Preparative Routes to Molecular Compounds

The most important synthetic routes continue to be (1) the elimination of an alkali halide between the salt of a transition-metal anion and a silicon halide, and (2) oxidative addition and addition-elimination reactions. The present position regarding the scope and limitations of these and other routes is outlined in this section. 

Reaction of a Transition-Metal Anion with a Silicon Halide 

The relative electronegativities of some of these groups appear to increase in the order (147, 174) 

Entry Anion Silicon halide Solvent Success1 r Remarks Ref. 

14 HjSilj Ether, isopentane yf Only disubstd. deriv. found (32) 

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The second synthetic route to PAE containing quinoxaline units involved the reaction of an aromatic dihydroxy quinoxaline or aromatic bis(hydroxy-quinoxaline) with activated aromatic difluoro compounds (Eq. (3)) [15]. The dihydroxy quinoxaline and bis(hydroxyquinoxaline) monomers were readily prepared from the condensation of 1,2-diaminobenzene with 4,4 -dihydroxyben-zil and aromatic bis(o-diamines) with 4-hydroxybenzil, respectively. The Tgs of a series of PAE containing quinoxaline units are presented in Tables 3 and 4. For these polymers, the trend for the Tg is sulfone > carbonyl > terephthaloyl-> isophthaloyl. This trend holds for most polymer families when polymers of similar molecular weights are compared. Several polyphenylquinoxalines of the same chemical structure as those in Table 3 were also prepared by the poly-... 

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