Ruthenium iron containing

The electroactive units in the dendrimers that we are going to discuss are the metal-based moieties. An important requirement for any kind of application is the chemical redox reversibility of such moieties. The most common metal complexes able to exhibit a chemically reversible redox behavior are ferrocene and its derivatives and the iron, ruthenium and osmium complexes of polypyridine ligands. Therefore it is not surprising that most of the investigated dendrimers contain such metal-based moieties. In the electrochemical window accessible in the usual solvents (around +2/-2V) ferrocene-type complexes undergo only one redox process, whereas iron, ruthenium and osmium polypyridine complexes undergo a metal-based oxidation process and at least three ligand-based reduction processes. 

The mononuclear metal carbonyls contain only one metal atom, and they have comparatively simple structures. For example, nickel tetracarbonyl is tetrahedral. The pentacarbonyls of iron, ruthenium, and osmium are trigonal bipyramidal, whereas the hexacarbonyls of vanadium, chromium, molybdenum, and tungsten are octahedral. These structures are shown in Figure 21.1. 

The skeleton of W4(/Lt4-C)(0)(0H2Bu )i2 is given in 7-XII. The carbon atom is frequently found as a discrete C4- unit encapsulated in scores of clusters of metals such as iron, ruthenium, osmium, cobalt, rhodium, nickel, and rhenium but a few contain encapsulated Q units (see later). 

The metal centres in the iron, ruthenium, and osmium alkynyl complexes listed in Table 1 possess 18 valence electrons. Table 2 contains HRS data at 1.064 p,m and two-level-corrected values for similar 18 valence electron alkynyl and chloro nickel complexes, and a particularly efficient example is illustrated in Figure 5. These data are substantially resonance enhanced, although the relative orderings are maintained with two-level-corrected values. 

Sample C, containing iridium and iron, exhibits the same reversible oxidation-reduction behavior, indicating the incorporation of the iron into the iridium clusters. The isomer shift for sample C, however, was not in good agreement with the value of 0.38 mm sec- (58) expected for dilute iron in iridium alloys. This difference may reflect an unusual chemical state for iron which is associated with surface iridium atoms in clusters. A similar situation has recently been reported and discussed for iron-ruthenium catalysts (59). 

Mixed metal clusters (clusters containing two different metals) have considerable potential for mechanistic studies. Three separate studies on iron-ruthenium clusters show the possibilities. Reactions of FeRu2(CO)i2 and Fe2Ru(CO)i2 in comparison to Fe3(CO)i2 and Ru3(CO)i2 show a very interesting activation of the iron center towards CO dissociation by ruthenium centers in the mixed metal-cluster system. Such an activation of the iron center by ruthenium has also been demonstrated for (/r-H)FeRu2(/r-COMe)(CO)io. The presence of different metal centers for H2FeRu3(CO)i2 allowed unusually detailed interpretation of the isomerization, substitution, and CO exchange reactions. ... 

Hassium, element 108, does not exist in nature but must be made in a particle accelerator. It was first created in 1984 and can be made by shooting mag-nesium-26 (ifMg) atoms at curium-248 ( HCm) atoms. The collisions between these atoms produce some hassium-265 (io Hs) atoms. The position of hassium in the periodic table (see Fig. 2.20) in the vertical column containing iron, ruthenium, and osmium suggests that hassium should have chemical properties similar to these metals. However, it is not easy to test this prediction—only a few atoms of hassium can be made at a given time and they last for only about 9 seconds. Imagine having to get your next lab experiment done in 9 seconds ... 

Turning now to smaller-volume commodity chemicals, there are already numerous descriptions in the literature to the synthesis of N-substi-tuted formamides, particularly N,N-dialkylformamides, from the corresponding alkylamines plus carbon monoxide (eq. 25). A range of catalysts may be employed, including metallic alkoxides (75), cobalt (76), iron (77), and ruthenium-containing compounds (78), and reaction (25) is the basis of the Leonard process for making N,N-dimethyl-formamide. 

Ruthenium-containing compounds are, in general, structurally similar to their iron analogs. Thus, coronands containing two polyoxa- and polyaza-oxa macrocycles, and from three to six polar atoms in each ring (oxygen and/or sulfur) have been synthesized and investigated [135-137]. 

Some "mixed" metal tetrahedra containing cobalt and either iron, ruthenium, or osmium are known. The first such compound to be prepared is the black HFeCo3(C0)i2 which may be obtained by heating a... 

Re2(CO)io]/ as well as cluster carbonyls of iron, ruthenium, osmium, rhodium, and iridium. " Catalysts that are obtained in basic aqueous-methanol solution of metal carbonyls of the type M(CO)6 (M = Cr, Mo, W) and M3(CO)i2 (M = Ru, Os) are active even in the presence of sodium sulfide.Most commonly utilized solvents have been mixtures of water with alcohols, methoxyethanol, pyridine, etc. (mainly in the case of neutral solutions and those containing bases, such as KOH, K2CO3). Catalysts that are active in acidic media include Rh2Cl2(CO)4- -HCl- -NaI (solvent H0Ac-hHCl + H20),<"" [Rh(bipy)2]Cl, " > and... 

In the iron, ruthenium, and osmium derivatives, there are cases of q q re-switch on thermolysis followed by the elimination of small ligands. Organo-ruthenium species containing pyrazol-l-ylborate or -methane ligands with bulky substituents often have uncoordinated pyrazol-l-yl moieties and agostic R—B(C) M interaction. The latter sometimes influences the properties of the / -coordinated species as well. 

---