Half sandwich complexes of Ru(II) and complexes of Pd(II) and Pt(II) with seleno and thio derivatives of pyrrolidine: Synthesis, structure and applications as catalysts for organic reactions

The reactions of PhSe−, PhS− and Se2− with N-{2-(chloroethyl)}pyrrolidine result in N-{2-(phenylseleno)ethyl}pyrrolidine (L1), N-{2-(phenylthio)ethyl}pyrrolidine (L2), and bis{2-pyrrolidene-N-yl)ethyl selenide (L3), respectively, which have been explored as ligands. The complexes [PdCl2(L1/L2)] (1/7), [PtCl2(L1/L2)] (2/8), [RuCl(η6-C6H6)(L1/L2)][PF6] (3/9), [RuCl(η6-p-cymene)(L1/L2)][PF6] (4/10), [RuCl(η6-p-cymene)(NH3)2][PF6] (5) and [Ru(η6-p-cymene)(L1)(CH3CN)][PF6]2·CH3CN (6) have been synthesized. The L1–L3 and complexes were found to give characteristic NMR (Proton, Carbon-13 and Se-77). The crystal structures of complexes 1, 3–6, 9 and 10 have been solved. The Pd–Se and Ru–Se bond lengths have been found to be 2.353(2) and 2.480(11)/2.4918(9)/2.4770(5) Å, respectively. The complexes 1 and 7 have been explored for catalytic Heck and Suzuki–Miyaura coupling reactions. The value of TON has been found up to 85 000 with the advantage of catalyst’s stability under ambient conditions. The efficiency of 1 is marginally better than 7. The Ru-complexes 3 and 9 are good for catalytic oxidation of primary and secondary alcohols in CH2Cl2 in the presence of N-methylmorpholine-N-oxide (NMO). The TON value varies between 8.0 × 104 and 9.7 × 104 for this oxidation. The 3 is somewhat more efficient catalyst than 9.

Graphical abstractN-{2-(phenylseleno)ethyl}pyrrolidine (L1), N-{2-(phenylthio)ethyl}pyrrolidine (L2), and bis{2-pyrrolidene-N-yl}ethyl selenide (L3) and complexes [Pd/PtCl2L] [RuCl(η6-C6H6/η6-p-cymene) L][PF6] (L = L1 or L2) [Ru(η6-p-cymene)(L1)(CH3CN)][PF6]2·CH3CN and [RuCl(η6-p-cymene)(NH3)2][PF6] have been synthesized and characterized by NMR (Proton, C-13 and Se-77) and X-ray crystallography (for some). The Pd–Se/Ru–Se bond length is 2.353(2)/2.4770(5)–2.4918(9) Å. Catalytic Heck and Suzuki–Miyaura coupling reactions using Pd complexes show TON up to 85 000. [RuCl(η6-C6H6)(L)][PF6] catalyzes oxidation of primary/secondary alcohols with N-methylmorpholine-N-oxide [TON = 8.0 × 104–9.7 × 104].Figure optionsDownload full-size imageDownload as PowerPoint slide