The Solid State Structure of [B₁₀H₁₁]^- and Its Dynamic NMR Spectra in Solution

Abstract

The structure of [PPh(3)(benzyl)][B(10)H(11)] was determined at -123 degrees C and 24 degrees C by single-crystal X-ray analyses. The B(10) core of [B(10)H(11)](-) is similar in shape to that of [B(10)H(10)](2)(-). The 11th H atom asymmetrically caps a polar face of the cluster and shows no tendency for disorder in the solid state. Variable temperature multinuclear NMR studies shed light on the dynamic nature of [B(10)H(11)](-) in solution. In addition to the fluxionality of the cluster H atoms, the boron cage is fluxional at moderate temperatures, in contrast to [B(10)H(10)](2)(-). Multiple exchange processes are believed to take place as a function of temperature. Results of ab initio calculations are presented. Crystal data: [PPh(3)(benzyl)][B(10)H(11)] at -123 degrees C, P2(1)/c, a = 9.988(2) A, b = 18.860(2) A, c = 15.072(2) A, beta = 107.916(8) degrees, V = 2701.5(7) A(3), Z = 4; [PPh(3)(benzyl)][B(10)H(11)] at 24 degrees C, P2(1)/c, a = 10.067(5) A, b = 19.009(9) A, c = 15.247(7) A, beta = 107.952(9) degrees, V = 2775(2) A(3), Z = 4.

Electron Density and Bonding in Borates: An Experimental Study of Tetrabutylammonium Heptahydridohexaborate, [(C4H9)4N][B6H7]

“…The very stable [B n H n ] 2– anions form closo clusterswith spherical aromaticity 1,2. [B 6 H 6 ] 2– , [B 7 H 7 ] 2– , [B 8 H 8 ] 2– and [B 10 H 10 ] 2– can be protonated forming stable monoanions 3,4. The structures of [B 6 H 7 ] – and [B 10 H 11 ] – have been determined by X‐ray diffraction3 and nonempirical calculations 5–7.…”

“…[B 6 H 6 ] 2– , [B 7 H 7 ] 2– , [B 8 H 8 ] 2– and [B 10 H 10 ] 2– can be protonated forming stable monoanions 3,4. The structures of [B 6 H 7 ] – and [B 10 H 11 ] – have been determined by X‐ray diffraction3 and nonempirical calculations 5–7. During our experimental charge density studies of compounds with multi‐center two‐electron bonds like B 2 H 6 8 we became interested in the charge‐density distribution ρ ( r ) and its topological analysis of[B 6 H 6 ] 2– and [B 6 H 7 ] – 9.…”

Mechanisms and Beyond: Elucidation of Fluxional Dynamics by Exchange NMR Spectroscopy

“…[248] Interaction of acids with boron-rich cage [B 10 H 10 ] 2À 167 was examined by exchange NMR spectroscopy (Scheme 52). [249] The B 10 core of [B 10 H 11 ] À in 167 is similar in shape to that of [B 10 H 10 ] 2À where the eleventhHatom asymmetrically caps a polar face of the cluster.V ariable-temperature multinuclear NMR studies shed light on the dynamic nature of 167-H in solution:incontrast to 167,the boron cage is fluxional at moderate temperatures. Multiple exchange processes are believed to take place in 167-H as af unctiono ft emperature.…”

“…Interaction of acids with boron‐rich cage [B 10 H 10 ] 2− 167 was examined by exchange NMR spectroscopy (Scheme ) . The B 10 core of [B 10 H 11 ] − in 167 is similar in shape to that of [B 10 H 10 ] 2− where the eleventh H atom asymmetrically caps a polar face of the cluster.…”

The Mechanism of Halogenation of Decahydro-closo-Decaborate Dianion by Hydrogen Chloride

“…many cases, the reaction stops at the second step, but for some systems such as [B 10 H 10 ] 2− with HX (X = Cl, Br, I) in CH 2 Cl 2 [26] or with ROOH [58] ] − is non-rigid and proton can flux [64] along the polyhedron facets and edges with activation barriers 4-15 kcal/mol in the gas phase [61]. In addition, for [ fac HB 10 H 10 ] − in the gas phase the activation barriers of H 2 elimination from the equatorial and apical boron atoms have been found to be 22.8 kcal/mol and 35.3 kcal/mol, respectively [62].…”