Synthesis of ortho-palladated phenol derivatives. Study of their reactivity with carbon monoxide and isonitriles

The reaction of 2-ROC6H4I with [Pd-2(dba)(3)]. dba ("Pd(dba)(2)"; dba = dib enzylidencacetone) in the presence of the appropriate ligand results in the formation of the arylpalladium complexes trans-[Pd(C6H4OR-2)I(PPh3)(2)] (R = H (1a), C(O)Me (1b), C(O)CH=CH2 (1c)) and [Pd(C6H4OR-2)I(bpy)] (bpy = 2, 2 ' -bipyridine; R = H (2a), C(O)Me (2b)). Complexes 1b and 1c react with b py in the presence of Tl(OTf) (OTf = OSO2CF3) to give the cationic species [Pd(C6H4OR-2)(bpy)(PPh3)] OTf(R = C(O)Me (3b), C(O)CH=CH2 (3c)). Complex 1a reacts with carbon monoxide, yielding the insertion complex trans-[Pd(C(O) C6H4OH-2)I(PPh3)(2)] (4a). Complexes 2a and 2b can also be carbonylated to give [Pd(C(O)C6H4OR-2)I(bpy)] (R H (5a), C(O)Me (5b)). Complex 4a reacts wi th bpy and Tl(OTf), giving [Pd(C(O)C6H4OH-2)(bpy)(PPh3)] OTf (6a). The reac tion of 2-ROC6H4I with Pd(dba)(2) and isonitriles R ' NC gives rise to the complexes trans- [PdCC(=NR ' )C6H4OR-2)I(CNR ' )2] (R = H, R ' = Xy = 2,6-d imethylphenyl) (7a), R ' = Bu-t (7a*); R = C(O)Me, R ' = Xy (7b), R ' = Bu- t (7b*)). Complexes 7a and 7b* can also be prepared by ligand displacement from 2a and 2b and XyNC and (BuNC)-Bu-t, respectively. Complexes 2a and 2b react with R ' NC (1:1) to give [Pd(C(=NR ' )C6H4-OR-2}I(bpy)] (R = H, R ' = Xy (8a), R ' = Bu-t (8a*); R = C(O)Me, R ' = Xy (8bj). Complex 7a reacts with bpy in the presence of Tl(OTf), yielding [Pd( C(=NR ' )C6H4OH-2)I(CNR ')(bpy)]-OTf (9a). Reaction of 5a with R ' NC gives trans- [Pd(C(O)C6H4OH-2 )I(CNR ')(2)] (R ' = Xy (10a), Bu-t (10a*)), which, in turn, react with fur ther R ' NC in the presence of Tl(OTf) to give [Pd(C(O)C6H4OH-2)(CNR ')(3)] OTf (R ' = Xy (11a), Bu-t (11a*)). Finally, the reaction of 7a with Pd(OAc )(2) results in the tetrameric [Pd(K-2(C,O)-mu2(O)-C(=NXy)C6H4O-2)(CNXy)](4 ) (12) and trans-[PdI2(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 de termined by X-ray diffraction methods. The following scale of trans influen ce has been established: bpy < I < C(=NXy)C6H4OC(O)Me-2 approximate to C(=O )C6H4OH-2 < C(=NXy)C6H4OH-2.