Complexes of Pd(II), η6‑C6H6Ru(II), and η5‑Cp*Rh(III) with Chalcogenated Schiff Bases of Anthracene-9-carbaldehyde and Base-Free Catalytic Transfer Hydrogenation of Aldehydes/Ketones and N‑Alkylation of Amines

The condensation of 2-(phenylsulfanyl)­ethylamine and 2-(phenylselenyl)­ethylamine with anthracene-9-carbaldehyde resulted in Schiff bases [PhS­(CH2)2C═N-9-C14H9]­(L1) and [PhSe­(CH2)2C═N-9-C14H9] (L2), respectively. Na2[PdCl4] treatment of L1/L2 in acetone–water mixture for 3 h at room temperature gave palladacycle [PdCl­(C–, N, S/Se)] (1/2; L1/L2–H = (C–, N, S)/(C–, N, Se)). The reaction of [(η6-C6H6)­RuCl­(μ-Cl)]2 with L1/L2 in methanol for 8 h at room temperature (followed by addition of NH4PF6) afforded half-sandwich complex [(η6-C6H6)­Ru­(L)­Cl]­[PF6], 3/4: (L = L1/L2 ≡ (N, E) ligand). The reaction of [(η5-Cp*)­RhCl­(μ-Cl)]2 with L1 /L2 in the presence of CH3COONa at 50°C (followed by treatment with NH4PF6) resulted in [(η5-Cp*)­Rh­(L-H)]­[PF6], 5/6: (L = L1/L2). On carrying out the reaction of [(η5-Cp*)­RhCl­(μ-Cl)]2 with these ligands at room temperature and in the absence of CH3COONa, complex [(η5-Cp*)­Rh­(L)­Cl]­[PF6], 7/8 (L = L1/L2 ≡ (N, E) ligand), was formed. Complexes 1–8 were authenticated with 1H, 13C­{1H}, and 77Se­{1H} NMR spectroscopy, high-resolution mass spectrometry, elemental analyses, and single-crystal X-ray diffraction. The moisture- and air-insensitive complexes of Pd­(II) (1, 2), Ru­(II) (3, 4) and Rh­(III) (5–8) were thermally stable. Palladium and rhodium (under base-free condition) species efficiently catalyzed transfer hydrogenation (propan-2-ol as H-source). At room temperature conversion was 90% in TH catalyzed with 0.2 mol % of 2. N-Alkylation of aniline with benzyl alcohol under base-free condition was promoted by 3–8. The 7 was most efficient for the two base-free catalytic reactions. For TH optimum loading of 1–2 and 5–8 as catalyst is 0.05–0.2 and 0.2–0.5 mol % respectively. The optimum temperatures are 80 and 100°C for TH and N-alkylation, respectively. The optimum loading of 3–8 for N-alkylation is 0.5 mol %. Mercury poisoning test supported homogeneous pathway for the two catalytic reactions. The rhodacycles probably gave real catalytic species by losing a Cp* group.