Rapid synthesis of redox-active dodecaborane B₁₂(OR)₁₂clusters under ambient conditions

Abstract

We have developed a fast and efficient route to obtain perfunctionalized ether-linked alkyl and benzyl derivatives of the closo-[B12(OH)12]2− icosahedral dodecaborate cluster via microwave-assisted synthesis. These icosahedral boron clusters exhibit three-dimensional delocalization of the cage-bonding electrons, tunable photophysical properties, and a high degree of stability in air in both solid and solution states. A series of closo-[B12(OR)12]2−, hypocloso-[B12(OR)12]1− and hypercloso-[B12(OR)12]0 clusters have been prepared with reaction times ranging from hours to several minutes. This method is superior to previously reported protocols since it dramatically decreases the reaction times required and eliminates the need for inert atmosphere conditions. The generality of the new microwave-based method has been further demonstrated through the synthesis of several new derivatives, which feature redox potentials up to 0.6 V more positive than previously known B12(OR)12 cluster compounds. We further show how this method can be applied to a one-pot synthesis of hybrid, vertex-differentiated species B12(OR)11(OR) that was formerly accessible only via multi-step reaction sequence.

Atomically precise organomimetic cluster nanomolecules assembled via perfluoroaryl-thiol SNAr chemistry

“…Notably, the initially dark red solution quickly turned colorless. 11 B NMR spectroscopy of this colorless solution revealed a singlet resonance at δ −15 characteristic of a reduced cluster in a [ 2 ] 2- oxidation state 35,36 , which is consistent with the reducing capacity of the thiolate species when exposed to [ 2 ] 0 (Fig. 2d).…”

“…Our laboratory has recently reported a rapid perfunctionalization strategy of [B 12 (OH) 12 ] 2- cluster ( 1 ) originally discovered by Hawthorne 31–34 featuring a wide scope of substituents 35 . Using this method, we synthesized perfunctionalized clusters grafted with rigid linkers containing peripheral pentafluoroaryl moieties (Fig.…”

Synthesis and Applications of Perfunctionalized Boron Clusters

“…43 Given our interest in the development of chemistry and applications of perfunctionalized boron clusters, 44–46 we reexamined the reactivity of the closo -[B 6 H 7 ] 1− anion. Under microwave heating conditions, the hexaborate anion can be substituted with benzyl bromide electrophiles (Fig.…”

“…To address this issue, our laboratory has reported a rapid microwave-assisted method to prepare peretherated clusters. 44 This method drastically reduces the reaction time from an average of multiple days to minutes to hours. Etherification of the perhydroxylated clusters has a profound effect on the redox properties of B 12 -clusters and is discussed separately in the text ( vide infra ).…”

“…8) while expanding the tunable window for the same redox event to a full 1 V (−0.61 V vs Fc/Fc + for the 1-/0 redox couple oxidation when R = n -hexyl, rising to +0.68 V vs Fc/Fc + for the same redox event when R = (3,5-bis)trifluoromethylbenzyl). 44,94 …”