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

The reaction of [W(CO)₅{C(NEt₂)Ph}] (3) with [PdClR(SMe₂)]₂ (R = Me, Ph) occurs with transfer of carbene and carbonyl groups to give [PdCl{C(O)R}{C(NEt₂)Ph}]₂ (R = Me, 4; R = Ph, 5). When the reaction is monitored for R = Me, only [PdCl(COMe)(SMe₂)]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−C₆F₅ 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.