Stable Carbon-Centered Radicals Based on N-Heterocyclic Carbenes

Rajendra S. Ghadwal

doi:10.1055/s-0037-1611887

Synlett, Table of Contents

Synlett 2019; 30(15): 1765-1775
DOI: 10.1055/s-0037-1611887

account

Stable Carbon-Centered Radicals Based on N-Heterocyclic Carbenes

Authors

Rajendra S. Ghadwal ∗

Anorganische Molekülchemie und Katalyse, Anorganische Chemie und Strukturchemie, Centrum für Molekulare Materialien, Fakultät für Chemie, Universität Bielefeld, Universitätsstraße 25, 33615 Bielefeld, Germany Email: rghadwal@uni-bielefeld.de

Abstract

All articles of this category

Abstract

Carbon-centered radicals and diradicaloids based on classical N-heterocyclic carbene (NHC) scaffolds are readily accessible as crystalline solids. The presence of an aryl (Ar) substituent at the C2-position is the key to the remarkable stability of these open-shell species as it provides appropriate room for the spin-density delocalization. Two catalytic as well as high-yielding protocols have been developed to install a suitable aryl group at the C2-position of NHCs. The spin-density in mono-radicals (NHC^Ar)^• is mostly located on the parent carbene carbon (C2) atom. The bridging of two NHCs through a phenylene spacer (C₆H₄) _n enables the isolation of various p-quinodimethane (p-QDM) derivatives, which may be considered as open-shell Kekulé diradicaloids. The diradical character of these NHC-analogues of Thiele (n = 1), Chichibabin (n = 2), and Müller (n = 3) hydrocarbons [(NHC)(C₆H₄) _n (NHC)] can be tuned by a rational choice of the size and/or the topology of spacers. In this account, the synthesis, structure, and properties of this new class of radical hydrocarbons is presented.

1 Introduction

2 NHC-Monoradicals

3 NHC-Diradicaloids

4 Conclusion

Key words

radical - diradical - diradicaloid - carbene - hydrocarbon - heterocycle - open-shell - paramagnetic

Full Text

References

References
1 Renaud P, Sibi MP. Radicals in Organic Synthesis . Wiley-VCH; Weinheim: 2008

2a Halliwell B, Gutteridge JM. C. Free Radicals in Biology and Medicine, 5th ed. Oxford University Press; UK: 2015
2b Chatgilialoglu C, Studer A. Encyclopedia of Radicals in Chemistry, Biology and Materials. Wiley-VCH; Weinheim: 2012
2c Berliner LJ. Spin Labeling: A Modern Perspective . In Stable Radicals . John Wiley & Sons; Hoboken: 2010. 521–534
2d Goldstein S, Samuni A. Biologically Relevant Chemistry of Nitroxides . In Stable Radicals . John Wiley & Sons; Hoboken: 2010. 567–576

3a Bielawski CW, Grubbs RH. Prog. Polym. Sci. 2007; 32: 1–29
3b Tomlinson EP, Hay ME, Boudouris BW. Macromolecules 2014; 47: 6145

4 Newcomb M. Radicals . In Reactive Intermediate Chemistry . Moss RA, Platz MS, Jones MJr. John Wiley & Sons; Hoboken: 2005. 121–163
5 The term ‘stable’ refers to a molecular entity that persists for many days in solution and can be isolated (or stored) at room temperature (25 °C) under an inert gas (nitrogen or argon) atmosphere without appreciable decomposition.

6a Hicks RG. Can. J. Chem. 2004; 82: 1119
6b Hicks RG. Stable Radicals: Fundamentals and Applied Aspects of Odd-Electron Compounds. John Wiley & Sons Ltd; Weinheim: 2010
6c Sloan GJ, Vaughan WR. J. Org. Chem. 1957; 22: 750

7a Ai X, Chen Y, Feng Y, Li F. Angew. Chem. Int. Ed. 2018; 57: 2869
7b Wilcox DA, Agarkar V, Mukherjee S, Boudouris BW. Annu. Rev. Chem. Biomol. Eng. 2018; 9: 83
7c Wang Y, Frasconi M, Stoddart JF. ACS Cent. Sci. 2017; 3: 927

8a Salem L, Rowland C. Angew. Chem. Int. Ed. Engl. 1972; 11: 92
8b Borden WT. Diradicals – A Fifty Year Fascination. In The Foundations of Physical Organic Chemistry: Fifty Years of the James Flack Norris Award, Vol. 1209. American Chemical Society; Washington, DC: 2015. p 251–303
8c Abe M. Chem. Rev. 2013; 113: 7011

9a Zeng Z, Shi X, Chi C, Lopez Navarrete JT, Casado J, Wu J. Chem. Soc. Rev. 2015; 44: 6578
9b Ratera I, Veciana J. Chem. Soc. Rev. 2012; 41: 303
9c Hu X, Wang W, Wang D, Zheng Y. J. Mater. Chem. C 2018; 6: 11232

10a Suga T, Nishide H. Rechargeable Batteries Using Robust but Redox Active Organic Radicals. In Stable Radicals. John Wiley & Sons, Ltd; Weinheim: 2010. 507–518
10b Luo J, Hu B, Debruler C, Liu TL. Angew. Chem. Int. Ed. 2018; 57: 231
10c Kim DJ, Hermann KR, Prokofjevs A, Otley MT, Pezzato C, Owczarek M, Stoddart JF. J. Am. Chem. Soc. 2017; 139: 6635

11 Muench S, Wild A, Friebe C, Häupler B, Janoschka T, Schubert US. Chem. Rev. 2016; 116: 9438

12a Beeson TD, Mastracchio A, Hong J.-B, Ashton K, MacMillan DW. C. Science 2007; 316: 582
12b Studer A, Curran DP. Angew. Chem. Int. Ed. 2016; 55: 58

13 Gomberg M. J. Am. Chem. Soc. 1900; 22: 757

14a Alcon I, Bromley ST. RSC Adv. 2015; 5: 98593
14b Tidwell TT. Triarylmethyl and Related Radicals . In Stable Radicals . John Wiley & Sons, Ltd; Weinheim: 2010. 1–3
14c Veciana J, Ratera I. Polychlorotriphenylmethyl Radicals: Towards Multifunctional Molecular Materials. In Stable Radicals. John Wiley & Sons, Ltd; Weinheim: 2010. 33–76

15a Jung Y, Head-Gordon M. ChemPhysChem 2003; 4: 522
15b Seierstad M, Kinsinger CR, Cramer CJ. Angew. Chem. Int. Ed. 2002; 41: 3894
15c Abe M, Ye J, Mishima M. Chem. Soc. Rev. 2012; 41: 3808
15d Grützmacher H, Breher F. Angew. Chem. Int. Ed. 2002; 41: 4006
15e Breher F. Coord. Chem. Rev. 2007; 251: 1007

16 Thiele J, Balhorn H. Ber. Dtsch. Chem. Ges. 1904; 37: 1463
17 Tschitschibabin AE. Ber. Dtsch. Chem. Ges. 1907; 40: 1810

18a Kanzaki Y, Shiomi D, Sato K, Takui T. J. Phys. Chem. B 2012; 116: 1053
18b McConnell HM. J. Chem. Phys. 1960; 33: 1868

19 Montgomery LK, Huffman JC, Jurczak EA, Grendze MP. J. Am. Chem. Soc. 1986; 108: 6004

20a Solà M.; Front. Chem.; 2013, 1; DOI: 10.3389/fchem.2013.00022 .
20b Clar E. The Aromatic Sextet . In Mobile Source Emissions Including Policyclic Organic Species . Rondia D, Cooke M, Haroz RK. Springer Netherlands; Dordrecht: 1983. 49–58

21 Müller E, Pfanz H. Ber. Dtsch. Chem. Ges. B 1941; 74: 1051

22a Kamada K, Ohta K, Kubo T, Shimizu A, Morita Y, Nakasuji K, Kishi R, Ohta S, Furukawa S.-i, Takahashi H, Nakano M. Angew. Chem. Int. Ed. 2007; 46: 3544
22b Sun Z, Ye Q, Chi C, Wu J. Chem. Soc. Rev. 2012; 41: 7857
22c Morita Y, Suzuki S, Sato K, Takui T. Nat. Chem. 2011; 3: 197
22d Nakano M, Champagne B. J. Phys. Chem. Lett. 2015; 6: 3236

23 Tan G, Wang X. Acc. Chem. Res. 2017; 50: 1997

24a Li G, Phan H, Herng TS, Gopalakrishna TY, Liu C, Zeng W, Ding J, Wu J. Angew. Chem. Int. Ed. 2017; 56: 5012
24b Liu J, Ma J, Zhang K, Ravat P, Machata P, Avdoshenko S, Hennersdorf F, Komber H, Pisula W, Weigand JJ, Popov AA, Berger R, Müllen K, Feng X. J. Am. Chem. Soc. 2017; 139: 7513

25 Wang J, Xu X, Phan H, Herng TS, Gopalakrishna TY, Li G, Ding J, Wu J. Angew. Chem. Int. Ed. 2017; 56: 14154
26 Kato K, Osuka A. Angew. Chem. Int. Ed. 2019; 58: 8978

27a Hopkinson MN, Richter C, Schedler M, Glorius F. Nature 2014; 510: 485
27b Rottschäfer D, Blomeyer S, Neumann B, Stammler H.-G, Ghadwal RS. Chem. Eur. J. 2018; 24: 380

28a Ghadwal RS, Azhakar R, Roesky HW. Acc. Chem. Res. 2013; 46: 444
28b Wang Y, Robinson GH. Inorg. Chem. 2014; 53: 11815
28c Wang Y, Robinson GH. Dalton Trans. 2012; 337
28d Yao S, Xiong Y, Driess M. Acc. Chem. Res. 2017; 50: 2026

29a Walton JC, Brahmi MM, Monot J, Fensterbank L, Malacria M, Curran DP, Lacote E. J. Am. Chem. Soc. 2011; 133: 10312
29b Ueng SH, Solovyev A, Yuan X, Geib SJ, Fensterbank L, Lacote E, Malacria M, Newcomb M, Walton JC, Curran DP. J. Am. Chem. Soc. 2009; 131: 11256
29c Walton JC, McFadden TR, Curran DP. J. Am. Chem. Soc. 2017; 139: 16514

30a Melaimi M, Jazzar R, Soleilhavoup M, Bertrand G. Angew. Chem. Int. Ed. 2017; 56: 10046
30b Soleilhavoup M, Bertrand G. Acc. Chem. Res. 2015; 48: 256
30c Martin CD, Soleilhavoup M, Bertrand G. Chem. Sci. 2013; 4: 3020
30d Mondal KC, Roy S, Roesky HW. Chem. Soc. Rev. 2016; 45: 1080
30e Hansmann MM, Melaimi M, Munz D, Bertrand G. J. Am. Chem. Soc. 2018; 140: 2546
30f Hansmann MM, Melaimi M, Bertrand G. J. Am. Chem. Soc. 2018; 140: 2206

31a Vummaleti SV. C, Nelson DJ, Poater A, Gomez-Suarez A, Cordes DB, Slawin AM. Z, Nolan SP, Cavallo L. Chem. Sci. 2015; 6: 1895
31b Mondal KC, Roy S, Maity B, Koley D, Roesky HW. Inorg. Chem. 2016; 55: 163

32 Viehe HG, Janousek Z, Merenyi R, Stella L. Acc. Chem. Res. 1985; 18: 148

33a Li Y, Chan Y.-C, Leong B.-X, Li Y, Richards E, Purushothaman I, De S, Parameswaran P, So C.-W. Angew. Chem. Int. Ed. 2017; 56: 7573
33b Gu L, Zheng Y, Haldón E, Goddard R, Bill E, Thiel W, Alcarazo M. Angew. Chem. Int. Ed. 2017; 56: 8790
33c Kundu S, Sinhababu S, Luebben AV, Mondal T, Koley D, Dittrich B, Roesky HW. J. Am. Chem. Soc. 2018; 140: 151
33d Kundu S, Samuel PP, Sinhababu S, Luebben AV, Dittrich B, Andrada DM, Frenking G, Stückl AC, Schwederski B, Paretzki A, Kaim W, Roesky HW. J. Am. Chem. Soc. 2017; 139: 11028
33e Braunschweig H, Krummenacher I, Légaré M.-A, Matler A, Radacki K, Ye Q. J. Am. Chem. Soc. 2017; 139: 1802

34a Mahoney JK, Martin D, Moore CE, Rheingold AL, Bertrand G. J. Am. Chem. Soc. 2013; 135: 18766
34b Hansmann MM, Melaimi M, Bertrand G. J. Am. Chem. Soc. 2017; 139: 15620
34c Styra S, Melaimi M, Moore CE, Rheingold AL, Augenstein T, Breher F, Bertrand G. Chem. Eur. J. 2015; 21: 8441
34d Mahoney JK, Martin D, Thomas F, Moore CE, Rheingold AL, Bertrand G. J. Am. Chem. Soc. 2015; 137: 7519

35a Eymann LY. M, Tskhovrebov AG, Sienkiewicz A, Bila JL, Živković I, Rønnow HM, Wodrich MD, Vannay L, Corminboeuf C, Pattison P, Solari E, Scopelliti R, Severin K. J. Am. Chem. Soc. 2016; 138: 15126
35b Back J, Park J, Kim Y, Kang H, Kim Y, Park MJ, Kim K, Lee E. J. Am. Chem. Soc. 2017; 139: 15300
35c Wang Y, Hickox HP, Xie Y, Wei P, Blair SA, Johnson MK, Schaefer HF, Robinson GH. J. Am. Chem. Soc. 2017; 139: 6859
35d Kim Y, Lee E. Chem. Eur. J. 2018; 24: 19110

36a Ghadwal RS, Lamm J.-H, Rottschäfer D, Schürmann CJ, Demeshko S. Dalton Trans. 2017; 7664
36b Ho NK. T, Neumann B, Stammler H.-G, Menezes da Silva VH, Watanabe DG, Braga AA. C, Ghadwal RS. Dalton Trans. 2017; 12027
36c Ho NK. T, Reichmann SO, Rottschäfer D, Herbst-Irmer R, Ghadwal RS. Catalysts 2017; 7: 262
36d Rottschäfer D, Schürmann CJ, Lamm J.-H, Paesch AN, Neumann B, Ghadwal RS. Organometallics 2016; 35: 3421
36e Ghadwal RS, Reichmann SO, Herbst-Irmer R. Chem. Eur. J. 2015; 21: 4247

37a Rottschäfer D, Ebeler F, Strothmann T, Neumann B, Stammler H.-G, Mix A, Ghadwal RS. Chem. Eur. J. 2018; 24: 3716
37b Rottschäfer D, Neumann B, Stammler H.-G, Ghadwal RS. Chem. Eur. J. 2017; 23: 9044
37c Rottschäfer D, Neumann B, Stammler H.-G, Kishi R, Nakano M, Ghadwal RS. Chem. Eur. J. 2019; 25: 3244
37d Sharma M, Blomeyer S, Neumann B, Stammler H.-G, Ghadwal RS. Chem. Eur. J. 2019; 25: 8249
37e Rottschäfer D, Sharma MK, Neumann B, Stammler H.-G, Andrada DM, Ghadwal RS. Chem. Eur. J. 2019; 25: 8127

38 Ghadwal RS. Dalton Trans. 2016; 16081
39 Gorodetsky B, Ramnial T, Branda NR, Clyburne JA. C. Chem. Commun. 2004; 1972
40 McKenzie I, Brodovitch J.-C, Percival PW, Ramnial T, Clyburne JA. C. J. Am. Chem. Soc. 2003; 125: 11565
41 Ghadwal RS, Rottschäfer D, Schürmann CJ. Z. Anorg. Allg. Chem. 2016; 642: 1236
42 Aldeco-Perez E, Rosenthal AJ, Donnadieu B, Parameswaran P, Frenking G, Bertrand G. Science 2009; 326: 556
43 Rottschäfer D, Neumann B, Stammler H.-G, van Gastel M, Andrada DM, Ghadwal RS. Angew. Chem. Int. Ed. 2018; 57: 4765
44 Giffin NA, Hendsbee AD, Masuda JD. Acta Crystallogr., Sect. E: Struct. Rep. Online 2010; 66: o2194
45 Rottschäfer D, Ho NK. T, Neumann B, Stammler H.-G, van Gastel M, Andrada DM, Ghadwal RS. Angew. Chem. Int. Ed. 2018; 57: 5838
46 Rottschäfer D, Neumann B, Stammler H.-G, Andrada DM, Ghadwal RS. Chem. Sci. 2018; 9: 4970
47 Rottschäfer D, Busch J, Neumann B, Stammler H.-G, van Gastel M, Kishi R, Nakano M, Ghadwal RS. Chem. Eur. J. 2018; 24: 16537
48 Barry BM, Soper RG, Hurmalainen J, Mansikkamaki A, Robertson KN, McClennan WL, Veinot AJ, Roemmele TL, Werner-Zwanziger U, Boere RT, Tuononen HM, Clyburne JA. C, Masuda JD. Angew. Chem. Int. Ed. 2018; 57: 749

49a Antoni PW, Bruckhoff T, Hansmann MM. J. Am. Chem. Soc. 2019; 141: 9701
49b Antoni PW, Hansmann MM. J. Am. Chem. Soc. 2018; 140: 14823

50 Ravat P, Baumgarten M. Phys. Chem. Chem. Phys. 2015; 17: 983
51 Kamada K, Ohta K, Shimizu A, Kubo T, Kishi R, Takahashi H, Botek E, Champagne B, Nakano M. J. Phys. Chem. Lett. 2010; 1: 937

52a Ito S, Nagami T, Nakano M. J. Photochem. Photobiol., C 2018; 34: 85
52b Nakano M. Chem. Rec. 2017; 17: 27
52c Minami T, Ito S, Nakano M. J. Phys. Chem. Lett. 2013; 4: 2133

53a Messelberger J, Grünwald A, Pinter P, Hansmann MM, Munz D. Chem. Sci. 2018; 9: 6107
53b Chen M, Bae YJ, Mauck CM, Mandal A, Young RM, Wasielewski MR. J. Am. Chem. Soc. 2018; 140: 9184
53c Casanova D. Chem. Rev. 2018; 118: 7164

54 Fukuda K, Suzuki Y, Matsui H, Nagami T, Kitagawa Y, Champagne B, Kamada K, Yamamoto Y, Nakano M. ChemPhysChem 2017; 18: 142