Pentamethylcyclopentadienyl-rhodium and -iridium complexes. Part XII. Tris(solvent) complexes and complexes of η⁶-benzene, -naphthalene, -phenanthrene, -indene, -indole, and -fluorene and η⁵-lndenyl and -indolyl

The tris(solvent) complexes [M(C5H5)(S)3][PF6]2(M = Rh, Ir; s = Me2CN, Me2SO, or pyridine) were prepared and characterised; evidence for less stable solvent complexes (M = Rh, Ir; s = Me2CO, MeOH, or CH2Cl2) was obtained. The dicationic RhIII and IrIIIη6-arene complexes [M(C5Me5)(arene)][PF6]2(M = Rh: arene = benzene, toluene, m-xylene, mesitylene, fluorene, or indole; M = Ir, arene = toluene, m-xylene, naphthalene, phenanthrene, indene, indole, or fluorene) were synthesised from the acetone solvent complexes (IVa; M = Rh)(IVa: M = Ir). Both the naphthalene- and phenanthrene-iridium complexes were very labile, but showed no evidence of fluxional behaviour; phenanthrene is bonded by the terminal 6-membered ring. Reaction of (IVa) with indene gave the η5-indenyl complex, [Rh(C5Me5)(C9H7)][PF6], which was protonated, with rearrangement, to the η5-indene complex. Similar reversible protonation–deprotonation reactions occurred for the iridium complexes, [Ir(C5Me5)(η6-C9H8)]2+⇌[Ir(C5Me5)(η5-C9H7)]++ H+. The iridium (but not the rhodium)-indole complex [Ir(C5Me5)(η6-C8H6NH)]2+ also underwent reversible deprotonation to the η5-indolyl complex [Ir(C5Me5)(η5-C8H6N)]+. From exchange studies with CF3CO2D on [Ir(C5Me5)(η6-C7H8)]2+ it is concluded that protonation/deprotonation is fast and that the rate-determming step in the overall reaction is the movement of the metal from the 5- to the 6-membered ring and vice versa. The η6-fluorene-rhodium complex is very labile but the iridium analogue is deprotonated by base to give a fluorenyl complex of undetermined structure. An order of stability of η5- and η6-arenes bonded to RhIII and IrIII is given.