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(η 5 -C 5 Me 5 )(C CPh) 2 (PPh 2 R)] (R = Ph (2a), Me (2b), CH 2 CHCH 2 (2c)) have been prepared by reaction of the complexes [Ir(η 5 -C 5 Me 5 )Cl 2 (PPh 2 R)] (R = Ph (1a), Me (1b), CH 2 CHCH 2 (1c)) and lithium phenylacetylide. Alternatively, complexes 2a,b have been synthesized by the treatment of the complexes [Ir(η 5 -C 5 Me 5 )I 2 (PPh 2 R)] (R = Ph (3a), Me (3b)) with [AgCCPh] n . The reactivity of the complex [Ir(η 5 -C 5 Me 5 )(CCPh) 2 (PPh 3 )] (2a) toward electrophiles is reported. Thus, complex 2a reacts with tetrafluoroboric acid to give the new butenynyl complex [Ir(η 5 -C 5 Me 5 ){η 3 -C(Ph)CCC(H)Ph}(PPh 3 )]-[BF 4 ] (4) after stirring for 15 min at room temperature. Complex 4 evolves to [Ir(η 5 -C 5 Me 5 ){κ 4 (P,C,C,C)-PPh 2 C 6 H 4 C(Ph)CHCC(H)-Ph}][BF 4 ] ( 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(η 5 -C 5 Me 5 ){κ 3 (C,C,C)-C 6 H 4 C(Me)CCC(H)Ph}(PPh 3 )][CF 3 SO 3 ] 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.