首页|Crystalline Boron-Centered Analogues of Müller's Hydrocarbon
Crystalline Boron-Centered Analogues of Müller's Hydrocarbon
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Müller's hydrocarbon is a well-known open-shell singlet diradicaloid,yet its structural determination and redox property remain elu-sive due to its extremely high reactivity.Herein,we report the successful synthesis and full characterizations of the first neutral bo-ron-centered analogue(4)of Müller's hydrocarbon,along with the first dianionic boron-centered analogue(52-)featuring three isola-ble redox states.In the presence of two equivalents of N-heterocyclic carbene(NHC),reduction of 4,4"-bis(triisopropylphenyl-bromoboryl)terphenyl 3 with potassium graphite afforded NHC-stabilized boryl diradicaloid 4 with a near-pure diradical character(y0=0.93).Stepwise reductions of 4,4"-bis(dimesitylboryl)terphenyl 5 in THF yielded the isolable monoradical anion 5"and diradical dian-ion 52-,respectively,accompanied by a decreasing aromaticity within the conjugated spacer.Experimental studies and theoretical analyses revealed that both 4 and 52-exhibit large spin distributions at boron atoms,open-shell singlet ground states,and small sin-glet-triplet energy gaps.
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