An experimental solution to the "missing hydrogens" question surrounding the macropolyhedral 19-vertex boron hydride monoanion [B19H22]-, a simplification of its synthesis, and its use as an intermediate in the first example of syn-B18H22 to anti-B18H22 isomer conversion.
The macropolyhedral [B(19)H(22)](-) monoanion 1 and the dianion [B(19)H(21)](2-) 2 are synthesized in consistent 86-92% yields by the reaction of [PSH](+)[syn-B(18)H(21)](-) with BH(3)(SMe(2)) in 1,2-Cl(2)C(2)H(4) at 72 degrees C. ['PS' is an abbreviation for 'Proton Sponge', 1,8-bis-(dimethylamino)naphthalene. 'PSH' is its protonated derivative.] The molecular structures of 1 and 2 were elucidated as their [PS{BH(2)}](+) and [PS{BH(2)}](2)(+) salts 1a and 2a by single-crystal X-ray diffraction studies, in which all atoms were located, and supported by mass spectrometric analyses together with calculations of the cluster molecular geometries (ab ignitio and/or DFT) and of (11)B chemical shifts based on GIAO-DFT shielding tensors. Acidification of dianion 2 with CF(3)COOH in acetonitrile, H(2)SO(4) in dichloromethane, or aqueous HCl results in the clean formation of the monoanion [B(19)H(22)](-) 1. Conversely, shaking a concentrated acetonitrile solution of 1 in 0.5 M aqueous NaOH cleanly yields the [B(19)H(21)](2-) dianion 2. Reaction of a dichloromethane solution of 1 with a 36% aqueous solution of HCHO in the presence of H(2)SO(4) quantitatively converts 1 at room temperature to a 1:1 mixture of the syn- and anti-isomers of B(18)H(22). This cluster dismantling process is the first example of a syn- to anti-B(18)H(22) isomer conversion.
Londesborough
Michael G S
MG
Institute of Inorganic Chemistry v.v.i., Academy of Sciences of the Czech Republic, Rez by Prague, 250 68, Czech Republic. michaell@iic.cas.cz
Bould
Jonathan
J
Base
Tomás
T
Hnyk
Drahomír
D
Bakardjiev
Mario
M
Holub
Josef
J
Císarová
Ivana
I
Kennedy
John D
JD