Carbene and Carbonyl Transfer from [W(CO)₅(carbene)] to Palladium, Affording Palladium(II) Carbene Acyl Complexes

Abstract

The reaction of [W(CO) 5 {C(NEt 2 )Ph}] (3) with [PdClR(SMe 2 )] 2 (R ) Me, Ph) occurs with transfer of carbene and carbonyl groups to give [PdCl{C(O)R}{C(NEt 2 )Ph}] 2 (R ) Me, 4; R ) Ph, 5). When the reaction is monitored for R ) Me, only [PdCl(COMe)(SMe 2 )] 2 and the final carbene 4 are observed, suggesting that the transfer and insertion of the carbonyl group are faster than the carbene transmetalation. Although CO insertion into M-X bonds is thermodynamically excluded in many systems (e.g., in M-halogen and M-C 6 F 5 bonds), this study warns of the fact that CO is easily available when [M(CO) 5 (carbene)] complexes are used as carbene sources, whether for stoichiometric or for catalytic reactions. This CO could react with the intermediates or the products in these reactions.

Acyl–Carbene and Methyl–Carbene Coupling via Migratory Insertion in Palladium Complexes

“…10 This reaction involves the transfer of carbene and CO from W to Pd, which leads to the formation of the acyl group bound to palladium. trans-1 undergoes isomerization in solution (CDCl 3 ) at room temperature ( Figure 1) to cis-1 ( 2 J C,P = 5.0 Hz for the carbene carbon resonance in 13 C NMR vs 2 J C,P = 102.1 Hz for trans-1).…”

Reactive Palladium Carbenes: Migratory Insertion and Other Carbene–Hydrocarbyl Coupling Reactions on Well‐Defined Systems

“…This process takes place for R = Me, Ph but not for R = C 6 F 5 , a group that disfavors the formation of the acyl group. The carbonyl transfer is faster than the carbene transfer for monoaminocarbenes, and for R = Me, Ph only the acyl palladium carbene is observed [Equation ] . However the rate of carbene transfer vs. acyl formation is closer for the methoxy carbene and the product of migratory insertion of the carbene into the Pd–Me bond ( 42 , path b, Scheme ) could be observed and characterized …”

Well‐Defined, Versatile and Recyclable Half‐Sandwich Nickelacarborane Catalyst for Selective Carbene‐Transfer Reactions

“…Carbene transferr eactions, particularly of diazo compounds with electron-withdrawing substituents, have been extensively studied using transition-metal catalysts or Lewisa cid catalysts, and successfully appliedi np reparation of many functional molecules. [1] Up to now,anumber of transition-metals, ranging from the middle (Cr group) [2] to the late groups (Cu andZ n groups), [3] have been capableo fc atalyzing these reactions via metal-carbene intermediates. Among them, rhodium [4] and copper [5] are by far the most widely used ones, followed by iridium and ruthenium.…”