Diruthenium Complexes Research Articles

Olefin metathesis for metal incorporation: Preparation of conjugated ruthenium-containing complexes and polymers

Olefin Metathesis for Metal Incorporation (OMMI) was used for the stoichiometric attachment of ruthenium to both small and large polyenes. The dinuclear complexes (PCy 3) 2C1 2Ru CH(CH CH) n CH Ru(PCy 3) 2Cl 2 ( n = 1, 2), were prepared by reacting 2 equiv. of the Grubbs first-generation catalyst (PCy 3) 2C1 2Ru (CHPh)) with 1 equiv. of the appropriate polyene (1,3,5-hexatriene for n = 1 and 1,3,5,7-octatetraene for n = 2). Use of excess hexatriene led to the formation of the monoruthenium complex (PCy 3) 2C1 2Ru CHCH CHCH CH 2. The mono- and di-ruthenium complexes exhibited marked differences in their spectroscopic and electrochemical properties, in addition to their Z– E isomerization rates. Nucleophilic attack of PCy 3 on the end CH 2 of the mono complex was observed, leading to both isomerization and phosphonium products. Extending the OMMI strategy to the second-generation catalyst was also done, despite the reduced initiation rate. The more reactive catalyst (H 2IMes)RuCl 2( CHPh)(3-bromopyridine) 2 allowed for ruthenium incorporation into polyacetylene, leading to the formation of polymers and oligomers with high ruthenium content.

2,2‘-Dipyridylketone (dpk) as Ancillary Acceptor and Reporter Ligand in Complexes [(dpk)(Cl)Ru(μ-tppz)Ru(Cl)(dpk)]n+where tppz = 2,3,5,6-Tetrakis(2-pyridyl)pyrazine

The tppz-bridged diruthenium(II) complex [(dpk)(Cl)Ru(II)(mu-tppz)Ru(II)(Cl)(dpk)](ClO4)2, [2](ClO4)2, and mononuclear [(dpk)(Cl)Ru(II)(tppz)](ClO4), [1](ClO4) [tppz = 2,3,5,6-tetrakis(2-pyridyl)pyrazine, dpk = 2,2'-dipyridylketone], have been synthesized. The 260 mV separation between successive one-electron oxidation couples in [2]2+ translates to a relatively small comproportionation constant, Kc, of 2.5 x 10(4) for the intermediate. It is shown how electrochemical data (E(ox), E(red), Kc) reflect the donor/acceptor effects of ancillary ligands L in a series of systems [(L)ClRu(mu-tppz)RuCl(L)]n, particularly the competition between L and tppz for electron density from the metal. According to EPR (g1 = 2.470, g2 = 2.195, and g3 = 1.873 at 4 K) the intermediate [2]3+ is a mixed-valent Ru(II)Ru(III) species which shows a rather narrow intervalence charge transfer (IVCT) band at 1800 nm (epsilon = 1500 M(-1) cm(-1)). The width at half-height (Deltanu(1/2)) of 700 cm(-1) of the IVCT band is much smaller than the calculated value of 3584 cm(-1), obtained by using the Hush formula Deltanu(1/2) = (2310E(op))(1/2) (E(op) = 5556 cm(-1), energy of the IVCT transition) which would be applicable to localized (Class II) mixed-valent Ru(II)Ru(III) systems. Valence delocalization in [2]3+ is supported by the uniform shift of the nu(C=O) band of the N,N'-coordinated dpk ligands from 1676 cm(-1) in the Ru(II)Ru(II) precursor to 1690 cm(-1) in the Ru(2.5)Ru(2.5) form, illustrating the use of the dpk acceptor to act as reporter ligand via the free but pi-conjugated organic carbonyl group. The apparent contradiction between the moderate value of Kc and the narrow IVCT band is being discussed considering "borderline" or "hybrid" "Class II-III" concepts of mixed-valency, as well as coordination aspects, i.e., the bis-tridentate nature of the pi-acceptor bridging ligand. Altogether, the complex ions [1]+ and [2]2+ display four and five successive reduction processes, respectively, involving both tppz- and dpk-based unoccupied pi orbitals. The one-electron reduced form [2]+ has been assigned as a tppz*- radical-anion-containing species which exhibits a free-radical-type EPR signal at 4K (g(parallel) = 2.002, g(perpendicular) = 1.994) and one moderately intense ligand-based low-energy band at 965 nm (epsilon = 1100 M(-1) cm(-1)).

Ruthenium‐Catalyzed Propargylic Reduction of Propargylic Alcohols with Silanes

Ru2 can do it! Substitution of the OH moiety in propargylic alcohols by hydride proceeds smoothly with triethylsilane by catalysis with the thiolate-bridged diruthenium complex 1 (see scheme; Cp*=η5-C5Me5). This reaction gives the corresponding alkynes in good to high yields with complete selectivity, in contrast to a monoruthenium-catalyzed hydrosilylation of propargylic alcohols with silanes.

Synthesis, Characterization, and Electrochemistry of Diruthenium(III,II) and Monoruthenium(III) Complexes Containing Pyridyl-Substituted 2-Anilinopyridinate Ligands

Reaction of the metal-metal bonded complex Ru(2)(O2CCH3)4Cl with 2-anilino-4-methylpyridine leads to the (3,1) isomer of the diruthenium(III,II) complex Ru2(ap-4-Me)4Cl, 1 while the same reaction with 2-anilino-6-methylpyridine gives the monoruthenium(III) derivative Ru(ap-6-Me)3, 2. Both compounds were examined as to their structural, electrochemical, and UV-visible properties, and the data were then compared to that previously reported for (4,0) Ru2(2-Meap)4Cl and other (3,1) isomers of Ru2(L)4Cl with similar anionic bridging ligands. ESR spectroscopy indicates that the monoruthenium derivative 2 contains low-spin Ru(III), and the presence of a single ruthenium atom is confirmed by an X-ray structure of the compound. The combined electrochemical and UV-vis spectroelectrochemical data indicate that the diruthenium complex 1 is easily converted to its Ru2(4+) and Ru2(6+) forms upon reduction or oxidation by one electron while the monoruthenium derivative 2 also undergoes metal-centered redox processes to give Ru(II) and Ru(IV) complexes under the same solution conditions. The reactivity of 1 with CO and CN- was also examined.

Divinylphenylene-Bridged Diruthenium Complexes Bearing Ru(CO)Cl(PiPr3)2Entities

The divinylphenylene-bridged diruthenium complexes (E,E)-[{(PiPr3)2(CO)ClRu}2(μ-HCCHC6H4CHCH-1,3)] (m-2) and (E,E)-[{(PiPr3)2(CO)ClRu}2(μ-HCCHC6H4CHCH-1,4)] (p-2) have been prepared and compared to their PPh3-containing analogues m-1 and p-1. The higher electron density at the metal atoms increases the contribution of the metal end groups to the bridge-dominated occupied frontier orbitals and stabilizes the various oxidized forms with respect to those of m-1 and p-1. This has been confirmed and quantified electrochemically, because the two reversible oxidation waves were observed at considerably lower potentials than for the PPh3 complexes. Owing to their greater stability, the one- and two-electron-oxidized forms m-2n+ and p-2n+ of both complexes could be generated and spectroscopically characterized inside an optically transparent thin layer electrolysis cell. UV/vis/near-IR and ESR spectroelectrochemistry indicates that the oxidation processes are centered at the organic bridging ligand. σ-Bonded divinylphenylenes thus constitute an unusual class of “noninnocent” ligands for organometallic compounds. Electronic transitions observed for the mono- and dioxidized forms closely resemble those of donor-substituted phenylenevinylene compounds, including oligo(phenylenevinylenes) (OPVs) and poly(phenylenevinylene) (PPV) in the respective oxidation states. Strong ESR signals and nearly isotropic g tensors are observed for the monocations in fluid and frozen solutions. The metal contribution to the redox orbitals is illustrated by a shift of the CO stretching bands to notably higher energies upon stepwise oxidation. The shifts strongly exceed those observed for the PPh3 containing, six-coordinated species (E,E)-[{(PPh3)2(CO)Cl(L)Ru}2(μ-HCCHC6H4CHCH)]n+ (L = substituted pyridine). IR spectroelectrochemistry reveals the presence of two electronically different transition-metal moieties in m-2+, while they resemble each other more closely in p-2+. Differences in electronic coupling are illustrated by the charge distribution parameters calculated from the spectra. Bulk electrolysis experiments confirm the results from the in situ spectroelectrochemistry and the overall stoichiometry of the redox processes. Quantum-chemical calculations were performed in order to provide insight into the nature and composition of the frontier orbitals. The electronic transitions observed for the neutral forms were assigned by TD DFT. IR frequencies calculated for m-2 and p-2 in their various oxidation states retrace the experimental observations. They fail, however, in the case of m-2+, where a symmetrical structure is calculated, as opposed to the distinctly asymmetric electron distribution observed by IR spectroscopy. Geometry-optimized structures were calculated for all accessible oxidation states. The structural changes following stepwise oxidation agree well with the experimental findings: e.g., a successive low-energy shift of the CC stretching vibration of the bridge. The radical cation m-2+ displays a broad composite electronic absorption band at low energy that extends into the mid-IR region.

Synthesis and structures of the silyl bridged bis(indenyl) diruthenium complexes and a novel indenyl nonanuclear ruthenium cluster Ru 9(μ 6-C)(CO) 14(μ 3-η 5:η 2:η 2-C 9H 7) 2

Thermal treatment of C 9H 7SiMe 2C 9H 7 and C 9H 7Me 2SiOSiMe 2C 9H 7 with Ru 3(CO) 12 in refluxing xylene gave the corresponding diruthenium complexes (E)[(η 5-C 9H 6)Ru(CO)] 2(μ-CO) 2 [E = Me 2Si ( 1), Me 2SiOSiMe 2 ( 2)]. A desilylation product [(η 5-C 9H 7)Ru(CO)] 2(μ-CO) 2 ( 3) was also obtained in the latter case. Similar treatment of C 9H 7Me 2SiSiMe 2C 9H 7 with Ru 3(CO) 12 gave a novel indenyl nonanuclear ruthenium cluster Ru 9(μ 6-C)(CO) 14(μ 3-η 5:η 2:η 2-C 9H 7) 2 ( 5) with carbon-centered tricapped trigonal prism geometry, in addition to the diruthenium complex (Me 2SiSiMe 2)[(η 5-C 9H 6)Ru(CO)] 2(μ-CO) 2 ( 4) and the desilylation product 3. Complex 4 can undergo a thermal rearrangement to form the product [(Me 2Si)(η 5-C 9H 6)Ru(CO) 2] 2 ( 6). The molecular structures of 1, 2, 4, 5, and 6 were determined by X-ray diffraction.

Synthesis and structures of cycloalkylidene‐bridged mixed cyclopentadienyl‐indenyl tetracarbonyl diruthenium complexes

AbstractA series of cycloalkylidene‐bridged mixed cyclopentadienyl‐indenyl tetracarbonyl diruthenium complexes (η5:η5‐RC5H3CR′2C9H6)Ru2(CO)2(µ‐CO)2 [R = H, R′, R′ = Me2 (1), (CH2)4 (2), (CH2)5 (3), (CH2)6 (4); R = tBu, R′, R′ = Me2 (5), (CH2)4 (6), (CH2)5 (7)] have been synthesized by reactions of the corresponding ligands RC5H4CR′2C9H7 with Ru3(CO)12 in refluxing xylene. The molecular structures of 2, 6 and 7 have been determined by X‐ray diffraction. Copyright © 2006 John Wiley & Sons, Ltd.

Synthesis, structure and properties of di- and mononuclear ruthenium(III) complexes with N-(benzoyl)- N′-(salicylidene)hydrazine and its derivatives

The reactions of [Ru(PPh 3) 3Cl 2], N-(benzoyl)- N′-(5- R-salicylidene)hydrazines (H 2bhsR, R = H, OCH 3, Cl, Br and NO 2) and triethylamine (1:1:2 mole ratio) in methanol afford mononuclear ruthenium(III) complexes having the general formula trans-[Ru(bhsR)(PPh 3) 2Cl]. In the case of R = H, a dinuclear ruthenium(III) complex of formula [Ru 2(μ-OCH 3) 2(bhsH) 2(PPh 3) 2] has been isolated as a minor product. The complexes are characterized by elemental analysis, magnetic, spectroscopic and electrochemical measurements. The crystal structures of the dinuclear complex and two mononuclear complexes have been determined. In the dinuclear complex, each metal centre is in distorted octahedral NO 4P coordination sphere constituted by the two bridging methoxide groups, one PPh 3 molecule and the meridionally spanning phenolate-O, imine-N and amide-O donor bhsH 2−. The terminal PPh 3 ligands are trans to each other. In the mononuclear complexes, bhsR 2− and the chlorine atom form an NO 2Cl square-plane around the metal centre and the P-atoms of the two PPh 3 molecules occupy the remaining two axial sites to complete a distorted octahedral NO 2ClP 2 coordination sphere. All the complexes display ligand-to-metal charge transfer bands in the visible region of the electronic spectra. The cryomagnetic measurements reveal the antiferromagnetic character of the diruthenium(III) complex. The low-spin mononuclear ruthenium(III) complexes as well as the diruthenium(III) complex display rhombic EPR spectra in frozen solutions. All the complexes are redox active in CH 2Cl 2 solutions. Two successive metal centred oxidations at 0.69 and 1.20 V (versus Ag/AgCl) are observed for the dinuclear complex. The mononuclear complexes display a metal centred reduction in the potential range −0.53 to −0.27 V. The trend in these potential values reflects the polar effect of the substituents on the salicylidene moiety of the tridentate ligand.

Reactions of CpArCHCHArCp with Ru3(CO)12: An Unexpected Cleavage of a Bridging C−C Bond and Coupling of the Two Cyclopentadienyl Rings to Fulvalene Diruthenium Complexes.

Reactions of CpArCHCHArCp with Ru₃(CO)₁₂: An Unexpected Cleavage of a Bridging C−C Bond and Coupling of the Two Cyclopentadienyl Rings to Fulvalene Diruthenium Complexes.

Equatorially Connected Diruthenium(II,III) Units toward Paramagnetic Supramolecular Structures with Singular Magnetic Properties

The reaction of Ru2Cl(O2CMe)(DPhF)3 (DPhF = N,N'-diphenylformamidinate) with mono- and polycarboxylic acids gives a clean substitution of the acetate ligand, leading to the formation of complexes Ru2Cl(O2CC6H5)(DPhF)3 (1), Ru2Cl(O2CC6H4-p-CN)(DPhF)3 (2), [Ru2Cl(DPhF)3(H2O)]2(O2C)2 (3), [Ru2Cl(DPhF)3]2[C6H4-p-(CO2)2] (4), and [Ru2Cl(DPhF)3]3[C6H3-1,3,5-(CO2)3] (5). The preparation of [Ru2(NCS)(DPhF)3]3[C6H3-1,3,5-(CO2)3] (6) and {[Ru2(DPhF)3(H2O)]3[C6H3-1,3,5-(CO2)3]}(SO3CF3)3 (7) from 5 is also described. All complexes are characterized by elemental analysis, IR and electronic spectroscopy, mass spectrometry, cyclic voltammetry, and variable-temperature magnetic measurements. The crystal structure determinations of complexes 2.0.5THF and 3.THF.4H2O (THF = tetrahydrofuran) are reported. The reactions carried out demonstrate the high chemical stability of the fragment [Ru2(DPhF)3]2+, which is preserved in all tested experimental conditions. The stability of this fragment is also corroborated by the mass spectra. Electrochemical measurements reveal in all complexes one redox process due to the equilibrium Ru2(5+) <--> Ru2(6+). In the polynuclear complex 7, some additional oxidation processes are also observed that have been ascribed to the presence of two types of dimetallic units rather than two consecutive reversible oxidations. The magnetic behavior toward temperature for complexes 1-7 from 300 to 2 K is analyzed. Complexes 1-7 show low values of antiferromagnetic coupling in accordance with the molecular nature in 1 and 2 and the absence of important antiferromagnetic interaction through the carboxylate bridging ligands in 3-7, respectively. In addition, the magnetic properties of complex 7 do not correspond to any magnetic behavior described for diruthenium(II,III) complexes. The experimental data of compound 7 are simulated considering a physical mixture of S = 1/2 and 3/2 spin states. This magnetic study demonstrates the high sensitivity of the electronic configuration of the unit [Ru2(DPhF)3]2+ to small changes in the nature of the axial ligands. Finally, the energy gap between the pi and delta orbitals in these types of compounds allows the tentative assignment of the transition pi --> delta.

Structure and Photochemical Properties of (μ-Alkoxo)bis(μ-carboxylato)diruthenium Complexes with Naphthylacetate Ligands

Two new dinuclear Ru(III) complexes containing naphthalene moieties, K[Ru2(dhpta)(mu-O2CCH2-1-naph)2] (1) and K[Ru2(dhpta)(mu-O2CCH2-2-naph)2] (2) (H5dhpta = 1,3-diamino-2-hydroxypropane-N,N,N',N'-tetraacetic acid, naph-1-CH2CO2H = 1-naphthylacetic acid, naph-2-CH2CO2H = 2-naphthylacetic acid), were synthesized. Complex 2 crystallized as an orthorhombic system having a space group of Pbca with unit cell parameters a = 10.6200(5) A, b = 20.270(1) A, c = 35.530(2) A, and Z = 8. EXAFS analysis of 1 and 2 in the solid states and in solution clarified that the dinuclear structures of 1 and 2 were kept in DMSO solutions. Variable-temperature magnetic susceptibility data indicated that the two Ru(III) centers are strongly antiferromagnetically coupled as shown by the large coupling constants, J = -581 cm(-1) (1) and -378 cm(-1) (2). In the cyclic voltammograms of 1 and 2, one oxidation peak and two reduction peaks which were assigned to the redox reaction of the ruthenium moieties were observed in DMF. The large conproportionation constants estimated from the reduction potentials of Ru(III)Ru(III) and Ru(III)Ru(II) indicated the great stability of the mixed-valent state. The mixed-valent species [Ru(III)Ru(II)(dhpta)(mu-O2CCH2-R)2](2-) (R = 1-naph (6) and R = 2-naph (7)) were prepared by controlled potential electrolysis of 1 and 2 in DMF. The electronic absorption spectra of 6 and 7 were similar to that of [Ru(III)Ru(II) (dhpta)(mu-O2CCH3)2](2-) which is a typical Class II type mixed-valent complex. The fluorescence decay of 1 and 2 indicated that there are two quenching processes which come from the excimer and monomer states. The short excimer lifetimes of 1 and 2 were ascribed to the energy transfer from the naphthyl moieties to the Ru centers. The different excimer ratio between 1 and 2 suggested that the excimer formation is affected by the conformation of the naphthyl moieties in the diruthenium(III) complexes.

Synthesis and Some Properties of Binuclear Ruthenocenes Bridged by Oligoynes: Formation of Bis(cyclopentadienylidene)cumulene Diruthenium Complexes in the Two‐Electron Oxidation

The monoynes [Rc*C[triple bond]CRc*] and [Rc'C[triple bond]CRc'] were obtained in improved yields using [Mo(CO)6]/2-FC6H5OH as a catalyst in the alkyne metathesis of [Rc*C[triple bond]CMe] and [Rc'C[triple bond]CMe], respectively (Rc = ruthenocenyl, Rc* = 1'',2'',3'',4'',5''-pentamethylruthenocenyl, and Rc' = 2',3',4',5'-tetramethylruthenocenyl groups). The diynes [Rc*(C[triple bond]C)2Rc*] and [Rc'(C[triple bond]C)2Rc'] were synthesized by the oxidative coupling of the corresponding terminal ethynes in good yields. The triyne [Rc*(C[triple bond]C)3Rc*] and the tetrayne [Rc*(C[triple bond]C)4Rc*] were prepared by the hetero- and homocoupling of [Rc*C[triple bond]CC[triple bond]CH], which was obtained from the reaction of [Rc*C[triple bond]CCHO] with Li[N2CSiMe3], respectively. Although the oxidation waves did not always exhibit a clear two-electron oxidation process, the oxidation potentials shifted to a lower potential with an increase in the number of methyl substituents on the ruthenocenyl ring, and shifted to a higher potential with the increase in the number of C[triple bond]C units; this result is in contrast to that found in the [Rc(CH=CH)(n)Rc] series. The chemical oxidation of [Rc'C[triple bond]CRc'] yielded a stable two-electron-oxidized species, the structure of which was confirmed by X-ray crystallography to be [Ru2(mu2-eta(6):eta(6)-C5Me4C=CC5Me4)(eta-C5H5)2](BF4)2. Changing the substituents (Rc, Rc*, and Rc') had no effect on the chemical oxidation, but in the case of the Rc' series the Me substituent increased the stability of the two-electron-oxidized species in solution. The diyne [Rc*(C[triple bond]C)2Rc*] and the triyne [Rc*(C[triple bond]C)3Rc*] also gave a similar but unstable two-electron-oxidized species. In acetone or acetonitrile, the two-electron-oxidized species of [Rc*C[triple bond]CRc*] and [Rc*(C[triple bond]C)2Rc*] gradually formed the corresponding bis(fulvene)-type complexes. This implies that the two-electron-oxidized species of [Rc*(C[triple bond]C)(n)Rc*] are destabilized with the increasing n.

Ruthenium‐Catalyzed Propargylic Substitution Reactions of Propargylic Alcohols with Oxygen‐, Nitrogen‐, and Phosphorus‐Centered Nucleophiles.

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Conversion of 2-Aminoethanethiolate (aet) to 2-Benzoylaminoethanethiolate (L) in a S-Bridged Diruthenium(II) Complex Composed of Two cis-[Ru(bpy)2] Units. Crystal Structures of ΔΔ/ΛΛ-[{Ru(bpy)2}2(μ-Haet)2]4+ and ΔΔ/ΛΛ-[{Ru(bpy)2}2(μ-L)2]2+

Abstract A diruthenium(II) complex, ΔΔ/ΛΛ-[{Ru(bpy)2}2(μ-L)2]2+ (ΔΔ/ΛΛ-[2]2+), in which two cis-[Ru(bpy)2]2+ units are bridged by two S atoms from two 2-benzoylaminoethanethiolate (L) ligands, was synthesized by the reaction of ΔΔ/ΛΛ-[{Ru(bpy)2}2(μ-Haet)2]4+ (aet = 2-aminoethanethiolate; ΔΔ/ΛΛ-[1]4+) with benzoyl chloride in the presence of a base. The molecular structure and electrochemical properties of ΔΔ/ΛΛ-[2]2+ were discussed in comparison with those of ΔΔ/ΛΛ-[1]4+.

Cover Picture: Ruthenium‐Catalyzed Propargylation of Aromatic Compounds with Propargylic Alcohols (Eur. J. Org. Chem. 4/2006)

AbstractThe cover picture shows that thiolate‐bridged diruthenium complexes promote intermolecular and intramolecular propargylation of aromatic compounds with propargylic alcohols to give the corresponding propargylated aromatic compounds in high yields with complete selectivity. The reaction is considered to be an electrophilic substitution of the aromatic compounds by the ruthenium‐stabilized propargyl cation. Details are described in the article by Y. Nishibayashi et al. on p. 881 ff.

Ruthenium‐Catalyzed Propargylation of Aromatic Compounds with Propargylic Alcohols

AbstractReactions of propargylic alcohols bearing a terminal alkyne moiety with aromatic compounds in the presence of a catalytic amount of thiolate‐bridged diruthenium complexes give the corresponding propargylated aromatic compounds in high yields with complete selectivity. Intramolecular reactions of propargylic alcohols bearing an aromatic moiety proceed smoothly to afford the cyclized products in high yields with complete selectivity. The stoichiometric reaction of the ruthenium–allenylidene complex [Cp*RuCl(μ2‐SMe)2RuCp*(=C=C=CHPh)]BF4 (Cp* = η5‐C5Me5) with 10 equiv. 2‐methylfuran results in the formation of 2‐methyl‐5‐(1‐phenyl‐2‐propynyl)furan in 34 % yield, indicating that these catalytic reactions proceed via ruthenium–allenylidene intermediates. The reaction is considered to be an electrophilic substitution of aromatic compounds by the ruthenium‐stabilized propargyl cation. (© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2006)

The PPh3-Substituted Hydroxycyclopentadienyl Ruthenium Hydride [2,5-Ph2-3,4-Tol2(η5-C4COH)]Ru(CO)(PPh3)H Is a More Efficient Catalyst for Hydrogenation of Aldehydes

The phosphine-substituted hydroxycyclopentadienyl ruthenium hydride [2,5-Ph2-3,4-Tol2(η5-C4COH)]Ru(CO)(PPh3)H (8) displayed behavior significantly different from that of the dicarbonyl analogue, including the failure to form an unreactive diruthenium complex analogous to the Shvo catalyst 5. Complex 8 shows no apparent reduction of aldehydes in the absence of a trap but exchanges deuterium between the hydride of 8-RuDOD and the aldehydic hydrogen of p-tolualdehyde. This provides evidence that aldehyde reduction by 8 occurs but is reversible. 8 catalyzes the hydrogenation of benzaldehyde under mild temperature and pressure conditions. A rate law of −d[RCHO]/dt = k[RCHO][8][H2]0 was obtained.

Reactions of CpArCHCHArCp with Ru3(CO)12: An Unexpected Cleavage of a Bridging C−C Bond and Coupling of the Two Cyclopentadienyl Rings to Fulvalene Diruthenium Complexes

Reactions of CpArCHCHArCp [Ar = Ph (1), p-MeOC6H4 (2)] with Ru3(CO)12 in refluxing xylene afforded the unexpected bridging C−C cleavage and cyclopentadienyl coupling products: the 2,2‘-bisubstituted fulvalene diruthenium complexes (η5:η5-2,2‘-ArCH2C5H3C5H3CH2Ar)Ru2(CO)4 [Ar = Ph (5), p-MeOC6H4 (9)] and the partially hydrogenated products (η5:η3-ArCH2C5H3C5H6CHAr)Ru2(CO)4 [Ar = Ph (4), p-MeOC6H4 (8)], in addition to the normal bridged bis(cyclopentadienyl) tetracarbonyl diruthenium complexes (ArCHCHAr)[(η5-C5H4)Ru(CO)]2(μ-CO)2 [Ar = Ph (7), p-MeOC6H4 (10)]. When ligand (tBuC5H4)PhCHCHPh(tBuC5H4) (3) reacted with Ru3(CO)12, the tetrasubstituted fulvalene diruthenium complex (η5:η5-PhCH2tBuC5H2C5H2tBuCH2Ph)Ru2(CO)4 (11) and three normal bridged bis(cyclopentadienyl) diruthenium complexes (PhCHCHPh)[(η5-tBuC5H3)Ru(CO)]2(μ-CO)2 (12−14) were obtained. The molecular structures of 4, 5, 7-meso, 7-rac, 8, 10-meso, 11, 12, 13, and 14 were determined by X-ray diffraction. The stereochemistry of the reaction was als...

Ruthenium‐Catalyzed Asymmetric Propargylic Substitution Reactions of Propargylic Alcohols with Acetone

The table of contents entry for this paper contained an incorrect figure. The corrected entry is shown below. 1 Enantioselective propargylic substitution reactions of propargylic alcohols with acetone catalyzed by a diruthenium complex give the propargylic alkylated products in good yields with up to 82 % ee (see scheme). A π–π interaction of phenyl rings between the ligand and allenylidene moieties is considered to play a crucial role in achieving such a high selectivity. Cp*=pentamethylcyclopentadiene.

Water-soluble diruthenium complexes bearing acetate and carbonate bridges: highly efficient catalysts for aerobic oxidation of alcohols in water

The aerobic oxidation of alcohols in water can be performed efficiently in the presence of a catalytic amount of the water-soluble diruthenium complex Ru2(micro-OAc)3(micro-CO3) under an atmospheric pressure (1 atm) of O2.