1,2,3-Triazole based ligands with phosphine and pyridine functionalities: synthesis, Pd II and Pt II chemistry and catalytic studies.

This manuscript describes the syntheses of pyridine appended triazole-based mono- and bisphosphines, [ o -Ph 2 P(C 6 H 4 ){1,2,3-N 3 C(Py)C(H)}] (2), [ o -Br(C 6 H 4 ){1,2,3-N 3 C(Py)C(PPh 2 )}] (3), [C 6 H 5 {1,2,3-N 3 C(Py)C(PPh 2 )}] (4), [Ph 2 P(C 6 H 4 ){1,2,3-N 3 C(Py)C(PPh 2 )}] (5) and [3-Ph 2 P-2-{1,2,3-N 3 C(Ph)C(PPh 2 )}C 5 H 3 N] (6), their palladium and platinum chemistry and catalytic applications. These ligands upon treatment with [M(COD)Cl 2 ] (M = Pd or Pt) yielded complexes with different coordination modes, depending on the reaction conditions. Both κ 2 - P , N and κ 2 - P , P coordination modes were observed in many of the complexes indicating the ambidentate nature of these ligands. Monophosphine 2 in the presence of a base afforded rare fused-5,6-membered PCN pincer complexes [MCl{ o -Ph 2 P(C 6 H 4 ){1,2,3-N 3 C(Py)C(H)}}-κ 3 - P , C , N ] (7, M = Pd; 8, M = Pt), whereas the reactions of 4 with [M(COD)Cl 2 ] (M = Pd, Pt) produced κ 2 - P , N chelate complexes [MCl 2 {C 6 H 5 {1,2,3-N 3 C(Py)C(PPh 2 )}-κ 2 - P , N }] (9, M = Pd; 10, M = Pt). Similar reactions of 5 and 6 resulted in κ 2 - P , P chelate complexes [MCl 2 {{3-Ph 2 P-2-{1,2,3-N 3 C(Ph)C(PPh 2 )}C 5 H 3 N}-κ 2 - P , P }] (11, M = Pd; 12, M = Pt) and [MCl 2 {3-Ph 2 P-2-{1,2,3-N 3 C(Ph)C(PPh 2 )}C 5 H 3 N}-κ 2 - P , P }] (13, M = Pd; 14, M = Pt), respectively. The palladium(II) complexes have shown excellent catalytic activity in the α-alkylation reaction of acetophenone derivatives.