A coordination chemistry dichotomy for icosahedral carborane-based ligands

Journal name:
Nature Chemistry
Year published:
Published online


Although the majority of ligands in modern chemistry take advantage of carbon-based substituent effects to tune the sterics and electronics of coordinating moieties, we describe here how icosahedral carboranes—boron-rich clusters—can influence metal–ligand interactions. Using a series of phosphine–thioether chelating ligands featuring meta- or ortho-carboranes grafted on the sulfur atom, we were able to tune the lability of the platinum–sulfur interaction of platinum(II)–thioether complexes. Experimental observations, supported by computational work, show that icosahedral carboranes can act either as strong electron-withdrawing ligands or electron-donating moieties (similar to aryl- or alkyl-based groups, respectively), depending on which atom of the carborane cage is attached to the thioether moiety. These and similar results with carborane-selenol derivatives suggest that, in contrast to carbon-based ligands, icosahedral carboranes exhibit a significant dichotomy in their coordination chemistry, and can be used as a versatile class of electronically tunable building blocks for various ligand platforms.

At a glance


  1. Coordination chemistry and electronic characteristics of phosphine–thioether (P,S) ligands.
    Figure 1: Coordination chemistry and electronic characteristics of phosphine–thioether (P,S) ligands.

    a, Coordination-based motifs derived from various possible interactions of hemilabile (P,S) ligands with Pt(II). b, Comparison of carbon-based and carborane-based ligands and corresponding Mulliken charge densities on sulfur atoms associated with the thioether moieties of the ligands.

  2. Structures of the carborane thiols (I, II, III and V) used to synthesize the (P,S) chelate ligands investigated in this study.
    Figure 2: Structures of the carborane thiols (I, II, III and V) used to synthesize the (P,S) chelate ligands investigated in this study.

    The point of attachment of the carborane to the sulfur atom is systematically altered.

  3. Synthetic scheme outlining the synthesis of Pt(II) complexes.
    Figure 3: Synthetic scheme outlining the synthesis of Pt(II) complexes.

    a,b, Reactions involving ligands 1a (a) and 1b (b). All transformations are quantitative as observed by in situ 31P and 31P{1H} NMR spectroscopy. Full details on synthesis and characterization can be found in the Supplementary Information.

  4. Characterization of the ligands.
    Figure 4: Characterization of the ligands.

    ac, Representative 31P/31P{1H} NMR spectra of complexes with ligand 1a (a), ligand 1b (b) and 11B/11B{1H} NMR data highlighting changes associated with the transformations involving ligand 1a (c). As B9 is the only substituted boron atom in the carborane cluster, it does not exhibit B–H coupling and can therefore be easily distinguished from other resonances assigned to other boron atoms of the carborane cage.

  5. Crystallographically derived X-ray structure representations of closed carborane-based Pt(II) complexes 4a–4d.
    Figure 5: Crystallographically derived X-ray structure representations of closed carborane-based Pt(II) complexes 4a–4d.

    Solvent molecules and anions are omitted for clarity. Atom colour code: pale red, B; grey, C; blue, P; black, Pt; white, H. Full details on crystallographic refinement can be found in Supplementary Section 3. (CCDC no. 824088–824091.)

  6. Studies of carborane-selenol derivatives.
    Figure 6: Studies of carborane-selenol derivatives.

    a, Synthetic scheme and conditions: (i) Se2Cl2, CH2Cl2, AlCl3, aqueous work-up followed by reduction w. NaBH4 in EtOH; (ii) n-BuLi, diethyl ether, 0 °C to room temperature, then elemental Se. b,c, Representative 77Se/77Se{1H} NMR spectra of meta-carborane selenol derivatives 5a and 5b and their computational models, respectively.


45 compounds View all compounds
  1. 9-(1,7-Dicarba-closo-dodecaboranyl)thiol
    Compound I 9-(1,7-Dicarba-closo-dodecaboranyl)thiol
  2. 1-(1,7-Dicarba-closo-dodecaboranyl)thiol
    Compound II 1-(1,7-Dicarba-closo-dodecaboranyl)thiol
  3. 12-(1,2-Dicarba-closo-dodecaboranyl)thiol
    Compound III 12-(1,2-Dicarba-closo-dodecaboranyl)thiol
  4. 1,2-Dimethyl-1,2-dicarba-closo-dodecaborane
    Compound IV 1,2-Dimethyl-1,2-dicarba-closo-dodecaborane
  5. 12-(1,2-Dimethyl-1,2-dicarba-closo-dodecaboranyl)thiol
    Compound V 12-(1,2-Dimethyl-1,2-dicarba-closo-dodecaboranyl)thiol
  6. (2-(9-(1,7-Dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine
    Compound 1a (2-(9-(1,7-Dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine
  7. (2-(1-(1,7-Dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine
    Compound 1b (2-(1-(1,7-Dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine
  8. (2-(12-(1,2-Dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine
    Compound 1c (2-(12-(1,2-Dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine
  9. (2-(12-(1,2-Dimethyl-1,2-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine
    Compound 1d (2-(12-(1,2-Dimethyl-1,2-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine
  10. (2-(t-Butylthio)ethyl)diphenylphosphine
    Compound 1e (2-(t-Butylthio)ethyl)diphenylphosphine
  11. (2-((3s,5s,7s)-Adamantan-1-ylthio)ethyl)diphenylphosphine
    Compound 1f (2-((3s,5s,7s)-Adamantan-1-ylthio)ethyl)diphenylphosphine
  12. (2-((2,4-Dimethylphenyl)thio)ethyl)diphenylphosphine
    Compound 1g (2-((2,4-Dimethylphenyl)thio)ethyl)diphenylphosphine
  13. (2-(Phenylthio)ethyl)diphenylphosphine
    Compound 1h (2-(Phenylthio)ethyl)diphenylphosphine
  14. (2-((2,3,5,6-Tetrafluorophenyl)thio)ethyl)diphenylphosphine
    Compound 1i (2-((2,3,5,6-Tetrafluorophenyl)thio)ethyl)diphenylphosphine
  15. cis-Dichloro-(((2-(9-(1,7-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κ2P,S) platinum(II)
    Compound 2a cis-Dichloro-(((2-(9-(1,7-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κ2P,S) platinum(II)
  16. cis-Dichloro-bis(((2-(1-(1,7-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κP) platinum(II)
    Compound 2b cis-Dichloro-bis(((2-(1-(1,7-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κP) platinum(II)
  17. cis-Dichloro-(((2-(12-(1,2-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κ2P,S) platinum(II)
    Compound 2c cis-Dichloro-(((2-(12-(1,2-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κ2P,S) platinum(II)
  18. cis-Dichloro-(((2-(12-(1,2-dimethyl-1,2-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κ2P,S) platinum(II)
    Compound 2d cis-Dichloro-(((2-(12-(1,2-dimethyl-1,2-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κ2P,S) platinum(II)
  19. cis-Dichloro-(((2-(t-butylthio)ethyl)diphenylphosphine)-κ2P,S) platinum(II)
    Compound 2e cis-Dichloro-(((2-(t-butylthio)ethyl)diphenylphosphine)-κ2P,S) platinum(II)
  20. cis-Dichloro-(((2-((3s,5s,7s)-adamantan-1-ylthio)ethyl)diphenylphosphine-κ2P,S) platinum(II)
    Compound 2f cis-Dichloro-(((2-((3s,5s,7s)-adamantan-1-ylthio)ethyl)diphenylphosphine-κ2P,S) platinum(II)
  21. cis-Dichloro-(((2-((2,4-dimethylphenyl)thio)ethyl)diphenylphosphine)-κ2P,S) platinum(II)
    Compound 2g cis-Dichloro-(((2-((2,4-dimethylphenyl)thio)ethyl)diphenylphosphine)-κ2P,S) platinum(II)
  22. Chloro-(((2-(9-(1,7-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κ2P,S)-(((2-(9-(1,7-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κP) platinum(II) chloride
    Compound 3a Chloro-(((2-(9-(1,7-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κ2P,S)-(((2-(9-(1,7-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κP) platinum(II) chloride
  23. Chloro-(((2-(9-(1,7-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κ2P,S)-(((2-(9-(1,7-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κP) platinum(II) tetrakis((3,5-trifluoromethyl)phenyl)borate
    Compound 3a' Chloro-(((2-(9-(1,7-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κ2P,S)-(((2-(9-(1,7-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κP) platinum(II) tetrakis((3,5-trifluoromethyl)phenyl)borate
  24. Chloro-(((2-(1-(1,7-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κ2P,S)-(((2-(1-(1,7-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κP) platinum(II) tetrakis((3,5-trifluoromethyl)phenyl)borate
    Compound 3b Chloro-(((2-(1-(1,7-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κ2P,S)-(((2-(1-(1,7-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κP) platinum(II) tetrakis((3,5-trifluoromethyl)phenyl)borate
  25. Chloro-(((2-(12-(1,2-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κ2P,S)-(((2-(12-(1,2-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κP) platinum(II) chloride
    Compound 3c Chloro-(((2-(12-(1,2-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κ2P,S)-(((2-(12-(1,2-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κP) platinum(II) chloride
  26. Chloro-(((2-(12-(1,2-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κ2P,S)-(((2-(12-(1,2-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κP) platinum(II) tetrakis((3,5-trifluoromethyl)phenyl)borate
    Compound 3c' Chloro-(((2-(12-(1,2-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κ2P,S)-(((2-(12-(1,2-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κP) platinum(II) tetrakis((3,5-trifluoromethyl)phenyl)borate
  27. Chloro-(((2-(12-(1,2-dimethyl-1,2-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κ2P,S)-(((2-(12-(1,2-dimethyl-1,2-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κP) platinum(II) chloride
    Compound 3d Chloro-(((2-(12-(1,2-dimethyl-1,2-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κ2P,S)-(((2-(12-(1,2-dimethyl-1,2-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κP) platinum(II) chloride
  28. Chloro-(((2-(12-(1,2-dimethyl-1,2-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κ2P,S)-(((2-(12-(1,2-dimethyl-1,2-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κP) platinum(II) tetrakis((3,5-trifluoromethyl)phenyl)borate
    Compound 3d' Chloro-(((2-(12-(1,2-dimethyl-1,2-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κ2P,S)-(((2-(12-(1,2-dimethyl-1,2-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κP) platinum(II) tetrakis((3,5-trifluoromethyl)phenyl)borate
  29. Chloro-(((2-(t-butylthio)ethyl)diphenylphosphine)-κ2P,S)-(((2-(t-butylthio)ethyl)diphenylphosphine)-κP) platinum(II) chloride
    Compound 3e Chloro-(((2-(t-butylthio)ethyl)diphenylphosphine)-κ2P,S)-(((2-(t-butylthio)ethyl)diphenylphosphine)-κP) platinum(II) chloride
  30. Chloro-(((2-(t-butylthio)ethyl)diphenylphosphine)-κ2P,S)-(((2-(t-butylthio)ethyl)diphenylphosphine)-κP) platinum(II) tetrakis((3,5-trifluoromethyl)phenyl)borate
    Compound 3e' Chloro-(((2-(t-butylthio)ethyl)diphenylphosphine)-κ2P,S)-(((2-(t-butylthio)ethyl)diphenylphosphine)-κP) platinum(II) tetrakis((3,5-trifluoromethyl)phenyl)borate
  31. Chloro-(((2-((3s,5s,7s)-adamantan-1-ylthio)ethyl)diphenylphosphine-κ2P,S)-(((2-((3s,5s,7s)-adamantan-1-ylthio)ethyl)diphenylphosphine-κP) platinum(II) chloride
    Compound 3f Chloro-(((2-((3s,5s,7s)-adamantan-1-ylthio)ethyl)diphenylphosphine-κ2P,S)-(((2-((3s,5s,7s)-adamantan-1-ylthio)ethyl)diphenylphosphine-κP) platinum(II) chloride
  32. Chloro-(((2-((2,4-dimethylphenyl)thio)ethyl)diphenylphosphine)-κ2P,S)-(((2-((2,4-dimethylphenyl)thio)ethyl)diphenylphosphine)-κ2P) platinum(II) chloride
    Compound 3g Chloro-(((2-((2,4-dimethylphenyl)thio)ethyl)diphenylphosphine)-κ2P,S)-(((2-((2,4-dimethylphenyl)thio)ethyl)diphenylphosphine)-κ2P) platinum(II) chloride
  33. Chloro-(((2-((2,3,5,6-tetrafluorophenyl)thio)ethyl)diphenylphosphine)-κ2P,S)-(((2-((2,3,5,6-tetrafluorophenyl)thio)ethyl)diphenylphosphine)-κP) platinum(II) tetrakis((3,5-trifluoromethyl)phenyl)borate
    Compound 3i Chloro-(((2-((2,3,5,6-tetrafluorophenyl)thio)ethyl)diphenylphosphine)-κ2P,S)-(((2-((2,3,5,6-tetrafluorophenyl)thio)ethyl)diphenylphosphine)-κP) platinum(II) tetrakis((3,5-trifluoromethyl)phenyl)borate
  34. Bis(((2-(9-(1,7-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κ2P,S) platinum(II) tetrafluoroborate
    Compound 4a Bis(((2-(9-(1,7-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κ2P,S) platinum(II) tetrafluoroborate
  35. Bis(((2-(1-(1,7-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κ2P,S) platinum(II) tetrafluoroborate
    Compound 4b Bis(((2-(1-(1,7-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κ2P,S) platinum(II) tetrafluoroborate
  36. Bis(((2-(12-(1,2-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κ2P,S) platinum(II) tetrafluoroborate
    Compound 4c Bis(((2-(12-(1,2-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κ2P,S) platinum(II) tetrafluoroborate
  37. Bis(((2-(12-(1,2-dimethyl-1,2-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κ2P,S) platinum(II) tetrafluoroborate
    Compound 4d Bis(((2-(12-(1,2-dimethyl-1,2-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κ2P,S) platinum(II) tetrafluoroborate
  38. Bis(((2-(t-butylthio)ethyl)diphenylphosphine)-k2P,S) platinum(II) tetrafluoroborate
    Compound 4e Bis(((2-(t-butylthio)ethyl)diphenylphosphine)-k2P,S) platinum(II) tetrafluoroborate
  39. Bis(((2-((3s,5s,7s)-adamantan-1-ylthio)ethyl)diphenylphosphine-κ2P,S) platinum(II) tetrafluoroborate
    Compound 4f Bis(((2-((3s,5s,7s)-adamantan-1-ylthio)ethyl)diphenylphosphine-κ2P,S) platinum(II) tetrafluoroborate
  40. Bis(((2-((2,4-dimethylphenyl)thio)ethyl)diphenylphosphine)-κ2P,S) platinum(II) tetrafluoroborate
    Compound 4g Bis(((2-((2,4-dimethylphenyl)thio)ethyl)diphenylphosphine)-κ2P,S) platinum(II) tetrafluoroborate
  41. Bis((2-(phenylthio)ethyl)diphenylphosphine)-κ2P,S) platinum(II) tetrafluoroborate
    Compound 4h Bis((2-(phenylthio)ethyl)diphenylphosphine)-κ2P,S) platinum(II) tetrafluoroborate
  42. Bis(((2-((2,3,5,6-tetrafluorophenyl)thio)ethyl)diphenylphosphine)-κ2P,S) platinum(II) tetrafluoroborate
    Compound 4i Bis(((2-((2,3,5,6-tetrafluorophenyl)thio)ethyl)diphenylphosphine)-κ2P,S) platinum(II) tetrafluoroborate
  43. 9-(1,7-Dicarba-closo-dodecaboranyl)selenol
    Compound 5a 9-(1,7-Dicarba-closo-dodecaboranyl)selenol
  44. 1-(1,7-Dicarba-closo-dodecaboranyl)selenol
    Compound 5b 1-(1,7-Dicarba-closo-dodecaboranyl)selenol
  45. Chloro-(((2-(9-(1,7-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κ2P,S)-(((2-((2,3,5,6-tetrafluorophenyl)thio)ethyl)diphenylphosphine)-κP) platinum(II) chloride
    Compound 6 Chloro-(((2-(9-(1,7-dicarba-closo-dodecaboranyl)thio)ethyl)diphenylphosphine)-κ2P,S)-(((2-((2,3,5,6-tetrafluorophenyl)thio)ethyl)diphenylphosphine)-κP) platinum(II) chloride


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Author information


  1. Department of Chemistry and the International Institute for Nanotechnology, Northwestern University, 2145 Sheridan Road, Evanston, lllinois 60208, USA

    • Alexander M. Spokoyny,
    • Charles W. Machan,
    • Daniel J. Clingerman,
    • Mari S. Rosen,
    • Michael J. Wiester,
    • Robert D. Kennedy,
    • Charlotte L. Stern,
    • Amy A. Sarjeant &
    • Chad A. Mirkin


A.M.S. originated and developed the concept with C.A.M., who supervised and guided the research. All experiments were designed and performed by A.M.S., C.W.M., D.J.C., M.S.R., M.J.W. and R.D.K. A.M.S. and C.W.M. performed all computational studies. C.L.S., A.A.S. and R.D.K. performed all crystallographic studies. A.M.S. and C.A.M. co-wrote the manuscript. All authors discussed the results and commented on the manuscript during its preparation.

Competing financial interests

The authors declare no competing financial interests.

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    Crystallographic data for compound 1a

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    Crystallographic data for compound 1c

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    Crystallographic data for compound 4g

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    Crystallographic data for compound 4i

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