Triazolyl-phosphole and triazolyl-azaphosphole: synthesis, transition metal complexes and catalytic studies

Abstract

Phosphole and azaphosphole derivatives with triazole functionalities, [C₆H₅{1,2,3-N₃CC₆H₄C(PPh)}] (L1) and [C₆H₄{1,2,3-N₃C(Ph)C(PPh)}] (L2) were synthesized by reacting [(C₆H₅)(1,2,3-N₃C = CH-o-Br-C₆H₄)] and [(o-Br-C₆H₄)(1,2,3-N₃C = CHC₆H₅)] with ⁿBuLi followed by the addition of dichlorophenylphosphine. The reactions of L1 and L2 with an excess of 30% H₂O₂ afforded phosphole oxides [C₆H₅{1,2,3-N₃CC₆H₄C(P(O)Ph)}] (L1_O) and [C₆H₄{1,2,3-N₃C(Ph)C(P(O)Ph)}] (L2_O) as white crystalline solids. Stoichiometric reactions of L1 and L2 with [Ru(η⁶-p-cymene)Cl₂]₂ in CH₂Cl₂ yielded [RuCl₂(η⁶-p-cymene)(L1-κ¹-P)] (1) and [RuCl₂(η⁶-p-cymene)(L2-κ¹-P)] (2), respectively. Similar reactions of L1 and L2 with [Pd(COD)Cl₂] and [Pd(η³-C₃H₅)Cl]₂ produced the corresponding complexes, trans-[PdCl₂(L1-κ¹-P)₂] (3), trans-[PdCl₂(L2-κ¹-P)₂] (4), [Pd(η³-C₃H₅)Cl(L1-κ¹-P)] (5), and [Pd(η³-C₃H₅)Cl(L2-κ¹-P)] (6). Treatment of L1 with [AuCl(SMe₂)] in dichloromethane afforded [AuCl(L1-κ¹-P)] (7). Ruthenium complex 1 showed moderate to good catalytic activity towards benzylic C–H oxidation, and the proposed mechanism for the catalysis was supported by spectroscopic data.