Intramolecular dehydrofluorinative coupling of pentamethylcyclopentadienyl and phosphine ligands in iridium complexes

Cationic iridium(III) complexes of bifunctional eta(5), kappaP-Cp-P and trifunctional eta5, kappaP, kappaL-Cp-PL ligands may be conveniently prepared by intramolecular dehydrofluorinative carbon-carbon coupling. The iridium(III) complex [(eta(5)-C5Me5)IrCl(dfppe)]BF4 (dfppe=(C6F5)(2)PCH2CH2P(C6F5)(2)) undergoes rapid dehydrofluorinative coupling on addition of proton sponge to produce [{eta(5), kappaP, kappaP-C5Me3[CH2C6F4-2-P(C6F5)CH2](2)-1,3} IrCl]BF4. The reaction requires less than the stoichiometric quantity of proton sponge and also occurs on addition of (Bu4NF)-N-n. The cationic phosphine-thioether complex [(eta(5)-C5Me5)IrCl{kappaP, kappaS- (C6F5)(2)PC6H4SMe-2}]BF4 undergoes rapid dehydrofluorinative coupling to [{eta(5), kappaP, kappaS-C5Me4CH2C6F4-2-P(C6F5)C6H4SMe-2} IrCl]BF4 on treatment with proton sponge. NMR studies indicate that on treatment with proton sponge the cations [(eta(5)-C5Me5)IrCl(CNR){PPh2(C6F5)}](+) (R=Ph or Bu-t) undergo coupling to give [(eta(5), kappaP-C5Me4CH2C6F4-2-PPh2)IrCl(CNR)](+), but at a much slower rate and less cleanly than for the cations containing chelating ligands. The neutral compound [(eta(5)- C5Me5)IrCl2{PPh2(C6F5)}] does not undergo coupling, indicating that a positive charge is necessary for the reaction. The results are analogous to those for rhodium complexes. (C) 2004 Elsevier Ltd. All rights reserved.