Electronic effects of 1-p-carboranyl group (p-B10H10C2H-)

Investigations of Electronic Interactions Between closo-Boranes and Triple-Bonded Substituents

“…The calculated and experimental X-Y distances in boron clusters 1-3 fall in a middle range between those found in bicyclo[2.2.2]octane [36][37][38] 6and acetylene 39,40 (5) derivatives and are generally close to those found in benzene [41][42][43] 4and cubane 44 (7). For instance, the calculated C-CN distances for carborane nitriles 1b-3b are between 1.452 and 1.435 Å which is approximately in the middle of a range defined by the longest and the shortest C-CN distances among the nitriles found in 6b (calculated 1.476 Å, experimental 38 1.471(4) Å) and dicyanoacetylene, 5b (calculated 1.390 Å, experimental 40 1.37 Å), respectively.…”

“…6 ). Spectroscopic studies demonstrated a rather moderate effect of the 12-vertex closo-borane on aromatic substituents 5,7,8 . Only in the case of inner salts of 12-vertex closo-borates substituted with a tropylium ion, a strong charge-transfer band 9,10 and a significant first hyperpolarizability β were observed 10 .…”

“…Other clusters, including the 6-vertex closo-borane, received very little attention in this context 4 . Early studies established that 12-vertex p-carborane has a small positive Hammett sigma value (σ p = +0.14), which was ascribed solely to the inductive effect 3,5 . Similar studies for the 10-vertex carborane gave a Hammett value of σ p = +0.05 (ref.…”

Four Decades of Organic Chemistry of closo-Boranes: A Synthetic Toolbox for Constructing Liquid Crystal Materials. A Review

“…Among other carbon electrophiles that react with carboranyl anions are PhOCN, preferred for preparation of the ten-vertex para-carborane nitriles 97 , and tosyl cyanide, the reagent of choice for synthesis of twelvevertex carboranenitriles 98 .…”

“…The reaction of orthoformates with ten- 97 Pd(Ph 3 P) 4 aldehyde was obtained in 23% overall yield based on para-carborane 6 (ref. 99 ).…”