Synthesis and Reactivity toward Isonitriles of (2-Aminoaryl)palladium(II) Complexes

Mixtures of “Pd(dba)₂” (dba = dibenzylideneacetone) and 2,2‘-bipyridine (bpy; 1:2) or N,N,N‘,N‘-tetramethylethylenediamine (tmeda; 1:1) react with 2-bromo-4-nitroaniline to give [Pd{C₆H₃NH₂-2-NO₂-5}Br(N−N)] (N−N = bpy (1b), tmeda (1b‘)). Reactions of 2-iodoaniline with mixtures of “Pd(dba)₂” and isonitriles RNC (R = C₆H₃Me₂-2,6 (Xy), 2:1:2 molar ratios; R = ^tBu, 2.9:1:2 molar ratios) result in the formation of the complexes [Pd{κ²C,N-C(NXy)C₆H₄NH₂-2}I(CNXy)] (2a) and trans-[Pd{C(N^tBu)C₆H₄NH₂-2}I(CN^tBu)₂] (3a*). The reactions of [Pd{C₆H₄NH₂-2}I(bpy)] and 1b‘ with RNC give the complexes trans-[Pd{C(NR)C₆H₃NH₂-2-Y-5}}X(CNR)₂] (Y = H, X = I, R = Xy (3a), ^tBu (3a*); Y = NO₂, X = Br, R = Xy (3b), ^tBu (3b*)). Complexes 3 react with Tl(TfO) (TfO = CF₃SO₃) to give decomposition products, with the exception of 3a, which gives the cyclopalladated complex cis-[Pd{κ²C,N-C(NXy)C₆H₄NH₂-2}(CNXy)₂]TfO (4a). Complex 2a or 3 reacts with Tl(TfO) in the presence of the corresponding ligand, L or L₂, to give the cationic complex [Pd{C(NR)C₆H₃NH₂-2-Y-5}(CNR)L₂]TfO (L = ^tBuNC, Y = H (5a*), NO₂ (5b*); L₂ = bpy, Y = H, R = Xy (6a), ^tBu (6a*)). When L = PPh₃, the resulting complexes trans-[Pd{C(NR)C₆H₃NH₂-2-Y-5}(CN^tBu)₂(PPh₃)]TfO (Y = H (7a*), NO₂ (7b*)) decompose easily to the Pd(I) complex [Pd₂(CN^tBu)₄(PPh₃)₂](TfO)₂ (8). The reaction of 2a with Tl(TfO) affords [{Pd[κ²C,N-C(NXy)C₆H₄NH₂](CNXy)}₂(μ-I)]TfO (9a), and that with a mixture of bpy and Tl(TfO) in acetone with subsequent bubbling of CO through the solution gives [Pd(R)(CNXy)(bpy)](TfO)₂ (10), where R is 2-(xylylamino)-3-xylylquinazolinium-4-yl. The crystal structures of 2a, 3a, 4a, 6a, 8, 9a·CH₂Cl₂, and 10·1.5CH₂Cl₂ have been determined by X-ray diffraction studies. Some hydrogen bond interactions (C_sp³−H···Pd, N−H···π−arene, N−H···I−Pd; eight-membered rings ···O−S−O···H−N−C−C−H··· and ···I−Pd−N−H···I−Pd−N−H···) lead to interesting supramolecular structures.