Apical aromatic

In all cases, except for 9-acetylanthracene, both Cs-symmetric amine clathrochelates with apical aromatic substituents and Ca-nonsymmetric imine sarcophaginates with substituents in the methylene units have been formed (Scheme 59). The reaction of 9-acetylanthracene under the same conditions led only to the aroyl-type sarcophaginate, since in this case a bulky substituent inhibits the condensation of a keto group with an amino group to give imine. 

The electrochemical data for cobalt(III) sarcophaginates with apical aromatic substituents are listed in Table 49 [137]. The nature of the aromatic substituents for the most part did not greatly affect the Co3+/2+ reduction potentials. The anthraquinone imine complex, however, showed a two-electron wave due to reduction of the anthraquinone substituent at ca 230 mV and a one-electron wave of... 

Cyclic voltammetric data (mV, vs SHE) for some cobalt(III) sarcophaginates with apical aromatic substituents [137],... 

The reduction potential of the anthraquinone moiety is more positive than that of any of the Co3+/= + couples in the sarcophaginates with apical aromatic substituents. Hence the opportunity now exists to place an electron donor (for example, anthracene in its excited state linked to the cage by a longer spacer group) and an electron acceptor (anthraquinone) at opposite ends of a cobalt(III) cage. After photolysis, charge separation could be achieved in a cascade, mediated by the encapsulated metal ion [137]. 

The solid state structure of complex 7b is shown in Figure 25.1. Similar to parent chelating ether complex [9b], the solid-state structure of 7b shows a distorted square-pyramidal structure with the benzylidene moiety at the apical position. The N-aryl ring is located above the benzylidene moiety resulting in the relatively close contact of the benzylidene proton with the 7r-aromatic system of the mesityl group. 

For example, both Hiickel aromatics B and C conform to the Wade-Mingos electron counting rules [2] (see Chapter 1.1.2) and to the structural systematics developed for boranes and heteroboranes [1] the hexagonal bipyramid with the apices removed is in agreement with an arachno electron count of 18 SE for (CH)g [2],... 

It is interesting to note that in 186 the two N-dimethylamino ligands are in cis positions relative to each other, despite the fact that hydrogens, and no electronegative ligands, are in the apical positions, and the likely expectation that the aromatic-ring planarity would prefer the lruns arrangement215. 

The effects of auxin upon the growth of plants were truly remarkable. As a result of the concerted effort and interest that plant scientists devoted to this highly fashionable and exciting field of research, much of what we know of the control of plant growth and development by auxin was discovered in these highly productive years. The hormone was derived from the aromatic amino acid tryptophan and was relatively abundant in the rapidly growing meristematic parts of plants such as apical buds and root tips. Inactive bound forms existed, as in seeds, where hydroly-... 

They noted that in dimethoxyethane or in iso-octane (path a), the major product was dicarbonylcyclopentadienylcobalt (2) which must arise as a result of a retro Diels-Alder reaction of the norbornadiene (which would lead to the formation of acetylene and cyclopentadiene). When the solvent was changed to an aromatic hydrocarbon such as benzene or toluene (path b), the major cobalt-containing product was shown to be a complex derived from Co4(CO)i2, with three CO ligands on an apical cobalt being replaced by a molecule of the aromatic solvent (3). The group noted that they were also obtaining hydrocarbon and ketonic products derived from norbornadiene, acetylene and carbon monoxide .1,2... 

The relatively low nucleophilicity of the apical amino substituent in cobalt(III) diaminosarcophaginate has been used in acylation and alkylation reactions leading to a variety of apical functionalized cobalt(III) sarcophaginates with apical pendant aromatic and heteroaromatic substituents [109],... 

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