OSMIUM THIOETHER CHEMISTRY - SYNTHESIS AND SINGLE-CRYSTAL X-RAY STRUCTURES OF [OS([9]ANES3)2][PF6]2.2MENO2, [OS(4-MEC6H4PRI)([9]ANES3)][BPH4]2.MENO2 AND [OSH(CO)(PPH3)([9]ANES3)]PF6.0.5CH2CL2 ([9]ANES3 = 1,4,7-TRITHIACYCLONONANE)

Treatment of [{OsCl2(4-MeC6H4Pri)}2] with 4 molar equivalents of [9]aneS3 in EtOH for 48 h followed by addition of NH4PF6 affords the bis(sandwich) complex [Os([9]aneS3)2][PF6]2 in 55% yield. An alternative and more direct route is by reaction of [NH4]2[OsCl6] with 2 molar equivalents of [9]aneS3 in refluxing water-dimethylformamide-MeOH (3:1:1 v/v/v) for 48 h followed by addition of NH4PF6. The complex [Os([9]aneS3)2][PF6]2.2MeNO2 crystallises in the monoclinic space group P2(1)/a (alt. P2(1)/c, no. 14) with a = 9.6621(5), b = 1 5.1 573(8), c = 10.6367(7) angstrom, beta = 100.524(5)-degrees and Z = 2. A single-crystal X-ray structure determination shows a centrosymmetric cation with homoleptic thioether co-ordination at Os(II), Os-S(1) 2.3313(18), Os-S(4) 2.3380(19) and Os-S(7) 2.3408(20) angstrom, consistent with a d6 metal centre. The ion [Os([9]aneS3)2]2+ shows a reversible oxidation at E 1/2 = +1.16 V vs. ferrocene-ferrocenium. Coulometry confirms this oxidation to be a one-electron process. Electrochemical or chemical oxidation of [Os([9]aneS3)2]2+ gives [Os([9]aneS3)2]3+ Which has been characterised by electronic and ESR spectroscopy. Reaction of [{OsCl2(4-MeC6H4Pri)}2] with 2 molar equivalents of [9]aneS3 in MeOH followed by addition of NaBPh, affords the mixed-sandwich complex [Os(4-MeC6H4Pri)([9]aneS3)][BPh4]2 in 65% yield. The complex [Os(4-MeC6H4Pri)([9]aneS3)][BPh4]2.MeNO2 crystallises in the triclinic space group P1BAR, a = 11.5027(8), b = 13.8509(13), c = 18.3983(12) angstrom, alpha = 94.72(1), beta = 105.01(3), gamma = 91.28(1)-degrees and Z = 2. The crystal structure shows facial co-ordination of both [9]aneS3 and 4-MeC6H4Pri at octahedral Os(II). Interestingly, there is an unusual disorder of the trithia macrocycle with two enantiomers of [9]aneS3 being present in the crystal: the two forms of the macrocycle were successfully modelled. Reaction of [MH2(CO)(PPh3)3] with 1 molar equivalent of [9]aneS3 in the presence of NH4PF6 in refluxing acetone (M = Ru) or refluxing 2-methoxyethanol (M = Os) for 2 h under N2 gives [MH(CO)(PPh3)([9]aneS3)]PF6. The complex [OsH(CO)(PPh3)([9]aneS3)]PF6. 0.5CH2Cl2 crystallises in the monoclinic space group P2(1)/n (alt. P2(1)/c, no. 14) with a = 1 5.955(6), b = 21.929(9), c = 8.895(7) angstrom, beta = 96.69(8)-degrees and Z = 4. The structure shows octahedral Os(II) with [9]aneS, bound facially, Os-S(1) 2.377(3) (trans to CO), Os-S(4) 2.369(3) (trans to PPh3), Os-S(7) 2.402(3) (trans to H), Os-H 1.60(9), Os-P 2.3344(24) and Os-C 1.868(11) angstrom. The reactivity of [MH(CO)(PPh3)([9]aneS3)]+ with O2 and chlorinated solvents is discussed.