Complexation of Rh(III) in diluted sulfuric acid solutions

Complex formation in a system Rh(III)-H₂SO₄-H₂O was studied by the ¹⁰³Rh and ¹⁷O NMR spectroscopy at room temperature. The formation of two interrelated systems of mononuclear and polynuclear complexes was established in the above solutions. The predominant species in the first system is a labile ionic pair {Rh(H₂O) ₆ ³⁺ SO ₄ ^2? }⁺, while in the second system, two inert binuclear complexes [Rh₂(μ-SO₄)₂(H₂O)₈]²⁺ and [Rh₂(μ-SO₄)(μ-OH)(H₂O)₈]³⁺ prevail.     

Nitration of rhodium(III) sulfates

Nitration of sulfate complexes of rhodium has been investigated by NMR ¹⁰³Rh, ¹⁴N, ¹⁵N, and ¹⁷O NMR. At high pH, [Rh(NO₂)₆]^3?, dimer [Rh₂(μ-OH)₂(NO₂)₈]^4?, and trimer [Rh₃(μ-OH)₄(OH)(NO₂)₉]^5? are the dominant species in solutions.     

Catalytic properties of binuclear rhodium(II) complexes in hydrogenation and isomerization of allylbenzene

Binuclear hexafluoroacetylacetonate complexes of Rh(II) with axial ligands (Py, H₂O) exhibit activity in hydrogenation and isomerization of allylbenzene, and the isomerization reaction also takes place in an atmosphere of Ar. The catalytic system [Rh₂(hfacac)₄(H₂O)₂]-Ph₃P is much more active than Rh(II) hexafluoroacetylacetonate complexes in transformation of allylbenzene. Treatment of the acetate complex [Rh₂(O₂CCH₂)₄] with sodium borohydride significantly increases its activity, probably due to the formation of [Rh₂(O₂CCH₃)₃]⁺ and [Rh₂(O₂CCH₂)₂]²⁺ complexes.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 1957–1961, September, 1989.     

Polynuclear rhodium complexes of phenothiazines: synthesis and characterization

Polynuclear complexes of RH^II and RH^III with fiveN-alkylphenothiazines as principal ligands have been prepared. The complexes were characterized by their elemental analyses, molar conductivities, and spectral data. The molecular formulae of the new complexes are as follows: [Rh₃(PTZ)₂(OH₂)₂Cl₈]Cl, where PTZ=chlorpromazine or promethazine; [Rh₃(EP)₂(OH₂)₂Cl₈][Rh(OH₂)₂Cl₄], where EP=ethopropazine; [Rh₄(TF)₂(OH₂)₅Cl₉]Cl·H₂O, where TF=trifluoperazine; and [Rh₂(TC)₃(OH₂)Cl₆]. H₂O, where TC=2-chlorophenothiazine. A tentative structure for each of the complexes is proposed. TMC 2627     

Halide substitutions in the [Rh2(O f2 p− )(OH)2(H2O) n ]3+ complex

Summary Transition metal complexes containing activated dioxygen continue to attract considerable attention and are widely used as models, either as oxygen carriers or as catalysts in biological and industrial oxidations ^(1,2).Cobalt complexes containing the coordinated O₂ molecule are well known^(3,4), but the rhodium analogues are rare^(5–8). The known complexes with coordinated O₂ are rhodium(III) compounds containing strong nitrogen donor ligands.Our recent studies have focused on a synthesis of dioxygen rhodium derivatives in which a superoxide anion (O _f2 ^p– ) is bound to the [Rh^III—Rh^III] core surrounded by other donor molecules, e.g. H₂O, RCO _f2 ^p– (7,8), to investigate the effect of a coordination sphere of the metal centre on the redox properties of the O _f2 ^p– radical combined to it⁽⁹⁾.The [Rh₂(O _f2 ^p– )(OH)₂(H₂O) _n ]³⁺ cation, the product of oxidative addition of dioxygen to the [Rh₂(H₂O)₁₀]⁴⁺ dimer, was isolated by us and examined in aqueous HC1O₄ ^(7,9). So far we have been unable to isolate its solid but the water molecules coordinated to the [Rh₂(O _f2 ^p– )-(OH)₂] ³⁺ moiety were found to undergo substitution relatively easily⁽⁸⁾.     

Platinum(IV) complexation with the nitrate ion in aqueous solutions according to 195Pt, 15N, 14N, and 17O NMR data

Solutions of platinum(IV) nitrate were studied by ¹⁹⁵Pt, ¹⁵N, ¹⁴N, and ¹⁷O NMR and IR and Raman spectroscopy. It was found that in nitric acid, two interrelated systems of nitrate complexes, mono- and polynuclear ones, coexist. The complexes predominating in concentrated solutions are [Pt₂(μ-OH)(μ-NO₃)(NO₃)₂(H₂O)_{6 ? x} (OH) _x ]^{(4 ? x)+}, [Pt₄(μ-OH)₃(μ-NO₃)₃(NO₃)₃(H₂O)_{9 ? x} (OH) _x ]^{(7 ? x)+}, [Pt4(μ-OH)₄(μ-NO₃)₂(NO₃)₄(H₂O)_{8 ? x} (OH) _x ]^{(6 ? x)+}, and [Pt₄(μ-OH)₆(NO₃)₃(H₂O)_{16 ? x} (OH) _x ]^{(7 ? x)+}.     

The Effect of Concentration Parameters on Complexation in the Iron(0)–Iron(II)–Glycine–Water System

The processes of formation of iron(II) complexes in aqueous glycine solutions in the pH range of 1.0–8.0 at 298 K and ionic strength of 1 mol/L (NaClO₄) are studied using Clark and Nikolskii’s oxidation potential method. The type and number of coordinated ligands, the nuclearity, and the total composition of the resulting complexes are determined. The following complex species are formed in the investigated system: [Fe(OH)(H₂O)₅]⁺, [FeHL(H₂O)₅]²⁺, [Fe(HL)(OH)(H₂O)₄]⁺, [Fe(OH)₂(H₂O)₄]⁰, [Fe₂(HL)₂(OH)₂(H₂O)₈]²⁺, and [Fe(HL)₂(H₂O)₄]²⁺. Their formation constants are calculated by the successive iterations method using Yusupov’s theoretical and experimental oxidation function. The model parameters of the resulting coordination compounds are determined.     

Binuclear rhodium(II) complexes with leucine and proline

The dimeric rhodium(II) complexes [Rh₂(leu)₄(H₂O)₂]- (ClO₄)₄ and [Rh₂(pro)₄(H₂O)₂](ClO₄)₄ have been prepared and characterized by elemental analyses, i.r., u.v.–vis. and ¹H-n.m.r. spectroscopy. The amino acid molecules are coordinated as bridging ligands via their carboxylato groups. Cyclic voltammetry in DMF has shown that the complexes undergo a quasi-reversible reduction to yield dimers containing a Rh ₂ ³⁺ core. Oxidation processes within the 0–1.5V range were not observed.     

A DFT study of uranyl hydroxyl complexes: structure and stability of trimers and tetramers

A DFT study of U(VI) hydroxy complexes was performed with special attention paid to the [(UO₂)₃(OH)₅(H₂O)_4–7]⁺ and [(UO₂)₄(OH)₇(H₂O)_5–8]⁺ species. It was established that the ionicity of the U=O bond increased when moving from [(UO₂)(H₂O)₅]²⁺, [(UO₂)₂(OH)(H₂O)₈]³⁺, [(UO₂)₂(OH)₂(H₂O)₆]²⁺, [(UO₂)₃(OH)₅(H₂O)_4–6]⁺ to [(UO₂)₄(OH)₇(H₂O)_5–8]⁺ species. In both [(UO₂)₃(OH)₅(H₂O)_4–6]⁺ and [(UO₂)₄(OH)₇(H₂O)_5–8]⁺ complexes, the U=O bond was observed to have a range of different lengths which depended on the composition of the first coordination sphere of UO₂ ²⁺. The cyclic structures of trimeric complexes were somewhat more stable than their linear structures, which was probably due to the steric effect.

     

Synthese und Charakterisierung von Trimethyl(sulfato)platin(IV)Komplexen

Syntheses and Characterization of Trimethyl(sufato)platinum(IV) Complexes [(PtMe₃I)₄] ( 1 ) reacts in benzene/acetone (1 : 1) with excess of freshly precipitated silver sulfate (Pt : Ag = 1 : 2) to give [{[PtMe₃(H₂O)]₂SO₄}_∞] ( 2 ) at working up from acetone (not dried) and water to [{PtMe₃(H₂O)₂}₂SO₄] ( 3 ), respectively. [(PtMe₃I)₄] ( 1 ) reacts with AgBF₄ in the corresponding solvent L to give complexes of the type [PtMe₃L₃]BF₄ (L = Me₂CO 4 , MeOH 5 , MeCN 6 , THF 7 ). The triaqua complex 8 (L = H₂O) has been obtained by reaction of 4 with water. All complexes are characterized by microanalysis and NMR spectroscopy (¹H, ¹³C, ¹⁹⁵Pt). X-ray diffraction analysis of 2 (monoclinic, P2₁) exhibits dinuclear units [Me₃Pt(μ-H₂O)PtMe₃(H₂O)]²⁺ at which oxo ligands of sulfate ions are coordinated in such a way that the crystal is threaded by double chains. The Pt–O bonds to μ-aqua ligand are considerably longer than that to terminal aqua ligand (2.322(9)/2.363(8) vs. 2.234(9) Å). The structural characterization of 3 (triclinic, P 1) reveals [PtMe₃(H₂O)₂]⁺ cations that are bridged by a sulfate ion yielding a dinuclear entity [(H₂O)₂Me₃Pt(μ-SO₄)PtMe₃ · (H₂O)₂]. These entities are linked in the crystal by a network of hydrogen bridges.     

Radiation reduction of binuclear Rh(II) complexes in aqueous-methanol solutions

Radiation reduction of binuclear [Rh₂(OAc)₂(phen)₂(H₂O)₂](OAc)₂, [Rh₂(OAc)(tpy)₂Cl₂]Cl·2H₂O and [Rh₂Cl₂(HCOO)₂(bpy)₂]·4H₂O complexes in aqueous-methanol solution have been studied. The reduction yields as equal to ca. 6 equiv/100eV and the rate constants of reactions: complex+e _solv ⁻ as equal to 2.9·10¹⁰, 3.2·10¹⁰ and 3.7·10¹⁰ M⁻¹·s⁻¹, respectively, have been determined. On the basis of electronic spectra it has been shown that Rh(II) compounds were reduced giving several Rh(I) complexes being in equilibrium. The mechanism of the processes has been discussed.     

Physicochemical study of rhodium sulfite

Diamagnetic rhodium sulfite Na₁₅(NH₄)₃[Rh₄(μ-SO₃)₆(SO₃)₇(H₂O)₅]·10H₂O was synthesized. An X-ray photoelectron spectroscopy study and chemical analysis revealed that rhodium in this compound was in the oxidation state 2+. The thermal and chemical properties of the compound were investigated. Based on XRPA, IR, and EPR spectroscopy and analytical data about the chemical properties, a hypothesis about the structure of the complex has been formulated.     

Synthese und dynamisches Verhalten von [Rh2(μ-H)3H2(PiPr3)4]+. Beiträge zur Reaktivität des Tetrahydridodirhodium-Komplexes [Rh2H4(PiPr3)4]

Synthesis and Dynamic Behaviour of [Rh₂(μ-H)₃H₂(PiPr₃)₄]⁺. Contributions to the Reactivity of the Tetrahydridodirhodium Complex [Rh₂H₄(PiPr₃)₄] An improved synthesis of [Rh₂H₄(PiPr₃)₄] ( 2 ) from [Rh(η³-C₃H₅)(PiPr₃)₂] ( 1 ) or [Rh(η³-CH₂C₆H₅)(PiPr₃)₂] ( 3 ) and H₂ is described. Compound 2 reacts with CO or CH₃OH to give trans-[RhH(CO)(PiPr₃)₂] ( 4 ) and with ethene/acetone to yield a mixture of 4 and trans-[RhCH₃(CO)(PiPr₃)₂] ( 5 ). The carbonyl(methyl) complex 5 has also been prepared from trans-[RhCl(CO)(PiPr₃)₂] ( 6 ) and CH₃MgI. Whereas the reaction of 2 with two parts of CF₃CO₂H leads to [RhH₂(η²-O₂CCF₃) · (PiPr₃)₂] ( 8 ), treatment of 2 with one equivalent of CF₃CO₂H in presence of NH₄PF₆ gives the dinuclear compound [Rh₂H₅(PiPr₃)₄]PF₆ ( 9a ). The reactions of 2 with HBF₄ and [NO]BF₄ afford the complexes [Rh₂H₅(PiPr₃)₄]BF₄ ( 9b ) and trans-[RhF(NO)(PiPr₃)₂]BF₄ ( 11 ), respectively. In solution, the cation [Rh₂(μ-H)₃H₂(PiPr₃)₄]⁺ of the compounds 9a and 9b undergoes an intramolecular rearrangement in which the bridging hydrido and the phosphane ligands are involved.     

The synthesis of platinum and palladium cluster compounds with isocyanide or functionalised phosphine ligands. Crystal structures of [Pt5(CO)(μ-CO)5{Ph2PCH2C(O) Ph}4 and [Pt5(μ-CNC6H3Me2-2, 6)3(CNC6H3Me2-2, 6)5 {Ph2PCH2C(O) Ph}2]

The reaction of the ketophosphine ligand Ph₂PCH₂C(O)Ph (P～O) with [PtCl₂(NCMe)₂] and carbon monoxide in THF in the presence of an excess of zinc afforded the 70 electron pentanuclear cluster [Pt₅(CO)(μ-CO)₅(P～O)₄] (1). Reaction of the palladium(0) complex [Pd₂(dba)₃] CHCl₃ (dba = dibenzylideneacetone) with Ph₂PCH₂C(O)R [R = Ph or C₅H₄Fe(C₅H₅)] under SO₂ led to the pentapalladium cluster compounds [Pd₅(μ₃-SO₂)₂ (μ-SO₂)₂ {Ph₂PCH₂C(O)R}₅] (2a,R = Ph;2b,R = C₅H₄Fe(C₅H₅)), Cluster (1) reacts with 2,6-xylyl isocyanide, CNC₆H₃Me₂-2,6 to give a red cluster of formula [Pt₅(μ-CNC₆H₃Me₂-2, 6)₃ (CNC₆H₃Me₂-2, 6)₅ (P～O)₂] (3) and a green complex (4). The corresponding complexes (6) and (7) were also obtained by using PPh₃ instead of P～O. Clusters (2a) and (2b) react with [NEt₃Bz] Cl to give[NEt₃Bz][Pd₃(μ-SO₂)₂ (μ-Cl){Ph₂PCH₂C(O)R}₃](8a,R = Ph;8b,R = C₅H₄Fe(C₅H₅)). The molecular structures of (1) and (3) were determined by single-crystal X-ray diffraction analyses.     

Hepta­aqua­tetra‐μ3‐hydroxy‐hexa‐μ2‐l‐leucine‐(l‐leucine)­tetraytterbium(III) tetrachlorozinc(II) tri­chloro­hydroxyzinc(II) tetrachloride octahydrate

The title bimetallic compound, [Yb₄(μ₃‐OH)₄(C₆H₁₃NO₂)₇(H₂O)₇][ZnCl₄][ZnCl₃(OH)]Cl₄·8H₂O, was synthesized at near physiological pH (6.0). The compound exhibits some novel structural features, including an asymmetric [Yb₄(μ₃‐OH)₄(l ‐leucine)₇(H₂O)₇]⁸⁺ complex cation in which four OH groups act as bridging ligands, linking four Yb³⁺ cations into a Yb₄O₄ structural unit. Each pair of adjacent Yb³⁺ ions is further bridged by one carboxy group from a leucine ligand. Water mol­ecules and a monodentate leucine ligand also coordinate to Yb³⁺ ions, completing their eight‐coordinate square‐antiprismatic coordination. The Yb₄(μ₃‐OH)₄(l ‐leu­cine)₇(H₂O)₇]⁸⁺ cation, the [ZnCl₄]²⁻, [ZnCl₃OH]²⁻ and Cl⁻ anions, and the lattice water mol­ecules are linked via hydrogen bonds.     

Ten complexes constructed by two reduced Schiff base tetraazamacrocycle ligands: syntheses,structures, magnetic and luminescent properties

Ten new complexes, [Cu₂(L¹)(NO₃)₂]·2H₂O (1), [Cu₄(L¹)₂]·4ClO₄·H₂O (2), [Cu₂(L¹)(H₂O)₂]·(adipate) (3), [Cu₆(L¹)₂(m-bdc)₄]·2DMF·5H₂O (4), [Cu₂(L¹)(Hbtc)]·5H₂O (5), [Cu₂(L¹)(H₂O)₂]·(ntc)·3H₂O (6), [Co₂(L²)]·[Co(MeOH)₄(H₂O)₂] (7), [Co₃(L²)(EtOH)(H₂O)] (8), [Ni₆(L²)₂(H₂O)₄]·H₂O (9) and [Zn₄(L²)(OAc)₂]·0.5H₂O (10), have been synthesized. 1 displays a [Cu₂(L¹)(NO₃)₂] monomolecular structure. 2 shows a supramolecular chain including [Cu₂L¹]²⁺. In 3, two Cu(II) ions are connected by L¹ to form a [Cu₂(L¹)(H₂O)₂]²⁺ cation. In 4, the m-bdc anions bridge Cu(II) ions and L¹ anions to form a layer. Both 5 and 6 display 3-D supramolecular structures. 7 consists of both [Co₂L²]^2? and [Co(MeOH)₄(H₂O)₂]²⁺ units. 8 and 9 show infinite chain structures. In 10, Zn(II) dimers are linked by L² to generate a 3-D framework. The magnetic properties for 4 and 8 and the luminescent property for 10 have been studied.     

Hydrothermal synthesis and characterization of LaIII and CuII coordination polymers with 5-nitroisophthalic acid (H2Nip), [La2(μ-Nip)(μ-SO4)2(H2O)5] n and {[Cu3(μ-OH)2(μ-Nip)2(μ-H2O)2] · 2H2O} n

3D La^III and 2D Cu^II coordination polymers with 5-nitroisophthalate anions, [La₂(μ-Nip)(μ-SO₄)₂(H₂O)₅] _n (1) and {[Cu₃(μ-OH)₂(μ-Nip)₂(μ-H₂O)₂] ·?2H₂O} _n (2), have been synthesized, characterized and studied by X-ray crystallography. The La atoms have eight–coordinate geometries in distorted square antiprism environments and the Cu atoms have five- and six–coordinate geometries with distorted square pyramidal and octahedral environments. Self-assembly of these compounds in the solid state occurs through coordination and hydrogen bonding.     

Chemie der Seltenerdmetalle, 11. Mitt.: Yttriumtartratkomplexe im sauren Bereich

Zusammenfassung Es wurde ein systematisches Studium des Systems im sauren Bereich durchgeführt. Aus den Ergebnissen der pH-Messungen wurden die Gleichgewichtskonstanten der Komplexe [YH₃ T]²⁺, [YH₂ T]⁺, [Y₂H₂ T]⁴⁺, [Y(H₂ T)₂]^– und HYT bestimmt. Es wurden die Verbindungen Y₂(H₂ T)₃ · 8 H₂O, Y₂(H₂ T)₃ · 5 H₂O und H[Y(H₂ T)₂] · 3 H₂O isoliert. Diese wurden mit Hilfe von Röntgenstreuung, Thermoanalyse und IR-Absorptionsspektren untersucht.

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A systematic investigation of the system in the acidic range was undertaken. The equilibrium constants of the complexes [YH₃ T]²⁺, [YH₂ T]^–, [Y₂H₂ T]⁴⁺, [Y(H₂ T)₂]^– and HYT were determined, making use of the results of p_H-measurements. The compounds Y₂(H₂ T)₃ · 8 H₂O, Y₂(H₂ T)₃ · 5 H₂O and H[Y(H₂ T)₂] · 3 H₂O were isolated. Their X-ray diffraction, thermal analysis and IR spectra were investigated.

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Mit 2 Abbildungen

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Zugleich 24. Mitt. der Reihe: Koordinationsverbindungen von organischen Oxoubstanzen; H₄ T=C₄H₆O₆.     

Paddlewheel dirhodium complexes bridged by para‐substituted benzoates

The dirhodium complex bis­(benzonitrile)tetra­kis[μ‐4‐(diethyl­amino)benzoato‐κ²O:O′]dirhodium(II)(Rh—Rh) benzonitrile disolvate, [Rh₂(C₁₁H₁₄NO₂)₄(C₇H₅N)₂]·2C₇H₅N, lies about an inversion centre. The dirhodium complex (methanol)tetra­kis(μ‐4‐nitro­benzoato‐κ²O:O′)(pyridine)dirhodium(II)(Rh—Rh) dichloro­methane solvate, [Rh₂(C₇H₄NO₄)₄(C₅H₅N)(CH₄O)]·CH₂Cl₂, lies in a general position in the unit cell, but the complexes dimerize around an inversion centre via O—H⋯O hydrogen bonding of the axial MeOH to a carboxyl­ate O atom. In the latter crystal structure, π–π stacking inter­actions between the bridging 4‐nitro­benzoate ligands and the axial pyridine ligand are observed between adjacent mol­ecules.     

Mechanistic Studies on the Oxidation of Nitrite by a μ‐Oxodiiron(III,III) Complex in Aqueous Acidic Media

Examined in this study is the kinetics of a net 2e⁻ transfer between [Fe₂(μ‐O)(phen)₄(H₂O)₂]⁴⁺ ( 1 ) and its hydrolytic derivatives [Fe₂(μ‐O)(phen)₄(H₂O)(OH)]³⁺ ( 2 ) and [Fe₂(μ‐O)(phen)₄(OH)₂]²⁺ ( 3 ) with in aqueous media and in presence of excess 1,10‐phenanthroline (phen). The reaction is quantitative with a 1 : 1 stoichiometry between the oxidant and reductant to produce ferroin ([Fe(phen)₃]²⁺) and . The order of reactivity of the oxidant species is 1 > 2 > 3 , in agreement with the progressive cationic charge reduction. The reactions appear to be inner‐sphere where the initial one‐electron proton‐coupled redox (1e⁻, 1H⁺; electroprotic) seems to be rate‐determining.