Interaction of pentaphenylantimony with carboranedicarboxylic acid

• Tetraphenylantimony carborane carboxylate (1) was obtained in high yield.
• The synthesis of tetraphenylantimony carborane carboxylate proceeds with CO2 elimination.
• Bis(tetraphenylantimony) carborane bis(carboxylate) (2) was obtained in high yield.
• There are no intramolecular contacts in 1 between Sb and О atom of CO group.
• Crystal structures are characterized by weak intermolecular hydrogen bonds H⋯O.

The reaction of equimolar amounts of pentaphenylantimony with carboranedicarboxylic acid in toluene lead to tetraphenylantimony carborane carboxylate (1) in high yield. When using 2:1 M ratio of initial reagents, bis(tetraphenylantimony) carborane bis(carboxylate) (2) was obtained in 94% yield. Sb atoms in 1 and 2 form the distorted trigonal-bipyramidal coordination with carboxylate and phenyl ligands in axial positions (CaxialSbO are 174.06(12)° and 175.74(13)°, 176.77(13)° respectively). The Sb–O и Sb–C bond distances are 2.469(3) Å and 2.095(4)−2.136(4) Å in 1 and 2.275(3), 2.364(3) and 2.112(4)−2.173(4) Å in 2. There are no intramolecular contacts in 1 between Sb and О atom of CO group. In 2 the bond distances Sb⋯O(=C) (3.203(4) и 3.213(4) Å) are much less than a sum of van der Vaals radii of Sb and O atoms. Crystal structures of 1 and 2 are characterized by weak intermolecular hydrogen bonds H⋯O (2.25–2.53 and 2.54 Å, respectively).

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