Synthesis and Applications of Perfunctionalized Boron Clusters

Tuning the electrochemical potential of perfunctionalized dodecaborate clusters through vertex differentiation

We report a new class of redox-active vertex-differentiated dodecaborate clusters featuring pentafluoroaryl groups. These [B12(OR)11NO2] clusters share several unique photophysical properties with their [B12(OR)12] analogues, while exhibiting significantly higher (+0.5 V) redox potentials. This work describes the synthesis, characterization, and isolation of [B12(O-CH2C6F5)11NO2] clusters in all 3 oxidation states (dianion, radical, and neutral). Reactivity to post-functionalization with thiol species via SNAr on the pentafluoroaryl groups is also demonstrated.

Synthesis and crystal structure of solvent-free dodecahydro closo-dodecaborate of nickel, NiB12H12

Ball milling of Na₂B₁₂H₁₂ + NiCl₂ mixtures followed by hydration in air produces closo-borate containing octahedral hexa-aqua complex. The water molecules are easily removed by heating under dynamic vacuum leading first to octahedral tetra-aqua complex, and then to anhydrous pseudo-cubic NiB₁₂H₁₂.

Efficient access to amides of the carborane carboxylic acid [1-(COOH)–CB11H11]−

The preparation of the carborane acid chloride [1-(COCl)–CB₁₁H₁₁]⁻ from the carboxylic acid [1-(COOH)–CB₁₁H₁₁]⁻ is reported. This acid chloride exhibits remarkable inertness towards moisture and can be stored under ambient conditions for several months. Reaction with amines affords secondary and tertiary carborane amides [1-(CONR¹R²)–CB₁₁H₁₁]⁻ in moderate to high yields under mild conditions. Two of the amide products were characterized by X-ray crystallography in addition to spectroscopic analysis. Preliminary studies show that the amides can be reduced to the corresponding amines and that the acid chloride has the potential to serve as a starting material for carborane ester formation.

The preparation of the carborane acid chloride [1-(COCl)–CB₁₁H₁₁]⁻ from the carboxylic acid [1-(COOH)–CB₁₁H₁₁]⁻ and subsequent amide formation are reported.