Duplex RNA reacts faster with the [RhIII(H2LtBu)Cl3] complex than duplex DNA, while shorter duplex DNA (15mer GG) reacts faster compared with 22mer GG duplex DNA. In addition, a higher reactivity is achieved with a DNA duplex with a centrally located GG-sequence than with a 22GTG duplex DNA, in which the GG-sequence is separated by a T base. Furthermore, the interaction of this metal complex 1 with calf thymus DNA (CT-DNA) and bovine serum albumin (BSA) was examined by absorption (UV-Vis) and emission spectral studies (EthBr displacement studies). Overall, the studied complex exhibited good DNA and BSA interaction ability. [ABSTRACT FROM AUTHOR]

Rhodium(ii)–fluorophore conjugates have strong rhodium-based fluorescence quenching that can be harnessed to report on a conjugate's cellular uptake and the intracellular decomposition rate. Information gleened from this study allowed the design of an improved STAT3 metalloinhibitor. [ABSTRACT FROM AUTHOR]

B12 is unique among the vitamins as it is biosynthesized only by certain prokaryotes. The complexity of its synthesis relates to its distinctive cobalt corrin structure, which is essential for B12 biochemistry and renders coenzyme B12 (AdoCbl) so intriguingly suitable for enzymatic radical reactions. However, why is cobalt so fit for its role in B12-dependent enzymes? To address this question, we considered the substitution of cobalt in AdoCbl with rhodium to generate the rhodium analogue 5′-deoxy-5′-adenosylrhodibalamin (AdoRbl). AdoRbl was prepared by de novo total synthesis involving both biological and chemical steps. AdoRbl was found to be inactive in vivo in microbial bioassays for methionine synthase and acted as an in vitro inhibitor of an AdoCbl-dependent diol dehydratase. Solution NMR studies of AdoRbl revealed a structure similar to that of AdoCbl. However, the crystal structure of AdoRbl revealed a conspicuously better fit of the corrin ligand for RhIII than for CoIII, challenging the current views concerning the evolution of corrins. [ABSTRACT FROM AUTHOR]

B12 is unique among the vitamins as it is biosynthesized only by certain prokaryotes. The complexity of its synthesis relates to its distinctive cobalt corrin structure, which is essential for B12 biochemistry and renders coenzyme B12 (AdoCbl) so intriguingly suitable for enzymatic radical reactions. However, why is cobalt so fit for its role in B12-dependent enzymes? To address this question, we considered the substitution of cobalt in AdoCbl with rhodium to generate the rhodium analogue 5′-deoxy-5′-adenosylrhodibalamin (AdoRbl). AdoRbl was prepared by de novo total synthesis involving both biological and chemical steps. AdoRbl was found to be inactive in vivo in microbial bioassays for methionine synthase and acted as an in vitro inhibitor of an AdoCbl-dependent diol dehydratase. Solution NMR studies of AdoRbl revealed a structure similar to that of AdoCbl. However, the crystal structure of AdoRbl revealed a conspicuously better fit of the corrin ligand for RhIII than for CoIII, challenging the current views concerning the evolution of corrins. [ABSTRACT FROM AUTHOR]

Rhodium(I), tungsten(0), and molybdenum(0) carbonyl complexes of the N-heterocyclic-carbene-phosphinidene adducts IPr ·PR [ 1a, R = H; 1b, R = Ph; 1c, R = Mes; IPr = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene; Mes = 2,4,6-trimethylphenyl] were prepared. The reaction of 1b with [Rh(µ-Cl)(CO)2]2 afforded the dicarbonyl rhodium(I) complex cis-[(IPr ·PPh)RhCl(CO)2] ( 2) as the major product together with the tetranuclear complex [{µ-(IPr ·PPh)}2Rh4(µ-Cl)4(CO)4] ( 3). The latter was characterized by X-ray diffraction analysis. The tungsten pentacarbonyl complexes [(IPr ·PR)W(CO)5] ( 4a, R = H; 4b, R = Ph; 4c, R = Mes) were isolated from the reactions of 1a- 1c with [(Me3N)W(CO)5], whereas the reactions of 1a and 1b with [(thf)Mo(CO)5] (thf = tetrahydrofuran) gave the corresponding molybdenum complexes [(IPr ·PR)Mo(CO)5] ( 5a, R = H; 5b, R = Ph). The molecular structures of the five carbonyl complexes were established by X-ray diffraction analyses. The IR spectroscopic analysis of the CO stretching frequencies of the carbonyl complexes 2, 4, and 5 revealed the strong electron-donating abilities of the phosphorus(I) ligands. [ABSTRACT FROM AUTHOR]

Synthetic access to previously elusive single enantiomers of an octahedral chiral-at-metal rhodium(iii) complex containing two cyclometalated 2-phenylbenzothiazoles and two acetonitrile ligands is reported. The complex is a superior chiral Lewis acid catalyst compared to its benzoxazole congener which can be rationalized with a higher steric congestion around the coordination sites. [ABSTRACT FROM AUTHOR]

The dihydrido germyl complex cis,fac-[Rh(GePh3)(H)2(PEt3)3] (2) was synthesized by an oxidative addition of HGePh3 at [Rh(H)(PEt3)3] (1). Treatment of 2 with neohexene generated the rhodium(i) germyl complex [Rh(GePh3)(PEt3)3] (3). Alternatively, treatment of the methyl complex [Rh(CH3)(PEt3)3] (4) with HGePh3 furnished at room temperature also 3. Low-temperature NMR measurements revealed an initial formation of the oxidative addition product fac-[Rh(GePh3)(H)(CH3)(PEt3)3] (5), which transforms into the intermediate complex [Rh(GePh3)(H)(CH3)(PEt3)2] (6) by dissociation of a triethylphosphine ligand. The reductive elimination of methane and coordination of PEt3 afforded the germyl complex 3. Treatment of 3 with CO gave the biscarbonyl complex [Rh(GePh3)(CO)2(PEt3)2] (7). The molecular structures of the complexes 2, 3 and 7 were determined by X-ray crystallography. The germyl complex 3 reacted with 2,3,5,6-tetrafluoropyridine or pentafluorobenzene to furnish the C–H activation products [Rh(4-C5NF4)(PEt3)3] (8) and [Rh(C6F5)(PEt3)3] (9), respectively. The reaction of 3 with hexafluorobenzene or perfluorotoluene gave selectively the C–F activation products 9 and [Rh(4-C6F4CF3)(PEt3)3] (10). Treatment of 3 with pentafluoropyridine resulted in the formation of the C–F activation products 8 and [Rh(2-C5NF4)(PEt3)3] (11) in a 1 : 10 ratio. The two isomeric activation compounds [Rh{(E)-CF=CF(CF3)}(PEt3)3] (12) and [Rh{(Z)-CF=CF(CF3)}(PEt3)3] (13) were obtained in a 3 : 1 ratio by reaction of 3 with hexafluoropropene. On exposure to oxygen the highly air sensitive complex 12 reacts to yield the peroxido-bridged dirhodium complex [Rh{(E)-CF=CF(CF3)}(μ–κ1:η2-O2)(PEt3)2]2 (14). The molecular structure of 14 was determined by X-ray crystallography. [ABSTRACT FROM AUTHOR]

The synthesis and characterisation of novel thioacetyl-functionalised terpyridine ligands and their ruthenium and rhodium complexes [Ru(tpy) 2 ](PF 6 ) 2 , [Rh(tpy) 2 ](PF 6 ) 3 , [Ru(phen)(tpy)Cl](PF 6 ), [Rh(phen)(tpy)Cl](PF 6 ) 2 (phen = phenanthroline; tpy = S-[ω-(2,2:6′,2″-terpyridin-4′-yl)phenoxy]alkyl ethanethioate) have been described. Ligands and complexes were characterised by 1 H NMR spectroscopy, mass spectrometry, elemental analysis and cyclic voltammetry data. The crystal structure of the complex [Rh(phen)(tpy)Cl](PF 6 ) 2 (phen = phenanthroline; tpy = 4′-phenyl-2,2′:6′,2″-terpyridine) ( 21 ), have been determined by X-ray crystallography. Complex 21 show a distorted octahedral geometry around the ruthenium centre. Antimicrobial activity toward Escherichia coli at concentrations as low as 5 μM was found for some of the studied complexes. For complexes [Rh(tpy C 6 H 4 O(CH 2 ) 8 SCOCH 3 ) 2 ](PF 6 ) 3 ( 19 ), [Rh(phen)(tpy C 6 H 4 O (CH 2 ) 8 SCOCH 3 )Cl](PF 6 ) 2 ( 31 ) and [Rh(phen)(tpy C 6 H 4 O (CH 2 ) 11 SCOCH 3 )Cl](PF 6 ) 2 ( 32 ), a strong inhibition of in vitro protein synthesis was observed using firefly luciferase. An investigation of cytotoxicity of the complexes against human embryonic kidney cells (HEK293 line) by the MTT assay demonstrates that the toxicity of all tested compounds is of similar magnitude, with IC 50 values of 3–30 μM. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of twenty new pentamethylcyclopentadienyl-rhodium and iridium complexes containing N^N and N^O-chelating chloroquine analogue ligands are described. The in vitro antimalarial activity of the new ligands as well as the complexes was evaluated against the chloroquine sensitive (CQS) NF54 and the chloroquine resistant (CQR) Dd2 strains of Plasmodium falciparum. The antimalarial activity was found to be good to moderate; although all complexes are less active than artesunate, some of the ligands and complexes showed better activity than chloroquine (CQ). In particular, rhodium complexes were found to be considerably more active than iridium complexes against the CQS NF54 strain. Salicylaldimine Schiff base ligands having electron-withdrawing groups (F, Cl, Br, I and NO2) in para position of the salicyl moiety and their rhodium complexes showed good antiplasmodial activity against both the CQS-NF54 and the CQR-Dd2 strains. The crystal structures of (η5-pentamethylcyclopentadienyl){N1-(7-chloroquinolin-4-yl)-N2-(pyridin-2-ylmethyl)ethane-1,2-diamine)} chlororhodium(iii) chloride and (η5-pentamethylcyclopentadienyl){(4-chloro-2-(((2-((7-chloroquinolin-4-yl)amino)ethyl)imino)methyl)phenolate)}chlororhodium(iii) chloride are reported. The crystallization of the amino-pyridyl complex (η5-pentamethylcyclopentadienyl){(N1-(7-chloroquinolin-4-yl)-N2-(pyridin-2-ylmethyl)ethane-1,2-diamine)}chloroiridium(iii) chloride in acetone resulted in the formation of the imino-pyridyl derivative (η5-pentamethylcyclopentadienyl){(N1-(7-chloroquinolin-4-yl)-N2-(pyridin-2-ylmethylene)ethane-1,2-diamine)}chloroiridium(iii) chloride, the crystal structure of which is also reported. [ABSTRACT FROM AUTHOR]

The pentane σ-complex [Rh{Cy2P(CH2CH2)PCy2}(η2:η2-C5H12)][BArF4] is synthesized by a solid/gas single-crystal to single-crystal transformation by addition of H2 to a precursor 1,3-pentadiene complex. Characterization by low temperature single-crystal X-ray diffraction (150 K) and SSNMR spectroscopy (158 K) reveals coordination through two Rh⋅⋅⋅H−C interactions in the 2,4-positions of the linear alkane. Periodic DFT calculations and molecular dynamics on the structure in the solid state provide insight into the experimentally observed Rh⋅⋅⋅H−C interaction, the extended environment in the crystal lattice and a temperature-dependent pentane rearrangement implicated by the SSNMR data. [ABSTRACT FROM AUTHOR]

Dehydrogenative oxidation of amines is a relevant process in metal-mediated catalysis, with the amines being either substrates or ligands. Transformation of amine- into imine-type ligands in the coordination sphere of a transition metal can be an important catalyst activation process. The behaviour of secondary pyridin-2-ylmethanamine (pma) ligands in the corresponding rhodium and iridium complexes upon N H deprotonation varies, depending on a number of factors. In this paper the behaviour of the Me-pma ligand [Me-pma = N-methyl-1-(pyridin-2-yl)methanamine] bound to [Rh(cod)]+ and [Ir(cod)]+ was studied. Whereas the iridium amido complex could be obtained upon N H deprotonation, the rhodium complex instantaneously disproportionated into a free pma ligand and an unusual dinuclear complex, adopting a structure with two RhI metal centres hosted by a dianionic (pma-2 H)2- ligand, and with the ligand coordinating to Rh2 as an 'aza-allyl' fragment. The study gives further proof for the effect of pyridine ligation on the previously observed charge-transfer from the ligand to the metal. Furthermore, the catalytic activity of both the Ir and the Rh species with Me-pma in carbene carbonylation reactions to generate ketenes was studied. [ABSTRACT FROM AUTHOR]

The electrochemical behaviour of a series of rhodium(I) complexes of the type [Rh(CH 3 COCHCOCH 3 )CO(Ph 2 POPh- p -R)], where R = H ( 1 ), CH 3 ( 2 ), t Bu( 3 ) and Cl( 4 )] revealed an irreversible oxidation of Rh(I) to Rh(III), an irreversible oxidation of the phosphorus atom followed by the decomposition of the phosphinite ligand. An unexpected reaction occurred between the electrochemical internal standard, free ferrocene, in its ferricinium ion form and the radical cation of the oxidised diphenyl phosphinite, leading to uncharacteristic electrochemical behaviour. Electronic communication between different molecular fragment was confirmed by the linear relationships obtained between the Gordy group electronegativities of the R-groups on the phosphinites ( χ R ) and the E pa of Rh and the phosphorus atoms as well as the binding energy (eV) (measured by XPS) of the Rh 3d and P 2p peak positions. V-shape correlations were found between the Hammett constants of the R-groups on the phosphinites ( χ R ) and the oxidation potentials and binding energies. This shows the difference in stabilisation either resonance or inductive between the electrondonating and electronwithdrawing substituents. [ABSTRACT FROM AUTHOR]

Rhodium complexes coordinated by Chenphos are very effective catalysts for the enantioselective hydrogenation of α-aryloxy- and α-alkoxy-substituted α,β-unsaturated carboxylic acids under mild conditions in CF3CH2OH. The catalytic system could be successfully employed in building the core structure of a new FDA approved drug LCZ 696. [ABSTRACT FROM AUTHOR]

The reaction of [Rh(acac)(PPh 2 Py) 2 ] (acac = acetylacetonate, PPh 2 Py = 2−(diphenylphosphino)pyridine) with [Cp*Ru(CH 3 CN) 3 ][OTf] (Cp* = pentamethylcyclopentadienyl, OTf = trifluoromethanesulfonate) provides a cationic bimetallic complex [Cp*Ru(PPh 2 Py) 2 Rh(acac)][OTf], in which a ruthenium–rhodium coordinate (dative covalent) bond is formed. The structure was ascertained by single crystal X-ray diffraction. The catalytic performances of the bimetallic complex were evaluated in the hydroformylation reaction of 1-octene and compared to those of the in situ formed catalysts and the mononuclear counterparts. The catalysis results point out that the bimetallic complex is fragmenting under hydroformylation conditions, which was confirmed by NMR analysis. [ABSTRACT FROM AUTHOR]

The preparation and characterization of a dimeric RhIII complex containing two SSi ligands on each rhodium fragment is reported. {Rh[SiMe2( o-C6H4SMe)]2Cl}2 ( 1) was obtained by reaction of thioether-silane SiMe2H( o-C6H4SMe) ( L1) with [Rh(cod)Cl]2. Mixed-valent RhI/RhIII complex {(cod)Rh(μ-Cl)2Rh[SiMe2( o-C6H4SMe)]2} ( 2), which is an intermediate in the formation of 1, was isolated. Furthermore, 1H NMR spectroscopic monitoring revealed the formation of cyclooctenyl intermediates. The tridentate pincer proligand, SiMeH( o-C6H4SMe)2 ( L2), reacts with [Rh(cod)Cl]2 to yield a robust cyclooctenyl RhIII complex, {Rh(η3-cyclooctenyl)[SiMe( o-C6H4SMe)2]Cl} ( 3). Complexes 1- 3 were characterized by X-ray crystallography. [ABSTRACT FROM AUTHOR]

Cyclobutadiene rhodium complexes bear high potential for applications in organometallic synthesis and catalysis. We have found that the cyclobutadiene complexes with substitutionally labile p-xylene ligands [(C4R4)Rh( p-xylene)]+ can be synthesized in one step from the commercially available bis(ethylene) complex [{(C2H4)2RhCl}2], p-xylene, and internal alkynes. The replacement of p-xylene by various ligands provides a general access to other [(C4R4)Rh] compounds, such as [(C4R4)RhCl] x, [(C4R4)RhL3]+, [(C4R4)Rh(C5H5)], and [(C4R4)Rh(arene)]+. Complex [(C4Et4)Rh( p-xylene)]+ also catalyzes an unusual cycloisomerization of a 1,11-dien-6-yne into a bicyclic diene. [ABSTRACT FROM AUTHOR]

The first example of efficient asymmetric hydrogenation of challenging β-aryloxyacrylic acids was realized using a RhI-complex based on the heterocombination of a readily available chiral monodentate secondary phosphine oxide (SPO) and an achiral monodentate phosphine ligand as the catalyst. Excellent enantioselectivities (92->99 % ee) were achieved for a wide variety of chiral β-aryloxypropionic acids with minor aryloxy elimination in most cases. The resultant products were readily transformed into biologically active compounds through simple synthetic manipulations. [ABSTRACT FROM AUTHOR]

Rhodium(I) carbenes were generated from propargylic alcohol derivatives as the result of a dehydrative indole annulation. Depending on the choice of the electron-withdrawing group on the aniline nitrogen nucleophile, either a cyclopropanation product or dimerization product was obtained chemoselectively. Intramolecular hydroamidation occurred for the same type of propargylic alcohol derivatives when other transition-metal catalysts were employed. [ABSTRACT FROM AUTHOR]

It was ascertained that in carbamide- and acetamide-chloride melts at anodic dissolution of rhodium some mixed complexes [Rh(NH3)4Cl2]+ form which are of quasi-octahedral structure and D4h symmetry. During cathodic reduction of the obtained complexes Rh(III) in the investigated melts the synthesis of nanoparticles Rh was carried out as well as nanocoating of Fe, Cu and Mo by them. [ABSTRACT FROM AUTHOR]

Controlling the relative and absolute configuration of octahedral metal complexes constitutes a key challenge that needs to be overcome in order to fully exploit the structural properties of octahedral metal complexes for applications in the fields of catalysis, materials sciences, and life sciences. Herein, we describe the application of a proline-based chiral tridentate ligand to decisively control the coordination mode of an octahedral rhodium(III) complex. We demonstrate the mirror-like relationship of synthesized enantiomers and differences between diastereomers. Further, we demonstrate, using the established pyridocarbazole pharmacophore ligand as part of the organometallic complexes, the importance of the relative and absolute stereochemistry at the metal toward chiral environments like protein kinases. Protein kinase profiling and inhibition data confirm that the proline-based enantiopure rhodium(III) complexes, despite having all of the same constitution, differ strongly in their selectivity properties despite their unmistakably mutual origin. Moreover, two exemplary compounds have been shown to induce different toxic effects in an ex vivo rat liver model. [ABSTRACT FROM AUTHOR]

Herein we report that 1,4-dilithio-1,3-butadienes, a type of 1,3-butadienyl dianion, can act as non-innocent ligands, taking electrons from low-valent transition metals. Dilithio reagents reacted with [{RhCl(cod)}2] to give dilithio rhodacycle 3 a. Single-crystal X-ray structural analysis revealed the structure of 3 a with averaged bond lengths. XPS data suggested that the oxidation state of Rh in 3 a was more likely to be Rh3+. CDA/ECDA confirmed the electron-transfer process. 7Li NMR spectra of 3 a and theoretical calculations revealed a considerable aromatic character. In this process, the dilithio compounds behaved as non-innocent ligands and formal oxidants. These results demonstrated that organolithium compounds with suitable π-conjugation could be used as electron acceptor. [ABSTRACT FROM AUTHOR]

Electrophilic, cationic Rh(III) complexes of composition [(η5-C5Me5)Rh(Ap)]+, (1+), were prepared by reaction of [(η5-C5Me5)RhCl2]2 and LiAp (Ap = aminopyridinate ligand) followed by chloride abstraction with NaBArF (BArF = B[3,5-(CF3)2C6H3]4). Reactions of cations 1+ with different Lewis bases (e.g., NH3, 4-dimethylaminopyridine, or CNXyl) led in general to monoadducts 1·L+ (L = Lewis base; Xyl = 2,6-Me2C6H3), but carbon monoxide provided carbonyl-carbamoyl complexes 1·(CO)2+ as a result of metal coordination and formal insertion of CO into the Rh-Namido bond of complexes 1+. Arguably, the most relevant observation reported in this study stemmed from the reactions of complexes 1+ with H2. ¹H NMR analyses of the reactions demonstrated a H2-catalyzed isomerization of the aminopyridinate ligand in cations 1+ from the ordinary κ²-N,N' coordination to a very uncommon, formally tridentate κ-N,η³ pseudoallyl bonding mode (complexes 3+) following benzylic C-H activation within the xylyl substituent of the pyridinic ring of the aminopyridinate ligand. The isomerization entailed in addition H-H and N-H bond activation and mimicked previous findings with the analogous iridium complexes. However, in dissimilarity with iridium, rhodium complexes 1+ reacted stoichiometrically at 20 °C with excess H2. The transformations resulted in the hydrogenation of the C5Me5 and Ap ligands with concurrent reduction to Rh(I) and yielded complexes [(η4-C5Me5H)Rh(η6, (2+), in which the pyridinic xylyl substituent is 6-bonded to the rhodium(I) center. New compounds reported were characterized by microanalysis and NMR spectroscopy. Representative complexes were additionally investigated by X-ray crystallography. [ABSTRACT FROM AUTHOR]

A wide range of electron-poor 4-bromo-/4-chloro-2-azabuta-1,3-dienes were synthesized by the Rh 2 (OAc) 4 -catalyzed reaction of diazo esters and diazo ketones with methyl 2-halo-2 H -azirine-2-carboxylates. The E stereoselectivity with respect to the configuration of the C C bond of the 2-azadiene moiety is in good agreement with the results of DFT (M06-2X/6-31+G(d,p)) calculations of the reaction pathway. The reaction proceeds via the formation of an azirinium ylide intermediate followed by ring opening with outward rotation of the halogen atom. Depending on the substitution pattern at C 1 electron-poor 4-halo-2-azabutadienes can undergo two types of cyclization at elevated temperatures: reversible 1,4-electrocyclization to give 2,3-dihydroazetes or 1,5- exo - trig cyclization to give 5-methylene-2,5-dihydrooxazoles, both in good yields. The dihydrooxazole derivatives can be also obtained at ambient temperature under DBU catalysis. [ABSTRACT FROM AUTHOR]

The rhodium(i) silyl carbonyl complexes [Rh{Si(OEt)3}(CO)(dippp)] (1) and [Rh{Si(OEt)3}(CO)(dippe)] (2) (dippp = 1,3-bis(diisopropylphosphino)propane, dippe = 1,2-bis-(diisopropylphosphino)ethane) were synthesized on treatment of the methyl compounds [Rh(CH3)(CO)(dippp)] (3) or [Rh(CH3)(CO)(dippe)] (4) with HSi(OEt)3 at low temperature. The methyl complexes 3 and 4 were prepared starting from the binuclear complexes [{Rh(μ-Cl)(dippp)}2] (5) and [{Rh(μ-Cl)(dippe)}2] (8), respectively. The silyl complexes 1 and 2 as well as the precursors [{Rh(μ-I)(dippp)}2] (6), [Rh(X)(CO)(dippp)] (3: X = CH3, 7: X = I) and [Rh(X)(CO)(dippe)] (4: X = CH3, 9: X = Cl) were characterized by NMR and IR spectroscopy and the structures in the solid state were determined by X-ray crystallography. The silyl complex 1 converts into the carbonyl-bridged complex [{Rh(μ-CO)(dippp)}2] (10) above temperatures of −30 °C by loss of the silyl ligand, whereas 2 is more thermally stable and a reaction to the binuclear complex [{Rh(μ-CO)(dippe)}2] (11) was observed at 50 °C. The silyl complex 2 reacted under irradiation with hexafluorobenzene and pentafluoropyridine to give the C–F activation products [Rh(C6F5)(CO)(dippe)] (12) and [Rh(2-C5F4N)(CO)(dippe)] (17), respectively. As additional products the silyl dicarbonyl complex [Rh{Si(OEt)3}(CO)2(dippe)] (13) and the cationic complex [Rh2(μ-H)(μ-CO)2(dippe)2]+[SiF5]− (14) were identified. Compound 13 was synthesized independently by treatment of 2 with gaseous CO. In a similar manner, the dippp analogue [Rh{Si(OEt)3}(CO)2(dippp)] (15) was also prepared starting from 1. Photochemical reaction of 2 with pentafluorobenzene and 2,3,5,6-tetrafluoropyridine resulted selectively in C–H bond activation to afford 12 and [Rh(4-C5F4N)(CO)(dippe)] (18), respectively. [ABSTRACT FROM AUTHOR]

A series of complexes of novel chelating thione-alkene S(η2-C=C)S tridentate ligands bound to late transition metals (Ir, Rh, Pd) were isolated and characterised. Counter-anions play an important role in the binding of the alkene moiety to the metals. Different solvents were observed to affect the stability of the rhodium complexes. [ABSTRACT FROM AUTHOR]

Metallaheteroboranes are versatile compounds that can be conveniently modified and eventually tailored by ligand modification at either the metal centre or the boron vertices. Recently, we have discovered that protonation of some rhodathiaboranes affords cationic clusters with interesting reaction chemistry. In order to tune the reactivity of some of these polyhedral boron-based compounds, we have prepared air-stable orange [1,1-(η2-dppe)-3-(NC5H5)-closo-1,2-RhSB9H8] (2) by the treatment of the known hydridorhodathiaborane [8,8,8-(H)(PPh3)2-9-(NC5H5)-nido-8,7-RhSB9H9] (1) with dppe. The new 11-vertex rhodathiaborane, 2, reacts readily with triflic acid (TfOH) in CH2Cl2 to give orange cationic [8,8-(η2-dppe)-9-(NC5H5)-nido-8,7-RhSB9H9]+ (3). VT NMR experiments have allowed the characterization of a structural closo↑nido tautomerism, which involves hapticity changes in the ligation of the {SB9H9-(NC5H5)} moiety to the {Rh(dppe)} fragment, with the proton moving between the Rh(1)–B(3) and the B(9)–B(10) edges of the closo- and nido-isomers, respectively. The proton enhances the stereochemical non-rigidity and Lewis acidity of 3versus the neutral 2. This modification of the chemical and structural basis permits the efficient heterolytic splitting of the H–H bond, leading to the formation of new hydridorhodathiaborane isomers [8,8,8-(H)(η2-dppe)-μ-8,9-(H)-9-(NC5H5)-nido-8,7-RhSB9H10]+ (4) that are in equilibrium with the reactants, H2 and 3. [ABSTRACT FROM AUTHOR]