Synthesis of 9,9′-Bis(m-Carboranyl) upon Catalytic Decomposition of 9,9′-Bis(m-Carboranyl) Mercury under Influence of (PPh₃)₃RhCl

Advances in the Synthesis of Biscarboranes

“…Meanwhile, the quantitative metallic mercury was also separated (Scheme 8). [19] However, when 9,9′‐bis( o ‐carborane)mercury was subjected to the above conditions, the desired 9,9′‐bis( o ‐carborane) has not been formed and only the o ‐carborane was afforded.…”

Pd-Catalyzed Oxidative Dehydrogenative Cross Coupling of Cage B–H/B–H Bonds at Room Temperature: Synthesis of Bis(o-carborane)s

“…In 1983, Usyatinskii and co-workers disclosed the first example of Pd-catalyzed B–H/B–H homocoupling of 1,2-Me 2 - o -carborane using stoichiometric Tl­(OCOCF 3 ) 2 . The method for preparing 9,9′-bis­( m -carborane) was reported using 9,9′-bis­( m -carboranyl)­mercury . Recently, the Cao group reported Pd/Ni-catalyzed dehydrogenative B–H/B–H homocoupling, affording 4,4′-bis­( o -carborane)­s and 4,5′-bis­( o -carborane)­s .…”

Catalytic Oxidative Dehydrogenative Coupling of Cage B–H/B–H Bonds for Synthesis of Bis(o-carborane)s

“…However, the 10 B−H bonds of o-carborane are not fully equal, and the electrophilic reactivity is reduced in the following order: B(9, 12) > B(8, 10) > B(4, 5, 7, 11) > B(3, 6). 18 Recently, we found that when the benzamide was introduced on B( 9), the charge distribution of 9-benzamide-o-carborane has a great change, and B (4,5,8,10,12) were much more negative than those in o-carborane. More importantly, the B(4)−H and B(5)−H bonds were more polarized when comparing the relative charge change of other B−H bonds.…”

“…Additionally, the B(4)−H bond is slightly more polarized than the B(5)−H bond. On the basis of this characteristic, we developed a selective arylation of 9-amide-o-carborane on B(4) with arylboronic acid; meanwhile, the electrophilic reaction on B (8,10,12) was inhibited completely. 16f Inspired by this result, we envisioned a general method for the synthesis of BBC via intermolecular oxidative dehydrogenative coupling of B(4)−H bonds with good selectivity.…”

“…Until 1983, the 9,9′-bis­(1,2-Me 2 - o -carborane) was precisely synthesized in the presence of a catalytic amount of Pd­(OAc) 2 and stoichiometric Tl­(OCOCF 3 ) 2 by Usyatinskii and coworkers (Scheme b). Then, the 9,9′-bis­( m -carborane) was further synthesized from 9,9′-bis­( m -carboranyl) mercury (Scheme c). However, the 4,4′-bis­( o -carborane) is only a proposed byproduct in the reaction of dinido-carborane with diborane .…”