The in situ generated species
[IrCl(C8H14)(PiPr3)2]
as well as the dihydrido complex [IrH2Cl(PiPr3)2] (15)
were found to be quite reactive toward alkynes and diynes with either H
or
SiMe3 as substituents at the C⋮C and C⋮CC⋮C units.
While the thermal or photochemical
reaction of
[IrCl(C8H14)(PiPr3)2]
with Me3SiC⋮CR (R = Ph, Me, nBu,
SiMe3, CH2OH,
CMe2OSiMe3, CO2Et) led to
trans-[IrCl{CC(SiMe3)R}(PiPr3)2]
(3−9) for R = CO2Et via
the
isolated π-alkyne metal intermediate
trans-[IrCl(η2-Me3SiC⋮CR)(PiPr3)2]
(2), photolysis of
15 in the presence of
Me3SiC⋮CC⋮CSiMe3 gave
trans-[IrCl{CC(SiMe3)C⋮CSiMe3}(PiPr3)2] (19).
Compound 19 was also obtained by thermal or
photochemical rearrangement
of
trans-[IrCl(η2-Me3SiC⋮CC⋮CSiMe3)(PiPr3)2]
(18). The dihydrido complex 15 reacted
with
HC⋮CC⋮CH at −60 °C to yield
[{IrHCl(PiPr3)2}2(μ-C⋮CC⋮C)]
(16) and with HC⋮CC⋮CSiMe3
to give
[IrHCl(C⋮CC⋮CSiMe3)(PiPr3)2]
(20), from which the vinylidene isomer
trans-[IrCl(CCHC⋮CSiMe3)(PiPr3)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‘ = iPr the
five-coordinate alkynyl hydrido complex
[IrHCl{C⋮CC(iPr)CMe2}(PiPr3)2]
(23) was formed, the six-coordinate carbonyl hydrido
vinyl
derivative
[IrHCl{(E)-CHCHPh}(CO)(PiPr3)2]
(25) was isolated for R = H and R‘ = Ph.
Treatment of 15 with HC⋮CCPh2OH
afforded, via
[IrHCl(C⋮CCPh2OH)(PiPr3)2]
(27) or the
isomer
trans-[IrCl(CCHCPh2OH)(PiPr3)2]
(28), the allenylideneiridium(I) compound
trans-[IrCl(CCCPh2)(PiPr3)2]
(29) in excellent yield. Hydrogenation of 29
gave the allene
complex
trans-[IrCl(η2-CH2CCPh2)(PiPr3)2]
(30), the structure of which was determined
by X-ray crystallography. The substituted vinylideneiridium
compound trans-[IrCl{CC(SiMe3)C⋮CCPh2OH}(PiPr3)2]
(33) was obtained from
[IrCl(C8H14)(PiPr3)2]
and Me3SiC⋮CC⋮CCPh2OH via the isomeric π-alkyne complex
32 as isolated intermediate.
The bis(triisopropylphosphine)rhodium(I) and -iridium(I) compounds [RhCKPiPrsXL (1) and [IrCKCgHi-iXPiPrsh] (2) react with 2 equiv of RR'C=CHC1 and 2 equiv of Na in benzene at room temperature to give the vinylidene complexes írans-[MCl(=C=CRR')(PiPr3)2] (3-7) in moderate to good yields. From 2, Ph2C=CHCl, and Na, the alkyne derivative trans-[IrCKPhC^CPhXPiPrsX] ( 8) is obtained as the main product. Preliminary studies aimed to elucidate the mechanism of the reaction indicate that from RR'C=CHC1 and Na a vinyl radical RR'C=CH• is possibly formed which, depending on the substituents R and R', either reacts to give the alkyne RC=CR', initiates polymerization, or attacks the metal center of the starting material, to give the metal vinylidenes. Whereas numerous vinylidene transition-metal complexes of general composition [M(=C=CRR'
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