Activation of Small Molecules

The main-group metal alkyls, including zinc alkyls, are extremely reactive toward dioxygen and water. To avoid side reaction in the preparation and handling of these compounds organometallic chemists commonly use anaerobic conditions and moisture free reaction media in daily laboratory work. Simultaneously, it is a big challenge to bring the hydrolysis reactions under control to favor the more rapid design and implementation of O2 and H2O-based reaction systems. We extend the chemistry of zinc hydroxides and explore reactivity of ZnOH species towards CO2 and related molecules.

Oxygenation reactions

The studies on the controlled oxygenation of main group metal alkyl complexes have been undertaken by our group for systems containing preformed complexes which have constituted breakthrough in 150 years lasting investigations of this type reactions. We have provided efficient methods for the selective oxygenation of zinc alkyls toward desired alkylperoxides, alkoxides and oxo complexes as well as a plausible hypothesis concerning the mechanism of O2 activation by organometallic compounds has certainly been advanced.1,2 We have also revealed the long overlooked decomposition pathway of zinc alkylperoxides affording ZnO• and RO• radicals as primary radical species, in the oxygenation of alkylzinc complexes.3 These extensive investigations clearly demonstrated that this approach is very attractive for the construction of new polynuclear zinc clusters with incorporated alkylperoxide, alkoxide or oxo units. Moreover, our recent investigations clearly demonstrate that controlled oxygenation of these groups of compounds leads to the formation of ZnO nanoparticles of desired size and morphology.

Hydrolysis reactions

Interactions of R2Zn compounds with water remain surprisingly a largely unexplored area, despite the rich history of study4 and potential applications of alkylzinc hydroxides in materials chemistry.5 Recent studies showed that the exposition of R2Zn towards H2O affords organozinc oxo clusters6 or crystalline ZnO nanoparticles of controlled morphology.7 In our group there was also isolated the unprecedented hexameric alkylzinc hydroxide [tBuZnOH]6, which appeared to be an excellent precursor of ZnO nanoparticles.8 Thus, systematic investigations on the hydrolysis of zinc alkyls are undoubtedly highly desirable and there are still challenges left to chemists concerning a more fundamental structural perspective.

Carbon dioxide fixation – the bioinspired sytems

The chemistry of zinc hydroxide complexes supported by multifuctional ligands is also the area of a great synthetic potential, because these entities are very important in biochemical systems as active centers in zinc enzymes.9 The enormous activity of zinc hydroxide moiety in the reversible capture of CO2 by carbonic anhydrase turned our attention to bioinspired functional materials. In this view LxZnyRm(OH)n compounds are excellent platforms for exploring chemical reactivity of ZnOH moiety towards small molecules. Our
efforts are directed to the reactions of the resulting zinc hydroxides with CO2 and but also its analogues such as CS2 or COS. It is worthy to note that CO2 activation may proceed via stoichiometric or catalytic route, so we propose to investigate these systems in both directions. Ultimately, the incorporation of carbonate ion (and its analogues) opens new perspectives in the design and synthesis of novel building blocks for functional materials.