Ruthenium clusters, trinuclear

A trinuclear ruthenium cluster blocked by three pentamethylcydopentadienyl ligands showed a unique reaction environment for C-C bond cleavage. C-C bonds in cydopentadiene and branched alkane are easily cleaved on the triruthenium cluster, giving organo(methylidyne)triruthenium complexes. For example, cydopentadiene coordinates to the trinuclear Ru cluster and cleaves a C-C bond to form ruthenacy-... 

A very interesting deoxygenation reaction, in which carbon monoxide serves as both, a deoxygenating agent as well as a carbonylating agent, was found recently by Bhaduri et al. The formation of phenyl isocyanate from nitrobenzene with carbon monoxide is catalyzed by trinuclear ruthenium clusters such as Ru3(CO),2 or [HRu3(CO) ] ... 

In the case of the cluster anion [HRu3(CO)i,j as hydroformylation catalyst, indirect evidence has been put forward for catalysis by intact trinuclear ruthenium clusters. The catalytic cycle proposed for the hydroformylation of ethylene by this cluster anion (55) is based on the isolation of the protonation product of the intermediate 56 in addition to isotope labeling studies 234) (Scheme 11). It is assumed that 55 is attacked by ethylene at the bridging carbon atom, possibly via an intermediary i/2-eth-... 

Trinuclear ruthenium cluster dimers of the type [Ru30(CH3C00)6(C0)(L)]2 (p-BL), where L = 4-dimethylaminopyridine (dmap) 1, pyridine (py) 2, or 4-cyanopyridine (cpy) 3 BL = pyrazine (Figure 5.3), first synthesised by Ito... 

Although the cyclic voltammetry for this complex seems fairly similar to the trinuclear ruthenium cluster dimers, the lower-lying LUMO (as evidenced by the lower reduction potential) of the triazine bridging ligand plays an important role in explaining the details of the spectroelectrochemistry observed for this LCD. The CO stretching frequency of the neutral complex appears at 1940 cm Upon application of— 1.050 V (vi. Ag pseudoreference, roughly 0 to... 

Analysis of the spectral lineshapes of 5 and 6 gave an uphill rate for charge transfer of 6.5 x lO" s (Table 5.2), and an equilibrium constant of 2.2 for the charge distribution, which compares well with previously reported rate constants for similar mixed-valence dimers of trinuclear ruthenium clusters. 

Some model reactions on related trinuclear ruthenium clusters, especially related to the reduction reactions of nitrobenzene to aniline, have also been reported by Bhaduri and coworkers and several papers have also been published by different groups on related reactions of ruthenium and osmium clusters containing imido. amido or isocyanate fragments, although the latter were not intended as models for catalytic reactions. 

Halides are known to labilize CO ligands in trinuclear ruthenium clusters. For a survey of these reactions see G. Lavigne in The Chemistry of Metal Cluster Complexes, D.F. Shriver, H.D. Kaesz and R.D. Adams (eds), VCH, New York, 1990, p. 201. 

Oxidative addition of hydrogen [reactions (3.55)-(3.57)] to clusters may change the multiplicity of M — M bonds, or cause their breaking. Most often, however, this process is accompanied by dissociation of a Lewis base and, in such cases, of course, the skeleton of the cluster does not change. Oxidative addition and reductive elimination of trinuclear ruthenium clusters have been investigated. Based on the kinetic equation, activation parameters, and isotope effects, the pathway for the reversible reaction... 

Bulky diphosphine ligands, for example, bis(dicyclohexylphosphino)methane and bis[bis(pentafluorophenyl)phosphino]ethane (Figure 1.7), form with Ru3(CO) 2 trinuclear ruthenium clusters of different stoichiometry mainly with Pi-T -coordination [28]. In the hydroformylation of ethylene and propylene, aldehydes were formed with superior activity in comparison to the use of dppe (l,2-bis(diphenylphosphino)ethane). Excellent Hb selectivities were also noted by the use of Xantphos as ligand [11]. In general, bidentate ligands provide higher yields than monodentate phosphines. 

Some model reactions on related trinuclear ruthenium clusters, especially related to the reduction reactions of nitrobenzene to aniline, have also been reported by Bhaduri and co-workers [159-162]. 

Trinuclear Ruthenium Clusters with Cyclopentadienyl Ligands ... 

For the synthesis of the trinuclear ruthenium cluster bearing the cyclopentadienyl ligand, chlororuthenium and methoxoruthenium complexes, such as [Cp RuCl2]2 (1, Cp = [Cp RuCl]4 Cp Ru(OMe) 2... 

---