Ruthenium thioether chemistry: the synthesis and structure of a host–guest complex [Ru([9]aneS3)2][BPh4]2·2Me2SO, and of [Ru([9]aneS3)2][BPh4]2·2MeNO2and [Ru([18]aneS6)][BPh4]2([9]aneS3=1,4,7-trithiacyclononane, [18]aneS6= 1,4,7,10,13,16-hexathiacyclo-octadecane)

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Abstract
Reaction of [{RuCl2(arene)}2](arene = C6H6, C6Me6, or 4-MeC6H4Pri) with four molar equivalents of 1,4,7-trithiacyclononane ([9]aneS3) in MeOH at 293 K affords a colourless or pale yellow solution. Addition of NaBPh4 gives [Ru([9]aneS3)2][BPh4]2 which can be recrystallised from Me2SO, MeNO2, or MeCN. The complex [Ru([9]aneS3)2][BPh4]2·2Me2SO crystallises in the monoclinic space group P21/c with a= 14.134(3), b= 11.096 3(19), c= 19.743(4)Å, β= 94.497(16)°, and Z= 2. The single crystal X-ray structure of the complex shows a centrosymmetric cation with homoleptic thioether co-ordination to an octahedral RuII ion. Each macrocycle is bound facially to the metal centre, Ru–S(1) 2.327 2(14), Ru–S(4) 2.335 7(14), Ru–S(7) 2.333 1 (14)Å. Two molecules of Me2SO are associated with each [Ru([9]aneS3)2]2+ cation; these interact with the rear cavities of the co-ordinated trithia macrocycles to form a host/guest-type interaction, with the oxygen atoms involved in hydrogen bonding with the methylene protons of [9]aneS3, O ⋯ H 2.201(8), 2.419(8), 2.790(8), and 3.291(8)Å. The Me2SO molecules in [Ru([9]aneS3)2][BPh4]2·2Me2SO can be replaced by MeCN or MeNO2 by recrystallisation of the complex from these solvents. The complex [Ru([9]aneS3)2][BPh4]2·2MeNO2 crystallises in the monoclinic space group P21/n with a= 11.200(5), b= 18.247(13), c= 14.323(17)Å, β= 90.78(4)°, and Z= 2. The single crystal X-ray structure of this species, however, shows that there is no secondary interaction between the two MeNO2 molecules and the complex cation, the closest contact between the methylene protons and the oxygen atoms of MeNO2 being over 3.5 Å. The complex cation [Ru([9]aneS3)2]2+ shows a quasi-reversible oxidation at platinum electrodes in MeCN at E½=+1.41 V vs. ferrocene–ferrocenium indicating that RuII is highly stabilised by RuS6 co-ordination. Reaction of RuCl3·3H2O with one molar equivalent of 1,4,7,10,13,16-hexathiacyclo-octadecane ([18]aneS6) in refluxing dimethylformamide (dmf)–methanol affords [Ru([18]aneS6)]Cl2as a white precipitate. Dissolution of this product in hot water followed by addition of an excess of NaBPh4 yields [Ru([18]aneS6)][BPh4]2 which crystallises in the monoclinic space group P21/c, with a= 12.801(4), b= 10.663(3), c= 20.036(9)Å, β= 109.09(3)°, and Z= 2. The single crystal X-ray structure of the complex shows a centrosymmetric cation with hexathia co-ordination of the macrocycle to RuII in a meso configuration, Ru–S(1) 2.322 2(23), Ru–S(4) 2.332 6(25), Ru–S(7) 2.337 2(23)Å, and confirms that [18]aneS6 can readily fully encapsulate a relatively large cation such as RuII. The oxidative chemistry of [Ru([9]aneS3)2]2+ and [Ru([18]aneS6)]2+ is discussed.