DOUBLY CYCLOPALLADATED COMPLEXES OF N,N,N',N'-TETRAETHYLBENZENE-1,3-BIS(METHYLAMINE)

N,N,N',N'-Tetraethylbenzene-1,3-bis(methylamine) (L) undergoes regiospecific double cyclopalladation with Li2[PdCl4] at the 4,6 positions of the benzene ring to produce the chloro-bridged polymeric complex [Pd2(L - 2H)Cl2], Reactions of this complex with PPh3, methylpyridines, acetylacetone, ethylacetoacetate, monothiodibenzoylmethane and trifluoro(thenoyl)acetone have been studied and the products characterized by H-1 and C-13 NMR spectroscopy. Treatment of [Pd2(L - 2H)(PPh3)2Cl2] with MeCO2H and LiCl produces at room temperature the nitrogen-protonated species [Pd2L(PPh3)2Cl4], but trans-[Pd2(PPh3)2Cl4] and the metal-free ligand (L) are formed at 80-degrees-C. The complex [Pd2(L - 2H)Cl2] undergoes exchange reaction with ligands capable of forming monocyclopalladated complexes. The crystal structure of [Pd2(L - 2H)(PPh3)2Cl2] has been determined: monoclinic, space group C2/c, a = 20.676(4), b = 12.436(3), c = 19.445(4) angstrom, beta = 14.29(3)-degrees and Z = 4; refinement led to R = 0.035 and R' = 0.043 using 3533 unique reflections with I > 2sigma(I).