Cationic Arylpalladium Complexes with Chelating Diamine Ligands, [PdAr(N−N)(solv)]BF₄(N−N=N,N,N‘,N‘-tetramethylethylenediamine, 2,2‘-bipyridine, 4,4‘-dimethyl-2,2‘-bipyridine). Preparation, Intermolecular Coupling of the Aryl Ligands, and Insertion of Alkyne and Allene into the Pd−C Bond

Iodo(aryl)palladium complexes, [PdI{C 6 H 3 (CF 3 ) 2 -3,5}(N−N)] (N−N = tmeda, bpy, 4,4‘-dimethyl-2,2‘-bipyridine (Me 2 bpy)), react with AgBF 4 in CH 3 CN, acetone, and THF to yield stable cationic arylpalladium complexes [Pd{C 6 H 3 (CF 3 ) 2 -3,5}(N−N)(solv)]BF 4 . A similar reaction of AgBF 4 with [PdI(C 6 H 3 Me 2 -3,5)(bpy)] in CH 3 CN gives [Pd(C 6 H 3 Me 2 -3,5)(bpy)(CH 3 CN)]BF 4 . The complex does not change its NMR spectrum for 1 h at room temperature in CD 3 CN but undergoes decomposition upon dissolution in acetone to release 3,3‘,5,5‘-tetramethylbiphenyl. Addition of AgBF 4 to acetone or THF solutions of [PdI(Ar)(bpy)] (Ar = Ph, C 6 H 3 Me 2 -3,5) and of [PdI(Ar)(Me 2 bpy)] (Ar = C 6 H 4 OMe-4, C 6 H 3 Me 2 -3,5) does not lead to isolation of the cationic arylpalladium complexes and causes intermolecular coupling of the aryl ligands to yield the corresponding biaryls. The reaction of AgBF 4 with [PdI(C 6 H 3 Me 2 -3,5)(bpy)] in the presence of an excess amount of dimethyl acetylenedicarboxylate (DMAD) in CH 3 CN gives [Pd(CZ CZ−CZ CZ−C 6 H 3 Me 2 -3,5)(bpy)(CH 3 CN)]BF 4 (Z = COOMe) via insertion of two acetylene molecules into the Pd−aryl bond. A similar reaction in acetone or THF causes insertion of three DMAD molecules into the Pd−aryl bond and cyclization of the formed Pd−(CZ CZ) 3 −Ar group to give the product containing a cyclopentadiene structure in the ligand. [PdI(CZ CZ−C 6 H 3 Me 2 -3,5)(bpy)] reacts with AgBF 4 in CH 3 CN to form a cationic complex, [Pd(CZ CZ−C 6 H 3 Me 2 -3,5)(bpy)(CH 3 CN)]BF 4 . A series of cationic Pd complexes, formed through insertion of one, two, and three alkyne molecules into the Pd−aryl bond, are characterized by X-ray crystallography or NMR spectroscopy. Phenylallene reacts with [PdI(C 6 H 3 Me 2 -3,5)(bpy)] in the presence of AgBF 4 to give [Pd{ η 3 -CH 2 C(C 6 H 3 Me 2 -3,5)CHPh}(bpy)]BF 4 via insertion of the C C double bond of the allene into the Pd−C bond of the cationic arylpalladium complex. The π-allylpalladium complex crystallizes exclusively in a form with a syn-oriented phenyl substituent but exists in solution as a mixture of the isomers with a syn or anti phenyl substituent.