Aggregation organozinc compounds

A few organozinc compounds containing the f-BuPOs bis-anion have been re-ported . They form complex aggregated structures containing up to ten zinc atoms, but are of less interest for organozinc chemists. 

SCHEME 1. The dynamic behavior of organozinc compounds involves C—Zn exchange and C—Zn bond inversion as main processes. Aggregation and ligand exchange dynamics complete the overall picmre describing the dynamics of these compounds... 

Unsolvated organozinc compounds of the type RZnOR are associated in solution and the formation of trimeric aggregates has been established by cryoscopic measurements for EtZnOCHPh2 and [RZnOC6H4NMe2]3 in benzene solution [4, 5], The structures of these trimers are unknown (although presumably cyclic) and X-ray crystal structure determinations of a significant number of solid state com-poxmds reveal a much more complex reality, with dimers, trimers, and tetramers being identified. 

The remarkable structural diversity of supramolecular aggregates of organozinc alkoxides and related compounds is possible because of the variations in the coordination numbers and geometry of the metal it is favored by the relatively strong donor-acceptor bonds formed between oxygen and zinc. Most of the supramolecular aggregates are preserved in hydrocarbon solution (e.g. benzene), when there is no competition from the solvent for the vacant coordination sites of the metal. 

As expected, the behavior of organozinc-selenium compounds is similar to that of the sulfur analogs. Dimeric self-assembled aggregates, 18, were reported for orga-nozinc diselenocarbamates, [RZnSe2CNR 2]2, R = Me, Et, R = Et [35] and R = MeaCCHj, R = Et ]36]. 

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