Synthesis of the Sterically Shielded Rhodium(I) Arene Complex by Cycloaddition of the Phosphorous‐Substituted Alkyne

Reaction of two molecules of o‐diphenylphosphino‐tolane with RhCl(PPh₃)₃ produces the metallacycle complex with C₄Rh(P₃)Cl core. Further addition of tolane leads to 2+2+2‐cycloaddition and gives the cationic complex [Rh(Ph₂P−C₆H₄−C₆Ph₄−C₆H₄−PPh₂)]Cl, in which the metal is coordinated to C₆Ph₄ aromatic ring as well to two chelating PPh₂ groups. The resulting bulky terphenyl‐diphosphine ligand with phosphorous atoms locked in cis‐position can be decoordinated from rhodium by a strong and non‐hindered ligand tBuNC. Peculiar structures of all the compounds were studied by the X‐ray diffraction.