ORGANIC SYNTHESES VIA TRANSITION-METAL COMPLEXES .80. ALLENYLIDENE COMPLEXES FROM [(2-AMINOETHENYL)CARBENE]CHROMIUM COMPLEXES

Allenylidene complexes (CO)(5)Cr=C=C=C(NRR(1))Ph (5a-d) (NRR(1) = NMe( 2), NMePh, NEtPh, indolinyl) are formed on reaction of (2-aminoalkenyl )carbene complexes (CO)(5)-Cr=C(OEt)-CH=C(NR(1))Ph (4a-d) with aluminu m chloride in carbon disulfide/dichloromethane in 53-73% isolated yiel d. The X-ray structure of complex 5d [NRR(1) = NMePh; monoclinic space group P2(1)/c (No. 14), a = 12.989(1) Angstrom, b = 13.520(2) Angstro m, c = 12.546(1) Angstrom, Z = 4, R = 0.044, R(w)2 = 0.143] indicates that a polarized iminium-alkynyl structure (COCr--C=CC(=N(+)MePh)Ph gi ves a more adequate description of the bond distances than the allenyl idene structure.