PREPARATION AND REACTIONS OF TRANS-PD(COPH)(CONR2)(PME3)2 AND TRANS-PDPH(CONR2)(PME3)2 COMPLEXES AS MODELS FOR INTERMEDIATES INVOLVED IN THE PALLADIUM-CATALYZED DOUBLE-CARBONYLATION AND SINGLE-CARBONYLATION REACTIONS OF PHENYL HALIDES

The reaction of trans-Pd(COPh)Cl(PMe3)2 (1) with secondary amines (R2NH) and CO under pressure at room temperature gives trans-Pd(COPh)(CONR2)(PMe3)2 complexes (R2N = Me2N (3a), CH2(CH2)4N (3b), CH2(CH2)3N (3)) quantitatively, together with the ammonium salts R2NH2Cl. Complexes 3a-c are prepared also by treating the cationic benzoylpalladium complex trans-[Pd(COPh) (acetone) (PMe3)2]X (2, X = BF4 or PF6) with the secondary amines and CO at atmospheric pressure. The reactions of 2 with amines and CO affording the benzoyl-carbamoyl complexes proceed rapidly at -20 °C, while the same systems at room temperature yield α-keto amides (PhCOCONR2) quantitatively. The isolated benzoylcarbamoyl complexes 3a-c are fairly stable toward direct reductive elimination to afford α-keto amides in solutions containing secondary amines under a CO atmosphere at room temperature. In the presence of an ammonium salt (R2NH2BF4), on the other hand, these complexes readily afford α-keto amides under the otherwise same conditions. Treatment of trans-[PdPh(acetone)(PMe3)2]PF6 (7) instead of the benzoyl complex 2 with secondary amines and C at -20 °C forms trans-PdPh(CONR2)(PMe3)2 complexes (R2N = Me2N (8a), CH2(CH2)4N (8b), CH2(CH2)3N (8c)), while the same systems give α-keto amides and amides at room temperature. Mechanisms of formation of the benzoyl- and phenyl-carbamoyl complexes and of α-keto amide and amide have been studied in detail in conjunction with proposed mechanisms for the catalytic double- and single-carbonylation reactions. © 1990, American Chemical Society. All rights reserved.