Synthesis of palladium complexes with ortho-functionalized aryl ligands

The complexes [Pd(C6H4X-2)BrL2] (L-2 = trans-(PR3)(2), R = Ph, X = CH=CH2 (1a), CHO (1b), C(O)Me (1c), CN (1d); R = p-To = 4-tolyl, X = CH=CH2 (1a'); La = 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 BrC6H4X-2 to Pd-a(dba)(2) (=[Pd-2(dba)(3)]. dba, dba = dibenzylideneacetone) in the presence of the appropriate ligand. The compound [Pd{C6H4(CH=CH2)-2}(bpy)(PPh3)]TfO (3a; TfO = CF3SO3) has been obtained by reacting 1a with bpy in the presence of TIOTf. The cyclopalladated [Pd{kappa(2)-C,O-C6H4{C(O)Me)-2}(bpy)]TfO (4c) has been prepared from 2c and TIOTf. The dimeric complexes [Pd(mu-Br)(C6H4X-2)(PR3)](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 [PdCl2(NCPh)(2)] in a 2:1 molar ratio or C6H4Br-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{kappa(2)-C,O-C6H4{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-1H-indenol (7) or 1-methyl-2,3-diethyl-1H-indenol (8), respectively. The crystal structures of complexes 1a . 2CH(2)Cl(2), 1b . CH2Cl2, 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.