ORGANIC SYNTHESES VIA TRANSITION-METAL COMPLEXES .74. NOVEL PHOSPHONIUM ALLENIDE AND 2-PHOSPHANYLETHENYL CARBENE CHROMIUM AND TUNGSTEN COMPLEXES

Alkynylcarbene complexes (CO)(5)M=C(OEt)-C drop C-R 1 (M = Cr, W; R = Ph, tBu, SiMe(3)) readily add tertiary phosphanes PPhR(2)' 4 (R' = Ph, Me) to form stable zwitterionic phosphonium allenide complexes (CO)(5 )M(-) -C(OEt) = C=C(R)-P(+)PhR(2)' 5. Complex 5a (M = Cr, R = R' = Ph) was characterized by X-ray diffraction. The addition of secondary pho sphanes PHR(2) 6 to 1 affords red (2-phosphanyl ethenyl)-carbene compl exes (CO)(5)M=C(OEt)-CH=C(R)-PR(2) (E)-8 (R = tBu, cC(6)H(11), Ph) in 34-89% isolated yields. Dinuclear complexes (CO)(5)M=C(OEt)-CH=C(R)-P( R(2))M(CO)(5) (E)-9 are obtained as byproducts. Compounds (E)-8b (M = Cr, R = cC(6)H(11)) and (E)-9i (M = Cr, R = Ph) were characterized by X-ray analyses.