Ruthenium spectrum

A typical SSIMS spectrum of an organic molecule adsorbed on a surface is that of thiophene on ruthenium at 95 K, shown in Eig. 3.14 (from the study of Cocco and Tatarchuk [3.28]). Exposure was 0.5 Langmuir only (i.e. 5 x 10 torr s = 37 Pa s), and the principal positive ion peaks are those from ruthenium, consisting of a series of seven isotopic peaks around 102 amu. Ruthenium-thiophene complex fragments are, however, found at ca. 186 and 160 amu each has the same complicated isotopic pattern, indicating that interaction between the metal and the thiophene occurred even at 95 K. In addition, thiophene and protonated thiophene peaks are observed at 84 and 85 amu, respectively, with the implication that no dissociation of the thiophene had occurred. The smaller masses are those of hydrocarbon fragments of different chain length. 

The ruthenium(II) aqua ion reacts with nitrogen at room temperature under high pressure (200 bar) forming yellow-brown [Ru(H20)5N2]2+, isolated as a tosylate salt, showing i/(N=N) at 2141cm-1 in its IR spectrum [59]. 

The most recent report of -coordination to a ruthenium porphyrin fragment details the reaction of [Ru(OEP)j2 with C o in benzene/THF (100 1) solution. The UV-visible spectrum of the complex showed a new band at 780 nm, not observed in the spectrum of either Ru(OEP) 2 or C(,o, and H and C NMR data also indicated the presence of a new complex. This has been formulated on the basis of the spectroscopic data as the fullerene complex Ru(OEP)(... 

Figure 1. X-ray absorption spectrum of a silica supported ruthenium-copper catalyst at 100 K In the vicinity of the K absorption edge of ruthenium. Reproduced with permission from Ref. 8. Copyright 1980, American Institute of Physics.

Figure 27. In situ X-ray absorption spectra around the ruthenium X-edge for an electrode modified with (A) one and (B) five monolayers of [Ru(v-bpy)3]2+. (C) Spectrum of bulk [Ru(bpy)3]2+.

Scheme 3 shows the details of the synthetic strategy adopted for the preparation of heteroleptic cis- and trans-complexes. Reaction of dichloro(p-cymene)ruthenium(II) dimer in ethanol solution at reflux temperature with 4,4,-dicarboxy-2.2 -bipyridine (L) resulted the pure mononuclear complex [Ru(cymene)ClL]Cl. In this step, the coordination of substituted bipyridine ligand to the ruthenium center takes place with cleavage of the doubly chloride-bridged structure of the dimeric starting material. The presence of three pyridine proton environments in the NMR spectrum is consistent with the symmetry seen in the solid-state crystal structure (Figure 24). 

In 1977 Ford and co-workers showed that Ru3(CO)12 in the presence of a ca. fiftyfold excess of KOH catalyzes the shift reaction at 100°C/1 bar CO (79). The effectiveness of the system increased markedly as temperature was increased (rate of hydrogen formation approximately quadrupled on raising the temperature from 100° to 110°C), and over a 30-day period catalyst turnovers of 150 and 3 were found for Ru3(CO)12 and KOH, respectively. Neither methane nor methanol was detected in the reaction products. Although the nature of the active ruthenium species could not be unambiguously established, infrared data indicated that it is not Ru3(CO)12, and the complexity of the infrared spectrum in the... 

Besides the electronic spectral studies noted above, we have also carried out in situ studies of the acidic ruthenium catalyst using nmr and infrared spectral techniques. A key set of observations derive from the and 13C nmr spectra of an operating catalyst at 90° and Pco 1 atm which indicate the presence of only one major ruthenium species. The proton spectrum shows a sharp singlet at 24.0 T which remains such when the solution is cooled to room temperature, although the slow formation of other species was observed over a period of hours at the latter conditions. The 1H-decoupled 13C spectrum of the... 

However upon standing at ambient conditions the solutions precipitate Ru3(CO)i2 in nearly quantitative yields. Infrared spectra under reaction conditions (400 atm of 1 1 H2/CO, 200°C) also correspond to the spectrum of Ru(CO)5 no acetate or cluster complexes are observed. However, there is evidence for the presence of small amounts of Ru3(CO) 2 under somewhat lower pressures (ca. 200 atm) Many other ruthenium complexes were used as catalyst precursors, and were found to be converted to the same ruthenium products under reaction conditions. For example, H4Ru4(CO)12 (13), [Ru(CO)2(CH3C02)2ln (14) ... 

For catalyst combinations containing initial I/Ru ratios 5, the product solutions also show strong new bands at 1999 and 2036 cm characteristic (6) of ruthenium pentacarbonyl. Where acetic acid homologation is run at [RuJ > 0.2 M, then another ruthenium iodocarbonyl, Ru(C0)3I2, may be isolated from the product mix as a yellow crystalline solid. A typical spectrum of this material is illustrated in Figure 3b. 

The reactions with ruthenium carbonyl catalysts were carried out in pressurized stainless steel reactors glass liners had little effect on the activity. When trimethylamine is used as base, Ru3(CO) 2> H Ru4(CO) 2 an< H2Ru4(CO)i3 lead to nearly identical activities if the rate is normalized to the solution concentration of ruthenium. These results suggest that the same active species is formed under operating conditions from each of these catalyst precursors. The ambient pressure infrared spectrum of a typical catalyst solution (prepared from Ru3(CO)i2> trimethylamine, water, and tetrahydrofuran and sampled from the reactor) is relatively simple (vq q 2080(w), 2020(s), 1997(s), 1965(sh) and 1958(m) cm ). However, the spectrum depends on the concentration of ruthenium in solution. The use of Na2C(>3 as base leads to comparable spectra. 

Although this spectrum does not correspond to any particular ruthenium carbonyl complex, it is consistent with the presence of one or more anionic ruthenium carbonyl complexes, perhaps along with neutral species. Work is in progress with a variable path-length, high pressure infrared cell designed by Prof. A. King, to provide better characterization of species actually present under reaction conditions. 

Figure 3.21 UPS spectrum of Xe physisorbed on Ru(OOl) showing the superposition of the Xe 5p levels with the d-band of Ruthenium. The position of the Xe 5pm peak with respect to the Fermi level of Ru is a measure of the work function of the adsorption site, as the potential diagram indicates (from Wandelt et al. L54J).

The top spectrum of Fig. 3.22 corresponds to a complete monolayer of Xe on the sample. It can be used for a quantitative titration of sites. The area under the two peaks indicates that about 27% of the Xe in the monolayer is adsorbed on silver, indicating that 27% of the ruthenium surface is covered by silver islands. As a peak at 7.25 eV, which would be characteristic of Ag-Ru boundary sites, is not observed, the results suggest that Ag is present in fairly large islands. 

---