Interaction between FeRu bimetallic carbonyl clusters and oxide Supports. III. Mechanism of interaction and decomposition on hydrated alumina

Initial steps of the interaction of Ru₃(CO)₁₂, Fe₃(CO)₁₂, Fe₂Ru(CO)₁₂ and H₂FeRu₃(CO)₁₃ clusters with hydrated alumina surfaces have been studied by FT-IR spectroscopy combined with data handling procedures. The first stage of the interaction is a pure physisorption. At the second stage the metal-metal bonds split producing a large variety of mobile subcarbonyls. In the case of Fe₃(CO)₁₂ the subcarbonyls form molecular Fe(CO)₅, while at the bimetallic clusters they form molecular Fe- (CO)₅ and Ru₃(CO)₁₂. Fe(CO)₅ loses CO ligands producing Fe²⁺ and Fe³⁺ anchored ions. Ru₃(CO)₁₂, through further intermediate subcarbonyls, slowly decomposes into incipient anchored species Ru^O- (CO)₂, Ru^II(CO)₂ and Ru^III(CO)₂.     

6-Halogenopyridin-2-olato complexes with the diruthenium(2+) core: Equilibria between head-to-head and head-to-tail structures

The dinuclear bis(6-X-pyridin-2-olato) ruthenium complexes [Ru₂(μ-XpyO)₂(CO)₄(PPh₃)₂] (X = Cl (4B) and Br (5B)), [Ru₂(μ-XpyO)₂(CO)₄(CH₃CN)₂] (X = Cl (6B), Br (7B) and F (8B)) and [Ru₂(μ-ClpyO)₂(CO)₄(PhCN)₂] (9B) were prepared from the corresponding tetranuclear coordination dimers [Ru₂(μ-XpyO)₂(CO)₄]₂ (1: X = Cl; 2: X = Br) and [Ru₂(μ-FpyO)₂(CO)₆]₂ (3) by treatment with an excess of triphenylphosphane, acetonitrile and benzonitrile, respectively. In the solid state, complexes 4B-9B all have a head-to-tail arrangement of the two pyridonate ligands, as evidenced by X-ray crystal structure analyses of 4B, 6B and 9B, in contrast to the head-to-head arrangement in the precursors 1-3. A temperature- and solvent-dependent equilibrium between the yellow head-to-tail complexes and the red head-to-head complexes 4A-7A and 9A, bearing an axial ligand only at the O,O-substituted ruthenium atom, exists in solution and was studied by NMR spectroscopy. Full ¹H and ¹³C NMR assignments were made in each case. Treatment of 1 and 2 with the N-heterocyclic carbene (NHC) 1-butyl-3-methylimidazolin-2-ylidene provided the complexes [Ru₂(μ-XpyO)₂(CO)₄(NHC)], X = Cl (11A) or Br (12A). An XRD analysis revealed the head-to-head arrangement of the pyridonate ligands and axial coordination of the carbene ligand at the O,O-substituted ruthenium atom. The conversion of 11A and 12A into the corresponding head-to-tail complexes was not possible.     

Generation of trans-dioxoruthenium(VI) porphyrins: A photochemical approach

trans-Dioxoruthenium(VI) porphyrin complexes have been developed as one of the best-characterized model systems for heme-containing enzymes. Traditionally, this type of compounds can be prepared by oxidation of ruthenium(II) precursors with peroxyacids and other terminal oxidants under different conditions, depending on the porphyrin ligands. In this work, a new photochemical generation of trans-dioxoruthenium(VI) porphyrins has been developed by extension of the known photo-induced ligand cleavage reactions. Refluxing ruthenium(II) carbonyl porphyrins [Ru^II(Por)(CO)] in carbon tetrachloride afforded dichlororuthenium(IV) complexes [Ru^IV(Por)Cl₂]. Facile exchange of the counterions in [Ru^IV(Por)Cl₂] with Ag(ClO₃) or Ag(BrO₃) gave the corresponding dichlorate [Ru^IV(Por)(ClO₃)₂] or dibromate [Ru^IV(Por)(BrO₃)₂] salts. Visible-light photolysis of the photo-labile porphyrin-ruthenium(IV) dichlorates or dibromates resulted in homolytic cleavage of the two O-Cl or O-Br bonds in the axial ligands to produce trans-dioxoruthenium(IV) species [Ru^VI(Por)O₂] bearing different porphyrin ligands.     

Ru2(CO)4(OOCR)2(PPh3)2 sawhorse-type complexes containing μ2-η-carboxylato ligands derived from biologically active acids

The thermal reaction of Ru₃(CO)₁₂ with the biologically active acids acetyl salicylic acid (Aspirin), α-methyl-4-(isobutyl)phenylacetic acid (Ibuprofen) and 3α,7α,12α-trihydroxy-5β-cholanic acid (cholic acid) in refluxing tetrahydrofuran, followed by addition of triphenylphosphine, gives the dinuclear complexes Ru₂(CO)₄(OOCR)₂(PPh₃)₂ (1: R = C₆H₄-2-OCOMe, 2: R = CHMe-C₆H₄-4-Buⁱ, 3: C₂₃H₃₉O₃). The single-crystal structural analysis of 1 and 2 reveals a dinuclear Ru₂(CO)₄ sawhorse structure, the diruthenium backbone being bridged by the carboxylato ligands, while the two phosphine ligands occupy the axial positions at the ruthenium atoms. However, chiral carbon atoms in the carboxylic acid undergo racemisation during the thermal reaction.     

Bis(dimethylphosphino)methane complexes of ruthenium carbonyl

Reaction of Me₂PCH₂PMe₂ with [Ru₃(CO)₁₂] in a 1:1 or 2:1 ratio in the presence of [(Ph₃P)₂N]CN catalyst gives [Ru₃(CO)₁₀(μ-Me₂PCH₂PMe₂)] and [Ru₃(CO)₈(μ-Me₂PCH₂PMe₂)₂] respectively. The complexes were characterized by elemental analysis, IR and ¹H and ³¹P NMR spectroscopies.     

The reaction of bis(isopropylphosphino)methane with ruthenium carbonyl

Reaction of ⁱPrHPCH₂PHⁱPr with [Ru₃(CO)₁₂] in the presence of [(Ph₃P)₂N]CN catalyst gave sequentially [Ru₃(CO)₁₀(μ-ⁱPrHPCH₂PHⁱPr)] and [Ru₃- (CO)₉(μ-H)(μ₃-ⁱPrHPCH₂PⁱPr)]. The former complex exists in two isomeric forms. The structures were determined by ¹H and ³¹P NMR spectroscopy.     

Electrochromic properties of mixed valence binuclear ruthenium complexes adsorbed on nanocrystalline SnO2 films

The electrochromic properties of two new mixed valence ruthenium complexes: K[(NC₅H₄CH₂PO₃H₂)Ru^III(NH₃)₄(NC)Ru^II(CN)₅] and K[(NC₅H₄PO₃H₂)Ru^III(NH₃)₄(NC)Ru^II(CN)₅], where phosphonic acid groups have been introduced at the pyridine ligand, have been studied in homogeneous solution and adsorbed on transparent nanocrystalline SnO₂ electrodes. These species exhibit a superior stability with respect to the previously studied, K[(NC₅H₄CO₂H)Ru^III(NH₃)₄NCRu^II(CN)₅] complex, showing negligible optical density changes after cycling 20 000 times the electrodes between −0.5 and 0.5 V versus SCE.     

Syntheses and molecular structures of 6-halogeno-pyridin-2-olate complexes with the diruthenium(2+) core

The complexes [Ru₂(CO)₅(μ-FpyO)₂]₂ (1), [Ru₂(CO)₄(μ-ClpyO)₂]₂ (2), and [Ru₂(CO)₄(μ-BrpyO)₂]₂ (3) were prepared from Ru₃(CO)₁₂ and 6-fluoro-2-hydroxypyridine (FpyOH), 6-chloro-2-hydroxypyridine (ClpyOH) and 6-bromo-2-hydroxypyridine (BrpyOH), respectively, in hot toluene. Compounds 1-3 are coordination dimers with a cyclo-RuORuO motif. By carrying out the reaction in hot methanol, the dinuclear complexes [Ru₂(CO)₄(μ-ClpyO)₂(CH₃OH)] (4) and [Ru₂(CO)₄(μ-BrpyO)₂(CH₃OH)] (5), respectively, were obtained. Treatment of 2 and 3 with triphenylphosphane provided the complexes [Ru₂(CO)₄(μ-ClpyO)₂(PPh₃)] (6) and [Ru₂(CO)₄(μ-BrpyO)₂(PPh₃)] (7), respectively. The solid-state structures of complexes 1, 2, 4, 6, and 7 were determined by single crystal X-ray diffraction. In all cases, a head-head coordination of the two 6-halopyridinolate ligands at the core was found. In all chlorine- or bromine-containing complexes, the axial coordination site at the ruthenium atom neighbored by two Cl or Br atoms remains unoccupied due to steric shielding by the halogen atom. In the fluoropyridinolate complex 1, the same coordination site is occupied by a carbonyl ligand.     

Dinuclear ruthenium sawhorse-type complexes containing carboxylato bridges and ferrocenyl substituents: Synthesis and electrochemistry

The ferrocenyl-containing diruthenium complexes [Ru₂(CO)₄(μ₂-η²-OOCFc)₂L₂] (Fc = ferrocenyl, fc = ferrocen-1,1′-diyl; 1: L = NC₅H₄-COOC₆H₄-OC₁₀H₂₁, 2: L = NC₅H₄-COOC₆H₄-OC₁₆H₃₃, 3: L = NC₅H₄-OOC-fc-C₁₂H₂₅) and [Ru₂(CO)₄(μ₂-η²-OOC₆H₅)₂(NC₅H₄-OOC-fc-C₁₂H₂₅)₂] (4) have been synthesized from Ru₃(CO)₁₂, ferrocene carboxylic or benzoic acid and the corresponding pyridine derivative. The synthesis of the new pyridine derivative NC₅H₄-OOC-fc-C₁₂H₂₅ used for the preparation of 3 and 4 is also reported. Complexes 1-4 posses a so-called sawhorse structure consisting of the Ru₂(CO)₄ backbone and two bridging carboxylato ligands, while the coordination sphere around the ruthenium atoms is completed by the pyridine-derived ligands bonded in the axial positions. The electrochemical behavior of 1-4 and their known analogues [Ru₂(CO)₄(μ₂-η²-OOCFc)₂L₂] (5: L = NC₅H₅, 6: L = P(C₆H₅)₃, 7: L = NC₅H₄-OOCFc) has been studied by voltammetry on rotating disc electrode and by cyclic voltammetry.     

New ruthenium complexes from Ru3(CO)12 and 6-Alkyl- or 6-Phenyl-2-hydroxypyridines

Trirutheniumdodecacarbonyl (Ru₃(CO)₁₂) reacts with 2-hydroxy-6-methylpyridine and with 2-hydroxy-5,6,7,8-tetrahydroquinoline in toluene to form centrosymmetric tetranuclear complexes of the type [Ru(η², μ-L)(CO)₂(μ₃-L)Ru(CO)₂]₂, where L is the respective (N,O)-pyridonate ligand (2 and 3). The structures of these complexes, which are almost insoluble in all common solvents, could be determined by single-crystal X-ray diffraction. Reaction of Ru₃(CO)₁₂ with 2-hydroxy-4,6-diphenylpyridine in methanol includes ortho-metallation at the phenyl ring, furnishing the dinuclear complex [Ru(κ²N,C-L)(CO)₂(μ-OCH₃)₂Ru(CO)₂ (κ²N,C-L)] (4), where L = (2-(6-hydroxy-4-phenylpyridin-2-yl)phenyl), according to an X-ray crystal structure determination.     

Dinuclear ruthenium sawhorse-type complexes containing bridging ligands with ferrocenyl substituents in endo/endo, endo/exo and exo/exo orientations

The dinuclear ruthenium complexes Ru₂(CO)₄(OOCC₅H₄FeC₅H₅)₂L₂ (L = NC₅H₅: 1, L = PPh₃: 2) have been synthesized from Ru₃(CO)₁₂, ferrocene carboxylic acid and pyridine or triphenylphosphine, respectively. The single-crystal X-ray structure analysis reveals for 1 and 2 a Ru₂(CO)₄ sawhorse backbone with the two ferrocenyl substituents of the two carboxylato bridges being endo/exo with respect to each other in the solid state. With the new pyridine derivative NC₅H₄OOCC₅H₄FeC₅H₅ (4-ferrocenoyl pyridine) (3) as axial ligand, the complex Ru₂(CO)₄(OOCC₅H₄FeC₅H₅)₂(NC₅H₄OOCC₅H₄FeC₅H₅)₂ (4) was obtained, the single crystal X-ray structure analysis showing an exo/exo orientation of the two carboxylato bridges in the solid state. The endo/endo orientation is found in the solid-state structure of Ru₂(CO)₄(HNOCC₅H₄FeC₅H₅)₂(PPh₃)₂ (5), the two OCNH bridges being transoïd with respect to each other; this complex is accessible from Ru₃(CO)₁₂, ferrocenamide and triphenylphosphine.     

Syntheses and michael additions to vinylidene diphosphine complexes of type [M(CO)4{(Ph2P)2CCH2}] (MCr,Mo or W)

Treatment of [M(CO)₄Ph₂PCHPPh₂]⁻ with CH₃- OCH₂Cl at 20 °C gave the methoxymethyl derivations [M(CO)₄{Ph₂PCH(CH₂OCH₃)PPh₂}] (MCr or W), but a similar treatment at 80 °C gave derivatives of a vinylidene diphosphine [M(CO)₄(Ph₂P)₂C CH₂]. Treatment of [M(CO)₄Ph₂PCHPPh₂]⁻with CH₃CHClOCH₃ at 20 or 80 °C gave only [M(CO)₄- (Ph₂P)₂CHCH(CH₃)OCH₃] (MCr or W). The vinylidene diphosphine complexes [M(CO)₄(Ph₂P)2- CCH₂] (MCr, Mo or W) were even more easily prepared by treating [M(CO)₆] with (Ph₂P)₂CCH₂ (vdpp) in hot solvents such as CH₃OCH₂CH₂OCH₂- CH₂OCH₃.Treatment of [W(CO)₄vdpp] with LiBuⁿ followed by methanol gave [W(CO)₄(Ph₂P)₂CHCH₂Buⁿ] (1c), i.e. conjugate addition to the CCH₂ occurs. 1c was also made by treating [W(CO)₄(Ph₂P)₂CH]⁻ with n-pentyl-iodide. Similarly LiMe was added to [W(CO)₄(Ph₂P)₂CCH₂]. Treatment of [M(CO)₄- vdpp] with NaCH(COOEt)₂ gave [M(CO)₄(Ph₂- P)₂CHCH₂CH(COOEt)₂] (MW or Mo). Pyrrolidine added to the CCH₂ bonds of [M(CO)₄vddp] to give [M(CO)₄(Ph₂P)₂CHCH₂NC₄H₈]. ³¹p and ¹H NMR and IR data are given.     

Aerobic oxygenation of organic sulfides using diruthenium activators

Diruthenium compounds supported by carboxylate or mixed carboxylate/carbonate bridging ligands were found to be active catalysts for aerobic oxygenation of organic sulfides. Ru₂(OAc)₃(CO₃) (A), Ru₂(O₂CCF₃)₃(CO₃) (B) and Ru₂(OAc)₄Cl (C) promote the conversion of organic sulfide to sulfoxide, and subsequently sulfone in an oxygen atmosphere at ca. 90 °C. The order of catalytic activity is A > B ? C. Catalytic reactions are operative in a number of 1:1 co-solvent-H₂O combinations, and the highest reactivity was found in aqueous media.     

Reaction of a bulky phosphite with [Ru3(CO)12]: The molecular structure of one of the decomposition products

Mono- and bis-substituted phosphite complexes [Ru₃(CO)_12−x L_x] (L = tris(2,4-di-tert-butylphenyl) phosphite; x = 1, 2) were synthesized by simple substitution reactions, and were characterized by spectroscopic methods. The monosubstituted ruthenium complex disproportionates in acetone producing a mononuclear ruthenium complex as one of the decomposition products. Single crystal X-ray diffraction analysis established the molecular structure of this new compound.     

μ3-S bonding mode in H2M3(CO)9S clusters of Ru and Os. An UVPES and theoretical study

The electronic structure of H₂M₃(CO)₉S clusters (M = Ru, Os) is discussed on the basis of their He I and He II excited gas-phase photoelectron spectra and on the basis of CNDO quantum mechanical calculations. The PE data clearly demonstrate the cleavage of two direct MM interactions by operation of the bridging hydrides, giving rise to three-center two-electron MHM levels. The μ₃-S bonding mode has been described in detail and compared with previous results on related μ₃-CY cluster derivatives. The CNDO results on Ru₃(CO)₉S⁼, HRu₃(CO)₉S^? and H₂Ru₃(CO)₉S indicate that the μ₃-S—cluster interaction is mostly independent of the presence of the bridging hydrides.     

Reactions of 1,8-bis(diphenylphosphino)naphthalene with ruthenium cluster carbonyls: C-H and C-P bond cleavage reactions

Reactions between Ru₃(CO)₁₂ and 1,8-bis(diphenylphosphino)naphthalene (dppn) have given the four complexes Ru₃(μ-H){μ₃-PPh₂(nap)PPh(C₆H₄)}(CO)₈ (1), Ru₄(μ-H){μ₃-PPh₂(nap)PPh(C₆H₄)}(μ-CO)₃(CO)₇ (2) and Ru₄(μ-H)(μ₃-C₆H₄){μ-PPh(nap)PPh₂}(CO)₁₁ (3) (in refluxing thf), and Ru₄{μ₄-P(nap)PPh₂}(μ₄-C₆H₄)(μ-CO)(CO)₉ (4) (in refluxing toluene) which have been characterised by single crystal X-ray studies. They have been formed by aryl C-H and aryl C-P bond cleavage reactions, presumably from an initial (unobserved) chelate dppn complex. The unchanged chelating ligand is found in Ru₃(μ-dppm)(CO)₈(dppn) (5), obtained from Ru₃(μ-dppm)(CO)₁₀ and dppn in refluxing thf.     

A bicarbonate bridged diruthenium(I) complex: Key evidence for the decarboxylation step in the base-assisted reduction of Ru2Cl4(CO)6

Base-assisted reduction of [Ru(CO)₃Cl₂]₂ in the presence of NP-Me₂ (2,7-dimethyl-1,8-naphthyridine) in thf provides an unsupported diruthenium(I) complex [Ru₂(CO)₄Cl₂(NP-Me₂)₂] (1). Two NP-Me₂ and four carbonyls bind at equatorial positions and two chlorides occupy sites trans to the Ru-Ru single bond. Reaction of [Ru(CO)₃Cl₂]₂, TlOTf, KOH and NP-Me₂ in acetonitrile, in a sealed container, affords a bicarbonate bridged diruthenium(I) complex [Ru₂(CO)₂(μ-CO)₂(μ-O₂COH)(NP-Me₂)₂](OTf) (2). The in situ generated CO₂ is the source for bicarbonate under basic reaction medium. Isolation of 2 validates the decarboxylation step in the base-assisted reduction of [Ru^II(CO)₃Cl₂]₂ → [Ru^I₂(CO)₄]²⁺.     

(C5Me5)2NbBH4, a new reagent for the synthesis of Ru and Co carbonyl clusters with interstitial boron or carbon

The reaction of Cp*₂NbBH₄ (Cp* = η⁵-C₅Me₅) with Ru₃(CO)₁₂ gave a mixture of compounds, from which only [Cp*₂Nb(CO)₂]₂[Ru₆(CO)₁₆C] (1) could be characterized by spectroscopic and crystallographic methods. ¹¹B NMR spectroscopy proved that interstitial boron may be present in other Ru₆ clusters, but these compounds did not crystallize. The reaction of Cp*₂NbBH₄ with Co₂(CO)₈ gave among others the salts [Cp*₂Nb(CO)₂]₂[Co₆(CO)₁₅C] (4) and [Cp*₂Nb(CO)₂]₃[Co₁₃(CO)₂₄C₂] (5), which were examined by X-ray diffraction studies. The true nature of the interstitial atoms in 5 was deduced from electrochemical investigations, which reveal similar redox properties as for the already known [Co₁₃(CO)₂₄C₂]³⁻ anion.     

Complexes of the imine/thioether mixed-donor ligand 8-methylthioquinoline with d-configurated transition metal centers: synthesis, structures and comparison with complexes of 1-methyl-2-(methylthiomethyl)-1H-benzimidazole

Coordination compounds of chelating 8-methylthioquinoline (MTQ) with the complex fragments Re^I(CO)₃Cl, [Ru^II(bpy)₂]²⁺, [Rh^III(C₅Me₅)Cl]⁺, [Ir^III(C₅Me₅)Cl]⁺, and Pt^IVMe₄ were synthesized and structurally characterized. Whereas the ruthenium(II) complex displays the strongest preference of bonding to N versus S, the compound (MTQ)PtMe₄ shows the most balanced metal-donor bonding within the chelate ring due to a relatively short bond to S (2.319 Å) versus N (2.150 Å). The complex fac-(MTQ)Re(CO)₃Cl exhibits a particularly long metal-sulfur bond at 2.472 Å. Cyclic voltammetry of [(MTQ)Ru(bpy)₂](PF₆)₂ reveals one reversible oxidation to Ru^III and three closely spaced reduction waves for the coordinated ligands. In comparison with the imine/thioether chelate ligand 1-methyl-2-(methylthiomethyl)-1H-benzimidazole (mmb) the MTQ ligand with its more rigid chelate setting N(sp²)-C(sp²)-C(sp²)-S forms generally shorter M-S bonds and displays stronger π acceptor behaviour.