Synthesis of Ortho-Palladated Phenol Derivatives. Study of Their Reactivity with Carbon Monoxide and Isonitriles

The reaction of 2-ROC 6 H 4 I with [Pd 2 (dba) 3 ]·dba (“Pd(dba) 2 ”; dba = dibenzylideneacetone) in the presence of the appropriate ligand results in the formation of the arylpalladium complexes trans -[Pd(C 6 H 4 OR-2)I(PPh 3 ) 2 ] (R = H ( 1a ), C(O)Me ( 1b ), C(O)CH CH 2 ( 1c )) and [Pd(C 6 H 4 OR-2)I(bpy)] (bpy = 2,2‘-bipyridine; R = H ( 2a ), C(O)Me ( 2b )). Complexes 1b and 1c react with bpy in the presence of Tl(OTf) (OTf = OSO 2 CF 3 ) to give the cationic species [Pd(C 6 H 4 OR-2)(bpy)(PPh 3 )]OTf (R = C(O)Me ( 3b ), C(O)CH CH 2 ( 3c )). Complex 1a reacts with carbon monoxide, yielding the insertion complex trans -[Pd{C(O)C 6 H 4 OH-2}I(PPh 3 ) 2 ] ( 4a ). Complexes 2a and 2b can also be carbonylated to give [Pd{C(O)C 6 H 4 OR-2}I(bpy)] (R = H ( 5a ), C(O)Me ( 5b )). Complex 4a reacts with bpy and Tl(OTf), giving [Pd{C(O)C 6 H 4 OH-2}(bpy)(PPh 3 )]OTf ( 6a ). The reaction of 2-ROC 6 H 4 I with Pd(dba) 2 and isonitriles R‘NC gives rise to the complexes trans -[Pd{C( NR‘)C 6 H 4 OR-2}I(CNR‘) 2 ] (R = H, R‘ = Xy = 2,6-dimethylphenyl) ( 7a ), R‘ = t Bu ( 7a *); R = C(O)Me, R‘ = Xy ( 7b ), R‘ = t Bu ( 7b *)). Complexes 7a and 7b * can also be prepared by ligand displacement from 2a and 2b and XyNC and t BuNC, respectively. Complexes 2a and 2b react with R‘NC (1:1) to give [Pd{C( NR‘)C 6 H 4 OR-2}I(bpy)] (R = H, R‘ = Xy ( 8a ), R‘ = t Bu ( 8 a * ); R = C(O)Me, R‘ = Xy ( 8b )). Complex 7a reacts with bpy in the presence of Tl(OTf), yielding [Pd{C( NR‘)C 6 H 4 OH-2}(CNR‘)(bpy)]OTf ( 9a ). Reaction of 5a with R‘NC gives trans -[Pd{C(O)C 6 H 4 OH-2}I(CNR‘) 2 ] (R‘ = Xy ( 10a ), t Bu ( 10 a * )), which, in turn, react with further R‘NC in the presence of Tl(OTf) to give [Pd{C(O)C 6 H 4 OH-2}(CNR‘) 3 ]OTf (R‘ = Xy ( 11a ), t Bu ( 11 a * )). Finally, the reaction of 7a with Pd(OAc) 2 results in the tetrameric [Pd{ κ 2 ( C, O ) - μ 2 ( O ) - C( NXy)C 6 H 4 O-2}(CNXy)] 4 ( 12 ) and trans -[PdI 2 (CNXy) 2 ]. Most of the reported aroyl ( 4 − 6, 10, 11 ) and iminoaroyl ( 7 − 9, 12 ) derivatives are new types of palladium complexes. The crystal structures of complexes 5a, 7a, 7b, 8b, 9a, and 12 have been determined by X-ray diffraction methods. The following scale of trans influence has been established: bpy < I < C( NXy)C 6 H 4 OC(O)Me-2 ≈ C( O)C 6 H 4 OH-2 < C( NXy)C 6 H 4 OH-2.