Half‐sandwich Ru (II) complexes: Effect of ligands on aerobic oxidation of benzylamine

Abstract

In this study, we compared carbene and pyridine substituted ligands {3‐Me‐1‐[2‐(CH2CH2SPh)]‐C7H4N2} (L1) and {2‐[(2,6‐iPr2‐C6H3)N=CH]‐6‐(MeO)C5H3N}(L2) for synthesis of ionic C,S‐ and N,N‐coordinated Ru (II) complexes [(κ2‐L1)RuCl(η6‐p‐cymene)]+Cl− (1), [(κ2‐L1)RuI(η6‐p‐cymene)]+I− (2), and [(κ2‐L2)RuCl(η6‐p‐cymene)]+Cl− (3), respectively. Stannylene ligand [{2,6‐(Me2NCH2)2C6H3}SnCl] (L3), as heavy carbene analog, was also used in this study to prepare neutral Sn‐coordinated Ru (II) complex [(κ1‐L3)RuCl2(η6‐p‐cymene)] (4). Finally, reaction of SnCl2 with 1, 3, and 4 was also studied to yield [(κ2‐L1)RuCl(η6‐p‐cymene)]+[SnCl3]− (5), [(κ2‐L2)RuCl(η6‐p‐cymene)]+[SnCl3]− (6), and [(κ1‐L3)RuCl (SnCl3)(η6‐p‐cymene)] (7). The catalytic activity of 1–7 was tested on aerobic oxidation of benzylamine. The effect of different ligands L1–3 as well as the effect of the SnCl3− moiety is discussed.

Ruthenium Complexes with N‐Bound 2‐Pyridonato Ligand as O‐Donors: A New Synthetic Approach and the Effect on Reactivity

“…Complex 1 and ligand L 1 were prepared according to literature procedure. [14,15] 1 H, 13 C{ 1 H}, 15 N and 119 Sn{ 1 H} NMR spectra were recorded on a Bruker Avance 400 and 500 MHz NMR spectrometer at 298 K. The 1 H and 13 C{ 1 H} NMR spectra were referenced internally to residual proton-solvent and solvent resonances, respectively, and are reported relative to Me 4 Si (δ = 0 ppm). Synthesis of [(η 6 -p-cymene)RuI(k 2 -L 1 )](I) (2).…”

“…[23] In the 119 Sn{ 1 H} NMR spectrum of 7, the broad signal at δ =-188.0 ppm was observed, that is shifted upfield as compared to Ph 3 SnCl (δ =-44 ppm) [24] and it defines a fivecoordinated Sn(IV) atom. [24,25] The 1 H- 15 N HMBC NMR spectra showed cross peaks of the CH = N and o-ArH protons with the corresponding nitrogen atoms at δ À 181.6 (7) and À 178.0 (8) ppm for N im and at δ À 123.0 (7) and À 120.6 (8) ppm for N py . The values are close to those in 3 (δ À 182.1 and À 124.7 ppm).…”

“…Recently, we reported reaction of the L 1 ligand (L 1 is {2-[(2,6-iPr 2 -C 6 H 3 )N=CH]-6-(OMe)C 5 H 3 N}) [14] with [(η 6 -p-cymene)RuCl 2 ] 2 which yielded the ionic N,N-chelated Ru complex [(η 6 -pcymene)RuCl(k 2 -L 1 )](Cl) (1). [15] Analogously, the reaction of the L 1 with…”

“…13 C{ 1 H} NMR (CDCl 3 , 125.758): δ (ppm) 17.0 (CH 3 (cym)), 21.9; 24.9; 25.2; 26.0; 26.9; 29.1 (CH 3 -iPr), 30.0 (CH(dipp)) 30.7 (CH(cym)), 34.4 (CH(dipp)), 82.7; 88.2; 88.3; 88.7 (Ar(cym)-C 2,3,5,6 ), 102.2; 109.6 (Ar(cym)-C 1,4 ), 118.3; 126.4; 126.8; 127.4; 131.3; 138.5; 143.2; 146.0; 151.6; 155.0 (ArÀ C + C-py), 172.8 (C=O), 175.3 (CH=N). 15 N NMR (CDCl 3 , 50.697 MHz): δ (ppm) À 124.7 (py); À 182.1 (imine). FT-IR (ATR): ν 1544 (m, ν (C=O), 1590 (vw, ν C=N (py)), 1615 (m, ν C=N (imine)) cm À 1 .…”

“…1 H-15 N HMBC NMR spectrum showed cross peaks of the CH = N and o-ArH protons with the corresponding nitrogen atoms at δ =-182.1 (3) and À 194.3 ppm (…”