Group 4 metal substituents interactions

The change to a silicon-based substituent group, e.g., SiMe3, has the opposite effect. The introduction of two more orbitals of 7r-symmetry appropriate for bonding stabilizes the metal-carbon interaction and increases the percentage electron density of the 7r-orbital on the carbyne ligand (28). 

Further work by Anson s group sought to find the effects that would cause the four-electron reaction to occur as the primary process. Studies with ruthenated complexes [[98], and references therein], (23), demonstrated that 7T back-bonding interactions are more important than intramolecular electron transfer in causing cobalt porphyrins to promote the four-electron process over the two-electron reaction. Ruthenated complexes result in the formation of water as the product of the primary catalytic process. Attempts to simulate this behavior without the use of transition-metal substituents (e.g. ruthenated moieties) to enhance the transfer of electron density from the meso position to the porphyrin ring [99] met with limited success. Also, the use of jO-hydroxy substituents produced small positive shifts in the potential at which catalysis occurs. 

Interaction of group 4 metal substituents with positive charge at the (3 position... 

Interaction of Group 4 Metal Substituents with Positive Charge at the (3... 

IX. COMMENT INTERACTION OF GROUP 4 METAL SUBSTITUENTS WITH SINGLY OCCUPIED ORBITALS... 

From the foregoing discussion it is evident that substituent groups in the organic inhibitor are likely to have a profound effect on the metal-inhibitor interactions and hence the inhibition efficiency. Thus structure-activity relationships in corrosion inhibition have evolved based on principles of physical organic chemistry. According to Hammett equation we have... 

As a first project we analyzed the metal-diyl interactions in the complexes Fe(CO)4-ECp (E = B -Tl) which have the strong donor group Cp as substituent [18]. The results of the energy decomposition analyses are given in Table 13.19. Only the axial isomers are... 

High selectivity for either the anti or the syn aldol product can be obtained by using an appropriate thioester and a boron-mediated aldol reaction. The trans-enolate and hence the anti aldol product can be obtained from the 5-tert-butyl ester and dibutylboron triflate (1.68). The trans-enolute (note the convention that the O-metal substituent takes a higher priority than the SR substituent) is favomed owing to the steric interaction of the bulky tert-butyl group with the ligands on the boron... 

A macromolecule bearing suitable ligand groups or substituents can interact with a metal part (metal ion, metal complex) by covalent, coordinative, ionic or 7i-complex interactions as schematically shown in Fig. 5-1 [1-5], A great variety of macromolecules can be employed for the binding of the metal part (Section 1.2.1) ... 

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