Synthesis of Palladium Complexes with ortho-Functionalized Aryl Ligands

The complexes [Pd(C 6 H 4 X-2)BrL 2 ] (L 2 = trans -(PR 3 ) 2, R = Ph, X = CH CH 2 ( 1a ), CHO ( 1b ), C(O)Me ( 1c ), CN ( 1d ); R = p -To = 4-tolyl, X = CH CH 2 ( 1a ‘); L 2 = bpy = 2,2‘-bipyridine, X = CHO ( 2b ), C(O)Me ( 2c ), CN ( 2d ); L 2 = tmeda = N,N, N ‘, N ‘-tetramethylethylenediamine, X = CHO ( 2b ‘), CN ( 2d ‘)) have been prepared by oxidative addition of the corresponding bromoarene BrC 6 H 4 X-2 to “Pd(dba) 2 ” (=[Pd 2 (dba) 3 ]·dba, dba = dibenzylideneacetone) in the presence of the appropriate ligand. The compound [Pd{C 6 H 4 (CH CH 2 )-2}(bpy)(PPh 3 )]TfO ( 3a; TfO = CF 3 SO 3 ) has been obtained by reacting 1a with bpy in the presence of TlOTf. The cyclopalladated [Pd{ κ 2 - C, O -C 6 H 4 {C(O)Me}-2}(bpy)]TfO ( 4c ) has been prepared from 2c and TlOTf. The dimeric complexes [Pd(μ-Br)(C 6 H 4 X-2)(PR 3 )] 2 (R = Ph, X = CHO ( 5b ), C(O)Me ( 5c ), CN ( 5d ); R = o -To = 2-tolyl, X = CHO ( 5b ‘ ‘), CN ( 5d ‘ ‘)) have been synthesized by reacting complexes 1b − d with [PdCl 2 (NCPh) 2 ] in a 2:1 molar ratio or C 6 H 4 Br-1-X-2 with “Pd(dba) 2 ” and P( o -To) 3 in 1:1:1 molar ratio. The latter method leads to the monomeric [Pd{ κ 2 - C, O -C 6 H 4 {C(O)Me}-2})Br{P( o -To) 3 }] ( 6c ‘ ‘) when X = C(O)Me. The complex 2c reacts with the alkyne PhC⋮CPh or EtC⋮CEt and TlOTf to give 1-methyl-2,3-diphenyl-1 H -indenol ( 7 ) or 1-methyl-2,3-diethyl-1 H -indenol ( 8 ), respectively. The crystal structures of complexes 1a ·2CH 2 Cl 2, 1b ·CH 2 Cl 2, 2b, d, and 6c ‘ ‘ have been determined by X-ray diffraction studies. An interesting supramolecular layered structure is formed through CN···H−C bpy and Br···H−C bpy hydrogen bonds in complex 2d .