Crystal engineering with heteroboranes. I. 1-Carboxy-1,2-dicarba-closo-dodecaborane(11).

The title compound, C(3)H(12)B(10)O(2) or 1-COOH-1,2-closo-C(2)B(10)H(11), forms centrosymmetric dimers through intermolecular hydrogen bonding between the carboxylic acid groups, resulting in the formation of an eight-membered ring [R(2)(2)(8)]. The C==O bond of the carboxylic acid group almost eclipses the unsubstituted cage C atom, with a C-C-C-O torsion angle of 2.6 (2) degrees.