Probing the Reactivity and Radical Nature of Oxidized Transition Metal-Thiolate Complexes by Mass Spectrometry

Focus: Distonic Ions: Research Article


Transition metal thiolate complexes such as [PPN]+[RuL3]- (PPN = bis(triphenylphosphoranylidene) ammonium and L = diphenylphosphinobenzenethiolate) are known to undergo addition reactions with unsaturated hydrocarbons via the formation of new C-S bonds in solution upon oxidation. The reaction mechanism is proposed to involve metal-stabilized thiyl radical intermediates, a new type of distonic ions such as [RuL3]+ ion in the case of [PPN]+[RuL3]-. This study presents the reactivity and structure investigation of [RuL3]+ by mass spectrometry (MS) in conjunction with ion/molecule reactions. The addition reactions of [RuL3]+ with alkenes or methyl ketones in the gas phase are indeed observed, in agreement with the proposed mechanism. Such reactivity is also maintained by several fragment ions of [RuL3]+, indicating the preserved thiyl diradical core structure is responsible for the addition reaction. The thiyl radical nature of [RuL3]+ was further verified by the ion/molecule reaction of [RuL3]+ with dimethyl disulfide, in which the characteristic CH3S• transfer occurs, both at atmospheric pressure and also at low pressure (~mTorr). These results provide, for the first time, clear mass spectrometric evidence of the radical nature of [RuL3]+ (i.e., the distonic ion structure of [RuL3]+), arising from the oxidation of non-innocent thiolate ligands of the complex [PPN]+[RuL3]-. Similar thiolate complexes, including ReL3 and NiL2, were also examined. Although reactions of oxidized ReL3 or NiL2 with CH3SSCH3 take place at atmospheric pressure, the corresponding reaction did not occur in vacuum. Consistent with these data, the addition of ethylene was not observed either, indicating lower reactivities of [ReL3]+ and [NiL2]+ in comparison to [RuL3]+.

Key words

Distonic ion Thiyl radical Mass spectrometry Ion/molecule reaction 

Supplementary material

13361_2012_537_MOESM1_ESM.doc (995 kb)
ESM 1(DOC 995 kb)


  1. 1.
    Ouch, K., Mashuta, M.S., Grapperhaus, C.A.: Metal-stabilized thiyl radicals as scaffolds for reversible alkene addition via C-S bond formation/cleavage. Inorg. Chem. 50, 9904–9914 (2011)CrossRefGoogle Scholar
  2. 2.
    Wang, K., Stiefel, E.I.: Toward separation and purification of olefins using dithiolene complexes: An electrochemical approach. Science 291, 106–109 (2001)CrossRefGoogle Scholar
  3. 3.
    Harrison, D.J., Nguyen, N., Lough, A.J., Fekl, U.: New insight into reactions of Ni(S2C2(CF3)2)2 with simple alkenes: Alkene adduct versus dihydrodithiin product selectivity is controlled by [Ni(S2C2(CF3)2)2]- anion. J. Am. Chem. Soc. 128, 11026–11027 (2006)CrossRefGoogle Scholar
  4. 4.
    Geiger, W.E.: Electrochemistry of cycloaddition products of olefins with nickel dithiolenes: A reinvestigation of the reduction of the 1:1 adduct between Ni(S2C2(CF3)2)2 and norbornadiene. Inorg. Chem. 41, 136–139 (2001)CrossRefGoogle Scholar
  5. 5.
    Hsieh, C.H., Hsu, I.J., Lee, C.M., Ke, S.C., Wang, T.Y., Lee, G.H., Wang, Y., Chen, J.M., Lee, J.F., Liaw, W.F.: Nickel complexes of o-amidochalcogenophenolate(2-)/o-iminochalcogenobenzosemiquinonate(1-) π-radical: Synthesis, structures, electron spin resonance, and X-ray absorption spectroscopic evidence. Inorg. Chem. 42, 3925–3933 (2003)CrossRefGoogle Scholar
  6. 6.
    Herebian, D., Bothe, E., Bill, E., Weyhermuller, T., Wieghardt, K.: Experimental evidence for the noninnocence of o-aminothiophenolates: Coordination chemistry of o-iminothionebenzosemiquinonate(1-) π-radicals with Ni(II), Pd(II), Pt(II). J. Am. Chem. Soc. 123, 10012–10023 (2001)CrossRefGoogle Scholar
  7. 7.
    Poturovic, S., Mashuta, M.S., Grapperhaus, C.A.: Carbon-sulfur bond formation between a ruthenium-coordinated thiyl radical and methyl ketones. Angew. Chem.-Int. Edit. 44, 1883–1887 (2005)CrossRefGoogle Scholar
  8. 8.
    Grapperhaus, C.A., Venna, K.B., Mashuta, M.S.: Carbon-sulfur bond formation via alkene addition to an oxidized ruthenium thiolate. Inorg. Chem. 46, 8044–8050 (2007)CrossRefGoogle Scholar
  9. 9.
    Grapperhaus, C.A., Ouch, K., Mashuta, M.S.: Redox-regulated ethylene binding to a rhenium-thiolate complex. J. Am. Chem. Soc. 131, 64–65 (2009)CrossRefGoogle Scholar
  10. 10.
    Grapperhaus, C.A., Kozlowski, P.M., Kumar, D., Frye, H.N., Venna, K.B., Poturovic, S.: Singlet diradical character of an oxidized ruthenium trithiolate: electronic structure and reactivity. Angew. Chem.-Int. Edit. 46, 4085–4088 (2007)CrossRefGoogle Scholar
  11. 11.
    Gronert, S.: Mass spectrometric studies of organic ion/molecule reactions. Chem. Rev. 101, 329–360 (2001)CrossRefGoogle Scholar
  12. 12.
    Nibbering, N.M.M.: Gas-phase ion/molecule reactions as studied by fourier transform ion cyclotron resonance. Acc. Chem. Res. 23, 279–285 (1990)CrossRefGoogle Scholar
  13. 13.
    Cooks, R.G., Chen, H., Eberlin, M.N., Zheng, X., Tao, W.A.: Polar acetalization and transacetalization in the gas phase: The Eberlin reaction. Chem. Rev. 106, 188–211 (2006)CrossRefGoogle Scholar
  14. 14.
    Eberlin, M.N.: Structurally diagnostic ion/molecule reactions: class and functional-group identification by mass spectrometry. J. Mass Spectrom. 41, 141–156 (2006)CrossRefGoogle Scholar
  15. 15.
    O'Hair, R.A.J.: The 3D quadrupole ion trap mass spectrometer as a complete chemical laboratory for fundamental gas-phase studies of metal mediated chemistry. Chem. Commun. (Cambridge, U. K.), 1469–1481 (2006)Google Scholar
  16. 16.
    Gronert, S.: Quadrupole ion trap studies of fundamental organic reactions. Mass Spectrom. Rev. 24, 100–120 (2005)CrossRefGoogle Scholar
  17. 17.
    Combariza, M.Y., Fahey, A.M., Milshteyn, A., Vachet, R.W.: Gas-phase ion-molecule reactions of divalent metal complex ions: Toward coordination structure analysis by mass spectrometry and some intrinsic coordination chemistry along the way. Int. J. Mass Spectrom. 244, 109–124 (2005)CrossRefGoogle Scholar
  18. 18.
    Speranza, M.: Enantioselectivity in gas-phase ion-molecule reactions. Int. J. Mass Spectrom. 232, 277–317 (2004)CrossRefGoogle Scholar
  19. 19.
    Santos, L.S.: Online mechanistic investigations of catalyzed reactions by electrospray ionization mass spectrometry: a tool to intercept transient species in solution. Eur. J. Org. Chem. 2, 235–253 (2008)Google Scholar
  20. 20.
    Schroeder, D., Heinemann, C., Koch, W., Schwarz, H.: Perspectives and challenges of physical organic chemistry. Pure Appl. Chem. 69, 273–280 (1997)CrossRefGoogle Scholar
  21. 21.
    Plattner, D.A.: Electrospray mass spectrometry beyond analytical chemistry: Studies of organometallic catalysis in the gas phase. Int. J. Mass Spectrom. 207, 125–144 (2001)CrossRefGoogle Scholar
  22. 22.
    Stirk, K.M., Orlowski, J.C., Leeck, D.T., Kenttämaa, H.I.: The identification of distonic radical cations on the basis of a reaction with dimethyl disulfide. J. Am. Chem. Soc. 114, 8604–8606 (1992)CrossRefGoogle Scholar
  23. 23.
    Grapperhaus, C.A., Poturovic, S., Mashuta, M.S.: Dichloromethane alkylates a trithiolato-ruthenium complex to yield a methylene-bridged thioether core. Synthesis and structural comparison to the thiolato-ruthenium precursor. Inorg. Chem. 41, 4309–4311 (2002)CrossRefGoogle Scholar
  24. 24.
    Dilworth, J.R., Hutson, A.J., Morton, S., Harman, M., Hursthouse, M.B., Zubieta, J., Archer, C.M., Kelly, J.D.: The preparation and electrochemistry of technetium and rhenium complexes of 2-(diphenylphosphino)benzenethiol. The crystal and molecular structures of [Re(2-Ph2PC6H4S)3] and [Tc(2-Ph2PC6H4S)3]. Polyhedron 11, 2151–2155 (1992)CrossRefGoogle Scholar
  25. 25.
    Kim, J.S., Reibenspies, J.H., Darensbourg, M.Y.: Characteristics of nickel(0), nickel(I), and nickel(II) in phosphino thioether complexes: Molecular structure and S-dealkylation of (Ph2P(o-C6H4)SCH3)2Ni0. J. Am. Chem. Soc. 118, 4115–4123 (1996)CrossRefGoogle Scholar
  26. 26.
    Poad, B.L.J., Pham, H.T., Thomas, M.C., Nealon, J.R., Campbell, J.L., Mitchell, T.W., Blanksby, S.J.: Ozone-induced dissociation on a modified tandem linear ion-trap: Observations of different reactivity for isomeric lipids. J. Am. Soc. Mass Spectrom. 21, 1989–1999 (2010)CrossRefGoogle Scholar
  27. 27.
    Hager, J.W., Yves Le Blanc, J.C.: Product ion scanning using a Q-q-Qlinear ion trap (Q TRAP™) mass spectrometer. Rapid Commun. Mass Spectrom. 17, 1056–1064 (2003)CrossRefGoogle Scholar
  28. 28.
    Londry, F.A., Hager, J.W.: Mass selective axial ion ejection from a linear quadrupole ion trap. J. Am. Soc. Mass Spectrom. 14, 1130–1147 (2003)CrossRefGoogle Scholar
  29. 29.
    Katritzky, A.R., Manzo, R.H., Lloyd, J.M., Patel, R.C.: Mechanism of the pyrylium/pyridinium ring interconversion. Mild preparative conditions for conversion of amines into pyridinium ions. Angew. Chem. Int. Ed. 19, 306–306 (1980)CrossRefGoogle Scholar
  30. 30.
    Chen, H., Ouyang, Z., Cooks, R.G.: Thermal production and reactions of organic ions at atmospheric pressure. Angew. Chem. Int. Ed. 45, 3656–3660 (2006)CrossRefGoogle Scholar
  31. 31.
    Ryzhov, V., Lam, A., O’Hair, R.A.J.: Gas-phase fragmentation of long-lived cysteine radical cations formed via no loss from protonated S-nitrosocysteine. J. Am. Soc. Mass Spectrom. 20, 985–995 (2009)CrossRefGoogle Scholar
  32. 32.
    Osburn, S., O’Hair, R.A.J., Ryzhov, V.: Gas-phase reactivity of sulfur-based radical ions of cysteine derivatives and small peptides. Int. J. Mass Spectrom. 316–318, 133–139 (2012)Google Scholar
  33. 33.
    Wickramanayake, P.P., Gardner, G.J., Siu, K.W.M., Berman, S.S.: Ion/molecular reaction between sulfur hexafluoride negative ion and water under atmospheric pressure ionization mass spectrometric conditions. Int. J. Mass Spectrom. Ion Processes 69, 39–43 (1986)CrossRefGoogle Scholar
  34. 34.
    Hirabayashi, A., Takada, Y., Kambara, H., Umemura, Y., Ohta, H., Ito, H., Kuchitsu, K.: Ion/molecule reaction and ion evaporation in atmospheric pressure spray ionization. Int. J. Mass Spectrom. Ion Processes 120, 207–216 (1992)CrossRefGoogle Scholar
  35. 35.
    Amad, M.H., Cech, N.B., Jackson, G.S., Enke, C.G.: Importance of gas-phase proton affinities in determining the electrospray ionization response for analytes and solvents. J. Mass Spectrom. 35, 784–789 (2000)CrossRefGoogle Scholar
  36. 36.
    Meurer, E.C., Sabino, A.A., Eberlin, M.N.: Ionic transacetalization with acylium ions: a class-selective and structurally diagnostic reaction for cyclic acetals performed under unique electrospray and atmospheric pressure chemical ionization in-source ion-molecule reaction conditions. Anal. Chem. 75, 4701–4709 (2003)CrossRefGoogle Scholar
  37. 37.
    Chen, H.: Characteristic ion/molecule reactions at low and at atmospheric pressure for selective detection of dangerous substances. PhD thesis, Purdue University (2005)Google Scholar
  38. 38.
    Chen, H., Touboul, D., Jecklin, M.C., Zheng, J., Luo, M., Zenobi, R.: Manipulation of charge states of biopolymer ions by atmospheric pressure ion/molecule reactions implemented in an extractive electrospray ionization source. Eur. J. Mass Spectrom. 13, 273–279 (2007)CrossRefGoogle Scholar
  39. 39.
    Campbell, J.L.: Using a dual inlet atmospheric pressure ionization source as a dynamic reaction vessel. Rapid Commun. Mass Spectrom. 24, 3527–3530 (2010)CrossRefGoogle Scholar
  40. 40.
    Van Berkel, G.J., Kertesz, V.: Using the electrochemistry of the electrospray ion source. Anal. Chem. 79, 5510–5520 (2007)CrossRefGoogle Scholar
  41. 41.
    Grapperhaus, C.A., Poturovic, S., Mashuta, M.S.: Oxygenation of a ruthenium(II) thiolate to a ruthenium(II) sulfinate proceeds via ruthenium(III). Inorg. Chem. 44, 8185–8187 (2005)CrossRefGoogle Scholar
  42. 42.
    Smith, R.L., Schweighofer, A., Keck, H., Kuchen, W., Kenttämaa, H.I.: Unusual reactivity of the radical cations of some simple trivalent organophosphorus compounds toward dimethyl disulfide and dimethyl diselenide. J. Am. Chem. Soc. 118, 1408–1412 (1996)CrossRefGoogle Scholar
  43. 43.
    Stirk, K.M., Kiminkinen, L.K.M., Kenttämaa, H.I.: Ion-molecule reactions of distonic radical cations. Chem. Rev. 92, 1649–1665 (1992)CrossRefGoogle Scholar
  44. 44.
    Thoen, K.K., Tutko, D., Pérez, J., Smith, R.L., Kenttämaa, H.I.: Disulfide bond cleavage in neutral substrates by the dimethylene ketene radical cation inside a mass spectrometer. Int. J. Mass Spectrom. Ion Processes 175, 173–177 (1998)CrossRefGoogle Scholar
  45. 45.
    Osburn, S., Steill, J.D., Oomens, J., O'Hair, R.A.J., van Stipdonk, M., Ryzhov, V.: Structure and reactivity of the cysteine methyl ester radical cation. Chem. Eur. J. 17, 873–879 (2011)CrossRefGoogle Scholar
  46. 46.
    Speranza, M.: Kinetics and mechanisms in gas-phase ion chemistry by radiolytic methods. Mass Spectrom. Rev. 11, 73–117 (1992)CrossRefGoogle Scholar
  47. 47.
    Knighton, W.B., Grimsrud, E.P.: Gas phase ion chemistry under conditions of very high pressure. Adv. Gas Phase Ion Chem. 2, 219–258 (1996)CrossRefGoogle Scholar
  48. 48.
    Chen, H., Cotte-Rodriguez, I., Cooks, R.G.: cis-Diol functional group recognition by reactive desorption electrospray ionization (DESI). Chem. Commun. 597–599 (2006)Google Scholar
  49. 49.
    Huang, G., Chen, H., Zhang, X., Cooks, R.G., Ouyang, Z.: Rapid screening of anabolic steroids in urine by reactive desorption electrospray ionization. Anal. Chem. 79, 8327–8332 (2007)CrossRefGoogle Scholar
  50. 50.
    Chen, H., Eberlin, L.S., Nefliu, M., Augusti, R., Cooks, R.G.: Organic reactions of ionic intermediates promoted by atmospheric-pressure thermal activation. Angew. Chem. Int. Ed. 47, 3422–3425 (2008)CrossRefGoogle Scholar
  51. 51.
    Badu-Tawiah, A., Campbell, D., Cooks, R.: Reactions of microsolvated organic compounds at ambient surfaces: Droplet velocity, charge state, and solvent effects. J. Am. Soc. Mass Spectrom. 23, 1077–1084 (2012)CrossRefGoogle Scholar
  52. 52.
    Perry, R.H., Splendore, M., Chien, A., Davis, N.K., Zare, R.N.: Detecting reaction intermediates in liquids on the millisecond time scale using desorption electrospray ionization. Angew. Chem. Int. Ed. 50, 250–254 (2011)CrossRefGoogle Scholar
  53. 53.
    Sipe Jr., H.J., Corbett, J.T., Mason, R.P.: In vitro free radical metabolism of phenolphthalein by peroxidases. Drug Metab. Dispos. 25, 468–480 (1997)Google Scholar
  54. 54.
    Karoui, H., Hansert, B., Sand, P.J., Tordo, P., Bohle, D.S., Kalyanaraman, B.: Spin-trapping of free radicals formed during the oxidation of glutathione by tetramethylammonium peroxynitrite. Nitric Oxide 1, 346–358 (1997)CrossRefGoogle Scholar
  55. 55.
    Davies, M.J., Forni, L.G., Shuter, S.L.: Electron spin resonance and pulse radiolysis studies on the spin trapping of sulphur-centered radicals. Chem. Biol. Interact. 61, 177–188 (1987)CrossRefGoogle Scholar
  56. 56.
    Kebarle, P., Tang, L.: From ions in solution to ions in the gas phase. Anal. Chem. 65, 972A–986A (1993)Google Scholar
  57. 57.
    Alfassi, Z.B.: S-Centered Radicals. John Wiley and Sons (1999)Google Scholar

Copyright information

© American Society for Mass Spectrometry 2013

Authors and Affiliations

  1. 1.Center for Intelligent Chemical Instrumentation, Department of Chemistry and BiochemistryOhio UniversityAthensUSA
  2. 2.ConcordCanada
  3. 3.Department of ChemistryUniversity of LouisvilleLouisvilleUSA

Personalised recommendations