Intramolecular Carbyne–Isocyanide Coupling to an Alkyne Ligand at a d4 Tungsten Center

Abstract

Oxidative decarbonylation of Cp*(CO)2W≡CNEt2 (1) with PhICl2 affords the aminocarbyne complex cis-Cp*(Cl)2(CO)W≡CNEt2 (2), which reacts with tBuNC to give the CO substitution product cis-Cp*(Cl)2(tBuNC)W≡CNEt2 (3) (Cp* = C5Me5). Complex 3 undergoes a carbyne–isocyanide coupling reaction with HCl to yield the alkyne complex Cp*(Cl)3W[η2-tBu(H)NC≡CNEt2] (4). In comparison, the reaction of cis-Cp*(Cl)2[P(OMe)3]W≡CNEt2 (5) with HCl affords the 16e carbene complex Cp*(Cl)3W=C(H)NEt2 (6) after elimination of P(OMe)3. Complex 5 was obtained from the CO ligand-exchange reaction of 2 with P(OMe)3. Treatment of 6 with tBuNC yields the cationic 18e carbene complex [Cp*(Cl)2(tBuNC)2W=C(H)NEt2]Cl (7). The mechanism of the C–C coupling reaction of 3 to give 4 is discussed and the crystal structures of 4 and 6 are described.