Transition metal complexes of sulfur monoxide

Transition metal complexes of sulfur monoxide refers to coordination complexes with sulfur monoxide (SO) as a ligand. The topic is relevant to the metal-promoted redox reactions of sulfur and sulfur oxides. Sulfur monoxide is unstable in condensed form, so its complexes are almost always prepared indirectly, e.g., using reagents that release SO.

Bonding modes

Structure of [Fe₃(SO)(CO)₉] . Color code: red = O, yellow = S.

SO can bond to metals in a number ways: ^{[2] [3]}

• a terminal ligand, with a bent M−S−O arrangement, analogous structurally to "bent" nitrosyl. In such cases, SO is a Lewis base. An example is IrCl(P(i-Pr)₃)₂(SO) (i-Pr = isopropyl). ^[4]
• triply bridging as in Fe₃(μ³-S)(μ³-SO)(CO)₉. In such cases SO is a 4-electron donor.
• Bridging with the μ-η¹,η¹-SO motif. ^[5] Another bridging mode is μ-η¹,η²-SO, as observed in some Rh₂ complexes. ^[6]

Complexes with the M−O−S arrangement have been observed using the techniques of laser ablation and low temperature spectroscopy. ^{[7] [8]}

Synthesis

SO complexes can be prepared from ethylene episulfoxides. This heterocycle binds metals through S, then releases ethylene. ^[2] Lewis acid adducts of sulfinylamines release SO when heated. In this way [RhCl(SO)(PPh₃)₂]₂ can be produced from RhCl(PPh₃)₃ (Ph = C₆H₅). ^[9]

Another approach involves redox reactions of metal sulfides. Some cases involve well-defined oxidants such as peroxides. In other cases, air is assumed to be the oxidant. ^[5]

References

1. Karet, G. B.; Stern, C. L.; Norton, D. M.; Shriver, D. F. (1993). "Synthesis and Reductive Sulfur-Oxygen Cleavage of Sulfur Oxide Clusters: [PPN][HFe₃(CO)₉SO₂] and [PPN]₂[Fe₃(CO)₉SO]". Journal of the American Chemical Society. 115 (22): 9979–9985. Bibcode:1993JAChS.115.9979K. doi:10.1021/ja00075a014.
2. Schenk, W. A. (1987). "Sulfur Oxides as Ligands in Coordination Compounds". Angewandte Chemie International Edition in English. 26 (2): 98–109. doi:10.1002/anie.198700981.
3. Woollins, J. D. (1995). "Sulfur: Inorganic Chemistry". Encyclopedia of Inorganic Chemistry. John Wiley and Sons. ISBN   0-471-93620-0.
4. Schenk, Wolfdieter A.; Leissner, Johanna; Burschka, Christian (1984). "Stabilization of Sulfur Monoxide by Coordination to Transition Metals". Angewandte Chemie International Edition in English. 23 (10): 806–807. doi:10.1002/anie.198408061.
5. Arikawa, Yasuhiro; Yamada, Motoki; Takemoto, Nobuko; Nagaoka, Takuya; Tsujita, Yusuke; Nakamura, Taiji; Tsuruta, Yusuke; Horiuchi, Shinnosuke; Sakuda, Eri; Yoshizawa, Kazunari; Umakoshi, Keisuke (2023). "Stepwise Sulfite Reduction on a Dinuclear Ruthenium Complex Leading to Hydrogen Sulfide". Journal of the American Chemical Society. 145 (40): 21729–21732. Bibcode:2023JAChS.14521729A. doi:10.1021/jacs.3c07248. PMID   37650604.
6. Bianchini, Claudio; Mealli, Carlo; Meli, Andrea; Sabat, Michal (1985). "Stepwise Metal-Promoted Conversion of η²-CS₂ into η²-SO. Synthesis and Crystal Structure of the Complex [(triphos)Rh(µ-SO)₂Rh(triphos)][BPh₄]₂·HCONMe₂[triphos = MeC(CH₂PPh₂)₃]". J. Chem. Soc., Chem. Commun. (15): 1024–1025. doi:10.1039/C39850001024.
7. Wei, R.; Chen, X.; Gong, Y. (2019). "End-On Oxygen-Bound Sulfur Monoxide Complex of Titanium Oxyfluoride". Inorganic Chemistry. 58 (17): 11801–11806. doi:10.1021/acs.inorgchem.9b01880. PMID   31441297. S2CID   201617509.
8. Wei, R.; Chen, X.; Gong, Y. (2019). "Side-On Sulfur Monoxide Complexes of Tantalum, Niobium, and Vanadium Oxyfluorides". Inorganic Chemistry. 58 (6): 3807–3814. doi:10.1021/acs.inorgchem.8b03411. PMID   30707575. S2CID   73438027.
9. Longobardi, Lauren E.; Wolter, Vanessa; Stephan, Douglas W. (2015). "Frustrated Lewis Pair Activation of an N -Sulfinylamine: A Source of Sulfur Monoxide". Angewandte Chemie International Edition. 54 (3): 809–812. Bibcode:2015ACIE...54..809L. doi:10.1002/anie.201409969. PMID   25376102.