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Londesborough MG, Bould J, Base T, Hnyk D, Bakardjiev M, Holub J, Cisarova I, Kennedy JD: An Experimental Solution to the "Missing Hydrogens" Question Surrounding the Macropolyhedral 19-Vertex Boron Hydride Monoanion [B (19) H (22)](-), a Simplification of Its Synthesis, and Its Use As an Intermediate in the First Example of syn-B (18) H (22) to anti-B (18) H (22) Isomer Conversion. Inorg Chem. 2010 Mar 29.
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. |
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