Organometallic complexes isomeric forms

According to experimental evidence, the allyl ligands may be eliminated from the surface as either 1,5-hexadiene (by reductive elimination of two allyl ligands) or propene. Two tris(trimethylophosphine) complexes of rhodium are formed, only one of which retains the allyl ligand. This is in fact the 7i-o-allyl isomerization in a well-defined surface organometallic complex. 

A decisive role may be played by the strength of the bond between olefin and the catalyst (4,47,57). This view is indirectly supported by the degree of stability of organometallic complexes of transition metals with olefinic ligands, which decreases with increasing isomerization ability of the given metal. It may be assumed that the relative adsorptivity of an olefin on the surface of various metals corresponds to the stability of compounds formed by the olefin with salts of the respective metals (62-64). 

Chemists have increasingly used computational chemistry to study aspects of organometallic chemistry. Although Chapter 2 and subsequent chapters make good use of qualitative molecular orbital theory, the ready availability of easy-to-use computational chemistry software and the powerful capability of modem desktop computers allow chemists to effectively model complex systems to obtain minimum energy geometry of molecules, determine transition state energies, and predict the course of chemical reactions, particularly if two or more isomeric products could form. Researchers have modeled entire catalytic cycles, which... 

Chattopadhyay P, Matsuo T, Tsuji T, Ohbayashi J, Hayashi T (2011) Thermal isomerization of A-bridged cobalt corrole complexes through a transiently formed axial carbenoid. Organometallics 30 1869-1873... 

The formation of such Lewis complexes may find increasing application in stereochemical studies. Two cases in point might be cited. First, etherate formation allows the isolation of the optically active tri-2-methylbutyl-aluminum etherate (97). This compound is stable to racemization up to 100°. Second, diphenylpalladium (II) has recently been prepared as its bis-triethylphosphine complex in both a cis- and a irans-planar complex form (20). The latter seems to represent the first example of geometrical isomerism among organometallic compounds (Section II.D). 

Beyond the ability to probe heterogeneous electron transfer reactions that occur on the micro, or even nano timescale, high-speed cyclic voltammetry has found application in the investigation of complex reaction mechanisms. An example of this is the following chemical (EC) reaction. The oxidation or reduction (E reaction) of an electroactive species can produce a chemically unstable product that undergoes a chemical reaction (C reaction) to form an electroinactive product. Electron transfer reactions can also lead to isomerizations and ligand loss in organometallic compounds, such as... 

Isomerization of olefins which takes place as a result of the transfer of hydrogen atoms with concomitant migration of the double bond is catalyzed by transition metal complexes which may react with olefins to form organometallic compounds. Often, it is necessary that cocatalysts be present as sources of hydrogen. Most commonly utilized cocatalysts are acids, water, alcohol, hydrogen, silanes, etc. The formation of hydrido complexes during isomerization reactions is crucial. The following mechanisms of olefin isomerization reactions are known ... 

The discovery that the nitrosyl ligand is capable of binding to tianation metals in two isomeric valence forms is one of the most dramatic recent developments in organometallic chemistry. Since bent NO donates 2 fewer electrons to the metal than the linear isomer does, linear-bent tautomerism raises the possibility of coordinative unsaturation and catalysis. In fact, complexes of nitric oxide are receiving increasing attention as catalysts, since they are more reactive than the corresponding carbonyls. ... 

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