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

Abstract

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....