Computational Mechanistic Study of Fused Phenol Formations from 1,6‐Heptadiyne Involving Carbyne Complexes

Abstract

The reaction of a tungsten carbyne complex, MeC≡WBr(CO)4, with 1,6‐heptadiyne was investigated using density functional theory (DFT) calculations. It was suggested that the plausible mechanism involves [2+2] cycloaddition of the carbyne with the diyne, subsequent insertion of CO and alkyne into a metallacyclobutadiene intermediate, and a final reductive elimination step from a metallacycloheptatrienone intermediate to produce a η5‐cyclohexadienyl complex. A related Ru‐catalyzed reaction of 1,6‐heptadiyne involving a hydroxycarbyne complex was investigated to propose a possible pathway starting from a bis(hydroxycarbyne) complex, (HOC≡)2Ru(CO)2. It was found that the biscarbyne complex undergoes carbyne‐carbyne coupling to generate a stable metallacyclopropene intermediate, which reacts with 1,6‐heptadiyne through two different pathways to produce the final η6‐arene complex. Moreover, a non‐carbyne pathway was also investigated to propose an alternative mechanism.

Organometallic Chemistry of Transition Metal Alkylidyne Complexes Centered at Metathesis Reactions

“…A computational study indicates that the reactions most likely proceed through initial [2 + 2] cycloaddition of the alkylidyne 124 with the diynes to give MCBDs (e.g., 128 from 127 , Scheme ). The kinetic barrier for the formation of the MCBD 128 from the alkyne complex 127 was calculated to be near 21 kcal/mol.…”

“…182 A computational study indicates that the reactions most likely proceed through initial [2 + 2] cycloaddition of the alkylidyne 124 with the diynes to give MCBDs (e.g., 128 from 127, Scheme 27). 183 The kinetic barrier for the formation of the MCBD 128 from the alkyne complex 127 was calculated to be near 21 kcal/mol. MCBD intermediates may also be involved in the reaction of the Mn-alkylidyne 131 with MeC�CNEt 2 to give the cyclic carbene 133 (Scheme 28), 184 the reaction of the W(IV) alkylidyne 134 with PhC�CH to give a mixture of the η 2alkyne complexes 135 and 136, 185 and the reaction of the W(IV) alkylidyne 124 with the enyne 137 to give the pentadienyl 139.…”