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The review covers the mechanism insights and recent achievements in catalyst design for oxidative coupling of benzoic acids and alkynes. This reaction is a straightforward effective approach to synthesis of isocoumarins or naphthalenes. The influence of catalyst nature and reaction conditions on the selectivity is also discussed. This contribution aims to focus attention of organic chemists on the possibility to use a wide range of catalysts, without being limited by only conventional complexes.

A series of new osmacarborane complexes were synthesized by treatment of the 11-vertex carborane [closo-СВ10Н11]–[Me4N]+ (1) with tris(triphenylphosphine)osmiumdichloride OsCl2(PPh3)3 (2). We managed to control the process of the carborane framework transformation {closo-CB10} → {hypercloso-OsCB10} → {hypercloso-OsCB9} → {hypercloso-OsCB8}, and each stage of this polyhedral carborane contraction was experimentally confirmed. The isolated clusters are electron-deficient hypercloso-osmacarboranes with 2n skeletal electrons. The structures of two “anti-Wade” complexes (10- and 11-vertex osmacarboranes) were confirmed by X-ray diffraction.

The heating of the isomeric [1-(η6-1,4-Me2C6H4)-3-Cl-isonido-1,2,4-RuC2B8H9] (1) or [1-(η6-1,4-Me2C6H4)-6-Cl-isonido-1,2,4-RuC2B8H9] (2) complexes (i) in a 1,4-Me2C6H4 solution at 85 °C as well as (ii) in a melt at 165 °C afforded mixtures of isomeric isonido- and closo-ruthenacarboranes, which differ in the positions of the chlorine substituent and the carbon atoms in the cage ligand. Structures of all new isomeric complexes have been established on the basis of analytical and multinuclear NMR data and were characterized by single-crystal X-ray diffraction studies. Also presented are the results of the quantum chemical calculations for the ground and the transition states of the reaction (i), which proved to be basis for the suggestion of interconversion scheme for these isomers.