Triruthenium species

Using solvent-containing triruthenium species 1 as a synthetic precursor, a series of pyridyl-substituted triruthenium derivatives [Ru30(0Ac)6(py)2(L)]+ (L = 4,4 -bpy 5, BPE 6, BPA 7) were prepared by Meyer et al. [9]. Electrochemical studies showed that these triruthenium complexes exhibit four to five reversible one-electron redox waves in the potential range of +2.0 to —2.0 V, suggesting that these complexes can... 

From structural characterization of 48 by X-ray crystallography [31], it is suggested that formation of stable Ru 11,111- cluster derivative 47 or 48 is involved in substitution of the axially coordinated methanol as well as one of the six bridging acetates in the Ru ni ni precursor 2 by an abpy or abcp, in which formal oxidation state of the triruthenium species is converted from 111,111,111 to III,III,II. 

Fig. 8 Plots of cyclic voltammograms of abcp-substituted triruthenium species 48 and the parent triruthenium complex [Ru30(0Ac)6(py)3]+ in chloromethane solution of (Bu4N)(PFg), showing anodic shifts of redox potentials in 48 relative to those in [Ru30(0Ac)6(py)3] +...

Ruthenium(II) has been complexed to each of the bidentate sites on the arms of 13, each ruthenium capped with two additional 2,2/-bipyridyl ligands.21 Each of these complexes, in particular the triruthenium species... 

In this article we have summarized the use of both photochemical and more classical thermal kinetics techniques to deduce the nature of intermediates in the ambient temperature, fluid solution chemistry of several triruthenium clusters. In some cases the photochemically generated intermediates appear to be the same as those proposed to be formed along thermal reaction coordinates, while in other cases unique pathways are the results of electronic excitation. The use of pulse photolysis methodology allows direct observation, and the measurement of the reaction dynamics of such transients and provides quantitative evaluation of the absolute reactivities of these species. In some cases, detailed complementary information regarding... 

The triruthenium derivatives 31-35 show characteristic intracluster charge transfer (IC) absorptions in the visible to near-infrared region (600-1000 nm) and cluster-to-ligand charge transfer (CLCT) transitions at 320-450 nm. Compared with the low energy bands in [Ru3n m m]+ complexes 31-35, those in the one-electron reduced neutral [Ru3 ]° species are remarkably red-shifted. The decrease in energy for these transitions by one-electron reduction reflects a rise of the occupied d% levels as the number of electrons increases. Complexes 31-35 exhibit... 

Reaction of triruthenium precursor 2 with one equivalent of bis(2,2 -bipyridyl) ligand gave monomeric species 38 or 39 with ort/iometallated bpyC=Cbpy or bpyC=C-C=Cbpy, respectively [30]. The dimeric species 40 or 41 is then... 

The 2,2 -bipyrazine (bpz)-substituted RU3 cluster monomer 42, dimer 43, and trimer 44 could be accessed by reaction of triruthenium precursor 2 with different amounts of 2,2/-bipyrazine [30]. The trimeric species 44 containing two parent Ru30(0Ac)6(py)2 n m and one derivate Ru30(0Ac)5(py)2II m m units could be directly prepared by reaction of 3.8 equivalents of 2 with 2,2/-bipyrizine. It is also accessible by reaction of dimeric species 43 with 1.8 equivalents of 2. The bpz adopts ri1 (N),(x-r 1 (N),r(1 (N) and p,4-r 1(N),r 1(N),r 1(C),r 2(N,N) bonding modes in 42, 43, and 44, respectively. Reduction of 3+ trimer 44 by addition of aqueous hydrazine allowed isolation of neutral intracluster mixed-valence species 44b containing three Ru 11,111,11 units. Oxidation of 44b with two... 

It appears that abpy- or abcp-substituted oxo-centered triruthenium derivatives exhibit a high stabilization on low-valence III,III,II and III,II,II species, which are usually unavailable through axial ligand substitution. The abpy or abcp exhibits a i-T 1(N),r 2(N,N) bonding mode, chelating one ruthenium center via azo N and pyridyl/pyrimidine N donors as well as bound to another ruthenium center via the other pyridyl/pyrimidine N donor. 

The carbonylation of imidazole derivatives with several olefins takes place in high yields with the aid of an Ru3(CO)i2 catalyst.112,112a The carbonylation occurs exclusively at the a-position to the sp2 nitrogen (Equation (85)). A wide range of olefins can be utilized in this reaction, and a variety of functional groups are compatible under the reaction conditions. The (/i-H)triruthenium clusters such as 12 are proposed as a key species in this carbonylation reaction. Other five-membered A-heteroaromatic compounds, such as pyrazoles, oxazoles, and thiazoles, can be used for the carbonylation reactions, where the carbonylation takes place at the a-C-H bond to the sp2 nitrogen. 

In the cases of [Ru3(CO)i2] and [Ru4H4(CO)i2], which have very unstable anion radicals, Lewis base substitution reactions are stoichiometric rather than catalytic in the reducing agent (167) dppe and the triruthenium cluster give [Ru3(CO)io(dppe)J, [Ru3(CO)n(dppe)], or [ Ru3(CO)n 2(/u.-dppe)], depending on the relative stoichiometries of the reactants (168). Complexes such as [Ru3(CO)uL] and [Ru4H4(CO)uL] [L = PPh2CH2CH2Si(OEt)3], precursors to surface-anchored species, have also been prepared by reductively induced substitution reactions (169). 

EXAFS spectroscopy has been successfully applied to silica- and y-Al203-supported triosmium (57), triruthenium (52), and triiridium (74) clusters. Structural parameters characterizing each surface species on alumina are summarized in Table IV. The results provide evidence for surface species such as HOs3(CO)h(OAI=), HRu3(CO)io(OSi ), and a raft ensemble of Ir(CO)2(OAI=)2 and Ir(CO)3(OAI)2, close analogs to the compounds [Ir(CO)2Cl2] and Ir(CO)3COPh, respectively. 

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