Organic Syntheses via Transition Metal Complexes, 74[1] Novel Phosphonium Allenide and 2‐Phosphanylethenyl Carbene Chromium and Tungsten Complexes

Abstract
Alkynylcarbene complexes (CO)5MC(OEt)‐C≡CR 1 (M = Cr, W; R = Ph, tBu, SiMe3) readily add tertiary phosphanes PPhR2′ 4 (R′ = Ph, Me) to form stable zwitterionic phosphonium allenide complexes (CO)5M‐C(OEt) = CC(R)‐P+PhR2′ 5. Complex 5a (M = Cr, R = R′ = Ph) was characterized by X‐ray diffraction. The addition of secondary phosphanes PHR2 6 to 1 affords red (2‐phosphanyl ethenyl)‐carbene complexes (CO)5MC(OEt)‐CHC(R)‐PR2 (E)‐8 (R = tBu, cC6H11, Ph) in 34–89% isolated yields. Dinuclear complexes (CO)5MC(OEt)‐CHC(R)‐P(R2)M(CO)5 (E)‐9 are obtained as byproducts. Compounds (E)‐8b (M = Cr, R = cC6H11) and (E)‐9i (M = Cr, R = Ph) were characterized by X‐ray analyses.

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