Australian Journal of Chemistry Australian Journal of Chemistry Society
An international journal for chemical science
RESEARCH FRONT

Electrochemical Oxidation of W(CO)4(LL): Generation, Characterization, and Reactivity of [W(CO)4(LL)]+ (LL = α-diimine ligands)

John P. Bullock A C , Chong-Yong Lee B , Brian Hagan A , Humair Madhani A and John Ulrich A
+ Author Affiliations
- Author Affiliations

A Division of Natural Science and Mathematics, Bennington College, Bennington, VT 05201, USA.

B Australian Research Council Centre of Excellence for Electromaterials Science, Intelligent Polymer Research Institute, Australian Institute for Innovative Materials, University of Wollongong, Innovation Campus, Wollongong, NSW 2522, Australia.

C Corresponding author. Email: jbullock@bennington.edu

Australian Journal of Chemistry 70(9) 1006-1015 https://doi.org/10.1071/CH17256
Submitted: 12 May 2017  Accepted: 27 June 2017   Published: 20 July 2017

Abstract

The electrochemistry of a series of W(CO)4(LL) complexes, where LL is an aromatic α-diimine ligand, was examined in coordinating and weakly coordinating media using several techniques. These compounds undergo metal-centred one-electron oxidations and the electrogenerated radical cations undergo a range of subsequent chemical steps, the nature of which depends on the substituents of the α-diimine ligand and the presence of coordinating species. In CH2Cl2/TBAPF6, where TBAPF6 is n-tetrabutylammonium hexaflurophosphate, the bulk oxidations are partially reversible at scan rates of 0.25 V s-1; the resulting tungsten(i) radicals react via disproportionation and loss of carbonyl, the rate constants for which were measured by double-potential step chronocoulometry. Large-amplitude a.c. voltammetry experiments suggest that the one-electron oxidized species are in equilibrium with the corresponding disproportionation products. Steric crowding of the metal centre prolongs the lifetime of the radical cations, allowing the infrared spectroelectrochemical characterization of two [W(CO)4(LL)]+ species. Electrogenerated [W(CO)4(LL)]+ cations are highly susceptible to attack by potential ligands; oxidations performed in CH3CN/TBAPF6, for example, were chemically irreversible. Kinetic studies in weakly coordinating media show that near-stoichiometric amounts of added pyridine and acetonitrile are enough to greatly diminish the reversibility of the bulk oxidations; the dominant path of the coupled chemistry depends on the ligand strength, with substitution being the major reaction with added pyridine, whereas disproportionation is favoured by the presence of acetonitrile. A reaction scheme that provides an overall framework of the reactions followed by the radical cations is presented and discussed in the context of the previously observed chemistry of the molybdenum analogues.


References

[1]  A. Vlček, Coord. Chem. Rev. 2002, 230, 225.
         | CrossRef |

[2]  (a) M. L. Clark, K. A. Grice, C. E. Moore, C. P. Kubiak, Chem. Sci. 2014, 5, 1894.
         | CrossRef | 1:CAS:528:DC%2BC2cXlsFOru7Y%3D&md5=ac32347960cc76c6f7bdaf1fa2d581a5CAS |
      (b) J. Tory, B. Setterfield-Price, R. A. W. Dryfe, F. Hartl, ChemElectroChem 2015, 2, 213.
         | CrossRef |

[3]  A. A. Vlček, Chemtracts – Inorg. Chem. 1993, 5, 1.

[4]  S. Ernst, W. Kaim, J. Am. Chem. Soc. 1986, 108, 3578.
         | CrossRef | 1:CAS:528:DyaL28XktFOjtbs%3D&md5=9524668fefec5daa0f9f05d1a9404f11CAS |

[5]  E. Ioachim, G. S. Hanan, Can. J. Chem. 2005, 83, 1114.
         | CrossRef | 1:CAS:528:DC%2BD2MXht1ygurbF&md5=9c38d057b52429b161ca57e4ff779cf8CAS |

[6]  I. R. Farrell, F. Hartl, S. Záliš, M. Wanner, W. Kaim, A. Vlček, Inorg. Chim. Acta 2001, 318, 143.
         | CrossRef | 1:CAS:528:DC%2BD3MXjvV2mtLc%3D&md5=48ede3d3e39e73d256214f507df80149CAS |

[7]  J. Hanzlík, L. Pospíšil, A. A. Vlček, M. Krejčík, J. Electroanal. Chem. 1992, 331, 831.
         | CrossRef |

[8]  R. Johnson, H. Madhani, J. P. Bullock, Inorg. Chim. Acta 2007, 360, 3414.
         | CrossRef | 1:CAS:528:DC%2BD2sXmsFCgt7g%3D&md5=674c51b035787f3c85434a253768711dCAS |

[9]  H. tom Dieck, E. Kühl, Z. Naturforsch. B: Anorg. Chem., Org. Chem. 1982, 37B, 324.
         | 1:CAS:528:DyaL3sXkt1OrtQ%3D%3D&md5=1c3c86a0e9a3d60ebf0674c0978dfac6CAS |

[10]  M. G. Hill, W. M. Lamanna, K. R. Mann, Inorg. Chem. 1991, 30, 4687.
         | CrossRef | 1:CAS:528:DyaK3MXms1Ghur4%3D&md5=813cac023e305c52806f68d6bc646320CAS |

[11]  R. Colton, Coord. Chem. Rev. 1971, 6, 269.
         | CrossRef | 1:CAS:528:DyaE3MXlt1Gqtrw%3D&md5=08f762c2d5ff4c1a044c551b0e0faecdCAS |

[12]  A. M. Bond, R. Colton, K. McGregor, Organometallics 1990, 9, 1227.
         | CrossRef | 1:CAS:528:DyaK3cXhs1OksrY%3D&md5=7a9d6a7c909e95e520c5b222d6178852CAS |

[13]  A. M. Bond, R. Colton, Coord. Chem. Rev. 1997, 166, 161.
         | CrossRef | 1:CAS:528:DyaK1cXktl2qsg%3D%3D&md5=24262e29bbbb01b56f4b208010eaf13eCAS |

[14]  (a) J. Handzlik, F. Hartl, T. Szymańska-Buzar, New J. Chem. 2002, 26, 145.
         | CrossRef | 1:CAS:528:DC%2BD38XntFCkuw%3D%3D&md5=cc09638218d732e0e7dde74b75bd9071CAS |
      (b) M. Górski, F. Hartl, T. Szymańska-Buzar, Organometallics 2007, 26, 4066.
         | CrossRef |

[15]  M. C. Baird, Chem. Rev. 1988, 88, 1217.
         | CrossRef | 1:CAS:528:DyaL1cXmtlWisr8%3D&md5=eb130e1c62734fb2b92e267e720e7b50CAS |

[16]  M. K. Hanafey, R. L. Scott, T. H. Ridgway, C. N. Reilley, Anal. Chem. 1978, 50, 116.
         | CrossRef | 1:CAS:528:DyaE1cXivFGksA%3D%3D&md5=fd1ad55073afba07cf9a44491098ca74CAS |

[17]  J. P. Bullock, E. Carter, R. Johnson, A. T. Kennedy, S. E. Key, B. J. Kraft, D. Saxon, P. Underwood, Inorg. Chem. 2008, 47, 7880.
         | CrossRef | 1:CAS:528:DC%2BD1cXptlCjsbY%3D&md5=813b34f91085df9b3fdfc0adaf7925f6CAS |

[18]  A. C. Ohs, A. L. Rheingold, M. J. Shaw, C. Nataro, Organometallics 2004, 23, 4655.
         | CrossRef | 1:CAS:528:DC%2BD2cXmvFyntrg%3D&md5=093cb9ffaf17926d5950c090d33e6d10CAS |

[19]  P. A. Eckert, K. J. Kubarych, J. Phys. Chem. A 2017, 121, 2896.
         | CrossRef | 1:CAS:528:DC%2BC2sXltlWgs7k%3D&md5=2b3beddb06a52caf342a8d1092d4efebCAS |

[20]  J. P. Bullock, M. C. Palazotto, K. R. Mann, Inorg. Chem. 1991, 30, 1284.
         | CrossRef | 1:CAS:528:DyaK3MXhvFClt7Y%3D&md5=5b04ec1ab0c6ff24bd3ef60151bd7178CAS |

[21]  A. M. Bond, N. W. Duffy, S.-X. Guo, J. Zhang, D. Elton, Anal. Chem. 2005, 77, 186A.
         | CrossRef | 1:CAS:528:DC%2BD2MXkslamu70%3D&md5=d5a49f0b782dbc4110e71bc8ce5e0925CAS |

[22]  J. P. Bullock, E. Mashkina, A. M. Bond, J. Phys. Chem. A 2011, 115, 6493.
         | CrossRef | 1:CAS:528:DC%2BC3MXmsFGjsbk%3D&md5=4a5626b6290518eae416f6b6b02d2c28CAS |

[23]  C.-Y. Lee, J. P. Bullock, G. F. Kennedy, A. M. Bond, J. Phys. Chem. A 2010, 114, 10122.
         | CrossRef | 1:CAS:528:DC%2BC3cXhtVyrtr%2FM&md5=1066542d16dad7308def706af2bfddaeCAS |

[24]  D. R. Tyler, Prog. Inorg. Chem. 1988, 36, 125.
         | CrossRef | 1:CAS:528:DyaK3cXnsFag&md5=b95bd7b08d71c17b65b16a575040f732CAS |

[25]  W. Kaim, S. Kohlmann, Inorg. Chem. 1987, 26, 68.
         | CrossRef | 1:CAS:528:DyaL2sXkt1yksA%3D%3D&md5=ed9a9cff9dcfe6a2da88e3aa276e077cCAS |

[26]  W. Strohmeier, Angew. Chem. Int. Ed. Engl. 1964, 3, 730.
         | CrossRef |

[27]  J. P. Bullock, D. C. Boyd, K. R. Mann, Inorg. Chem. 1987, 26, 3084.
         | CrossRef | 1:CAS:528:DyaL2sXlt1eisr0%3D&md5=351a6e7913e52a1c96a206ef4cf0f02fCAS |

[28]  A. N. Simonov, G. P. Morris, E. A. Mashkina, B. Bethwaite, K. Gillow, R. E. Baker, D. J. Gavaghan, A. M. Bond, Anal. Chem. 2014, 86, 8408.
         | CrossRef | 1:CAS:528:DC%2BC2cXhtFOqtb3P&md5=cfd7af05578ee5d893479d44c7f8d6abCAS |

[29]  G. F. Kennedy, A. M. Bond, A. N. Simonov, Curr. Opin. in Electrochem 2017, 1, 140.
         | CrossRef |

[30]  See Ch. 5 in A. J. Bard, L. R. Faulkner, Electrochemical Methods: Fundamentals and Applications (2nd Edn) 2001 (Wiley: New York, NY).



Rent Article (via Deepdyve) Supplementary MaterialSupplementary Material (1.6 MB) Export Citation

View Altmetrics