Tris[4-(dimethylamino)pyridine][tris(pyrazol-1-yl)methane]ruthenium(II) bis(hexafluoridophosphate) diethyl ether monosolvate

In the title compound, [Ru(C10H10N6)(C7H10N2)3](PF6)2·C4H10O, the RuII cation is coordinated by one tris(1-pyrazolyl)methane (Tpm) and three dimethylaminopyridine (dmap) ligands in a slightly distorted octahedral geometry. The asymmetric unit consists of one complex cation, two hexafluoridophosphate anions and one diethyl ether solvent molecule in general positions. Although quite a large number of ruthenium complexes of the facially coordinating tridentate Tpm ligand have been structurally characterized, this is only the second one containing three pyridyl co-ligands. The average Ru—N(Tpm) distance is 2.059 (12) Å, while the average Ru—N(dmap) [dmap = 4-(dimethylamino)pyridine] distance is somewhat longer at 2.108 (13) Å. The orientation of the dmap ligands varies greatly, with dihedral angles between the pyridyl and opposite pyrazolyl rings of 14.3 (2), 23.2 (2) and 61.2 (2)°.

In the title compound, [Ru(C 10 H 10 N 6 )(C 7 H 10 N 2 ) 3 ](PF 6 ) 2 Á-C 4 H 10 O, the Ru II cation is coordinated by one tris(1-pyrazolyl)methane (Tpm) and three dimethylaminopyridine (dmap) ligands in a slightly distorted octahedral geometry. The asymmetric unit consists of one complex cation, two hexafluoridophosphate anions and one diethyl ether solvent molecule in general positions. Although quite a large number of ruthenium complexes of the facially coordinating tridentate Tpm ligand have been structurally characterized, this is only the second one containing three pyridyl co-ligands. The average Ru-N(Tpm) distance is 2.059 (12) Å , while the average Ru-N(dmap) [dmap = 4-(dimethylamino)pyridine] distance is somewhat longer at 2.108 (13) Å . The orientation of the dmap ligands varies greatly, with dihedral angles between the pyridyl and opposite pyrazolyl rings of 14.3 (2), 23.2 (2) and 61.2 (2) .
The new compound (I) was synthesized simply by substituting all three chloride ligands in Ru III Cl 3 (Tpm) (Llobet et al., 1988) with 4-(dimethylamino)pyridine (dmap) under reducing conditions, by adapting a method used previously to prepare [Ru II (Tpm)(vpy) 3 ][PF 6 ] 2 (vpy = 4-vinylpyridine) (Calvert et al., 1983). The isolated yield is reasonably high, while the blue colour is attributable to traces of the Ru(III) form of the complex which is rendered relatively electron-rich by the three dmap ligands. If a drop of ascorbic acid solution is added to an acetone solution of (I), the solution turns pale yellow immediately, indicating complete reduction to the Ru(II) species. The signals in the 1 H NMR spectrum show no broadening, consistent with an adequately pure sample.
The complex salt (I) shows an intense, broad UV absorption band at λ max = 322 nm in acetonitrile. This absorption is attributable to d→π* metal-to-ligand charge-transfer (MLCT) transitions from the Ru-based HOMO to the LUMOs localized on the dmap ligands. An additional band at λ max = 264 nm is ascribed to ligand-based π→π* transitions, while a very weak band at λ max ca 590 nm is due to the blue-coloured Ru(III) form that disappears upon reduction with ascorbic acid. By way of comparison, the compound [Ru II (Tpm)(py) 3 ][PF 6 ] 2 shows a MLCT band at 344 nm in acetonitrile; this is red-shifted when compared with that for (I) because the py ligands are more strongly electron-accepting than dmap.
The molecular structure of the complex cation in (I) is as indicated by 1 NMR spectroscopy, with a facially coordinating Tpm ligand and a slightly distorted octahedral coordination geometry. The N(Tpm)-Ru-N(Tpm) angles cover the range ca 85.3-86.5°, and the other angles at the Ru centre show small deviations from the ideal values. The average Ru-N(Tpm) distance of 2.059 (5) Å is similar to that reported for [Ru II (Tpm)(py) 3 ][PF 6 ] 2 (2.074 (16) Å; Laurent et al., 1999).
After cooling to room temperature, the solution was evaporated to a minimum volume and 0.1 M aqueous NH 4 PF 6 (5 cm 3 ) was added. The light-blue precipitate was filtered off, then dissolved through the glass sinter in acetone, removing a white residue. The acetone solution was evaporated to a minimum volume and diethyl ether was added, forming a blue oil. The diethyl ether was decanted off and the oil was dissolved in dichloromethane and washed (5 times) with water.

Refinement
The structure was solved by direct methods. The H atoms were placed in calculated positions (methyl H atoms were allowed to rotate but not to tip) and were refined isotropically with U iso (H) = 1.2 U eq (C) (1.5 for methyl H atoms) using a riding model with C-H lengths of 0.95(CH), 0.99(CH 2 ) & 0.98(CH 3 ) Å.
Hydrogen atoms are omitted for clarity.

Crystal data
[Ru(C 10 H 10 N 6 )(C 7 H 10 N 2 ) 3 ](PF 6 ) 2 ·C 4 H 10 O M r = 1045.88 Triclinic, P1 a = 12.1005 (9) Å b = 12.5711 (9) Å c = 15.7032 (11) Å α = 80.047 (1) where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 1.03 e Å −3 Δρ min = −0.98 e Å −3 Special details Geometry. All e.s.d.'s are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.