Carbon core

Docht, m. wick. kohle,/. Elec.) cored carbon. Docke,/. bundle, skein plug baluster mandrel doll dock. 

All these molecules contain 86 electrons associated with the valence shells of the 6 metal atoms (the core carbon atoms of the carbides are considered to contribute all their valence shell electrons to these clusters). In the hydride H2Rufl(CO)i8, for example, the metal atoms supply 48 electrons, the carbonyl ligands 36, and the hydrogen atoms 2. Formally, this hydride maj be regarded as derived from the anion [Ru(CO)3]g , which, in turn, can be shown to be formally related to the c(oso-borane anion RgHe " as follows (199, 200). 

Ytterbium oxide is used in cored carbon rods for industrial lighting. The oxide also is used as an additive in special glasses. Other uses are in dielectric ceramics and special alloys. 

Fig. 3.5. Structure of hard-core carbonate-benzenesulfonate RMs. The mineral core is mainly made up of amorphous carbonate. The carbonate colloidal core has a radius of about 3 nm and the surfactant layer thickness is about 2 nm...

Table 3.9. The antiwear characteristics and extreme-pressure properties of non-modified and modified hard-core carbonate-sulfonate RMs in mineral oil measured by a four-ball test under 60 decanewtons (daN) load.

Fig. 29 TEM image of metal core/carbon sheath nanocables with a long, iron-containing core and a spindle-like tip. The TEM image is reprinted with permission from [216]. Copyright 2005, Wiley-VCH...

The molecule in Figure 10.2 has four core carbons also. In this case all four are cores for different groups. Starting from the left side of the molecule we have C—(C)(H)3, then the second carbon gives us C—(C)(Crf)(H)2, the third carbon gives us Cj—(C)(H), and the fourth carbon Cj—(H>2. 

Table 2(a) Carbon dioxide data from polar ice cores. Carbon dioxide concentrations and carbon isotope values (in per mil relative to the PDB standard) are listed for the LGM ( 18-24 ka), the Holocene Epoch (1-10 ka), and the most recent pre-industrial part of the Holocene Epoch (1000-1800 AD). Key references for the CO2 data from each core site are hsted in the right-hand colunrn. The superscript letters in the data table indicate the references from which the indicated values were derived. Values for Vostok (LGM and Holocene)... 

Using molecular modeling software, draw the core carbon-centered cluster of Ru5C(CO)]7 (see Figure 15-22), and calculate its molecular orbitals. Identify and display the following ... 

Reactor Core Carbon dioxide coolant Steam Generator Ion Exchange Systems ... 

Carbon-arc lighting The US Army, Navy, and Coast Guard searchlights all use lanthanide-cored carbons. 

Figure 4.11. Skeletal structures of some metal carbide clusters. In [Osio(CO)24C], 4 of the 10 osmium atoms cap a tetrahedrally related set of faces of the inner Oss octahedron that contains the core carbon atom.

The NMR resonances due to the core carbon atoms in f c iCC ())id and the other metal carbonyl carbides shown in Figure 4.11 tend to lie well downfield. As these core carbon atoms serve as the sites at which carbonyl ligands may coordinate, they can alternatively be regarded as sequestered electron-deficient carbonium ions rather than as carbanionic carbides. 

If the square pyramidal metal carbonyl carbides Fe5(CO)i5C ° and Os5(CO)i5C are treated in a similar manner to I xyi ( ()) i T that is, as clusters in which all four of the core carbon atom s valence shell electrons are used for skeletal bonding, then they are seen to have the expected nido shapes of systems with five skeletal atoms (the metal atoms) held together by seven skeletal bond pairs. By contrast, if these carbide carbon atoms had occupied polyhedral vertex sites, with a lone pair of electrons in an exo-oriented sp hybrid orbital, then the number of skeletal bond pairs would have been reduced by one and the number of skeletal atoms would have increased by one. The five metal atoms and the carbide carbon atom would have had to be accommodated in some way on a trigonal bipyramidal skeleton. Clearly, the assumption that all four valence shell electrons from the carbide carbon atom are involved in the skeletal bonding is vindicated. 

Figure 4.14. Localized 4c-2e bonds used to describe the metal-carbon bonding to the core carbon atoms in the octahedron of [Fe6(CO)i6C]L (For simplicity, only half of the Me octahedron containing two 4c-2e bonds is shown.)...

Figure 4.15. Schematic representation of the types of skeletal bonding MOs of [Rhe(CO)e(n -CO)9C] that can be stabilized by the core carbon AOs. " (Metal AOs are shown monolobal for simplicity).

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