Ruthenium frequency

Figure 2. A comparison of the rate (turn-over frequency) of methane synthesis over single crystal and supported ruthenium catalysts. Total reactant pressure for the single crystal studies was 120 Torr.

The ruthenium-phosphine-diamine catalysts exhibit high turnover numbers and frequencies, and near-perfect chemoselectivity for ketone/aldehyde over... 

The first application of a heterocyclic carbenoid achiral ligand for hydrogenation of alkenes was reported in 2001 by Nolan and coworkers. Both ruthenium [36] and iridium [37] complexes proved to be active catalysts. Turnover frequency (TOF) values of up to 24000 b 1 (at 373 K) were measured for a ruthenium catalyst in the hydrogenation of 1-hexene. 

The 1,2-oxaborolide anion (Figure 1), an analog of furan, has been prepared by two different routes and sandwich complexes with ruthenium and manganese 136, 137 have been characterized.153 Comparison of IR stretching frequencies suggests that oxaborolide is a weaker electron donor and better electron acceptor than cyclopentadienyl. 

It is realised that both ruthenium and the substituted porphyrins are expensive catalyst components for industrial applications. Both turnover frequencies and turnover numbers are modest. Nevertheless it remains an interesting option to use dioxygen directly in epoxidation reactions. 

While ruthenium dichlorides always showed an undesirable initiation time, these novel catalysts start the reaction without delay. For compounds not containing functional groups their turnover frequencies can be several thousands per hour, but for polar molecules the total turnover may be as low as fifty, obtained in several hours. 

Table 1 Selected metal-nitrido bond distances and stretching frequencies for ruthenium and osmium...

The ruthenium cluster [Ru2(i76-C6H6)H6]C12 is a catalyst for fumaric acid hydrogenation in aqueous solutions, with a turnover frequency of 35 h 1 at 50°C (86). 

The carbide atom in 1 is located in the center of the square face such that it is partially exposed whereas the carbide atom in 2 is completely encapsulated by the six ruthenium atoms. From a spectroscopic viewpoint, carbide atoms are very distinctive and the earlier reviews have dealt with these aspects in detail.7 8 The IR spectrum of 1 contains peaks at 701 (s) and 670(m) cm 1, and 2 contains peaks at 717(sh), 703(s), 680(m), and 669(m) cm-1.22 I3C-NMR spectra of 1 and 2 do not appear to have been reported. This is probably due to the low yields in which these compounds were initially obtained at a time when, 3C-NMR was still not in widespread use in cluster chemistry. In general, the 13C-NMR resonance of carbide atoms ranges from 8 250 to 500. The high frequency resonances exhibited in 13C-NMR spectra reflect the different diamagnetic and paramagnetic effects experienced by a nucleus in such an unusual chemical environment.23... 

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