Transition metal carbonyl compounds

Vibrational spectra of transition metal carbonyl compounds. L. M. Haines and M. H. B. Stiddard, Adv, Inorg. Chem. Radiochem., 1969,12, 53-133 (340). 

Despite the apparent generality of this Wittig-type process, it must be noted that the reactions of Ph3P=C=PPh3 with transition-metal carbonyl compounds do not always result in the formation of phosphonioacetylide moieties. Thus, replacement of, instead of addition to (see Scheme 24), the CO group has been observed in some... 

Our earlier work with Rh6(CO)i6 was the first example of using a transition metal carbonyl compound for catalyzed oxidations. We now find that Rh6(CO)16 is not unique in functioning as a homogeneous catalyst for oxidizing ketones. The dimer Re2(CO)10 is equally effective. The reaction mixture is homogeneous throughout the catalytic reaction. The carbonyl is not decomposed and can be recovered quantitatively at the end of the oxidation. This latter situation even prevails when the oxidations are carried out in the absence of carbon monoxide. Species characterization is done by isolation methods or by IR spectroscopy in the carbonyl region. 

Of the linear clusters, the organogermanium-substituted transition metal carbonyl compounds are the simplest. In every case, the coordination at germanium is tetrahedral, while the transition element retains the geometry of the parent carbonyl compound (50,108,119,155, 157, 181). The Ge—M bond is almost without exception shorter than the sum of the Ge—M covalent radii (Table VI), which is cited as evidence for (d — d)-n multiple bonding. 

Many transition metal carbonyl compounds are known. The one that is the most significant toxicologically, because of its widespread occurrence and extremely poisonous nature, is the nickel carbonyl compound, Ni(CO)4. Perhaps the next most abundant is Fe(CO)5. Other examples are... 

Whereas discrete low oxidation state compounds of the transition metals are common in organometallic chemistry, the most typical series of examples being the transition metal carbonyl compounds see Carbonyl Compound), there are at present significantly fewer classes of compounds containing main group elements in low oxidation states. An... 

The lanthanide halides are usually bi(cyclopentadienyl) and related lanthanide complexes M is an alkali metal or silver, and A is an anionic transition metal carbonyl compound or tetraphenyl borate. The formation of the insoluble salt MX is a driving force for this reaction. 

The electrocatalytic oxygen reduction in DMFC systems requires the development of highly selective electrodes in the presence of methanol. Present electrolyte membranes based on Nafion 117 are permeable to methanol (crossover effect), which depolarizes the platinum cathode [81,82]. For this reason, our strategy, some years ago, was to produce electrocatalytic materials from the thermal decomposition of some neutral transition-metal carbonyl compounds in the presence... 

Transition metal carbonyl anions are now synthesized primarily by the reduction of transition metal carbonyl compounds in donor solvents. For example, in liquid ammonia solvent Cr(CO)6 can be reduced by sodium to form the disodium salt of [Cr(CO)5]2 plus the explosive compound disodium acetylenediolate ... 

Most transition metal complexes are sensitive towards oxygen and/or water, especially under irradiation. This fact sometimes impedes photochemical work in this field. Detailed information about the properties and thermal chemistry of transition metal carbonyl compounds is found in 519>2 and there are excellent reviews on arene complexes 177 387,525,532) and olefin complexes i78,22i) ... 

A thorough study of the photochemical dimerization of norbornadiene with a variety of transition metal carbonyl compounds has revealed some systematic effect of the nature of the transition metal involved on the stereospecifity of the dimerization observed, which is increased going from left to right across the transition metal series 571). 

Novel photochemical (and thermal) reactions of macrocyclic oxa-sila-acetylenic ring systems (expected to show unusual optical properties because of electronic effects arising from orbital overlap of the acetylenic n system with the silicon a bonds and the oxygen lone-pair electrons) were described. While thermolysis in the presence of a transition metal carbonyl compound gave cyclization to both benzenoid and fulvene species, photolysis in the presence of the transition metal carbonyl compound (which catalyzes 1,2-silyl shifts across a carbon-carbon triple bond) gave fulvene and vinylidene products, the latter being readily photolyzed to the fulvene 159 (equation 101). 

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