Transmetalation of Acyclic Tungsten Carbenes to Coinage Metals: Distinct Behavior of Silver toward Carbene Transfer and Hydrolysis

Abstract

The transmetalation of acyclic monoamino and alkoxo carbenes from tungsten to group 11 metals has been studied for all three metals by analyzing the new metal carbenes formed and also their decomposition products in solution. The ease of transmetalation follows the trend: Au > Cu > Ag and the gold carbenes can be isolated, a copper carbene could be detected but we found no experimental evidence of the formation of any silver carbene. The electrophilic character of copper and gold carbenes is supported by the identity of the products formed upon hydrolysis of the carbenes involved. Silver shows a distinct behavior and the presence of Ag + ions in an acetonitrile solution of a tungsten aminocarbene leads to the formal protonation of the carbene fragment to give an iminium salt. This outcome, a seemingly nucleophillic behavior, is unexpected for group 11 carbenes but DFT calculations show that the protonation of a putative cationic silver carbene is energetically accessible.

Storable, Dual-Component Systems for Frontal Ring-Opening Metathesis Polymerization

“…Literature precedence exists for such a pathway in the transmetalation of heavy-metal-ligated carbenes onto coinage metals. 64 Additionally, stoichiometric catalyst activation experiments by the Mauduit group 52 provided insight into the catalyst speciation after activation. Treatment of D899 with CuCl in the presence of 2-isopropoxy styrene as a trapping agent afforded an equivalent of Cu(NHC)Cl and a Hoveyda−Grubbslike mono-NHC Ru species.…”

“…In this proposed mechanism, increases in the [Cu] 0 would result in a faster catalyst activation process, thereby increasing the effective concentration of ROMP active Ru centers. Literature precedence exists for such a pathway in the transmetalation of heavy-metal-ligated carbenes onto coinage metals . Additionally, stoichiometric catalyst activation experiments by the Mauduit group provided insight into the catalyst speciation after activation.…”

Visible-Light-Induced In Situ Generation of Fischer-Type Copper Carbene Complexes from Acylsilanes and Its Application to Catalytic [4 + 1] Cycloaddition with Siloxydienes

“…So far, various synthetic reactions of Fischer-type Group 6 metal–carbene complexes have been reported, but in recent years, many efforts have been devoted to the chemistry of Fischer-type carbene complexes bearing a transition-metal center other than Group 6 metals. Typically, such transition metal–carbene complexes were more reactive and could be generated in situ by carbene transfer reaction from the presynthesized Group 6 metal–Fischer carbene complex to a stoichiometric or catalytic amount of appropriate transition-metal compounds (Scheme ). Those complexes were found to be applicable to synthetic reactions such as carbene dimerization, cyclization reactions, and coupling reactions with aryl halides or organoboronates …”

Concatenating Structural Constraint Effects at Tin for the Sequential Generation, Stabilization, and Transfer of Acyclic Aminocarbenes

“…Coinage metal carbene complexes often act as an entry point and allow a wide range of applications. , Especially, the previous use of Cu­(I) carbene complexes as catalysts for various transformations and their photophysical properties − made these complexes ideal targets. Copper­(I) halide complexes of acyclic aminocarbenes are underrepresented in literature with only a few examples of acyclic diaminocarbenes complexes been isolated, , aryl­(amino)­carbene complexes being characterized in situ , and alkyl­(amino)­carbene adducts even being unknown in literature. No solid-state molecular structure of such complexes has been reported so far.…”