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. 2021 Jul 7;143(26):9842-9848.
doi: 10.1021/jacs.1c03568. Epub 2021 Jun 23.

Carborane Stabilized "19-Electron" Molybdenum Metalloradical

Kuldeep Jaiswal  1 , Naveen Malik  2 , Boris Tumanskii  1 , Gabriel Ménard  3 , Roman Dobrovetsky  1
Affiliations

Carborane Stabilized "19-Electron" Molybdenum Metalloradical

Kuldeep Jaiswal et al. J Am Chem Soc. .

Abstract

Paramagnetic metal complexes gained a lot of attention due to their participation in a number of important chemical reactions. In most cases, these complexes are dominated by 17-e metalloradicals that are associatively activated with highly reactive paramagnetic 19-e species. Molybdenum paramagnetic complexes are among the most investigated ones. While some examples of persistent 17-e Mo-centered radicals have been reported, in contrast, 19-e Mo-centered radicals are illusive species and as such could rarely be detected. In this work, the photodissociation of the [Cp(CO)3Mo]2 dimer (1) in the presence of phosphines was revisited. As a result, the first persistent, formally 19-e Mo radical with significant electron density on the Mo center (22%), Cp(CO)3Mo•PPh2(o-C2B10H11) (5b), was generated and characterized by EPR spectroscopy and MS as well as studied by DFT calculations. The stabilization of 5b was likely achieved due to a unique electron-withdrawing effect of the o-carboranyl substituent at the phosphorus center.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Scheme 1
Scheme 1. Mechanism of [Cp(CO)3Mo]2 Dimer (1) Dissociation in the Presence of R3P; Formation of Cp(CO)3(R3P)Mo+ (3) and Cp(CO)3Mo– (2)
Figure 1
Figure 1
(a) EPR spectrum of 4. (b) DFT calculated Mulliken atomic spin densities and g-value of 4.
Scheme 2
Scheme 2. Photochemical Reaction of Dimer 1 in the Presence of Excess of Ph3P and Formation of an Unstable Cp(CO)3Mo• (4) and a Persistent 6, with Proposed Pathway Leading to 6
Figure 2
Figure 2
(a) EPR spectrum of 6 (blue) and its simulation (red). (b) MS of 6 (647.9559 (M + H)+) (red) and its simulation (blue). (c) DFT calculated Mulliken atomic spin densities and EPR parameters in 6.
Scheme 3
Scheme 3. Reaction of Dimer 1 with Ph2P(o-C2B10H11) (8) to Generate the Persistent Radical 5b; Decay of 5b by Cl Atom Abstraction Giving 9 (b) and Oxidation of 5b by [Ph3C][B(C6F5)4] Giving 3b (a)
Figure 3
Figure 3
(a) EPR spectrum of 5b (blue) and its simulation (red). (b) MS of 5b (573.1174 (M–H)−) (red) and its simulation (blue). (c) DFT calculated Mulliken atomic spin densities and EPR parameters in 5b.
Figure 4
Figure 4
POV-ray depiction of cation 3b (a) and of 9 (b); thermal ellipsoids at the 50% probability level. Hydrogens and the [B(C6F5)4]− anion are omitted for clarity.
Figure 5
Figure 5
CV of 3b (5.99 mM) in dry 0.1 M [nBu4N][B(C6F5)4]/CH2Cl2 solution obtained at various scan rates with glassy carbon electrodes, Pt wire, and Ag/Ag+ as the working, counter, and reference electrodes, respectively.
Scheme 4
Scheme 4. Reduction Reaction of Cation 3b by FeCp*2
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References

    1. Tolman C. A. The 16 and 18 Electron Rule in Organometallic Chemistry and Homogeneous Catalysis. Chem. Soc. Rev. 1972, 1, 337–353. 10.1039/cs9720100337. - DOI
    1. Elschenbroich C.; Salzer A.. Organometallics: A Concise Introduction, 1st ed.; VCH: Weinheim, 1989.
    1. Kochi J. K.Preface. In Organometallic Mechanisms and Catalysis; Kochi J. K., Ed.; Academic Press: 1978; pp xiii–xiv.
    1. Astruc D. Nineteen-Electron Complexes and Their Role in Organometallic Mechanisms. Chem. Rev. 1988, 88, 1189–1216. 10.1021/cr00089a010. - DOI
    1. Song J. S.; Bullock R. M.; Creutz C. Intrinsic Barriers to Atom Transfer (Abstraction) Processes; Self-Exchange Rates for Cp(CO)3M• Radical/Cp(CO)3M-X Halogen Couples. J. Am. Chem. Soc. 1991, 113, 9862–9864. 10.1021/ja00026a029. - DOI

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