Unfairly Forgotten Member of the Iodocarborane Family: Synthesis and Structural Characterization of 8-Iodo-1,2-dicarba-closo-dodecaborane, Its Precursors, and Derivatives.

Abstract

8-Iodo-1,2-dicarba-closo-dodecaborane (7) was prepared in three steps starting from decaborane-14 with 20% overall yield. In the presence of nucleophiles, compound 7 undergoes selective removal of the boron vertex in the position para to the iodine substituent to form the anionic nido-carborane 1-iodo-7,8-dicarba-nido-undecaborate. Capping of the corresponding dicarbollide dianion with BI(3) led to formation of the new carborane, 3,10-diiodo-1,2-dicarba-closo-dodecaborane (15). The same dicarbollide dianion reacts with cobalt and nickel acetylacetonates in anhydrous tetrahydrofuran to form the corresponding bis(dicarbollide) complexes with excellent yields. All compounds were characterized by multinuclear NMR and high-resolution mass spectroscopy. Structures of 2-iododecaborane (2), 8-iodo-1,2-dicarba-closo-dodecaborane (7), 1-ethoxycarbonyl-8-iodo-1,2-dicarba-closo-dodecaborane (10), cesium 1-iodo-7,8-dicarba-nido-undecaborate (13), 3,10-diiodo-1,2-dicarba-closo-dodecaborane (15), and cesium 3,3'-commo-(10-iodo-1,2-dicarba-3-cobalta-closo-dodecaborane)-(10'-iodo-1',2'-dicarba-3'-cobalta-closo-dodecaborane) (16) were established by X-ray analysis of single crystals.

New ligand platforms featuring boron-rich clusters as organomimetic substituents

“…The magnitude of this effect can be really substantial, where both strongly electron-withdrawing (similar to perfluorinated aryl moieties) and strongly electron-donating (similar to electron-donating bulky alkyl moieties) influences could be observed. Furthermore, given several recent developments enabling synthetic routes towards precise functionalization of the vertices in these clusters previously considered difficult or impossible to attain, one can anticipate a much broader scope of ligand tuning [78–82]. Therefore, this unique property of icosahedral carboranes may potentially provide a way for chemists to overcome a fundamental limitation associated with the electronic tunability window and inability to orthogonalize steric and electronic properties of ligands when using classical carbon-based substituents.…”

Straightforward synthesis of radioiodinated Cc-substituted o-carboranes: towards a versatile platform to enable the in vivo assessment of BNCT drug candidates

“…1), which were separated by recrystallization in hot heptane following a previously reported method. 19 Previous results suggest a higher propensity of 2-iododecaborane to undergo deiodination, 19 and hence 1-iododecaborane was used in subsequent radiolabelling experiments and preparation of o-carborane derivatives. 125 I-radiolabelling was carried out by adapting the previously reported palladium catalyzed iodine exchange reaction on iodinated dicarba-closo-dodecaboranes.…”

Off-Cycle Processes in Pd-Catalyzed Cross-Coupling of Carboranes

“…For example, deboronation and halogenation followed by boron vertex reinsertion enable the synthesis of some non-B(9)-vertex halogenated regioisomers. 39,40 Alternatively, thermal isomerization of Br-B(9) occurs at temperatures >300°C and produces a statistical distribution of 9/5/ 4/2-bromo-m-carborane (Br-mCB) isomers. 41−44 The thermal isomerization process is one of the few methods to synthesize Br-B(5) and Br-B(4).…”