Metal promoted charge and hapticities of phosphines: The uniqueness of carboranylphosphines

• closo- and nido-carboranylphosphines are unconventional ligands.
• P in carboranylphosphines grants a unique plasticity to CclusterCcluster distance.
• Neutral carboranylphosphines can be converted easily to anionic on complexation.
• Anionic nido-carboranylphosphines liberate one position in a metal complex.
• Carboranylphosphines act as mono, bi or tridentate ligands depending on the metal.

The accurate selection of a ligand for a metal-catalyzed homogeneous reaction can be as decisive as the selection of the metal. Incorporating a carborane cage as a backbone to produce new phosphines often leads to remarkable properties, which are not accessible employing conventional organic entities. The synergy effects between the o-carborane cluster and the P atom in these closo- and nido-carboranylphosphines is observed from two points of view: the cluster and the P atom. The P atoms in the closo-carboranylmonophosphines grant to the cluster a unique plasticity on the CclusterCcluster distance. The cooperation between the carboranyl moiety and the P atom may result in mono-, di- and tridendicity according to the necessities of the metal, not an ever-available property for organic phosphines.

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