Cationic Dinuclear Pd−Allyl−Halide Complexes with N-Heterocyclic Carbenes

Reaction of the mononuclear N-heterocyclic carbene complexes (η3-C3H5)Pd{C(N(R)CH)2}X
(R = tBu, X = Cl, I (1a,b); R = C6H3-2,6-iPr2, X = Cl, I (2a,b)) with TlPF6 and TlOTf in
CH2Cl2 or THF results in partial halide substitution to afford the ionic dinuclear complexes
[{(η3-C3H5)Pd(C(N(R)CH)2)}2(μ-X)]Y (R = tBu, X = Cl, Y = PF6 (3a), OTf (3b) and X = I, Y
= OTf (3c); R = C6H3-2,6-iPr2, X = Cl, Y = PF6 (4a), OTf (4b) and X = I, Y = OTf (4c)).
According to solution NMR the dinuclear complexes are present as mixtures of diastereomers.
The crystal structure of 3a·0.5(C4H10O)·0.5(CH2Cl2) has been determined by X-ray crystallography. From the reaction of 2a with LiMe the PdMe derivative (η3-C3H5)Pd{C(N(C6H3-2,6-iPr2)CH)2}Me (6) has been obtained. When 1a was reacted with B(C6F5)3, the NHC ligand
was transferred to give (C6F5)3B−C(N(tBu)CH)2 and the starting {(η3-C3H5)Pd(μ-Cl)}2.