A comprehensive understanding of carbon–carbon bond formation by alkyne migratory insertion into manganacycles

Abstract

Migratory insertion (MI) is one of the most important processes underpinning the transition metal-catalysed formation of C–C and C–X bonds. In this work, a comprehensive model of MI is presented,...

Understanding Precatalyst Activation and Speciation in Manganese-Catalyzed C–H Bond Functionalization Reactions

“…Once again, toluene complex 6b was the initially formed photoproduct, but over the course of ca. 500 ns, bands corresponding to both 9b and the previously observed 12 alkyne complex fac-[Mn(C^N)(CO) 3 (η 2 -HC�CPh)] (7b) appeared.…”

“…In previous studies, the interaction of the light-activated complexes 1a and 1b with toluene solutions of PhC 2 H, 3, was reported. 6,12 In these cases, the initial formation of toluene complexes (e.g., 6a; Figure 1c) was followed by substitution by PhC 2 H to give alkyne complexes (e.g., 7a) and finally C−C bond formation to give the seven-membered metallacycles (e.g., 8a), which are a key intermediates in Mn-catalyzed reactions. 15 To understand the speciation of the precatalyst following activation via CO loss, the interaction between light-activated 1a and 2phenylpyridine in toluene solution was explored using TR M PS.…”

“…As shown in our previous work, the complex arising from the subsequent alkyne insertion into the metal−carbon bond lies at lower energy than the corresponding alkyne complex. 6,12 Identical calculations on the 1,1-bis(4-methoxyphenyl)methanimine system provided insight into the difference between the two systems. In this case, the substitution of toluene from 6b by either 2b or PhC 2 H was shown to be exergonic by 80 and 36 kJ mol −1 , respectively.…”

“…The experiments have harnessed the ability of the time-resolved multiple-probe spectroscopy (TR M PS) method , to acquire spectra with pump–probe delays ranging from picoseconds to milliseconds. This has allowed for the observation of (i) solvent-coordinated complexes following CO loss; (ii) coordination and subsequent insertion of alkynes, alkenes, and isocyanates into the Mn–C bond ,,, (Figure a); (iii) proton-shuttling events with the coordination sphere of the metal, including the microscopic reverse of the concerted metalation–deprotonation (CMD) mechanism; (iv) competition between water and N 2 ligands for the manganese; and (v) the intermediates involved in the borylation of aryl and heteroaryl diazonium salts …”

A manganese(i)tricarbonyl-catalyst for near room temperature alkene and alkyne hydroarylation

“… 5 More recently, Fairlamb, Lynam and co-workers were able to further experimentally characterize, with time-resolved infrared spectroscopy, the dissociation and association processes going from I to III, by facilitating the dissociation of CO through photochemical activation. 6 Interestingly, Liebeskind showed in 1989 that Mn(CO) 4 -complex VI is unreactive towards alkynes. 7 However, when a stoichiometric amount of a CO scavenger is added, the desired product is formed at room temperature, demonstrating the higher reactivity of Mn(CO) 3 -species.…”