REACTIONS OF THE TUNGSTEN CARBYNE COMPLEX W(CME)CL(PME(3))(4) WITH PI-ACCEPTOR LIGANDS - CARBON-MONOXIDE, ALKYNES, AND ALKENES

The tungsten-carbyne complex W(=CCH3)Cl(PMe(3))(4) (1) reacts with carbon monoxide to initially form the monocarbonyl adduct W(=CCH3)Cl(PMe(3))(3)(CO), which reacts further with CO to give an oxametallacyclopentenone complex, W[OC(PMe(3))=CMeC(O)]Cl(CO)(2)(PMe(3))(2) (3). An X-ray crystal structure of 3 shows a seven coordinate tungsten complex with the metal bound to an acyl carbon and an enolate oxygen of the metallacycle, which results from an unusual double carbonylation of the carbyne ligand. Crystal data for 3.C4H8O, at 24 degrees C: monoclinic, P2(1)/c, a = 14.945(3) Angstrom, b = 9.259(3) Angstrom, c = 20.226(3) Angstrom, beta = 102.27(1)degrees, Z = 4, R = 0.035, R(W) = 0.040. Reaction of 1 with 2 equiv of p-tolyl isocyanate gives CO and the tungsten-ureato-N,N' complex W(=CCH3)Cl[(NTol)(2)C=O](PMe(3))(2). Alkynes react with 1 to displace two PMe(3) ligands and form the first examples of carbyne-alkyne complexes, W(=CCH3)Cl(RC=CR')(PMe(3))(2) (RC=CR'=MeC=CMe, PhC=CPh, HC=C(t)Bu]. The diphenylacetylene and tert-butylacetylene complexes rearrange to give the new carbyne-alkyne complexes W(=CPh)Cl(CH3C=CPh)(PMe(3))(2) and W(=C(t)Bu)Cl(CH3C=CH)(PMe(3))(2), respectively. These rearrangements resemble alkyne metathesis, in that the carbyne ligand is exchanged with one end of the alkyne ligand. Vinylalkoxysilanes react with 1 to give carbyne-alkene complexes, W(=CCH3)Cl[CH2=CHSi(OMe)(3)](PMe(3))(2) and W(=CCH3)Cl-[CH2=CHSi(OEt)Me(2)](PMe(3))(2), in which the silane appears to be bound through both the alkene and silyl ether functionalities.