Diruthenium compounds

Di-/i-chloro(dichloro)bis[77 -T7 -2,7-dimethylocta-2,6-diene-l,8-diyl)diruthenium (compound A) is a purple crystalline compound, that is indefinitely stable at room temperature under a nitrogen atmosphere. For short periods it can also be handled in air. MS (El) m/z 616 (M + ). In the solid state the product shows symmetry Ci, ° but it exists as a mixture of two diastereomers in solution. It reacts with various Lewis bases L to form the monomers Ru(t7 77 -CioHi6)Cl2L and it shows catalytic activity in ROMP polymerization. ... 

In the reaction of azulene with [Ru(CO)4SiMe3]2, two other products were isolated, namely Ru2(CO)2(C1oHg) (10% yield) and Ru2(SiMe3)2 (CO)4(C10Hg) (5% yield). The probable structure of the diruthenium compound 94) is... 

An interesting diruthenium compound (entry 33) has the structure shown in (XLVII) the ring is planar, bisected by a metal-metal bond, and the Si-Ru distances vary noticeably according to their bridging or terminal position and, in the former case, whether they are trans to carbonyl or silicon. The remaining ruthenium derivatives in entries... 

The process has been established for a series of pentaamminemetal(III) compounds (of Co, Rh, or Ir) with bridging imidazolate (21). The (jl-pyrazine mixed decaammine diruthenium(II)/(III) dimer has also been prepared (180), in addition to a diruthenium compound with a 1,4-dicyanobicyclo[2.2.2]octane bridging ligand and a mixed ruthe-nium(III)/cobalt(III) compound with the same bridging ligand (8). Osmium(III) dimers have also been reported (192). 

Keywords Acceptorless alcohol dehydrogenatiOTi AUylic C-H activation Axial reactivity Carbenoid C-H insertion C-H activation Cycloprpanation Diruthenium compounds Metal nitride Metal-ligand cooperation Metal-metal bond... 

Phosphorus-bridging units constitute a major class of ligands for diruthenium compounds. Phosphido ligands span the metal centers with a single phosphorus donor atom, while two phosphorus donors arc employed in diphosphine and diphosphazane complexes to bridge the dinuclear unit. 

Thiolate ligands have dominated the complexes of the heavier chalcogen donors and continue to be employed in stabilizing the dimthenium unit. Many of the catalytic applications found for diruthenium compounds over the last decade have involved thiolate-bridged species. 

The analogous diruthenium(II, II) compounds can be made starting from the blue solution of reduced RuC13 in ethanol (section 1.3.5) on extended refluxing with sodium acetate, whereupon the solvate Ru2(OAc)4(MeOH)2 separates. This loses methanol readily on drying the resulting anhydrous acetate will form weak adducts Ru2(OAc)4L2 (L, e.g. H20, thf). These are all paramagnetic with two unpaired electrons [100]. 

Matsumoto et al. reported some reactions of diruthenium complexes containing a bridging disulfide ligand with unsaturated compounds such as olefins and ketones [135]. These diruthenium complexes show unique reactivities towards double-bond systems since the S-S bond has some double bond character from the contribution of the canonical structure B in Scheme 36. 

As described in the previous sections, a variety of nucleophiles attack the Cy atom of ruthenium-allenylidene intermediates. Aromatic compounds should also be suitable candidates and this was found to be the case [30]. Thus, reactions of propargylic alcohols with heteroaromatic compounds such as furans, thiophenes, pyrroles, and indoles in the presence of a diruthenium catalyst such as la proceeded smoothly to afford the corresponding propargylated heteroaromatic compounds in high yields with complete regioselectivity (Scheme 7.25). The reaction is considered to be an electrophilic aromatic substitution if viewed from the side of aromatic compounds. 

Use of cationic thiolate-bridged diruthenium complexes 84 promotes the catalytic propargylation of aromatic compounds with propargylic alcohols bearing not only a terminal alkyne but also an internal alkyne unit (Equation (34)). " A variety of propargylated aromatic compounds are isolated in high to excellent yields. Although... 

Arene(tricarbonyl)chromium complexes, 19 Nickel boride, 197 to trans-alkenes Chromium(II) sulfate, 84 of anhydrides to lactones Tetrachlorotris[bis(l,4-diphenyl-phosphine)butane]diruthenium, 288 of aromatic rings Palladium catalysts, 230 Raney nickel, 265 Sodium borohydride-1,3-Dicyano-benzene, 279 of aryl halides to arenes Palladium on carbon, 230 of benzyl ethers to alcohols Palladium catalysts, 230 of carboxylic acids to aldehydes Vilsmeier reagent, 341 of epoxides to alcohols Samarium(II) iodide, 270 Sodium hydride-Sodium /-amyloxide-Nickel(II) chloride, 281 Sodium hydride-Sodium /-amyloxide-Zinc chloride, 281 of esters to alcohols Sodium borohydride, 278 of imines and related compounds Arene(tricarbonyl)chromium complexes, 19... 

Ruthenium Compounds Bis[2,2 -bis(diphenylphosphine)-l,l -binaphthyl] (tetrachloro) (triethyl-amine)diruthenium, 36 Bis(T)5-cyclooctadienyl)ruthenium(II), 35... 

A diruthenium bisporphyrin, Ru2(DBP)(l-tBu-5-PhIm)2, which does not carry an axial ligand within the diporphyrin site, directly binds dihydrogen in benzene to form a bimetallic bridging dihydrogen complex, Ru2(H2XDBP)-(l-tBu-5-PhIm)2 [231], From NMR spectra it is deduced that there is a linear array of the Ru-H-H-Ru system in this compound. 

Propargylic alcohols bearing a terminal triple bond react with electron-rich aromatic compounds in the presence of thiolate-bridged diruthenium complexes to give the propargylated aromatic compounds.30 l-Phenylprop-2-yn-l-ol, for example, reacts with 2-methylfuran to form (15). Intramolecular examples of the reaction were also reported. The process is believed to involve electrophilic attack by the ruthenium-stabilized propargyl cation. 

The thiolate-bridged diruthenium complex 101 can promote a cycloaddition reaction between propargylic alcohols and 1,3-dicarbonyl compounds to provide 3-acyM//-pyrans in excellent yield (Scheme 33). The reaction proceeds via formation and alkylation of the allenylidene complex 102 to form the vinylidene intermediate 103, which upon cyclization furnishes 4//-pyrans (Scheme 33) <2004JOC3408>. 

Thiolate-bridged diruthenium complexes such as Cp RuCl(p2-SR)2RuCp Cl catalyze the propargylic substitution reaction of propargylic alcohol derivatives with various carbon-centered nucleophiles [118-120]. Ketones [119] (Eq. 88), aromatic compounds [120] (Eq. 89), or alkenes thus selectively afford the corresponding propargylated products with C-C bond formation. An allenylidene intermediate is proposed in these reactions. They are detailed in the chapter Ruthenium Vinylidenes and Allenylidenes in Catalysis of this volume. 

R. P. Tooze, M. Motevalli, M. B. Hursthouse, and G. Wilkinson, Alkyl Compounds of Diruthenium(III) and Diosmium(III). X-Ray Crystal Structure of the First Ruthenium Peralkyl, Hexakis(neopentyl)diruthenium(III), J. Chem. Soc., Chem. Comm. 1984,799-800. 

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