Doubly and Triply Charged Species Formed from Chlorobenzene

Subscriber access provided by UNIV OF SCIENCES PHILADELPHIA

Doubly and Triply Charged Species Formed from Chlorobenzene Reveal Unusual C-Cl Multiple Bonding Felipe Fantuzzi, Benedikt Rudek, Wania Wolff, and Marco Antonio Chaer Nascimento J. Am. Chem. Soc., Just Accepted Manuscript • DOI: 10.1021/jacs.7b12749 • Publication Date (Web): 12 Mar 2018 Downloaded from http://pubs.acs.org on March 12, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Journal of the American Chemical Society

Doubly and Triply Charged Species Formed from Chlorobenzene Reveal Unusual C-Cl Multiple Bonding Felipe Fantuzzi1, Benedikt Rudek2, Wania Wolff3,*, Marco A. C. Nascimento1,* 1

Instituto de Química, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ 21941-909, Brazil. 2 Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany. 3 Instituto de Física, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ 21941-972, Brazil.

* email: [email protected] ; [email protected] Phone: +55 21 3938.7563 Fax: +55 21 3938.7265

Abstract In free-radical halogenation of aromatics singly charged ions are usually formed as intermediates. These stable species can be easily observed by time-of-flight mass spectrometry (TOF-MS). Here we used electron and proton beams to ionize chlorobenzene (C6H5Cl) and investigate the ions stability by TOF-MS. Additionally to the singly charged parent ion and its fragments we find a significant yield of doubly and triply charged parent ions not previously reported. In order to characterize these species we used high-level theoretical methods based on Density Functional Theory (DFT), Coupled-Cluster (CC) and Generalized Valence Bond (GVB) to calculate the structure, relative stabilities, and bonding of these dications and trications. The most stable isomers exhibit unusual carbon-chlorine multiple bonding: a terminal C=Cl double bond in a formyl-like CHCl moiety (1,rC-Cl=1.621 Å) and a ketene-like C=C=Cl cumulated species (2,rC-Cl=1.542 Å). The calculations suggest that an excited state of 2 has a nitrile-like C≡Cl triple bond structure.

1 ACS Paragon Plus Environment

Journal of the American Chemical Society 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 20

Introduction Main-group chemistry has greatly advanced in the last decades. The development of experimental and theoretical techniques has led to the prediction, synthesis, isolation, and characterization of a variety of novel neutral and charged main-group compounds containing unusual multiple bonding. Room-temperature stable compounds of homo-atomic double and triple bonds, such as Sn=Sn1, Si=Si2, P=P3, Ge=Ge4, Pb=Pb5, B=B6,7 and B≡B8, illustrate some of the previously inaccessible bonding motifs that were recently achieved by different groups. Examples of multiple bonds involving mixed-main-group systems9 and between main-group atoms and transition metals, are now extensively found in the literature and appear to be quite common10,11. In this respect, carbon stands out among the main-group elements for forming multiple bonds with different families of the periodic table, including lanthanides12 and actinides13.

Several new classes of compounds containing multiple bonds between carbon and another main-group atom have been recently discovered, but so far limited to elements from maingroups 13 to 1611,14. Few examples of simple molecules with multiple bonds involving carbon and a halogen X atom (X = F, Cl) are the diatomic CX+ molecules. However, there is still no consensus about their bond orders15–17. Spectroscopic and computational studies18 on the nature of C-X bonds of halogen-stabilized carbocations found that the halogen atom becomes positively charged, partially establishing a double bond. In particular, Cremer and coworkers reported that a C-X double bond is fully developed for some Cl-substituted carbenium ions, such as CCl+ but not for the corresponding F-derivatives17. However, the multiple bond character for these molecules was established based on force constants and not on bond orders17,19, a criterion that might be questionable because these properties do not necessarily correlate20. Koch and Frenking21 examined the CF22+ and CF2+ molecules at the MP2 level of calculation and based on the Mulliken analysis of the wave functions attributed a double bond 2 ACS Paragon Plus Environment

Page 3 of 20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


character to the C-F bonds. Multiple bond character was also suggested for the halocarbenium species CX3+ (X= F, Cl, Br, I)22 which have experimentally observed at low temperatures matrices.

In order to generate novel Cl-stabilized carbocations as candidates for bearing multiple C-Cl bonds, we used electron and proton beams to ionize chlorobenzene (C6H5Cl) and investigated structural changes by means of time-of-flight mass spectroscopy (TOF-MS). Additionally to the singly charged parent ion and its fragments, we find a significant yield of doubly and triply charged parent ions stable enough to be detected by TOF-MS and which are the focus of this report. Computational calculations, based on Density Functional Theory (DFT), Coupled-Cluster (CC) and Generalized Valence Bond (GVB) methods23,24 show that the most stable isomers of the multiply charged species exhibit unusual C-Cl multiple bonding, with bond lengths (rC-Cl) that range from 1.621 Å to 1.542 Å.

Results and Discussion Production of multiply charged ions by proton and electron impact. Figure 1 shows the mass spectra of chlorobenzene (m=112 amu) for proton impact of 155 keV energy. The ranges depicted in (a), (b) and (c) cover the singly, doubly, and triply charged molecular parent ion with its position identified by a red line. The reflectron geometry of the time-of-flight spectrometer also allowed to resolve peaks at higher masses stemming from isotopes 37Cl and 13

C and lower masses created by a sequence of hydrogen-losses ((M-nH)+ in Fig.1(a) and (M-

nH)2+ in Fig.1(b)). While the isotopic distribution is independent from the charge state, the hydrogen-loss peaks become larger and change their relative intensity when the parent ion undergoes another ionization process: single hydrogen-loss (C6H4Cl+) is dominant for the singly charged parent ion, but at double-ionization the loss of a pair of hydrogen atoms (C6H3Cl2+) becomes most likely. The triply charged parent ion Fig.1(c) is partly overlapped with other less3 ACS Paragon Plus Environment


charged fragment-ions and only the stable trication

Page 4 of 20

C61H535Cl3+ at m/z = 37.3 can be

12

discriminated by eye in the time-of-flight spectra. The dications show narrower peak widths (FWHM) than the neighboring peaks of singly ionized fragments (see Fig. 1(c)) that gain kinetic energy in the fragmentation process. The narrow peaks of the doubly charged fragments, C6H52+ and C6H32+, in Fig. 1(c) indicate a neutral-ion fragmentation at low kinetic energy release (KER).

In Figure 2, the mass spectra for electron impact at different energies is shown. It is normalized to the fragment peak with m=51amu and the chlorobenzene dication at m/z=56 is indicated by a red line. The first ionization potential of chlorobenzene is 9.07 eV25 and thus we observe the parent ion already at our lowest electron energy of 10 eV. Based on an empirical equation for successive ionization energies, the double ionization energy is 2.8-fold and the triple ionization energy 5.04-fold larger than the single ionization energy26, so that the dication is expected at energies around 26 eV and the trication around 46 eV. In fact, the double ionization energy for chlorobenzene was experimentally found to be at 25.9 eV27. We scanned the energy in steps of 5 eV between 20 eV and 50 eV and find the onset of the dication to be at 30 eV (Fig. 2) and that for the trication at 40 eV of electron impact energy. A more detailed discussion of the underlying ionization processes at different energies will be provided in a separate report.

Molecular structures. Figure 3 shows the molecular structure of selected C6H5Cl dications. The most stable structure at the PBE0/cc-pVTZ(-f) level is the trans-cyclopropenyliumallylidenechloronium (1) system. The carbon-chlorine bond distance in 1 is 1.621 Å, which is significantly shorter than the ones in carbon tetrachloride (1.785 Å), neutral chlorobenzene (1.725 Å) and chlorotrinitromethane at the solid state (1.694 Å)28. Together with the GVB analysis, the results suggest that the system exhibits a terminal C=Cl double bond in a formyllike CHCl moiety (see Figure 4). This C-Cl bond is conjugated to an allylic double bond and to a 4 ACS Paragon Plus Environment

Page 5 of 20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


cyclopropenylium cation, which could account for the high stability of this structure in comparison to its isomers.

Isomer 2 is the chloronium-methylidene-cyclopentadienylium species, a planar C6H5Cl2+ system composed of a five-membered ring. The enthalpy value of 2 at 298 K (H298) relative to that of 1 is 6.6 kcal mol-1. Among the studied dication geometries, 2 has the smallest rC-Cl value, namely 1.542 Å. The GVB analysis (see Figure 5) shows that a ketene-like cumulene C=C=Cl+ moiety is found for the system. This particular short C-Cl bond length is not found for any other fivemembered ring species (isomer 3), which could be described as the chloronium-methylenecyclopentenylium system. In this case, the rC-Cl value is 1.609 Å which suggests a C-Cl double bond leading to the cyclic ketone-like character of 3. The H298 value of 3 is only 1.4 kcal mol-1 higher than 1, indicating that high-level calculations are required to resolve the most stable isomer.

Isomer 4 is a chlorine-substituted variant of the pentagonal pyramidal benzene dication, which contains a hexacoordinate carbon. In the C6H62+ molecule, a donor-acceptor bond is formed from the π cloud of a six-electron C5H5- moiety to an empty orbital of a CH3+ cap group29. Structure 4 presents a chlorine atom as substituent on the pentagonal ring base. Its H298 value lies 7.8 kcal mol-1 above 1. An isomer with a chlorine atom located on the cap group was also found. However, it corresponds to a high energy isomer and will not be discussed in this work.

The remaining isomers 5 (H298 = 8.2 kcal mol-1) and 6 (H298 = 9.9 kcal mol-1) are cyclic, containing six- and four-membered rings, respectively. Based on the C-Cl internuclear distance (rC-Cl = 1.617 Å for 5) as an indicator of the bond order, geometry 5 corresponds to the planar p-chloronium-cyclohexadienylium system. In contrast, the four-membered ring of 6 is



Page 6 of 20

puckered. The presence of this non-planar ring structure is associated to the formation of a cyclobutadiene dication moiety, which is bent30.

The adequacy of the DFT results were verified by comparing the H298 results with the ones obtained by high-level CCSD(T) calculations with the triple-zeta cc-pVTZ basis set. No significant changes were observed in the results obtained by both methods, apart from a higher stabilization of the six-membered ring isomer 5 in comparison to structures 2 and 4. The H298 with respect to 1 at the CCSD(T)/cc-pVTZ//PBE0/cc-pVTZ(-f) level are, as follows: 2 (7.4 kcal mol-1), 3 (0.8 kcal mol-1), 4 (11.7 kcal mol-1), 5 (5.8 kcal mol-1), 6 (11.8 kcal mol-1).

Several structural features of the doubly charged C6H5Cl species are also present among the triply charged species. The global minimum of C6H5Cl3+ at the PBE0/cc-pVTZ(-f) level resembles the most stable C6H5Cl2+ isomer, 1. Similarly to this dication, the C-Cl bond length of the trication (1.606 Å) suggests a double bond and a CHCl moiety analogous to the formyl group. Structures related to 2 (H298 = 7.2 kcal mol-1) and 6 (H298 = 2.6 kcal mol-1) are also found among the most stable C6H5Cl3+ isomers.

The triplet states manifold has been also investigated but only three among all the structures considered presented enthalpy values less than 20 kcal mol-1 relative to the global minimum 1 at 298 K (8.9 kcal mol-1, 11.7 kcal mol-1 and 16.4 kcal mol-1, respectively). This finding contrasts with the results of the hexa-substituted perchlorobenzene dication, C6Cl62+, which has a triplet six-membered ring ground state as suggested by electron paramagnetic resonance (EPR) experiments31. Further calculations are required to investigate which are the electronic factors that favor the triplet structure (or hinder the singlet analogous of 1) in the hexachlorobenzene dicationic species, and how structure 1 responds to the increase in the number of chlorine


Page 7 of 20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


atoms. The triplet C6H5Cl2+ structures can be found in the Supporting Information and will be no further discussed in this paper.

Bonding analysis. Figure 4 shows selected GVB orbitals of the most stable C6H5Cl2+ system 1. The two p-like orbitals are involved the 3-center-2-electron (3c-2e) bond in the cyclopropenyl moiety, as evidenced in Fig.4(a). This aromatic ring is conjugated to the C-C and C-Cl π bonds, whose GVB p-like orbitals are respectively shown in Figs.4(b) and 4(d). On the other hand, the C-Cl σ bond is formed by the two underlying lobe orbitals, shown in Fig.4(c). In the p-like orbitals of the C-Cl π bond (Fig.4(d)), the second orbital is centered on the chlorine atom, and the first one centered on the carbon atom, but highly polarized to the chlorine cation due to the large difference in polarizability between these atoms. Similar profiles are also observed for GVB orbitals in other polar bonds32. This finding indicates that the most stable C6H5Cl2+ isomer contains carbon-chlorine double bonding in a full conjugated system.

Figure 5 shows the GVB orbitals of the most stable five-membered ring isomer, 2. The two plike orbitals take part in the C-C π bond, as evidenced in Fig.5(a). This double bond is cumulated to the C-Cl π bond, whose orbitals are shown in Fig.5(c). Finally, the lobe orbitals that are involved in the C-Cl σ bond are shown in Figure Fig.5(b). To the best of our knowledge, this is the first example of a molecule containing a ketene-like C=C=Cl bonding motif and, according to the present calculations, the synthesis of such unusual species could be achieved.

The GVB calculations also revealed that a carbon-chlorine triple bond could be obtained for a singlet excited state of isomer 2. Selected GVB orbitals of this state are shown in Figure 6. The results suggest that the C-Cl bonding motif in 5 is analogous to the CN triple bond of a nitrile, but with a doubly charged chlorine atom. The energy difference between the ground state and the triply bonded excited state is ~ 6.6 eV. This is the first case in which a chlorine atom is 7 ACS Paragon Plus Environment


Page 8 of 20

involved in a triple bond. However, modifications in the molecular structure of such species are still necessary to force the system to preferentially link the chlorine atom to a carbon skeleton in a triple bond arrangement, instead of a ketene-like motif.

Conclusions The present work is a joint theoretical and experimental investigation on the molecular structure and formation of doubly and triply charged species generated from chlorobenzene. The TOF-MS experiments revealed the existence of doubly and triply charged ions not previously reported. Based on DFT, CC and GVB calculations, the most stable structures of such halogen-containing multiply charged species show a variety of new and unusual C-Cl multiple bonds in different molecular environments - isolated, conjugated, and cumulated. We believe that this work brings significant new contributions to the chemistry of main group 17 elements, and the authors hope that the results presented herein will stimulate and encourage experimentalists to look for ways of synthesizing these novel chlorine-containing species with unusual bonding pattern.

Methods Proton and Electron Experiments. For the electron and proton induced ionization studies, an electron gun and a low-energy proton accelerator were used with a high-resolution time-offlight spectrometer at the Physikalisch-TechnischeBundesanstalt (PTB). With a single-ended electrostatic acceleration stage, a maximum proton-energy of 155 keV was reached. The beam was pulsed at 50 kHz repetition rate and 1.1 ms pulse length. A set of three deflectors and three quadrupoles were used to steer and focus the proton-beam into the experimental chamber (see reference 33 for more details of the beam line). The parameters were optimized 8 ACS Paragon Plus Environment

Page 9 of 20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


for maximum current and smallest focus size, monitored by a movable Faraday cup and a YAG(Ce) scintillating screen, respectively. At 155 keV, typical currents for the pulsed proton beam were 350 pC with a beam diameter of about 1 mm. For electron impact measurements, we used a Kimball ELG-2 electron gun with an energy range of 1 eV to 2 keV. The Wehnelt aperture in the gun was capacitively pulsed to provide electron bunches of 100 ns width at 50 kHz repetition rate. In this mode, an electron current of 10 nA was achieved. The two extraction electrodes of a compact reflectron time-of-flight mass-spectrometer by Kore Technology were enclosed with the gas cell. Two 4 mm wide apertures were added for beam entry and exit. A 1 µs long voltage pulse of -350 V was applied to the isolated extraction electrode to start the time-of-flight recording. The delay between the extraction pulse and the pulsed proton or electron beam was set as short as possible not to lose fast fragments but long enough not to deflect the beam before its exit and monitoring by the Faraday cup. The detector gain was adjusted for highest efficiency for large masses. The ion yield was corrected for beam current and gas density fluctuations.

Theory. From one hundred and five different initial structures, geometry optimizations and frequency calculations of doubly and triply charged C6H5Cl species at the PBE0/cc-pVTZ(-f) level were performed. For the doubly charged species singlet and triplet states were investigated, while for the triply charged system only doublet states were considered. Only singlet and triplet structures are shown in this work. The initial structures were built by varying the presence of rings (open-chain or cyclic), the number of atoms in the ring (from three to seven), the type of chain (linear or branched), and the position of the hydrogen and chlorine atoms relative to the carbon skeleton. Hessian calculations were performed for the optimized geometries in order to obtain the respective zero point energies and to characterize the nature of the stationary points. The vibration frequencies of each optimized geometry were computed at the same level of calculation and verified to be real (see Supporting Information). 9 ACS Paragon Plus Environment


Page 10 of 20

The validity of the DFT energy results were checked by the use of high-level CCSD(T)/cc-pVTZ single-point calculations. Finally, two optimized doubly charged isomers (1 and 2) were selected to be studied through GVB calculations, in order to obtain information about their bonding profiles. The GVB ansatz provides a set of interpretable, univocally determined, monoelectronic and atomic-like self-consistently optimized orbitals, enabling the characterization of the chemical structure of a molecular system34.The DFT calculations were performed with the Jaguar 7.935 program. The CCSD(T) energies were obtained using GAMESS36 and the GVB calculations were performed withVB200037.

Acknowledgements. The authors would like to thank CNPq, FAPERJ, and CAPES for the financial support.

Competing Interests. The authors declare that they have no competing financial interests.

Supporting Information Available: Energy, structure and vibrational frequencies of C6H5Cl2+ and C6H5Cl3+ isomers. This material is available free of charge via the Internet at http://pubs.acs.org/.

References (1)

Goldberg, D. E.; Harris, D. H.; Lappert, M. F.; Thomas, K. M. J. Chem. Soc. Chem. Commun. 1976, 7, 261.

(2)

West, R.; Fink, M. J.; Michl, J. Science. 1981, 214, 1343.

(3)

Yoshifuji, M.; Shima, I.; Inamoto, N.; Hirotsu, K.; Higuchi, T. J. Am. Chem. Soc. 1981, 103, 4587.

(4)

Snow, J. T.; Murakami, S.; Masamune, S.; Williams, D. J. Tetrahedron Lett. 1984, 25, 4191. 10 ACS Paragon Plus Environment

Page 11 of 20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(5)

Klinkhammer, K. W.; Fässler, T. F.; Grützmacher, H. Angew. Chemie Int. Ed. 1998, 37, 124.

(6)

Wang, Y.; Quillian, B.; Wei, P.; Wannere, C. S.; Xie, Y.; King, R. B.; Schaefer, H. F.; Schleyer, P. V. R.; Robinson, G. H. J. Am. Chem. Soc. 2007, 129, 12412.

(7)

Fantuzzi, F.; Chaer Nascimento, M. A. Chem. - A Eur. J. 2015, 21, 7814.

(8)

Braunschweig, H.; Dewhurst, R. D.; Hammond, K.; Mies, J.; Radacki, K.; Vargas, A. Science. 2012, 336, 1420.

(9)

Duchamp, J. C.; Pakulski, M.; Cowley, A. H.; Zilm, K. W. J. Am. Chem. Soc. 1990, 112, 6803.

(10)

Schrock, R. R. J. Chem. Soc. Dalt. Trans. 2001, 18, 2541.

(11)

Fischer, R. C.; Power, P. P. Chem. Rev. 2010, 110, 3877.

(12)

Gregson, M.; Lu, E.; McMaster, J.; Lewis, W.; Blake, A. J.; Liddle, S. T. Angew. Chemie Int. Ed. 2013, 52, 13016.

(13)

Cantat, T.; Arliguie, T.; Noël, A.; Thuéry, P.; Ephritikhine, M.; Floch, P. Le; Mézailles, N. J. Am. Chem. Soc. 2009, 131, 963.

(14)

Frenking, G.; Tonner, R.; Klein, S.; Takagi, N.; Shimizu, T.; Krapp, A.; Pandey, K. K.; Parameswaran, P. Chem. Soc. Rev. 2014, 43, 5106.

(15)

Pyykkö, P.; Riedel, S.; Patzschke, M. Chem. - A Eur. J. 2005, 11, 3511.

(16)

Pyykkö, P.; Atsumi, M. Chem. - A Eur. J. 2009, 15, 12770.

(17)

Kalescky, R.; Kraka, E.; Cremer, D. Int. J. Quantum Chem. 2014, 114, 1060.

(18)

Oomens, J.; Morton, T. H. Int. J. Mass Spectrom. 2011, 308, 232.

(19)

Kalescky, R.; Zou, W.; Kraka, E.; Cremer, D. J. Phys. Chem. A 2014, 118, 1948.

(20)

Kaupp, M.; Danovich, D.; Shaik, S. Coord. Chem. Rev. 2017, 344, 355.

(21)

Koch, W.; Frenking, G. Chem. Phys. Lett. 1985, 114, 178.

(22)

Frenking, G.; Fau, S.; Marchand, C. M.; Grützmacher, H. J. Am. Chem. Soc. 1997, 119, 6648. 11 ACS Paragon Plus Environment


(23)

Goddard, W. A. Phys. Rev. 1967, 157, 73.

(24)

Goddard, W. Phys. Rev. 1967, 157, 81.

(25)

Ruscic, B.; Klasinc, L.; Wolf, A.; Knop, J. V. J. Phys. Chem. 1981, 85, 1486.

(26)

Kingston, R. G.; Guilhaus, M.; Brenton, A. G.; Beynon, J. H. Org. Mass Spectrom. 1985,

Page 12 of 20

20, 406. (27)

Harris, F. M.; Jackson, P. J.; Rontree, J. A.; Griffiths, W. J. Org. Mass Spectrom. 1992, 27, 261.

(28)

Göbel, M.; Tchitchanov, B. H.; Murray, J. S.; Politzer, P.; Klapötke, T. M. Nature Chem. 2009, 1, 229.

(29)

Fantuzzi, F.; de Sousa, D. W. O.; Chaer Nascimento, M. A. Comput. Theor. Chem. 2017, 1116, 225.

(30)

Krogh-Jespersen, K.; Schleyer, P. von R.; Pople, J. A.; Cremer, D. J. Am. Chem. Soc. 1978, 100, 4301.

(31)

Wasserman, E.; Hutton, R. S.; Kuck, V. J.; Chandross, E. A. J. Am. Chem. Soc. 1974, 96, 1965.

(32)

Fantuzzi, F.; Nascimento, M. A. C. J. Chem. Theory Comput. 2014, 10, 2322.

(33)

Rudek, B.; Bennett, D.; Bug, M. U.; Wang, M.; Baek, W. Y.; Buhr, T.; Hilgers, G.; Champion, C.; Rabus, H. J. Chem. Phys. 2016, 145, 104301.

(34)

Fantuzzi, F.; de Sousa, D. W. O.; Nascimento, M. A. C. ChemistrySelect 2017, 2, 604.

(35)

Bochevarov, A. D.; Harder, E.; Hughes, T. F.; Greenwood, J. R.; Braden, D. A.; Philipp, D. M.; Rinaldo, D.; Halls, M. D.; Zhang, J.; Friesner, R. A. Int. J. Quantum Chem. 2013, 113, 2110.

(36)

Schmidt, M. W.; Baldridge, K. K.; Boatz, J. A.; Elbert, S. T.; Gordon, M. S.; Jensen, J. H.; Koseki, S.; Matsunaga, N.; Nguyen, K. A.; Su, S.; Windus, T. L.; Dupuis, M.; Montgomery, J. A. J. Comput. Chem. 1993, 14, 1347.

(37)

Li, J.; McWeeny, R. Int. J. Quantum Chem. 2002, 89, 208. 12 ACS Paragon Plus Environment

Page 13 of 20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 1. Mass spectra of chlorobenzene for proton impact at 155 keV energy in mass/charge ranges of (a) singly charged, (b) doubly charged, and (c) triply charged molecular parent ion (position marked with red line). 13 ACS Paragon Plus Environment


Page 14 of 20

Figure 2. Mass spectra of chlorobenzene for electron impact from 25 eV to 2000 eV energy in mass/charge ranges of the dication. The doubly charged parent ion position at m/z=56 is marked with red line.


Page 15 of 20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 3. Geometry of the most stable C6H5Cl2+ species at the PBE0/cc-pVTZ(-f) level. The isomerization enthalpies at 298 K (H298) with respect to 1 are, as follows: 2 (6.6 kcal mol-1), 3 (1.4 kcal mol-1), 4 (7.8 kcal mol-1), 5 (8.2 kcal mol-1), 6 (9.9 kcal mol-1). The rC-Cl values are, as follows: 1 (1.621 Å), 2 (1.542 Å), 3 (1.609 Å), 4 (1.628 Å), 5 (1.617 Å), 6 (1.626 Å). The most stable geometry of the trication C6H5Cl3+ has a binding length rC-Cl of 1.606 Å, and is structurally similar to the dication in geometry 1.



Page 16 of 20

Figure 4. Selected GVB orbitals of the trans-cyclopropenylium-allylidenechloronium (1) system, depicting the conjugated C-Cl π bond.


Page 17 of 20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 5. Selected GVB orbitals of the ground state of the chloronium-methylidenecyclopentadienylium (2) system, depicting the ketene-like C=C=Cl bonding motif. See text for details.



Page 18 of 20

Figure 6. Selected GVB orbitals of the C-Cl triply bonded excited state of the chloroniummethylidene-cyclopentadienylium (2) system. See text for details.


Page 19 of 20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


For Table of Contents Only


Journal of the American Chemical Society 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46

ACS Paragon Plus Environment

Page 20 of 20

Doubly and Triply Charged Species Formed from Chlorobenzene

Recommend Documents