Transition metal clusters carbonyl bonding

Reviews have appeared of photochemical disproportionation of metal-metal bonded carbonyl dimersphotofragmentation of transition metal cluster carbonyls in the gas phase, and f-element photochemistry. ... 

Wade also extended the application of his rules to transition metal clusters the further extension by D. M. P. Mingos mainly concerns the bonding in metal carbonyl and metal phosphane clusters, i.e. organometallic compounds (Wade-Mingos rules) these are beyond the scope of this book. 

Following the many recent developments in the chemistry of metal carbonyl clusters and other metal-metal bonded species, interest has developed in silicon-transition-metal clusters. These will be defined for the present purpose as compounds containing (1) at least one metal-metal bond and (2) at least one silicon atom directly linked to two or more metal atoms. Thus compounds such as Me3SiOs(CO)4Os(CO)4-SiMe3 and R3SiOCCo3(CO)9 are excluded examples of compounds that meet these criteria are shown in Table XXIII. 

High Nuclearity Metal Carbonyl Clusters, 14, 285 Infrared Intensities of Metal Carbonyl Stretching Vibrations, 10, 199 Infrared and Raman Studies of -Complexes, 1, 239 Insertion Reactions of Compounds of Metals and Metalloids, 5, 225 Insertion Reactions of Transition Metal-Carbon Bonded Compounds I. Carbon Monoxide Insertion, 11, 87... 

Although the principles of cluster bonding developed for main-group clusters carry over to transition-metal clusters of the group 8/9 metals with carbonyl ligands, we fully expect transition metals to exhibit variations on this cluster bonding theme as well as novel behavior not seen in main-group systems. In this section we introduce those aspects of cluster chemistry characteristic of transition-metal clusters. 

Pt and Pd Carbonyl Complexes. Prom reactivity measurement with carbon monoxide, Cox et al. [18] determined the relative CO bonding strength to transition metal clusters ... 

Bonding in clusters and condensed cluster compounds that extend in one, two and three dimensions Principles of bonding and reactivity in transition metal cluster compounds Mathematical cluster chemistry Graph-theory derived models for the skeletal chemical bonding in organometallic metal carbonyl clusters... 

In 1977 we reported a method based on graph theory for study of the skeletal bonding topology in polyhedral boranes, carboranes, and metal clusters Q). Subsequent work has shown this method to be very effective In relating electron count to cluster shape for diverse metal clusters using a minimum of computation. Discrete metal clusters treated effectively by this method Include post-transition metal clusters (, ) > osmium carbonyl clusters (O, gold clusters, platinum carbonyl clusters (J., 7 ) > and... 

It is now clear that a variety of elements form clusters of atoms which are held together, at least in part, hy bonds between like atoms. Transition metals do this and the structures of some representative compounds are illustrated in Figure 3.3. Note that in Ta Cln the oxidation state of tantalum is +7/3. Non-integral oxidation states are also observed in other transition metal clusters. Some metal carbonyls also contain clusters of metal atoms for example, in Co4(CO)i2 there is a tetrahedron of cobalt atoms and in Rh6(CO)i6 the six rhodium atoms are arrayed at the comers of an octahedron. A measure of the stability of some of these clusters is the fact that C04 units survive conditions in a mass spectrometer which strip all the CO s from a Co4(CO)i2 molecule. At present, the metal cluster which contains the largest number of metal atoms, the champion, is [H2Pt38(CO)44]". ... 

The most electropositive elements, including lanthanides. Favoured where organic anion is stable. Multicentre bonds involving carbon. Carbon atom associated with two or more metal atoms in multicentre m.o.s. Electropositive elements where cation would be strongly polarizing (Chapter 3). Carboranes. Some transition metal clusters, especially carbonyls (Chapter 11). 

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