Alkynes and Diynes as Precursors for Organoiridium Complexes Containing Iridium−Carbon Single and Double Bonds,1

The in situ generated species [IrCl(C 8 H 14 )(P i Pr 3 ) 2 ] as well as the dihydrido complex [IrH 2 Cl(P i Pr 3 ) 2 ] ( 15 ) were found to be quite reactive toward alkynes and diynes with either H or SiMe 3 as substituents at the C⋮C and C⋮CC⋮C units. While the thermal or photochemical reaction of [IrCl(C 8 H 14 )(P i Pr 3 ) 2 ] with Me 3 SiC⋮CR (R = Ph, Me, n Bu, SiMe 3, CH 2 OH, CMe 2 OSiMe 3, CO 2 Et) led to trans -[IrCl{ C C(SiMe 3 )R}(P i Pr 3 ) 2 ] ( 3 − 9 ) for R = CO 2 Et via the isolated π-alkyne metal intermediate trans -[IrCl(η 2 -Me 3 SiC⋮CR)(P i Pr 3 ) 2 ] ( 2 ), photolysis of 15 in the presence of Me 3 SiC⋮CC⋮CSiMe 3 gave trans -[IrCl{ C C(SiMe 3 )C⋮CSiMe 3 }(P i Pr 3 ) 2 ] ( 19 ). Compound 19 was also obtained by thermal or photochemical rearrangement of trans -[IrCl(η 2 -Me 3 SiC⋮CC⋮CSiMe 3 )(P i Pr 3 ) 2 ] ( 18 ). The dihydrido complex 15 reacted with HC⋮CC⋮CH at −60 °C to yield [{IrHCl(P i Pr 3 ) 2 } 2 (μ-C⋮CC⋮C)] ( 16 ) and with HC⋮CC⋮CSiMe 3 to give [IrHCl(C⋮CC⋮CSiMe 3 )(P i Pr 3 ) 2 ] ( 20 ), from which the vinylidene isomer trans -[IrCl( C CHC⋮CSiMe 3 )(P i Pr 3 ) 2 ] ( 22 ) was generated on heating. The reaction of 15 with propargylic alcohols HC⋮CCR(R‘)OH led to different types of products, depending on the substituents R and R‘. Whereas for R = R‘ = i Pr the five-coordinate alkynyl hydrido complex [IrHCl{C⋮CC( i Pr) CMe 2 }(P i Pr 3 ) 2 ] ( 23 ) was formed, the six-coordinate carbonyl hydrido vinyl derivative [IrHCl{( E) -CH CHPh}(CO)(P i Pr 3 ) 2 ] ( 25 ) was isolated for R = H and R‘ = Ph. Treatment of 15 with HC⋮CCPh 2 OH afforded, via [IrHCl(C⋮CCPh 2 OH)(P i Pr 3 ) 2 ] ( 27 ) or the isomer trans -[IrCl( C CHCPh 2 OH)(P i Pr 3 ) 2 ] ( 28 ), the allenylideneiridium(I) compound trans -[IrCl( C C CPh 2 )(P i Pr 3 ) 2 ] ( 29 ) in excellent yield. Hydrogenation of 29 gave the allene complex trans -[IrCl(η 2 - C H 2 C CPh 2 )(P i Pr 3 ) 2 ] ( 30 ), the structure of which was determined by X-ray crystallography. The substituted vinylideneiridium compound trans -[IrCl{ C C(SiMe 3 )C⋮CCPh 2 OH}(P i Pr 3 ) 2 ] ( 33 ) was obtained from [IrCl(C 8 H 14 )(P i Pr 3 ) 2 ] and Me 3 SiC⋮CC⋮CCPh 2 OH via the isomeric π-alkyne complex 32 as isolated intermediate.