Triple bond: defined, 6 examples

The empirical valence bond model has shown good predicting power if one defines the bond multiplicity to be two for compounds such as CePd or BaPd and three for compounds such as LaRh, Ylr, or RhTh. The limitations of the model could also be shown (40) when applied to assumed quadruple bond formation, as in RuV or ThRu or to double bond formation as in CePt or ThPt. The case of ThRu (41) shows that quadruple bonding is approached where suitable valence states are available, but not fully achieved, apparently because of the directional requirements of the bonding in a diatomic molecule. The examples of CePt and ThPt (40) show the calculated values that have been based on an assumed double bond to be too low. Platinum has no suitable valence state for triple bond formation, but apparently forms triple bonds with other... 

Just as we can define an average bond enthalpy, we can also define an average bond length for a number of common bonds (A TABLE 8.5). Of particular interest is the relationship, in any atom pair, among bond enthalpy, bond length, and number of bonds between the atoms. For example, we can use data in Tables 8.4 and 8.5 to compare the bond lengths and bond enthalpies of carbon-carbon single, double, and triple bonds ... 

Triple bond formation at nitrogen and oxygen The stereoelectronic control of reactivity at multiple bonds is not limited to all carbon species. Due to the presence of a stereoelectronically defined lone pair, sp -hybrid-ized nitrogen compounds provide a number of illustrative examples of slereochemically directed reactivity (Figure 7.34). 

The program AIPHOS may be described here because a reaction is defined as a process of intermolecular isomerization of a multiple molecular system into another. The generation of precursors is related to the automatic structure elucidation system CHEMICS. In AIPHOS the system contains a list of forbidden substructures, for example triple bond in a ring of size <8, or C=C=C=C, etc. When a precursor is generated it is checked against this list and if it contains one of the forbidden substructure it is rejected. If the precursor is chemically viable, the reacting part is checked with the knowledge base of known reactions and if it is present the process has a probability of practicability. 

In contrast to the above examples, calculations modeling the gold-catalyzed formation of conjugated enones and enals from propargylic acetates could not define a pathway based on the initial activation of the C C triple bond. Instead, the observation that this transformation was promoted by the addition of water led to the suggestion that [(NHC)Au(OH)] may be the... 

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