In Quest of a Superhalogen Supported Covalent Bond Involving a

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In Quest of a Superhalogen Supported Covalent Bond involving a Noble Gas Atom Debdutta Chakraborty, and Pratim Kumar Chattaraj J. Phys. Chem. A, Just Accepted Manuscript • Publication Date (Web): 02 Mar 2015 Downloaded from http://pubs.acs.org on March 4, 2015

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The Journal of Physical Chemistry

MS No.: jp-2014-13018v.R1 In Quest of a Superhalogen Supported Covalent Bond involving a Noble Gas Atom Debdutta Chakraborty and Pratim Kumar Chattaraj* Department of Chemistry and Centre for Theoretical Studies Indian Institute of Technology, Kharagpur 721302, West Bengal, India *

To whom correspondence should be addressed. E-mail: [email protected], Telephone: +91 3222 283304, Fax: 91-3222-255303.

Abstract The possibility of having neutral Xe bound compounds mediated by some representative transition metal fluorides of general formula MX3 (where M=Ru, Os, Rh, Ir, Pd, Pt, Ag, Au and X=F) has been investigated through density functional theory based calculations. Nature of interaction between MX3 and Xe moieties has been characterized through detailed electron density, charge density and bond energy decomposition analyses. The feasibility of having compounds of general formula XeMX3 at 298K has been predicted through thermodynamic considerations. The nature of interaction in between Xe and M atoms is partly covalent in nature and the orbital interaction is the dominant contributor towards these interactions as suggested by energy decomposition analysis.

Keywords Density functional theory; Superhalogen; Xenon compound; Covalent interaction; Orbital interaction; Transition metal fluoride.

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1. Introduction In terms of chemical reactivity, the group 18 elements of the periodic table remain an enigma to a large extent. Owing to the closed shell electronic configuration, group 18 elements show a natural tendency to maintain their inherent electronic distribution. Thus, in general, they show a remarkable apathy towards forming stable chemical compounds as compared to their counterparts belonging to other groups in the periodic table. Finding appropriate physical or chemical conditions which may lead to stable noble gas (Ng) compounds remained an illusive dream until 1962 when Bartlett successfully synthesized 1, 2

the first reported Ng-compound. Earlier to this development, Pauling

3

predicted

theoretically, the viability of having Ng-compounds based on the high polarizability and low ionization potential of heavier Ng analogues. These early successes were further vindicated by the identification of Ng-containing compounds 4-7 within a short time span. Räsänen and co-workers

8-15

made important contributions by synthesizing series of

compounds of general formula H(Ng)Y (Ng=Ar, Kr, Xe; Y=electron-withdrawing group). Ng hydrides were characterized by Feldman and co-workers

16-17

and all these

developments18 ushered in a new branch of chemistry. The theoretical investigations of different Ng-containing compounds by different research groups 19-52 have revealed many important information regarding the reactivity of Ng-compounds. Theoretically predicted Ng-compounds were synthesized on many instances. From a theoretical perspective, noble gas chemistry poses a few unique challenges. Apart from the obvious goal to predict stable Ng-containing compounds at physically realizable temperatures, identifying the nature of interactions and bonding in between Ng atoms and different substituent groups is a problem worth considering. Novel bonding and interaction patterns pertaining to Ng-compounds can potentially enrich the current understanding of chemical bonding. As an example, weak non-covalent type of interactions that prevails in many Ng-containing compounds, are not restricted to noble gas chemistry alone but are important in other branches of chemistry as well. Pivotal concept to the problem of finding an appropriate ligand which can potentially form an Ng compound, is the electron affinity (EA) of the concerned ligand. Ligands with sufficiently high EA can remove one electron from the outer shell of an Ng atom 2 ACS Paragon Plus Environment

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thus initiating the process of bonding type interaction. An exciting choice of ligand in this regard is the superhalogen

53-61

class of moieties. Originally pioneered by Boldyrev and

co-workers, it has been shown over the years that it is possible to realize a class of (primarily) metal clusters, which have EA far greater than the most electronegative elements of the periodic table. The most abundant class of superhalogens has the general formula MXn+1 where M is a metal atom and X constitutes a halogen atom (n= maximal valence of the central metal atom). With this background in mind, it is thus reasonable to explore whether a suitable superhalogen can form neutral Ng-compound or not. In this work we seek to investigate the possibility of having neutral Xe compounds mediated by some representative neutral transition metal halides of general formula MX3 (where M= Ru, Os, Rh, Ir, Pd, Pt, Ag, Au and X=F)

62-69

. It is a well known fact that due to their

unique electronic distribution, transition metals can exist in different valence states and can form metal-halide compounds of different compositions. Thus it is possible to alter the charge distribution on the central metal atom to a varied extent. As a result transition metal halides present an ideal opportunity to explore the reactivity patterns of a Xe atom. The choice of the metal halides is dictated by their ease of experimental availability as well as to present a systematic study on the reactivity of Xe atom with transition metal halides which could possibly lead to a generalization. In order to address these issues, we have performed density functional theory (DFT) based calculations aided by detailed electron density analysis as provided by an Atoms-in a-Molecule (AIM) approach. The observed bonding type interactions have been further explored by carrying out a bond energy decomposition analysis.

2. Computational Details All the structures under consideration have been modelled with graphical software GaussView 5.0.8

70

. The neutral MX3 compounds as well as their Xe-bound analogues

have been optimized at dispersion corrected hybrid DFT level of theory (wb97xd/Def2TZVP) using the Gaussian 09 program package 71. Given the nature of the problem where 3 ACS Paragon Plus Environment


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dispersion effect should play an important role, it seems necessary to employ dispersion corrected hybrid DFT level of theory. It is a well known fact that advanced level of DFT theory comprising state-of-the-art functionals such as wb97xd produces excellent results for different physicochemical problems and the results are often comparable to that obtained from other state-of-the-art ab initio calculations. No symmetry constraint has been added during optimization calculation in order to locate the preferred geometry of the Xe-bound moiety. Given the expected role of relativistic effects in governing the electronic properties of the concerned systems, effective core polarization (ECP) potential has been used for all the metal atoms as well as the Xe atom in the present study. For all the metal atoms as well as Xe atom, Def2-TZVP basis set have been used. All structures reported herein correspond to minima on the potential energy surface (NIMAG=0). In all the studied systems the lowest possible spin state was chosen out of many possible spin multiplicities. Natural population analysis (NPA) has been done in order to understand the respective charge concentration/depletion on each atomic site. Wiberg bond index (WBI) has been calculated to determine the bond order of the aforementioned systems. In order to characterize the nature of interaction in between Xe atom and various metal centers, electron density analysis decomposition analysis (EDA)

73, 74

72

augmented by bond energy

have been performed with the help of Multiwfn

75

and ADF softwares respectively. Relativistic effects have been taken into account while calculating the EDA data by incorporating zero-order regular approximation (ZORA). Dissociation energy (D0), which serves as a good indicator to check the thermodynamic stability of the studied systems has also been calculated.

3. Results and Discussion Firstly, let us consider the optimized geometries of the studied metal fluorides in their pristine form (Figures 1, 2) as well as Xe-bound states (Figures 3, 4). The point groups (PG) as well as the electronic states of the concerned species have been depicted therein. In the cases of Rh and Ir complexes, significant loss of molecular symmetry is being 4 ACS Paragon Plus Environment

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observed upon insertion of Xe as compared to their corresponding metal fluoride structures as their point groups transform C2V to C1. For Ru, Pt, Ag and Au, however, the Xe-bound moiety retains the C2V PG just like their parent metal clusters whereas Os and Pd retain the C1 PG. The observed Gibbs free energy change (∆G) and reaction enthalpy change ( ∆H ) associated with the formation of neutral Xe-bound moiety from their neutral parent species as well as their respective zero point energy (ZPE) corrected dissociation energy (D0) into individual neutral fragments at 298K have been presented in Table

1.

All

the

observed

Xe-bound

compound

formation

processes

are

thermodynamically stable as evidenced from the negative values of ∆G except for the cases of Ru and Ir. Table 1 also reveals that all the observed Xe-bound compound formation processes are exothermic in nature. The positive values of D0 provide further important information regarding the stability of the XeMF3 species. Generally, it is expected that going from a lighter analogue to a higher one among the transition metal complexes, the thermodynamic parameters pertaining to bonding type situations should improve along a favorable direction because of the nature of the orbitals that get involved in interaction with Xe atom. This trend gets vindicated if we consider the cases of Os, Pd, Pt, Ag and Au. However, Rh and Ir present somewhat anomalous result. Rh, despite being among the lightest among the metal atoms considered in the present study, produces the best result among all the cases from a thermodynamic point of view. The unfavorable ∆G value associated with the formation of XeRuF3 and XeIrF3 is clearly dominated by creation of a large entropic barrier. Upon Xe insertion, all the moieties lose some degree of freedom as compared to their pristine form thereby augmenting the unfavourable T ∆S term. The low values of ∆H in the cases of XeRuF3 and XeIrF3 clearly can not compensate for this unlike its counterparts and as a result makes Xe insertion onto RuF3 and IrF3 a thermodynamically unfavorable process. The HOMOLUMO gap is a proven stability indicator for a large class of atoms and molecules and it has been shown that it is related to global hardness

76-78

. We have computed the above

stated parameter (Table 1) for the bare metal cluster as well as the Xe-bound moieties in order to further investigate the respective stability of the systems under consideration. It is clear, that apart from the cases of Ru and Ir all other systems show a marked increase in the values of the said indicator upon insertion of Xe as compared to their bare metal 5 ACS Paragon Plus Environment


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fluoride structures. Just like the thermochemistry analysis mentioned above, Rh again gives the best possible result thus establishing important information regarding the stability of the concerned system. The M-Xe bond distances generally decrease while moving down along a series and all the observed bond distances have been tabulated in Table 1. In order to ascertain the nature of charge accumulated/depleted on each atomic site, we now consider the calculated NPA values (Table 1). Given that the central metal atoms are bound to highly electronegative F atoms, it is obvious that they attain some positive charge on them. This positive charge should play an important role in polarizing the Xe atoms and we can expect that as the charge generated on the metal centers gets higher, the metal fluoride system can interact with the Xe atom more prominently. Thus the fate of the present study rests largely on the ability of F atoms in polarizing the central metal atoms. It should be noted that the F atoms in the Xe-bound species are asymmetrically negatively charged. For the cases of Rh and Ir moieties, the F atom belonging to the MXe plane attains slightly higher negative charge (-0.48 and -0.51 respectively for XeRhF3 and XeIrF3) than the other two F atoms (-0.45 and -0.45 respectively for XeRhF3 and XeIrF3) which stay above and below the molecular plane respectively. Similar trend is observed for XeAgF3 and XeAuF3 where the accumulated negative charge on F atoms are given as -0.44, -0.54; -0.48, -0.58 for Ag and Au species respectively. In the case of XePtF3, however, the polarization of the F atoms (-0.49 and -0.50) is less asymmetric given that all the F atoms are placed almost on the molecular plane and thus are able to interact with intervening Pt and Xe atoms to an almost equal extent. The net positive charge on the Xe atoms in all the reported structures confirms the fact that electron density shifts from Xe to the metal fluoride moiety. As we move towards heavier metals, the extent of charge depletion on Xe increases which is dictated clearly by the higher charge generation on the central metal atoms. XeIrF3 again presents a slight deviation from the expected trend as the extent of positive charge on Ir is slightly lower than its lighter congener Rh. The fact that Xe in XeIrF3 still attains higher positive charge than that in XeRhF3 clearly demonstrates that F atoms also play important roles in polarizing the Xe atoms. In fact, the Xe atoms see an overall negative electrostatic field in the form of the overall metal fluoride moiety and that average field is responsible for polarizing 6 ACS Paragon Plus Environment

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the Xe atoms. The observed M-Xe bond distances (Table 1) are important indicators in order to further explain the nature of interaction between the concerned moieties. It clearly demonstrates that there could be a correlation between the observed NPA charges on metal fluorides and the observed M-Xe bond distances and it is clear that higher the net negative charge on the metal fluoride systems lower would be the M-Xe bond distance. Let us now consider the calculated WBI values (Table 1) on the Xe atoms in the inserted state. The total WBI as well as the WBI values for individual M-Xe bonds for the Xe atoms have been tabulated therein. Clearly, the lower values of WBI on Xe atoms in the lighter metal fluorides along a series indicate that the nature of interaction between M and Xe could be of non-covalent or of partially covalent type in nature. As we start considering the heavier analogues, however, WBI value increases significantly on Xe thereby illustrating the onset of some degree of covalent interaction between the metal fluorides and Xe. In order to understand the nature of interaction between Xe and MF3 species further, the orbitals that take part in bonding type interaction need a closer look. That could possibly provide a clue to various observations noted thus far and most importantly the anomalous behavior of Ir could be understood better through this. The valence shell orbital population for Xe as well as that for the central metal atoms have been tabulated in Table 2. The principle orbital involved in interaction for Xe in all the cases is 5p with some contribution from 5s. Clearly, from an energetic point of view, those M atoms should be in an advantageous position whose valence orbitals are comparable in energy to 5s and 5p orbitals of Xe. The excellent thermodynamic properties noted earlier for Rh complex can thus be explained from the kind of valence orbitals that get involved in interaction which clearly acts as a key driving force. Thus the compound formation process for Rh is the most favored one among all the cases considered. In all other cases M atoms, in order to participate in bonding type interaction, have to invoke orbitals which are somewhat not comparable in energy in comparison to valence orbitals of Xe and thus makes the formation of Xe-bound species thermodynamically less favorable than that with Rh. It becomes clear that in all the cases significant electron density gets drifted from Xe atom towards the metal fluoride moiety. It is worthwhile at this point to consider the valence shell electronic configuration of Ir 7 ACS Paragon Plus Environment


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and Rh in IrF3 and RhF3 respectively and they are as follow: Ir= 6s( 0.57)5d( 7.04)6p( 0.12)7s( 0.01)

5f(0.01)6d(

0.01)

and Rh=

5s(

0.21)

4d(

7.33)

5p(

0.04)

4f(

0.01)

6p(

0.11)

. Considering the

corresponding electronic configuration of Xe bound states, it becomes clear that Rh can accumulate a significant amount of electron density on 5s and 5p orbitals while the same in case of Ir is marginal and only confined to 6p orbital. Given the inherent tendency of any atom is to attain most stable electronic configuration by virtue of taking part in interaction with other atoms, Xe probably does not offer a suitable candidate for Ir to do so and thus the complexation process becomes thermodynamically unfavorable. With this information in mind, it is rather reasonable to assume that if we can incorporate more positive charge on Rh, Xe-bound metal fluoride could give even better result. We give particular emphasis on Rh mediated Xe-complexes as apart from their excellent thermodynamic properties, Rh-Xe interaction patterns have probably not been discussed in detail in the literature before. We have thus computed the optimized geometry of XeRhF4 (Figure 2). The corresponding electronic configuration in both Rh and Xe clearly shows a much improved orbital interaction. The NPA charges on Rh and Xe as well as the WBI values are 1.27 and 0.60; 0.78 (on Xe) respectively. It is evident that significant covalent interaction persists by virtue of addition of an extra F atom onto the metal fluoride system and as a result the Rh-Xe bond distance is found to be 2.54 Ǻ which is significantly shorter than systems considered thus far in the present study. We have computed the corresponding behavior in the cases of Ru, Os and Ir tetra fluorides as well to compare the respective role being played by the addition of an extra F atom into the system. All the concerned results have been tabulated in Tables 1 and 2. Clearly, Ru produces remarkably improved result as far as Xe-Ru interaction is concerned. There seems to be very little change in Xe-M interaction in the case of Os with the addition of an extra F atom whereas Ir shows a marked apathy towards interaction with Xe. In order to further characterize the nature of interaction between the studied systems, we take help of AIM theory. The electron density descriptors at the M-Xe bond critical point (BCP) have been presented in Table 3. It is worthwhile at this point, to mention the well known electron density descriptors. The primary indicators are the electron density value (ρ(rc)) and the Laplacian of electron density (∇2ρ(rc)) at the BCP. Generally a high value of ρ(rc) and a negative value of ∇2ρ(rc) signify some degree of covalent interaction. 8 ACS Paragon Plus Environment

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However these two conditions are not sufficient if one considers heavy metal atoms and one needs to invoke other descriptors such as local electron energy density (H(rc)), ratio of local kinetic energy density (G(rc)) to local potential energy density (V(rc)), ratio of local kinetic energy density to the electron density at the BCP etc. to correctly characterize the nature of interaction

79-84

. Generally if ∇2ρ(rc) > 0 and H(rc) < 0, then

the observed interaction is of partly covalent type. On the other hand, if -G(rc)/V(rc) and G(rc)/ρ(rc) are greater than one then it indicates purely non covalent type of interaction

whereas if the value lies below one then some degree of covalent character may be stated. It could be clearly seen from the Table 3, in all cases considered in the present study the nature of interaction between Xe and central metal atom is of partially covalent type in nature. As we move towards heavier analogues of the transition metal fluorides, the degree of covalent character increases. Particularly noteworthy is the covalent interaction in the cases of XePtF3 and XeAuF3.

18, 51, 52

Remarkable improvement in the nature of

interaction is obtained when we consider XeRuF4 and XeRhF4 and it becomes clear that the net negative charge on the superhalogen moiety plays a key role in polarizing the Xe atom thereby enhancing the extent of interaction. The distribution of electron density around the Xe-M plane could be nicely characterized if we consider the contour diagrams of Laplacian of electron density (Figures 5, 6). We can clearly see a gradual distortion in the appearance of this scalar field as we go from lighter metals to heavier ones. There is clearly an extent of charge concentration centred around the M-Xe axis which gives vital information regarding the validation of the nature of interaction as noted earlier. The extent of deformation of the scalar field are the largest in the cases of XeRuF4 and XeRhF4 which further confirm the results obtained from earlier observations. Given the complexity associated with the characterization of the nature of interaction in the cases of Ng as well as heavy transition metal atoms, it is useful to track the problem from different perspectives to check whether all observations lead to similar trends so that a logical conclusion could be reached at. It is worthwhile, thus to consider the electron localization function (ELF). It is a proven index which characterizes covalent bonds, ionic interactions or lone pairs present in the molecule. Generally for a typical covalent bond there exists a maximum in between two atoms with ELF values in the vicinity of 01. As the ELF value increases, the nature of interaction transforms gradually into that of 9 ACS Paragon Plus Environment


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covalent type. The ELF for all the systems considered thus far, has been plotted in Figures 7 and 8 and it becomes apparent that the electron localization index increases significantly as we encounter the heavier metal atoms. For all the systems ELF values do indicate some extent of covalent interaction in between Xe and M while XeRuF4 and XeRhF4 again give the best result as far as covalent interaction is concerned. Thus all the above observations bear a nice correlation among them and it could be stated that Xe-M interactions have some extent of covalent characteristics. In order to further analyze the nature of Xe-M binding, we now consider the EDA data as presented in Table 4. The net interaction energy (∆Etotal) in between MF3 and Xe is negative in all cases considered here, thereby establishing the fact that the observed Xebound species are stable from an energetic point of view. The principle contributors are the electrostatic interaction (∆Eelest) and the orbital interaction (∆Eorb) in between the concerned fragments. The ∆Eorb is the major contributor in all the cases and the extent of contribution increases as we go to heavier metals. As expected, the Pauli repulsion (∆EPauli) is the main destabilizing factor as far as Xe- MF3 binding is concerned. It is useful to note the contribution from the dispersion energy (∆Edisp) towards total interaction energy as it gives a handful of information with regard to any non-covalent type of binding. Since the contribution from ∆Edisp is significantly lower than other attractive terms, we can state that the nature of interaction is certainly not of van der Walls type, rather it confirms to some extent of covalent nature. As we consider the heavier metal atoms, ∆Edisp contribution comes down to a certain extent thereby augmenting the earlier observations from AIM analysis that the nature of interaction shifts gradually towards covalent character. Remarkable interaction energies are obtained for XeRhF4 which further bolster our earlier observations. It is useful to note the peculiar behavior of XeIrF3 at this point. The ∆Etotal is clearly favorable for binding of Xe with IrF3 which poses a unique challenge. It clearly indicates that although the formation of Xe-bound species is not thermodynamically favorable as noted in Table 1, once formed the species is somewhat stable. The positive D0 value as presented in Table 1 also gives support to the above mentioned argument. XeRuF3 and XeIrF4 show a marked deviation from the trend noted above. One significant destabilizing factor that emerges in these two species apart from other factors is the positive values of orbital interaction term. One may 10 ACS Paragon Plus Environment

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note that the corresponding M-Xe distances for these two compounds and the enhanced distance in between the intervening Xe and M orbitals could play a role in explaining the observed results. Upon further decomposition of the orbital interaction terms into smaller fragments, we observe a marked increase in the kinetic energy term which plays an important role in destabilizing the chemical entity. Considering all the aforementioned analyses, we may infer that the metal fluorides act as a Lewis acid whereas Xe atom playing the role of a base. It is clear, that the key to finding covalent interaction among M and Xe centres is the ability of the ligand in polarizing the noble gas atom thereby initiating the bonding interaction process and the stronger the oxidising power of the Lewis acid concerned, better will be the covalent interaction. We note at this point that some of the metal fluorides considered in the present study may exist in polymeric form (solid state) at 298K temperature and as a result one need to bring the concerned metal fluoride into gaseous phase in order to achieve the goal of forming compounds with Xe atom as described in the present study. Such process of evaporating the solid could be achieved via some external energy source such as high intensity laser beam. After obtaining the gaseous metal-tri and tetra fluorides and taking sufficient precaution to prevent condensation of the gas into solid, the Xe atom could possibly form compounds with the concerned ligand at experimental conditions. Other chemical conditions which may potentially enable the observed theoretical study to materialize in actual experimental set up is to consider a low coordination number environment for the metal fluorides thereby facilitating the interaction with Xe. In this context it is worth mentioning the seminal work of Seppelt and co-workers who demonstrated18 the feasibility of having Xe-Au compounds in superacidic chemical conditions. It is quite possible to find other geometrical alignment of the studied systems pertaining to different point groups. We have seen that geometrical proximity as well as the respective orientation of the Xe and MF3/4 moieties plays a significant role in affecting the overall characteristics of the Xe-M bond. We also note that given the feasibility of obtaining different spin multiplicity for the central metal atoms, the Xe-M interactions should show a distinct behaviour under such conditions. All these points deserve further careful investigation.



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4. Conclusion Through DFT calculations, the possibility of having superhalogen mediated neutral Xe compounds has been explored in this work. It has been shown that compounds of the general formula XeMF3 (where M= Ru, Os, Rh, Ir, Pd, Pt, Ag, Au) could be realized at 298K as evidenced from detailed thermochemical analysis. The general trend for the trifluorides seems to indicate a gradual increase in the covalent character of the M-Xe bond as we go for heavier elements. Although the case of Ir poses a few difficult problems from a thermodynamic point of view, it has been shown through EDA analysis that it could have a possibility of being materialized. The nature of interaction between Xe and M atoms have been investigated through various perspectives such as AIM, EDA, WBI, NPA analyses and it could be stated that the nature of binding in between the XeMF3 species is of partially covalent nature. The heavier analogues of metals considered herein interact in more covalent manner with Xe than its lighter counterparts. The net accumulated charge on the metal fluoride also plays an important role in polarizing the Xe atom thereby initiating the process of binding. Thus we obtained excellent binding characteristics in the cases of XeRuF4 and XeRhF4. The orbital interaction between the Xe and M atoms play the principle role as far as binding is concerned. The nice correlation found among all the electron density, charge density, bond index, thermodynamic as well as stability indicators rationalizes our observations. Acknowledgements DC thanks CSIR, New Delhi for the financial assistance. PKC would like to thank DST, New Delhi for the J. C. Bose National Fellowship.

References [1] Bartlett, N. Xenon Hexafluoroplatinate (V) Xe+[PtF6]−.Proc. Chem. Soc. 1962, 218. [2] Graham, L.; Graudejus, O.; Jha, N. K.; Bartlett, N. Concerning the Nature of XePtF6. 12 ACS Paragon Plus Environment

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[78] Pan, S.; Solà, M.; Chattaraj, P. K. On the Validity of the Maximum Hardness Principle and the Minimum Electrophilicity Principle during Chemical Reactions. J. Phys. Chem. A 2013, 117, 1843-1852.

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wb97xd/Def2-TZVP level have been presented as all other systems have been reported at that level. In Table 1, the reported values are calculated at the MP2/ Def2-TZVP level. The XePdF3 compound, as calculated at B3LYP, wb97xd and MP2 levels of theory, follows the qualitative trend nicely in all the levels of theory.

Tables Table 1. Free energy change (∆G, kcal/mol) and reaction enthalpy ( ∆H ,kcal/mol) at 298K for the process: Xe + MF3 → XeMF3; ZPE corrected dissociation energy (D0, kcal/mol) for the dissociation process: XeMF3 → Xe + MF3; HOMO-LUMO Gap (eV) for bare MF3 cluster (Gap1) and XeMF3 moiety (Gap2); NPA charge (a.u.) on metal centres (QK(M)) and Xe (QK(Xe)); Total Wiberg bond Index (WBItot) for Xe atom in the bound state and the same for M-Xe bond (WBIMXe); Xe-M bond distance (RXe-M, Ǻ) calculated at wb97xd/Def2-TZVP level of theory85. Systems

∆G

∆H

D0

Gap1 Gap2 QK(M) QK(Xe) WBItot WBIMXe RXe-M

XeRuF3

2.1

-5.2

4.6

6.8

6.7

1.15

0.18

0.35

0.30

2.97

XeOsF3

-1.5

-9.5

8.9

2.5

2.9

1.20

0.18

0.36

0.31

2.95

XeRhF3

-16.2

-21.4

21.8

6.2

7.7

1.21

0.17

0.32

0.27

2.96

XeIrF3

3.5

-3.8

3.7

7.2

6.7

1.20

0.22

0.43

0.36

2.82



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Page 22 of 34

XePdF3

-5.8

-12.9

12.27 13.2

13.5

1.62

0.20

0.37

0.33

2.81

XePtF3

-7.1

-14.9

14.7

7.4

7.8

1.22

0.26

0.50

0.41

2.74

XeAgF3 -3.6

-10.9

10.8

7.4

7.7

1.26

0.25

0.46

0.36

2.79

XeAuF3 -9.1

-17.2

17.0

7.3

8.2

1.35

0.29

0.52

0.40

2.69

XeRuF4

-1.9

-11.1

10.5

6.4

6.9

1.27

0.49

0.79

0.73

2.62

XeOsF4

1.2

-5.1

4.5

7.6

6.2

1.64

0.17

0.35

0.30

2.94

XeRhF4

-2.8

-10.6

10.0

6.3

6.7

1.27

0.60

0.89

0.78

2.54

XeIrF4

6.3

-0.8

0.2

6.9

5.9

1.6

0.11

0.22

0.19

3.06

Table 2. The valence shell orbital populations of metal and Xe atoms in the Ng-bound clusters Systems

M

Xe

XeRuF3

5S( 0.39)4d( 6.20)5p( 0.24)4f( 0.01) ( 0.01) 5d

5S( 1.98)5p( 5.83)

XeOsF3

6S( 0.61)5d( 5.98)6p( 0.18)7S( 0.01) ( 0.02) ( 0.01) 5f 6d

5S( 1.97)5p( 5.84)5d( 0.01)

XeRhF3

5s( 0.26)4d( 7.25)5p( 0.27)5d( 0.01)

5s( 1.98)5p( 5.85)

XeIrF3

6s(0.52)5d(7.05)6p(0.21)5f(0.01)6d( 5s( 1.97)5p( 5.80)5d( 0.01) 0.01)


Page 23 of 34

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XePdF3

5S( 0.29)4d( 7.80)5p( 0.27)4f( 0.01) ( 0.01) 5d

XePtF3

6s(

0.54)

5d(

8.00)

6p(

5S( 1.97)5p( 5.82)

0.22)

5f( 5s( 1.96)5p( 5.76)5d( 0.01)

0.01)

6d( 0.01)

XeAgF3

5s( 0.32)4d( 9.10)5p( 0.30)

5s( 1.98)5p( 5.77)

XeAuF3

6s( 0.52)5d( 8.93)6p( 0.13)5f(

5s( 1.97)5p( 5.74)5d( 0.01)

0.01)

7p( 0.06)

XeRuF4

5S( 0.23)4d( 6.06)5p( 0.41)4f( 0.01) ( 0.02) 5d

5S( 1.94)5p( 5.56)5d( 0.01)

XeOsF4

6S( 0.26)5d( 5.79)5f( 0.02)6d( 0.01) ( 0.28) 7p

5S( 1.97)5p( 5.84)5d( 0.01)

XeRhF4

5s(0.25)4d(7.02)5p(0.43)4f(0.01)5d( 5s( 1.93)5p( 5.45)5d( 0.01) 0.01)

6S( 0.52)5d( 6.59)6p( 0.26)5f( 0.02) ( 0.01) ( 0.01) 6d 7p

XeIrF4

5S( 1.98)5p( 5.90)

Table 3. Electron density descriptors (in a.u.) at the bond critical points (BCP) in between Xe and M atoms obtained from the wave functions generated at wb97xd/Def2-TZVP level of theory. Systems

BCP

ρ(rc)

∇2ρ(rc)

H(rc)

-

G(rc)/ρ(rc)

G(rc)/V(rc)

XeRuF3

Xe-Ru

0.0295

0.0983

-0.0019

0.9331

0.8970

XeOsF3

Xe-Os

0.0325

0.0984

-0.0036

0.8864

0.8672

XeRhF3

Xe-Rh

0.0279

0.0938

-0.0018

0.9374

0.8993

XeIrF3

Xe-Ir

0.0426

0.1299

-0.0068

0.8520

0.9215

XePdF3

Xe-Pd

0.0379

0.1137

-0.0038

0.8950

0.8496



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XePtF3

Xe-Pt

0.0534

0.1350

-0.0109

0.8041

0.8360

XeAgF3

Xe-Ag

0.0416

0.1099

-0.0050

0.8657

0.7816

XeAuF3

Xe-Au

0.0597

0.1239

-0.0129

0.7728

0.7349

XeRuF4

Xe-Ru

0.0608

0.1845

-0.0104

0.8446

0.9301

XeOsF4

Xe-Os

0.0320

0.1062

-0.0035

0.8960

0.9379

XeRhF4

Xe-Rh

0.0738

0.1460

-0.0165

0.7622

0.7183

XeIrF4

Xe-Ir

0.0333

0.0790

-0.0023

0.9060

0.6615

Table 4. EDA results of the systems studied at revPBE-D3/TZ2P//wb97xd/Def2-TZVP level of theory. All energy terms are in kcal/mol. Systems XeRuF3

Fragments

∆Etotal

∆Eelest

∆Eorb

∆EPauli

∆Edisp

[Xe]+[RuF3] 35.92

-11.74

26.90

22.71

-1.94

(85.82%) XeOsF3

XeRhF3

XeIrF3

XePdF3

XePtF3

[Xe]+[OsF3]

-6.70

[Xe]+[RhF3] -5.21

[Xe]+[ IrF3]

[Xe]+[PdF3]

[Xe]+[PtF3]

-10.27

-12.97

-21.30

(14.18%)

-16.61

-20.99

(42.47%)

(53.67%)

-14.19

-15.57

(44.82%)

(49.18%)

-23.43

-27.33

(45.01%)

(52.06%)

-15.71

-24.64

(37.28%)

(58.47%)

-26.21

-41.09

32.40

-1.51 (3.86%)

26.45

-1.90 (6%)

42.23

-1.74 (3.31%)

29.16

-1.79 (4.24%)

47.71

-1.71


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XeAgF3

XeAuF3

XeRuF4

XeOsF4

XeRhF4

XeIrF4

[Xe]+[AgF3] -9.89

[Xe]+[AuF3] -16.51

[Xe]+[RuF4] -21.59

[Xe]+[OsF4]

-7.41

[Xe]+[RhF4] -79.57

[Xe]+[IrF4]

38.83

(37.98%)

(59.54%)

-18.81

-24.70

(41.50%)

(54.50%)

-31.53

-40.32

(42.84%)

(54.79%)

-66.01

-83.47

(43.44%)

(54.93%)

-15.84

-19.89

(42.02%)

(52.76%)

-83.93

-144.87

(36.30%)

(62.66%)

-20.05

20.87

(88.17%)

(2.48%) 35.43

-1.81 (3.99%)

57.08

-1.74 (2.36%)

130.35

-2.47 (1.63%)

30.28

-1.97 (5.23%)

151.62

-2.39 (1.03%)

40.70

-2.69 (11.83%)



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Figures

Figure 1: Optimized geometries of bare metal fluorides. The point groups and the corresponding electronic states have been shown in the parentheses respectively.


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Figure 2: Optimized geometries of bare metal fluorides. The point groups and the corresponding electronic states have been shown in the parentheses respectively.



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Figure 3: Optimized geometries of Xe-bound metal fluorides. The point groups and the corresponding electronic states have been shown in the parentheses respectively.


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Figure 4: Optimized geometries of Xe-bound metal fluorides. The point groups and the corresponding electronic states have been shown in the parentheses respectively.



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Figure 5. Contour line diagrams of the Laplacian of the electron density of different Xebound clusters at the XZ plane. (Green solid lines show areas of the charge depletion (∇2ρ(rc) > 0), and blue dotted lines show areas of the charge concentration (∇2ρ(rc) < 0)).


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Figure 6. Contour line diagrams of the Laplacian of the electron density of different Xebound clusters at the XZ plane. (Green solid lines show areas of the charge depletion (∇2ρ(rc) > 0), and blue dotted lines show areas of the charge concentration (∇2ρ(rc) < 0)).



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Figure 7. ELF plots for different Xe-bound metal fluorides at the XZ plane.


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Figure 8. ELF plots for different Xe-bound metal fluorides at the XZ plane.



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50x50mm (300 x 300 DPI)

ACS Paragon Plus Environment

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In Quest of a Superhalogen Supported Covalent Bond Involving a

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