Monocarbaborane Anion Chemistry. Syntheses and Structures Within the closo Nine-Vertex System

Abstract

Reaction of HCHO with B10H14 under aqueous alkaline conditions yields the arachno 10-vertex [6-CB9H14]- anion 2 (60%) which upon solid-state thermolysis as its Cs+ salt yields the closo 9-vertex [4-CB8H9]- anion 1 (45%). MeCHO reacts similarly to give the C-methylated arachno [6-Me-6-CB9H13]- anion 4 (37%) which upon thermolysis gives the closo [4-Me-4-CB8H8]- anion 3 (72%). PhCHO with B10H14 under alkaline conditions gives the nido 10-vertex [6-Ph-6-CB9H11]- anion 6 (85%) which upon thermolysis of its [NEt4]+ salt gives the closo [4-Ph-4-CB8H8]- anion 5 (73%). In a preliminary iodination investigation, unsubstituted closo anion 1 with elemental I2 in CH2Cl2 gives approximately equimolar closo [4-CB8H8-3-I]- 12 and closo [4-CB8H8-5-I]- 13 (ca 60%) and smaller amounts of closo [4-CB8H7-5,6-I2]- 14 (12%). The [NEt4]+ salts of 1, 3 and 5 are characterised crystallographically, as is the [PMePh3]+ salt of 12.