Transition metal thioether complex

Transition metal thioether complexes comprise coordination complexes of thioether (R2S) ligands. The inventory is extensive.

Structure of [Ru(NH3)5(SMeEt)]2+.[1]

Dimethylsulfide complexes

As the simplest thioether, dimethyl sulfide forms complexes that are illustrative of the class.[2] Well characterized derivatives include cis-[TiCl4L2], VCl3L2, NbCl5L, NbCl4L2, Cr(CO)5L, CrCl3L3, RuCl2L4, RuCl3L3, RhCl3L3, cis- and trans-[IrCl4L3]-, cis-MCl2L2 (M = Pd, Pt), [PtCl3L]−, cis- and trans-[PtCl4L2] (L = SMe2). With respect to donor properties, dimethyl sulfide is a soft ligand with donor properties weaker than phosphine ligands.[3]

Stereochemistry
Diastereotopic methylene protons in complexes of diethyl sulfide.

Thioether complexes feature pyramidal sulfur centers. Typical C-S-C angles are near 99° in both free thioethers and their complexes. The C-S distance in dimethylsulfide is 1.81 Å, which is also unaffected in its complexes.[4] The stereochemistry of thioether complexes have been extensively studied.[5] Unsymmetrical thioethers, e.g., SMeEt, are prochiral ligands, and their complexes are chiral. One example is [Ru(NH3)5(SMeEt)]2+. The complex cis-VOCl2(SMeEt)2 exists as meso- and a pair of enantiomers.[6] In complexes of thioethers of the type S(CH2R)2 (R ≠ H), the methylene protons are diastereotopic. Examination of the NMR spectra of such complexes reveal that they undergo inversion at sulfur, without dissociation of the M-S bond.[7]

Thioether as a bridging ligand
Structure of Nb2Cl6(SMe2)3, illustrating a bridging thioether.[8]

Unlike ethers, thioethers occasionally serve as bridging ligands. The complexes Nb2Cl6(SMe2)3 is one such example. It adopts a face-sharing bioctahedral structure with a Nb(III)=Nb(III) bond, spanned by two chloride and one dimethylsulfide ligands. The complex Pt2Me4(μ-SMe2)2 is a source of "PtMe2".[9]

Complexes chelating thioether ligands
  • Structure of [Ag(18-ane-S6)]2+. The Ag-S distances are 2.62 Å.
  • Structure of [Ru(15-ane-S5)Cl]+.[10]
  • Structure of (DTCO)PdCl2.[11]

Thiacrown ligands are analogous to crown ethers. The best studied thiacrown ligands have the formula (SCH2CH2)n (n = 3,4,5,6). The tridentate tri-thioether 9-ane-S3 forms extensive families of complexes of the type M(9-ane-S3)L3 and [M(9-ane-S3)2]2+. Examples of Cu(II)-thioether complexes were prepared from 14-ane-S4[12] and 15-ane-S5.[10] The hexadentate ligand 18-ane-6 also forms extensive family of complexes, including unsual examples of Pd(III) and Ag(II).[13] Examples of homoleptic complexes [M(SR2)6]n+ are otherwise rare.

Occurrence

Thioether complexes in nature arise from coordination of the sulfur substituent found in the amino acid methionine. One of the axial ligands in cytochrome c is illustrative. Methionine sulfur weakly binds to copper in azurin.

References
  1. Krogh-Jespersen, Karsten; Zhang, Xiaohua; Ding, Yanbo; Westbrook, John D.; Potenza, Joseph A.; Schugar, Harvey J. (1992). "Molecular and Electronic Structures of Pentaammineruthenium(II)-Thioether Complexes. The Nature of Ru(II)-S Back Bonding Elucidated by Structural, Electronic Spectral, and Molecular Orbital Studies". Journal of the American Chemical Society. 114 (11): 4345–4353. doi:10.1021/ja00037a047.
  2. Murray, Stephen G.; Hartley, Frank R. (1981). "Coordination chemistry of thioethers, selenoethers, and telluroethers in transition-metal complexes". Chemical Reviews. 81 (4): 365–414. doi:10.1021/cr00044a003.
  3. Lever, A. B. P. (1990). "Electrochemical Parametrization of Metal Complex Redox Potentials, Using the Ruthenium(III)/Ruthenium(II) Couple to Generate a Ligand Electrochemical Series". Inorganic Chemistry. 29 (6): 1271–1285. doi:10.1021/ic00331a030.
  4. Iijima, T.; Tsuchiy, S.; Kimura, M. (1977). "The Molecular Structure of Dimethyl Sulfide". Bull. Chem. Soc. Jpn. 50: 2564. doi:10.1246/bcsj.50.2564.
  5. Abel, Edward W.; Bhargava, Suresh K.; Orrell, Keith G. (2007). "The Stereodynamics of Metal Complexes of Sulfur-, Selenium-, and Tellurium-Containing Ligands". Progress in Inorganic Chemistry: 1–118. doi:10.1002/9780470166338.ch1.
  6. Matsuura, Masatoshi; Fujihara, Takashi; Nagasawa, Akira (2013). "Cis-Dichloridobis(ethyl methyl sulfide-κS)oxidovanadium(IV)". Acta Crystallographica Section E. 69 (4): m209. doi:10.1107/S1600536813006703. PMC 3629486. PMID 23634004.
  7. Turley, Patricia C.; Haake, Paul. (1967). "Proton Magnetic Resonance Epectra of Platinum(II) Complexes. II. Cis- and trans- Bis(dialkyl sulfide)dichloroplatinum(II) Complexes. Mechanism of Inversion at Sulfur and Vicinal Platinum-Proton Couplings". Journal of the American Chemical Society. 89 (18): 4617–4621. doi:10.1021/ja00994a009.
  8. Kakeya, Masaki; Fujihara, Takashi; Nagasawa, Akira (2006). "Di-μ-chloro-μ-(dimethyl sulfide)-bis[dichloro(dimethyl sulfide)niobium(III)]". Acta Crystallographica Section E. 62 (3): m553–m554. doi:10.1107/S1600536806005149.
  9. Hill, Geoffrey S.; Irwin, Michael J.; Levy, Christopher J.; Rendina, Louis M.; Puddephatt, Richard J. (1998). "Platinum(II) Complexes of Dimethyl Sulfide". Inorganic Syntheses. 32: 149–153. doi:10.1002/9780470132630.ch25. ISBN 9780470132630.
  10. Janzen, Daron E.; Vanderveer, Donald G.; Mehne, Larry F.; Grant, Gregory J. (2010). "Ruthenium(II) Thiacrown Complexes: Synthetic, Spectroscopic, Electrochemical, DFT, and Single Crystal X-ray Structural Studies of [Ru([15]aneS5)Cl](PF6)". Inorganica Chimica Acta. 364: 55–60. doi:10.1016/j.ica.2010.08.021.
  11. Musker, W. Kenneth (1992). "Coordination Chemistry of Bidentate Medium Ring Ligands (Mesocycles)". Coordination Chemistry Reviews. 117: 133–57. doi:10.1016/0010-8545(92)80022-J.
  12. Pett, Virginia B.; Diaddario, Leonard L.; Dockal, Edward R.; Corfield, Peter W.; Ceccarelli, Christopher; Glick, Milton D.; Ochrymowycz, L. A.; Rorabacher, D. B. (1983). "Ring Size Effects on the structure of macrocyclic ligand complexes: Copper(II) complexes with 12-16-membered cyclic tetrathia ethers". Inorganic Chemistry. 22 (24): 3661–3670. doi:10.1021/ic00166a033.
  13. Shaw, Jennifer L.; Wolowska, Joanna; Collison, David; Howard, Judith A. K.; McInnes, Eric J. L.; McMaster, Jonathan; Blake, Alexander J.; Wilson, Claire; Schröder, Martin (2006). "Redox Non-innocence of Thioether Macrocycles: Elucidation of the Electronic Structures of Mononuclear Complexes of Gold(II) and Silver(II)". Journal of the American Chemical Society. 128 (42): 13827–13839. doi:10.1021/ja0636439. PMID 17044711.
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