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M. Sc. Stefan Meier

Stefan Meier 150p

Room: 329 (Chemie I)

Telephone: +49 (0) 761 203-6157

e-Mail: stefan.meier@ac.uni-freiburg.de

 

Keywords: Organocobalt compounds; Co(I) oxidation state, weakly coordinating anions

 

I am interested in the synthesis, characterization and structure of new (Organo)Cobalt(I) complexes stabilized by Weakly Coordinating Anions (WCA). A possible application of such complexes might be in catalysis. For instance, Co2CO8 and HCo(CO)4, respectively, are catalysts for the hydroformulation of alkenes to aldehydes.[1]
The highest reactivity of a cobalt(I) compound would be a “naked” cobalt(I) cation. In order to come closer to this objective, some of the following points might be helpful for the realization:
  • use of WCA’s
  • use of low-coordinating solvents
  • use of weakly coordinating ligands
  • use of bulky ligands to reduce the coordination number on the metal center

 

Figure_1.png

Fig. 1: Crystal structure of `[Co(CO)5]+.

At the very beginning it was attempted to get a “naked” cobalt(I) salt by using commercially available Co2CO8[2] as a starting material. However, the reaction between Co2CO8 and Ag[PF][3] ([PF] = [Al(OC(CF3)3)4]) yields [Co(CO)5][PF] (cf. Fig. 1). The cation [Co(CO)5]+ has already been described by Willner et al. in 2003.[4] As no further chemistry of [Co(CO)5]+ has been reported so far, I am trying to obtain further cobalt(I) complexes by using [Co(CO)5][PF] as a precursor. For instance, [Co(CO)5][PF] reacts with arenes, e.g. with toluene, benzene, fluorobenzene etc. to give Co-Arene complexes (cf. Scheme 1).
Another idea is the use of (All)Co(CO)3[5] (All = allyl = C3H5−) as starting material. It can also be obtained from Co2CO8. For example, (All)Co(CO)3 reacts with NO[PF] to give [(All)Co(CO)2(NO)][PF].
Typically, all compounds are characterized by IR- and Raman spectroscopy and single crystal X-ray diffraction. If possible, NMR or EPR spectroscopy are also performed. Quantum chemical calculations can be useful to guess, which product has been formed if no crystal structure could be obtained
In future, the catalytic activity of some complexes shall be tested.
 
Scheme_1.png

Scheme 1: Small overview of selected reactions and products. The complexes are depicted are also characterized by X-ray diffraction. NB: [Co(All)(CO)2(NO)]+ is highly disordered in the crystal structure and only the presumed molecular structure is shown.

 
 
References
[1]   C. E. Housecroft, A. G. Sharpe, Inorganic chemistry, Pearson, Harlow, England, New York, 2012.
[2]   L. Mond, H. Hirtz, M. D. Cowap, J. Chem. Soc., Trans. 1910, 97, 798.
[3]   a) I. Krossing, I. Raabe, Angew. Chem. 2004, 116, 2116–2142; b) I. Krossing, Chem. Eur. J. 2001, 7, 490–502.
[4]   a) E. Bernhardt, M. Finze, H. Willner, C. W. Lehmann, F. Aubke, Angew. Chem. Int. Ed. Engl. 2006, 12, 8276–8283; b) E. Bernhardt, M. Finze, H. Willner, C. W. Lehmann, F. Aubke, Angew. Chem. Int. Ed. Engl. 2003, 42, 2077–2079.
[5]   a) R. F. Heck, D. S. Breslow, J. Am. Chem. Soc. 1960, 82, 750–751; b) R. F. Heck, D. S. Breslow, J. Am. Chem. Soc. 1961, 83, 1097–1102.

 

 

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