在過往報導過的鈷三價錯合物中，順磁錯合物的數量少於逆磁錯合物，這是因為鈷三價錯合物在八面體的結構下，其鈷三價中心具有低自旋的d6電子組態。相較於八面體結構的鈷三價錯合物，五配位雙三角錐的結構通常呈現順磁的性質。因此我們使用富含硫的四牙配位基 H3[PS3"] (H3[PS3"] = H3[P(C6H3-3-SiMe3-2-S)3]) 來合成一系列的鈷三價錯合物 [NBu4][CoⅢ(PS3")(N3)] (1)，[AsPh4][CoⅢ(PS3")(Cl)] (2)， [CoⅢ(PS3")(PPh3)] (3)， [CoⅢ(PS3")(C2H5CN)] (4) 和 [CoⅢ(PS3")(CH3CN)] (5)。除了錯合物 3 沒有晶體結構外，所有錯合物皆通過X光晶體學得到晶體結構及其他光譜的鑑定。在這些錯合物中鈷三價中心與三個位於赤道位的硫原子，和以反式連接位於軸位的磷原子和及添加的單牙配位基形成雙三角錐幾何結構。並且分別由SQUID (超導量子干涉磁量儀) 和Evans' method 測量固態和液態的磁性數據。磁性數據的結果皆一致地表示電子自旋態為S = 1，此結果也符合鈷三價離子在d6雙三角錐幾何結構下的自旋三重態。

There are fewer reported paramagnetic Co(Ⅲ) complexes than diamagnetic cases because they frequently use octahedral geometry with low spin d6 electronic configurations. Unlike Co(Ⅲ) complexes that use octahedral geometry, five-coordinate trigonal-bipyramidal Co(Ⅲ) complexes are frequently paramagnetic. At this work, we synthesize a class of Co(Ⅲ) complexes using a tetradentate sulfur-rich ligand [PS3"] (H3[PS3"] = H3[P(C6H3-3-SiMe3-2-S)3]), [NBu4][CoⅢ(PS3")(N3)] (1), [AsPh4][CoⅢ(PS3")(Cl)] (2), [CoⅢ(PS3")(PPh3)] (3), [CoⅢ(PS3")(C2H5CN)] (4) and [CoⅢ(PS3")(CH3CN)] (5). Except for complex 3 that lacks X-ray structure, all have been well characterized by X-ray crystallography and various spectroscopies. The cobalt(Ⅲ) centers in these complexes all have trigonal bipyramidal geometry, with three thiolato donors in the equatorial plane and a P atom in the axial position, trans to an additional monodentate ligand. For the solid and solution states, magnetic data were measured using SQUID (superconducting quantum interference device) and the Evans’ method, respectively. The results agree and point to a S = 1 spin state with a spin-triplet configuration for d6 trigonal-bipyramidal Co(Ⅲ) ions.

1. Levason, W.; Ogden, J. S.; Spicer, M. D., Coordination chemistry of higher oxidation states. 30. Five-coordinate cobalt(III) phosphine complexes. Spectroscopic and cobalt K-edge EXAFS studies. Inorg. Chem. 1989, 28 (11), 2128-2131.
2. Godfrey, S. M.; McAuliffe, C. A.; Pritchard, R. G., Extreme symbiosis: the facile one-step synthesis of the paramagnetic cobalt(III) complex of triphenylantimony, Col3(SbPh3)2, from the reaction of triphenylantimonydiiodine with unactivated coarse grain cobalt metal powder. J. Chem. Soc., Chem. Commun. 1994, (1), 45-46.
3. Jaynes, B. S.; Ren, T.; Liu, S.; Lippard, S. J., Tuning the stereochemistry of pentacoordinate cobalt(III) halide complexes: a rare case of trigonal bipyramidal stereochemistry for cobalt(III). J. Am. Chem. Soc. 1992, 114 (24), 9670-9671.
4. Franz, K. J.; Doerrer, L. H.; Spingler, B.; Lippard, S. J., Pentacoordinate Cobalt(III) Thiolate and Nitrosyl Tropocoronand Compounds. Inorg. Chem. 2001, 40 (15), 3774-3780.
5. Cho, C.-H.; Chien, T.-Y.; Chen, J.-H.; Wang, S.-S.; Tung, J.-Y., Intermediate (S = 1) spin state in five-coordinate cobalt(iii): Magnetic properties of N-o-hydroxy-benzamido-meso-tetraphenylporphyrin cobalt(iii), Co(N-NCO(o-O)C6H4-tpp). Dalton Trans. 2010, 39 (10), 2609-2614.
6. Sarkar, P.; Tiwari, A.; Sarmah, A.; Bhandary, S.; Roy, R. K.; Mukherjee, C., An elusive vinyl radical isolated as an appended unit in a five-coordinate Co(iii)–bis(iminobenzosemiquinone) complex formed via ligand-centered C–S bond cleavage. Chem. Commun. 2016, 52 (70), 10613-10616.
7. Thyagarajan, S.; Shay, D. T.; Incarvito, C. D.; Rheingold, A. L.; Theopold, K. H., Intramolecular C−H Activation by Inferred Terminal Cobalt Imido Intermediates. J. Am. Chem. Soc. 2003, 125 (15), 4440-4441.
8. Ellermann, J.; Bauer, W.; Dotzler, M.; Heinemann, F. W.; Moll, M., Chemie polyfunktioneller Moleküle, 132. Mitt. [1]. Synthese und Kristallstruktur paramagnetischen fünffach-koordinierten eines Cobalt(III)-Komplexes ausgehend von Co2(CO)8, Ph2P-N*PPh2-PPh2*N-PPh2 und Lufta. Monatsh. Chem. 1999, 130 (12), 1419-1430.
9. Fryzuk, M. D.; Leznoff, D. B.; Thompson, R. C.; Rettig, S. J., One-Electron Transformations of Paramagnetic Cobalt Complexes. Synthesis and Structure of Cobalt(II) Amidodiphosphine Halide and Alkyl Complexes and Their Reaction with Alkyl Halides. J. Am. Chem. Soc. 1998, 120 (39), 10126-10135.
10. Gibson, V. C.; Spitzmesser, S. K.; White, A. J. P.; Williams, D. J., Synthesis and reactivity of 1,8-bis(imino)carbazolide complexes of iron, cobalt and manganese. Dalton Trans. 2003, (13), 2718-2727.
11. Murugesan, S.; Stöger, B.; Carvalho, M. D.; Ferreira, L. P.; Pittenauer, E.; Allmaier, G.; Veiros, L. F.; Kirchner, K., Synthesis and Reactivity of Four- and Five-Coordinate Low-Spin Cobalt(II) PCP Pincer Complexes and Some Nickel(II) Analogues. Organometallics 2014, 33 (21), 6132-6140.
12. MacBeth, C. E.; Hammes, B. S.; Young, V. G., Jr.; Borovik, A. S., Hydrogen-Bonding Cavities about Metal Ions:  Synthesis, Structure, and Physical Properties for a Series of Monomeric M−OH Complexes Derived from Water. Inorg. Chem. 2001, 40 (18), 4733-4741.
13. Martín, C.; Whiteoak, C. J.; Martin, E.; Escudero-Adán, E. C.; Galán-Mascarós, J. R.; Kleij, A. W., Synthesis and Structural Features of Co(II) and Co(III) Complexes Supported by Aminotrisphenolate Ligand Scaffolds. Inorg. Chem. 2014, 53 (21), 11675-11681.
14. Holler, S.; Tüchler, M.; Knaus, A. M.; Belaj, F.; Mösch-Zanetti, N. C., Di-tert-butyl thiopyridazine boratrane complexes of Co, Ni and Cu. Polyhedron 2017, 125, 122-129.
15. Kung, I.; Schweitzer, D.; Shearer, J.; Taylor, W. D.; Jackson, H. L.; Lovell, S.; Kovacs, J. A., How Do Oxidized Thiolate Ligands Affect the Electronic and Reactivity Properties of a Nitrile Hydratase Model Compound? J. Am. Chem. Soc. 2000, 122 (34), 8299-8300.
16. Yano, T.; Wasada-Tsutsui, Y.; Ikeda, T.; Shibayama, T.; Kajita, Y.; Inomata, T.; Funahashi, Y.; Ozawa, T.; Masuda, H., Co(III) Complexes with N2S3-Type Ligands as Structural/Functional Models for the Isocyanide Hydrolysis Reaction Catalyzed by Nitrile Hydratase. Inorg. Chem. 2018, 57 (8), 4277-4290.
17. Buchwald, J. R.; Kal, S.; Civic, M. R.; deJoode, I. M.; Filatov, A. S.; Dinolfo, P. H., Spin modulation and electrochemical behavior of a five-coordinate cobalt(III) salen complex. J. Coord. Chem. 2016, 69 (11-13), 1695-1708.
18. Jiang, H.; Xie, Y.-S.; Zhou, Z.-Y.; Xu, X.-L.; Liu, Q.-L., Syntheses, Structures and Characterization of Cobalt(II) and Cobalt(III) Complexes with N-Benzylated Polyamines and a Terminal Azido Ligand. J. Coord. Chem 2003, 56 (9), 825-832.
19. Goher, M. A. S.; Youssef, A. A.; Mautner, F. A., Synthesis and structural characterization of two new anionic cobalt(III) azide complexes of 2,3- and 2,5-pyridine dicarboxylic acids. Polyhedron 2006, 25 (7), 1531-1536.
20. Hojilla Atienza, C. C.; Bowman, A. C.; Lobkovsky, E.; Chirik, P. J., Photolysis and Thermolysis of Bis(imino)pyridine Cobalt Azides: C−H Activation from Putative Cobalt Nitrido Complexes. J. Am. Chem. Soc. 2010, 132 (46), 16343-16345.
21. Bikas, R.; Hosseini Monfared, H.; Lis, T.; Siczek, M., Synthesis, structural characterization and electrochemical studies of an ionic cobalt complex derived from a tridentate hydrazone Schiff base and azide ligands. Inorg. Chem. Commun. 2012, 15, 151-155.
22. Nath, J. K.; Baruah, J. B., Azide containing bipyridine complexes of cobalt(III). Polyhedron 2012, 36 (1), 1-5.
23. Wojciechowska, A.; Dobrzyńska, D.; Janczak, J., Structural and spectroscopic study of cobalt(III) ternary complexes. Polyhedron 2012, 47 (1), 118-125.
24. Das, M.; Chattopadhyay, S., Synthesis and structures of two cobalt(III) complexes with N4 donor ligands: Isolation of a unique bis-hemiaminal ether ligand as the metal complex. Polyhedron 2013, 50 (1), 443-451.
25. Meghdadi, S.; Mereiter, K.; Amirnasr, M.; Karimi, F.; Amiri, A., Synthesis, crystal structure and electrochemistry of cobalt(III) carboxamide complexes with amine and azide ancillary ligands. Polyhedron 2014, 68, 60-69.
26. Shit, S.; Saha, D.; Saha, D.; Guru Row, T. N.; Rizzoli, C., Azide/thiocyanate incorporated cobalt(III)-Schiff base complexes: Characterizations and catalytic activity in aerobic epoxidation of olefins. Inorg. Chim. Acta 2014, 415, 103-110.
27. Thamilarasan, V.; Sengottuvelan, N.; Sudha, A.; Srinivasan, P.; Chakkaravarthi, G., Cobalt(III) complexes as potential anticancer agents: Physicochemical, structural, cytotoxic activity and DNA/protein interactions. J. Photochem. Photobiol B., 2016, 162, 558-569.
28. Romanović, M. Č.; Milenković, M. R.; Pevec, A.; Turel, I.; Spasojević, V.; Grubišić, S.; Radanović, D.; Anđelković, K.; Čobeljić, B., Crystal structures, magnetic properties and DFT study of cobalt(II) azido complexes with the condensation product of 2-quinolinecarboxaldehyde and Girard’s T reagent. Polyhedron 2018, 139, 142-147.
29. Sheldrick, G., SADABS; University of Göttingen: Germany, 1996.
30. Sheldrick, G., SHELXTL; SHELXTL: Madison,WI, 1994.
31. Addison, A. W.; Rao, T. N.; Reedijk, J.; van Rijn, J.; Verschoor, G. C., Synthesis, structure, and spectroscopic properties of copper(II) compounds containing nitrogen–sulphur donor ligands; the crystal and molecular structure of aqua[1,7-bis(N-methylbenzimidazol-2′-yl)-2,6-dithiaheptane]copper(II) perchlorate. J. Chem. Soc., Dalton Trans. 1984, (7), 1349-1356.
32. Ryutaro, T., Absorption Spectra of Co-ordination Compounds. I. Bull. Chem. Soc. Japan 1938, 13 (5), 388-400.
33. Shimura, Y.; Tsuchida, R., Absorption spectra of Co (III) complexes. II. Redetermination of the spectrochemical series. Bull. Chem. Soc. Japan 1956, 29 (3), 311-316.
34. Chandler, D. J.; Jones, R. A.; Whittlesey, B. R., THE JAHN-TELLER EFFECT IN A TRIGONAL BIPYRAMIDAL Ni(III) COMPLEX; SYNTHESIS AND X-RAY CRYSTAL STRUCTURE OF trans-NiI3 (PMe3)2. J. Coord. Chem. 1987, 16 (1), 19-24.
35. Evans, D. F., 400. The determination of the paramagnetic susceptibility of substances in solution by nuclear magnetic resonance. J. Chem. Soc. 1959, (0), 2003-2005.
36. Bain, G. A.; Berry, J. F., Diamagnetic Corrections and Pascal's Constants. J. Chem. Educ. 2008, 85 (4), 532.