The 1-Phosphaallyl Anion as a Versatile Building Block in Reactions with Alkynes and Fischer-Type Alkynyltungsten Carbene Complexes^†

The anionic 1,3-cycloaddition reaction of the (1,2,3-triphenyl-1-phosphaallyl)lithium species Li(dme)₃[PhP−CPhC(Ph)H] (1) with diphenylacetylene followed by protonation of the anionic intermediate 2 gave diastereoselectively 1,2,3,4,5-pentaphenyl-2,3-dihydrophosphole (3). The relative cis,trans-stereochemistry of the C4,C5,P-unit has been established by X-ray structure analysis. Addition of 1 to the Fischer-type tungsten amino alkynyl carbene complex (CO)₅WC[N(CH₂)₄]−C⋮CPh (4) yielded, after protonation, the metal carbene modified dihydrophosphole 8, which, in contrast, exhibits a trans,trans-diphenyl substitution pattern. Thus, a different reaction pathway is suggested, containing an acyclic intermediate, which could be trapped by deuteration to give the (vinylphosphino)vinylcarbene complex (CO)₅WC[N(CH₂)₄]−CDC(Ph)−P(Ph)−CPhC(Ph)H (10). Thermal decarbonylation of 10 led to the chelate complex (CO)₄WC[N(CH₂)₄]−CDC(Ph)−P(Ph)−CPhC(Ph)H (11). The reaction of 1 with the tungsten methoxy alkynyl carbene complex (CO)₅WC−(OCH₃)−C⋮C(p-Tol) (5) and subsequent protonation afforded the acyclic (vinylphosphino)vinyl carbene complex (CO)₅WC(OCH₃)−CHC(p-Tol)−P(Ph)−CPhC(Ph)H (9), which underwent rearrangement to the allenyl(vinyl)phosphane complex [(OCH₃)CHCC(p-Tol)][PhCC(H)Ph](Ph)P[W(CO)₅]Ph−CPhC(Ph)H (12).