Collect. Czech. Chem. Commun. 2005, 70, 1873-1890

Polyhedral Monocarbaborane Chemistry. Functionality and Isomerism: Reactions of the [6-Ph-nido-6-CB9H11]- Anion with Aminopyridines NC5H4NH2 to Yield Neutral arachno and closo Ten-Vertex Monocarbaborane Derivatives

Neil J. Bullen and John D. Kennedy*

The School of Chemistry of the University of Leeds, Leeds, UK LS2 9JT, England, U.K.


Reaction of NC5H4-2-NH2 with the [6-Ph-nido-6-CB9H11]- anion (1) in the presence of hydrated FeCl3 gives [6-Ph-9-(NC5H4-2-NH2)-arachno-6-CB9H12] (4) and thence [1-Ph-2-(NC5H4-2-NH2)-closo-1-CB9H8] (5), in which the pyridine substituent is on a boron atom α to the cluster carbon atom. This behaviour contrasts to the reactions of organyl-substituted pyridines NC5H4R to yield neutral 9-pyridine arachno species [6-Ph-9-(NC5H4R)-arachno-6-CB9H12] and thence neutral 6-pyridine closo species [1-Ph-6-(NC5H4R)-closo-1-CB9H8], in which the pyridine substituent is on a boron atom β to the cluster carbon atom. The chlorinated analogue [1-Ph-2-(NC5H4-2-NH2)-4-Cl-closo-1-CB9H7] (7) is also identified as a minor by-product from the reaction system. Reaction of anion 1 with NC5H4-4-NH2 does not proceed further than [6-Ph-9-(NC5H4-4-NH2)-arachno-6-CB9H12] (8). The 2-NH2 compounds 4, 5 and 7 exhibit intramolecular BH-HN dihydrogen bonding, whereas the 4-NH2 compound 8 exhibits an intermolecular BH-HN dihydrogen-bonded network that involves inversion-related pairs of dihydrogen-bonded chains.

Keywords: Boranes; Monocarbaboranes; Carboranes; Amine-functionalised carbaboranes; Pyridine adducts; Crystal and molecular structure; X-Ray diffraction; NMR spectroscopy; Dihydrogen bonding.

References: 46 live references.