Transition metal complexes with functionalized indenyl phosphine ligands: structures and catalytic properties

Transition-metal indenyl complexes usually exhibit different reactivities compared with their cyclopentadienyl analogues. Up to now, at least 10 metal-indenyl bonding modes have been reported. Because of the "indenyl effect", transition-metal indenyl complexes usually show enhanced reactivity in substitution and related reactions. This review provides an overview on the use and impact of indenyl phosphines in organometallic chemistry and transition-metal-catalysed reactions in the recent two decades. Some cationic and zwitterionic metal complexes supported by P,N-substituted indene or indenide ligands are described. They have been reported to induce the cleavage of E-H (E = H, Si and B) bonds and can be used as catalysts for addition of E-H bonds to unsaturated substrates. 2-Aryl indenyl phosphine ligands L3-L11 have been proven to be a class of versatile ligands for palladium-catalysed C-C and C-N cross-coupling reactions. Moreover, optically active tethered indenyl phosphine ligands can have better stereoselective control over the chirality arising at the metal center in the oxidative addition of their rhodium complexes with alkyl halides.