Synthesis of Pentamethylcyclopentadienyl Dialkynyl Phosphane Iridium(III) complexes. Reactivity of the Complex [Ir(η5-C5Me5)(C≡CPh)2(PPh3)] toward Electrophiles

Dialkynyl iridium­(III) complexes [Ir­(η5-C5Me5)­(C≡CPh)2(PPh2R)] (R = Ph (2a), Me (2b), CH2CH═CH2 (2c)) have been prepared by reaction of the complexes [Ir­(η5-C5Me5)­Cl2(PPh2R)] (R = Ph (1a), Me (1b), CH2CH═CH2 (1c)) and lithium phenylacetylide. Alternatively, complexes 2a,b have been synthesized by the treatment of the complexes [Ir­(η5-C5Me5)­I2(PPh2R)] (R = Ph (3a), Me (3b)) with [AgC≡CPh]n. The reactivity of the complex [Ir­(η5-C5Me5)­(C≡CPh)2(PPh3)] (2a) toward electrophiles is reported. Thus, complex 2a reacts with tetrafluoroboric acid to give the new butenynyl complex [Ir­(η5-C5Me5)­{η3-C­(Ph)≡CC═C­(H)­Ph}­(PPh3)]­[BF4] (4) after stirring for 15 min at room temperature. Complex 4 evolves to [Ir­(η5-C5Me5)­{κ4(P,C,C,C)-PPh2C6H4C­(Ph)­CHC═C­(H)­Ph}]­[BF4] (5) after stirring for 24 h at room temperature. The reaction of complex 2a with methyl trifluoromethanesulfonate leads to the formation of the complex [Ir­(η5-C5Me5)­{κ3(C,C,C)-C6H4C­(Me)═C═C═C­(H)­Ph}­(PPh3)]­[CF3SO3] as a 1:1.5 mixture of the Z (6) and E (7) stereoisomers. The structures of complexes 2c, 5, and 7 have been resolved by X-ray diffraction analysis.