Crystal structure of η⁶-p-cymene-iodido-(N-isopropyl-1-(pyridin-2-yl)methanimine-κ²N,N′)ruthenium(II) hexafluorophosphate(V), C₁₉H₂₆IN₂F₆Ru

Source of material

To a suspension of [(η⁶-p-cymene)Ru(μ-I)I]₂ (0.2 mmol) in methanol (20 mL) was added the ligand (0.42 mmol). The mixture was stirred at room temperature for 3 h followed by reduction of the solvent volume in vacuo to about (10 mL) before adding NH₄PF₆ (0.42 mmol). The mixture was then cooled in an ice bath while stirring for 2 h leading to a precipitate, which was collected by filtration. The filtrate was washed with diethyl ether and dried in vacuo. Crystals were grown by the liquid diffusion method by layering a solution of the compound in acetone with hexane and left undisturbed for 2 days. Orange crystals, yield = 80%, m.p. 150 °C (decomp.).

¹H NMR (400 MHZ, DMSO-d₆). δ [ppm] 9.51 (d, J_HH = 5.4 Hz, 1H, Py); 8.80 (s, 1H, CH=N); 8.23–8.21 (M, 1H, Py); 8.15 (d, J_HH = 7.2 Hz, 1H, Py); 7.80 (s, 1H, Py); 6.26 (d, J_HH = 6.26 Hz, 1H, (p-cyAr)); 6.18 (d, J_HH = 6.10 Hz, 1H(p-cyAr)); 5.94 (d, J_HH = 6.10 Hz, 1H, (p-cyAr)), 5.89 (d, J_HH = 6.30 Hz, 1H, (p-cyAr)), 4.88 (sep, 1H, CH) 2.63 (m, 1H, CH (Me)2); 2.16 (s, 3H, (Me)); 1.59 (d, J_HH = 6.80 Hz, 3H, (Me); 1.41 (d, J_HH = 6.64 Hz, 3H, (Me)(0.95 (d, J_HH = 6.88 Hz, 3H, (Me). ¹³C NMR (400 MHZ, DMSO-d₆). δ [ppm] 165.3 (CH=N), 155.7 (Py), 155.5 (Py); 139.8 (Py); 128.8 (Py); 128.2 (Py); 104.2 (Ar); 103.4 (Ar); 87.6 (Ar); 84.5 (Ar) ; 65.5 (CH) ; 30.5 (Me); 23.8 (Me); 22.3 (Me); 22.1 (Me); 21.30 (Me); 18.4 (Me). IR (solid state):γ (C=N) 1622.1 cm⁻¹. MS (ESI, M/Z): 520.98 [C₁₉H₂₆IN₂Ru]⁺.

Experimental details

Crystal evaluation and data collection were done on a Bruker Smart APEX2 diffractometer equipped with an Oxford Cryostream low temperature apparatus operating at 100(1) K. The structure was solved by direct method using the SHELXS [2] program and refined with SHELXL [2]. All hydrogen atoms were placed in idealized positions and refined in riding models with U_iso assigned the values of 1.2 times those of their parent atoms and the distances of C—H were constrained to 0.93 Å for all the aromatic H atoms, 0.960 Å for methyl hydrogens and 0.98 Å for methine hydrogen. The visual crystal structure information was performed using ORTEP-3 [3].

Comment

Ruthenium half-sandwich complexes have found many applications as metallodrugs and as catalysts in various reactions [4], [5]. Biologically, ruthenium complexes have shown potential as anticancer agents [6], [7] and as antimicrobial agents [6]. In catalysis, ruthenium half-sandwich complexes have found applications in, oxidative transformations of alkanes [4], cleavage of double bonds [8], oxidation of alcohols [9] and in transfer hydrogen of ketones [10].

The title compound is part of our continuing studies of half-sandwich ruthenium(II) complexes [6], [7], [8], [9], [10], [11]. The asymmetric unit contains one cationic ruthenium complex featuring a “pseudo-octahedral three-legged piano stool” structure and one counter anion (see the figure). In this arrangement, the ruthenium centre is coordinated to the N,N′-bidentate ligand, through the N atom of the pyridine moeity and the imine N atom, and one iodido ligand to form the base of the stool while the p-cymene ring acts as the apex of the stool [6], [7], [8], [9], [10]. In the complex, the Ru—N bond distances are 2.0714(14) and 2.0761(14) Å . This value is comparable to those reported for other arene ruthenium complexes with N,N′ donor ligands [4], [5], [6], [7], [8], [9], [10]. The N—Ru—N bond angle is 76.99(6) while those of N—Ru—I are 84.44(4) and 83.95(4)°. These values are close to those reported for related compounds [6], [12]. All C—C, C—N and P—F bond length and angles are in the expected range [6], [7], [8], [9], [10], [11], [12], [13].