Synthesis of closo- and nido-biscarboranes with rigid unsaturated linkers as precursors to linear metallacarborane-based molecular rods

Abstract

Several biscarborane-type derivatives of 8-iodo-1,2-dicarba-closo-dodecaborane (1), suitable as the precursors of linear metallacarborane-based molecular rods, were prepared. The synthesized closo-compounds contained two carborane moieties connected through a rigid linear unsaturated linker. The linkers were based on ethynylene and para-phenylene fragments and their combinations. The deboronation of all reported closo-compounds was selective and afforded nido-products with open pentagonal faces on opposite sides of the molecule, parallel to each other and perpendicular to the main molecular axis. All of the closo and nido products were characterized by a variety of physical methods (NMR, HRMS, IR). The structures of closo-carboranes 3, 6, 9, and 14 and nido-carboranes 15 and 17 were established by X-ray diffraction.

1,12-Diiodo-Ortho-Carborane: A Classic Textbook Example of the Dihalogen Bond

“…Selective chemical substitution of hydrogen atoms at carbon or boron atoms in these clusters allows for their use as rigid, three dimensional scaffolds upon which to construct new materials, such as liquid crystals [2][3][4][5], nonlinear optical materials [6][7][8][9], carboranebased anticrowns [10], and even in drug design [11,12]. As rigid molecules of fixed length, carboranes can be used as building blocks ("molecular tinkertoys") [13][14][15][16][17][18] for supramolecular assemblies, such as porous coordination polymers or metal-organic frameworks (MOFs) [19][20][21][22]. Another type of supramolecular structures with the participation of carboranes is based on the acidity of their CH groups, which demonstrate a high potential for hydrogen bonding.…”

Rodlike Polymers Containing Nickel and Cobalt Metal Bis(dicarbollide) Anions: Synthesis and Characterization

“…The bis­(dicarbollyl)nickel system, a well-studied complex in this family, is known for its capability as a molecular motor with redox-controlled motion. − Metallacarborane-decorated dendrimers , and conducting conjugated-polypyrrole polymers either doped with a bis­(dicarbollyl)cobalt complex or having the same side chain were shown to have enhanced thermal stabilities and overoxidation thresholds. ,− Therefore, polymers with a bis­(dicarbollyl)metal moiety in their backbone linked by rigid unsaturated linkers are expected to be conductive and serve as molecular wires. ,− However, introducing transition-metal bis­(dicarbollides) into the polymer backbone has remained a challenge due to the synthetic difficulties associated with substitution at the para position of metal bis­(dicarbollides). Recently, we reported a series of precursors: (i) the multigram synthesis of 8-iodo-1,2-dicarba- closo -dodecaborane and the corresponding diiodo-substituted metal bis­(dicarbollides) ( 1 ) and (ii) nido- bis­(carboranes) with an acetylene linker ( 2 ), which paved the way for the introduction of metal bis­(dicarbollides) into the polymer backbone.…”

One-Pot Synthesis of B-Aryl Carboranes with Sensitive Functional Groups Using Sequential Cobalt- and Palladium-Catalyzed Reactions

“…The reaction was found to be tolerate to many functional groups including nitriles and esters. Earlier this approach was used for synthesis of 1,4-bis(ortho-carboran-8′-yl)benzene staring from 8-iodo-ortho-carborane [51].…”