Synthesis of Arylpalladium(II) Complexes Derived from Benzyl Alcohol, Reactivity toward Alkyl Halides, and Synthesis of Dinuclear Arylpalladium(II) Complexes

摘要

The aryl palladium complexes [Pd-(C6H4CH2OH-2)(N<^>N)] (N<^>N = bpy = 2,2'-bipyridyl (1a), tbbpy 4,4'-di-tert-butyl-2,2'-bipyridine (1b), tmeda = N,N,N',N'-tetramethylethylenediamine (1c)) were synthesized by oxidative addition of 2-iodobenzyl alcohol to one equivalent of "[Pd(dba)2]" (dba = dibenzylideneacetone) in the presence of the N<^>N ligands. By reaction of la with three equivalents of XyNC (Xy = 2,6-dimethylphenyl) the insertion complex trans [PdI{C(=NXy) (C6H4CH2OH-2)} (CNXy)(2)] (2) was formed. The reaction of 1a with (KOBu)-Bu-t resulted in the formation of the chelate complex [Pd(kappa(2)-C,O-C6H4CH2O-2)(bpy)] (3), which crystallizes as pairs of molecules bridged by hydrogen bonds to water of crystallization. Complex 3 reacts with XyNC, forming the cyclic imidate N-(2,6-dimethylphenyl)-2-benzofuran-1(3H)-imine (4). By various primary alkyl halides RCH2X, the complexes [PdX(C6H4CH2OCH2R-2)(bpy)] (X = I, R = H (5a), X = Br, R = Ph (5b), p-C6H4CH2Br (5c), p-C6H4Br (5d), and p-C6H4I (5e)) were obtained. When the reaction of 3 with p-C6H4(CH2Br)(2) was carried out in a 2:1 ratio, the dinuclear arylpalladium complex [{(bpy)BrPd(C6H4CH2OCH2-2)}2(C6H4-1,4)] (6) formed. An halide exchange reaction on Se, using AgOTf and an excess of NaI, afforded [PdI{C6H4(CH2OCH2(C6H4I-4))-2}(bpy)] (5f), which by oxidative addition to [Pd(dba)(2)] in the presence of bpy formed another dinuclear arylpalladium complex, Rbpy)IPd(C6H4CH2-2)O(CH2C6H4-4)PdI(bpy)] (7). All the complexes have been extensively characterized by NMR spectroscopy. The crystal structures of la, 3 center dot H2O, and Se were determined by X-ray diffraction studies.