Transition metals carbonyl complexes, photochemistry

To date, most of the photochemical data available for transition metal complexes comes from condensed phase studies (1). Recently, the primary photochemistry of a few model transition metal carbonyl complexes has been investigated in gas phase (5.). Studies to date indicate that there are many differences between the reactivity of organometallic species in gas phase (5.6) as conq>ared with matrix (7-10) or solution (11-17) environments. In most cases studied, photoexcitation of isolated transition metal... 

The photochemistry of transition-metal carbonyl complexes has been the focus of many investigations. This is due to the central role that metal carbonyl complexes play in various reactions. 

We hope that this review has shown that ever more elaborate experimental and computational techniques continue to be applied to elucidate the structure, assign spectra, and rationalize photochemical reaction mechanisms in transition metal carbonyl complexes. These systems provide a wealth of fascinating vibronically induced chemistry that we are only beginning to understand, and it is expected that as experimental and computational techniques further evolve many more studies of these systems will take place. Transition metal carbonyl systems are of primary importance in organometallic chemistry and unsaturated complexes are of key importance in industrial synthesis. Their photochemistry has many aspects that require a true multi-disciplinary approach, requiring knowledge and expertise in the fields of transition metal chemistry, ultrafast spectroscopy, computational spectroscopy, computational photochemistry and conical intersection theory, Jahn-Teller... 

Photochemistry of transition metal carbonyl complexes as the borderline between organic and inorganic chemistry is mentioned in Section 6.3.9. Since the dissociation energy of a common metal carbonyl oxide bond is usually low, photodecarbonylation, that is, release of the CO molecule, is the most common photoprocess observed (entry 8). 

More interest, however, has been focused on the photochemistry of phosphine complexes of the second- and third-row transition metals in their lower oxidation states. This interest is primarily the result of the fact that such complexes are widely used as homogeneous catalysts in the solution phase, and it is theorized that photochemical techniques can be used to generate reactive excited states, or at least to generate reactive, coordinately unsaturated species. A primary goal of such work is the generation of a photocatalytic system whereby the photoproduct is a thermal catalyst, thereby making the transformation catalytic in the number of incident photons. Many of these ideas that have been pursued with tertiary phosphine complexes have also been followed for transition metal carbonyl complexes, with this latter photochemistry being discussed in Chapter 6. 

Carbene Complexes Carbonyl Complexes ofthe Transition Metals Cyanide Complexes of the Transition Metals Dinuclear Organometallic Cluster Complexes Electron Transfer in Coordination Compounds Electron Transfer Reactions Theory Electronic Structure of Organometallic Compounds Luminescence Nucleic Acid-Metal Ion Interactions Photochemistry of Transition Metal Complexes Photochemistry of Transition Metal Complexes Theory Polynuclear Organometallic Cluster Complexes. 

The majority of such systems involves the coordination of a Group 14 organometallic to a transition metal, in most cases a carbonyl complex. This section falls into two categories—the formation of such complexes by photochemical means, and their photochemistry once formed. 

The photochemistry of rhenium complexes occupies a prominent position in the photochemistry of transition metal complexes. Along with early preparative studies on photosubstitution of carbonyl species like Re(CO)sX, the preparation of the remarkably stable yellow complex /ac-Re(CO)3(phen)Cl foreshadowed the discovery of the a large class of related luminescent materials by Wrighton and co-workers in the 1970s [ 1 ]. As pointed out by Vogler and Kunkley, the current photochemistry of rhenium complexes is rich, spanning eight oxidation states from formal Re(0) (for example, Re2(CO)io) to formal Re(VII) (for example MeReOs) [2],... 

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