Synthesis, structure, and weakly coordinating nature of new carborane anions

Direct halogenation of 1-CH3-CB11H 11- or C-methylation of 1-H-CB11H 5X6- gave several weakly coordinating anions 1-CH3-CB11X6- (X = Cl, Br, I) which show to have better solubility than their parent anion in various organic solvents. Their silver(I) salts were prepared and structurally characterized by X-ray crystallography. A common feature for the solid-state structures of these silver(I) carborane complexes is that the carborane acts as a bridging ligand to give an alternating cation-anion zigzag chain which is maintained in one-dimension throughout the lattice. For comparison, several silver(I) salts of cobalt bis(dicarbollide) ions have also been prepared. Their solid-state structures exhibit both monomeric and one-dimensional coordination polymeric structures.;A new methodology (sealed-tube reaction) has been developed for the synthesis of highly halogenated carborane anions, which led to the isolation and structural characterization of a series of new weakly coordinating anions including 1-H-CB 11X11-, 1-CH3-CB11X 11-, 1-H-CB9X9- , 1-NH2-CB9X9- and 1-H-CB11Y5X6- (X, Y = Cl, Br, I). Their weakly coordinating nature was approached by comparing the 29Si NMR data of compounds Pri 3Si(carborane) and structural data of complexes Ag(carborane). These findings suggest that the coordinating ability of these anions depend mainly upon the nature of the substituents at 7--12 positions, and the contribution from the substituents of the upper belt (2--6 positions) is relatively small. The structural studies on silver(I) salts of these per-halo and mixed-halo carborane anions indicate the rich coordination chemistry of this type of compounds, varying from monomeric through one-dimensional polymeric to three-dimensional polymeric structures.;This newly-developed method also led to the preparation of several peralkylated carborane anions including 1-H-CB11R11- (R = Me, Et), 1-H-CB9Me9- and 1,2-Cl2-CB10Me10. The features of this method are clean, economical, quantitative yield and organic solvent-free. It may be the best synthetic route to peralkylated carborane anions ever reported in the literature.;Treatment of the silver(I) salts of carborane anion with HCl(aq) in CH 2Cl2 gave several hydronium salts of carborane anions. They are weighable and stable at room temperature. However, the water molecules of the hydronium salts can be removed under high temperature and high vacuum conditions to afford highly acidic species that can protonate organic solvents such as DMF, OEt2 and acetic acid, and olefin such as cyclohexene. The molecular structures of the hydronium salts and protonated organic solvents were all confirmed by single-crystal X-ray analyses.