Organometallics 1994, 13, 2467-2471
2467
Reactions of Alkynols with (Alkynyla1koxycarbene)metal Complexes (Metal = Chromium, Tungsten) Antonia Segundo, Josep M. MoretB, Josep M. Vifias, and Susagna Ricart' Departament de Qutmica Orghnica i Biolbgica, CID (CSIC), CIJ. Girona 18-26, 08034-Barcelona, Spain
Elies Molins Institut de CiBncia de Materials de Barcelona, Campus Universitari de Bellaterra, 08193-Cerdanyola, Spain Received December 2 0 , 1 9 9 P
(Alkyny1alkoxycarbene)metalcomplexes react with alkynols to give different types of products depending fundamentally on the substitution of the triple bond (mono- or disubstituted alkynes) and the spacing between the triple bond and the hydroxy functions. Since the early work in metal carbene chemistry, the ambivalent electrophilic character of (alkynylalkoxycarbene)metal complexes has been recognized. Under conditions of kinetic control (-80 "C) attack by amines occurs only at the carbene center, but at higher temperatures the product is that arising from amine addition to the triple b0nd.l In addition, carbanions,2 as well as alcohols, phenols, and thiol^,^ also add readily to the triple bond, giving the corresponding alkenyl complexes. The activated triple bond in these complexes has also been found to readily suffer cycloaddition reactions with a variety of
Table 1. Reaction of Monosubstituted Alkynols with (Alkynyla1koxycarbene)metal (Cr, W)Complexes (0c)5M%1
Ph
2
aM=W b M= Cr
a n=I b n=2 e n=3
(OC)5M
