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Cationic Polyhedral Chalcogenaboranes: Activation without breaking Wade's Rules
Josef Holub1, Šimon-Petr Náhlík2, Zdeňka Růžičková2
1Institute of Inorganic Chemistry, Czech Academy of Sciences 250 68, Řež, Czech Republic.
Abstract:
Wade's rules are a well-established tool for the description of the geometry of inorganic clusters. Among others, they state that a decrease or increase in charge is always accompanied by a change in the number of skeletal electron pairs (SEPs). This work reports the synthesis of the first cationic chalcogenaboranes closo-[12-X-2-IPr-1-EB11H10]BF4 (IPr=1,3-(2,6-iPr2C6H3)-imidazole-2-ylidene; X=H, I; E=S, Se 3 a/b, 4 a/b) featuring the same SEP count as their neutral precursors, EB11H11, but bearing a positive charge. This ionisation significantly enhances the activity towards the electrophiles. It unlocks reactivity with very weak bases and offers the control of the regioselectivity towards hard/soft bases by the modulation of LUMO. The localisation of the positive charge within the borane cluster has been confirmed experimentally, spectroscopically and theoretically.
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