Oxygen Atom Transfer Reactions from Mimoun Complexes to Sulfides

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Oxygen Atom Transfer Reactions from Mimoun Complexes to Sulfides and Sulfoxides. A Bonding Evolution Theory Analysis Patricio Gonzalez-Navarrete, Fabricio Sensato, Juan Andrés, and Elson Longo J. Phys. Chem. A, Just Accepted Manuscript • DOI: 10.1021/jp504172g • Publication Date (Web): 10 Jul 2014 Downloaded from http://pubs.acs.org on July 11, 2014

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The Journal of Physical Chemistry

Oxygen Atom Transfer Reactions from Mimoun Complexes to Sulfides and Sulfoxides. A Bonding Evolution Theory Analysis Patricio González-Navarrete*1,2, Fabricio R. Sensato3, Juan Andrés*2 and Elson Longo1,4 1

Institute of Chemistry, São Paulo State University, Interdisciplinary Laboratory of Electrochemistry and Ceramics, Francisco Degni 55, Araraquara 14800-900, Brazil 2

Departamento de Química Física y Analítica, Universitat Jaume I, 12071, Castelló de la Plana, Spain.

3

Departamento de Ciências Exatas e da Terra, Universidade Federal de São Paulo, UNIFESP, R. São Nicolau, 210,09913-030 Diadema, Brazil 4

Department of Chemistry, University Federal of São Carlos, Interdisciplinary Laboratory of Electrochemistry and Ceramics, Rod. Washington Luís 235, São Carlos 13565-905, Brazil E-mail: [email protected]; [email protected]

Abstract In this research, a comprehensive theoretical investigation has been conducted on oxygen atom transfer (OAT) reactions from Mimoun complexes to sulfides and sulfoxides. The joint use of the electron localization function (ELF) and Thom´s catastrophe theory (CT) provides a powerful tool to analyze the evolution of chemical events along a reaction pathway. The progress of the reaction has been monitored by structural stability domains from ELF topology while the changes between them are controlled by turning points derived from CT which reveal that the reaction mechanism can be separated in several steps: first, a rupture of the peroxo O1-O2 bond, then a rearrangement of lone pairs of the sulphur atom occurs and subsequently the formation of S-O1 bond. The OAT process involving the oxidation of sulfides and sulfoxides is found to be an asynchronous process where O1-O2 bond breaking and S-O1 bond formation processes do not occur simultaneously. Nucleophilic/electrophilic characters of both dimethyl sulfide and dimethyl sulfoxide, respectively, are sufficiently described by our results which hold the key to unprecedented insight into the mapping of electrons which compose the bonds while the bonds change. Keywords: Thom´s Catastrophe Theory, Electronic Localization Function, Peroxomolybdenum Complexes, Topological Analysis, Diperoxo Complexes * To whom correspondence should be addressed

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1. Introduction An important technical application of the oxygen atom transfer (OAT) reaction is the oxidation of sulfides and sulfoxides. Contemporary interest in the oxidation of sulfur compounds has been fueled by the utility of sulfoxides as fine chemicals. In addition, oxidative desulfurization processes are emerging as an important strategy for the deep removal of sulfur in transportation fuels. Sulfoxide and sulfone compounds are important due to their wide applications as reagents in organic chemistry as well as biologically active molecules. Therefore the selective oxidation of thioethers to sulfoxides and sulfones is of immense interest due to their key role in biological systems.1,2 Organic and inorganic peroxides are able to oxidize sulfides by OAT reactions. The oxidation of thioethers and sulfoxides has also received considerable attention for its use as a mechanistic probe of the electronic character of oxidants.3-5 In the last few years, peroxometal complexes (i.e., Ti(IV), V(V), Mo(VI) and W(VI)) have also received increased interest due to their biological implications and catalytic applications in oxidation reactions.6 In particular, the use of peroxo Mo(VI) complexes emerged in 1969 after Mimoun and co-workers discovered stable oxo-diperoxo metal complexes [MO(η2-O2)2Ln] (M = Mo, W; L = HMPA, DMF, pyride, etc, and n = 1,2)7-10 Molybdenum peroxo complexes are extensively used as either stoichiometric reactants or as catalysts (almost always formed in situ) in conjunction with terminal oxidants such as H2O2 or organic peroxides or dioxygen via homogeneous and heterogeneous routes. In addition, Mimoun complexes are rather strong oxidants of a large variety of organic substrates such as olefins,11-16 alkyl benzenes12,17 amines,18,19 alcohols,13,20 sulfides,3,4,21-25 and chalcogenides,26 In particular, the OAT reaction mechanism related to the epoxidation of olefins using Mimoun complexes has been discussed, and two main hypotheses have created a long-standing debate through the years which principally involves the stepwise versus the concerted oxygen transfer mechanism. A stepwise mechanism for olefin epoxidation has been proposed by Mimoun and coworkers9 whereas Sharpless and coworkers27 have suggested a concerted mechanism. Previous computational studies5,28,29 have demonstrated that the Sharpless mechanism is more feasible, i.e., a direct attack of the nucleophilic olefin on an electrophilic peroxo oxygen center occurs by a spiro structure transition state. We have recently investigated the epoxidation of olefins by Mimoun MoO(η2-O2)2-OPH3 complex30 in the framework of the bonding evolution theory (BET)31 which combines a topological analysis of the electron localization function (ELF)32,33 and Thom’s catastrophe theory (CT).34 In particular, this study was the first application of BET analysis to chemical reactions involving metal complexes. Now, to further increase our understanding of reaction pathways for these types of chemical reactions, we have investigated the OAT reaction from Mimoun-type complex MoO(η2-O2)2OPH3 to dimethyl sulfide which produces dimethyl sulfoxide (Channel I) as well as to dimethyl sulfoxide which yields dimethyl sulfone (Channel II; see Scheme 1a and 1b, respectively) by applying BET analysis to ACS Paragon Plus Environment

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characterize each elementary chemical process (i.e., a bond forming/breaking process, electron density rearrangements, the creation/annihilation of lone pairs, etc.) which occur along the intrinsic reaction path linking reactants and products. In particular, the oxygen transfer from Mimoun complexes to sulfides and sulfoxides, investigated by Di Furia and co-workers4,24 have shown that no coordination between the metal and the substrates occurs, and therefore the reaction involves a direct attack of the substrate on a peroxo oxygen atom via Sharpless mechanism which has been proven for olefin epoxidation. In our previous study, we already characterized the molecular mechanism for the oxidation of sulfides to sulfoxides and the subsequent oxidation to sulfones by diperoxo, and monoperoxo, complexes of molybdenum in the framework of density functional theory (DFT) and transition state theory (TST).35 The results revealed that monoperoxo complexes are proven to be less reactive than their diperoxo counterparts whereas diperoxo Mimoun complexes are stronger electrophilic oxidants toward sulfide than they are toward sulfoxides. The paper is organized as follows. First, the computational details are described; secondly, results and discussions are presented in two subsections which focus primarily on energetic and geometrical parameters; the next subsection is devoted to the ELF topological analysis; and finally, the conclusions of this study are reported. 2. Computational Details All computations have been performed with the Gaussian 09 (G09) code.36 The stationary points on the potential energy surface (PES) have been localized and characterized by employing the B3LYP37,38 hybrid functional together with the 6-311+G(2df,2p) basis set39 for H, C, O, P and S atoms and the Mo atom with the triple-ξ basis set of Ahlrich,40 TZVPalls2 (19s14p9d)/[8s6p5d] augmented with a single set of f-polarization functions. The inclusion of relativistic effects on molybdenum atom has not been considered in this study even though the scalar relativistic effects on Mimoun-type of complexes affect the activation energy barrier associated with OAT reactions. Nevertheless, in order to get the best description of the electron density we have only considered the use a full all electron basis set for all atom. Certainly, the use of pseudopotentials in our system deteriorates the description of the electron density and therefore it avoids an accurate description of the breaking/forming process along the reaction coordinate. However, we have also performed the ECP calculations for reactants, TSs and products in order to verify the role of the relativistic effects on the structure and energy of the system which confirms a reduction of energy barrier and also minor differences in the geometry of the species.62 Starting from the transition state (TS), the reaction pathway has been traced by following the intrinsic reaction coordinate (IRC)41,42 using a Rx in mass-weighted step of 0.05 amu1/2bohr until the minimum has been reached. The wave function has been obtained for each point along the IRC ACS Paragon Plus Environment


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pathway, and the ELF analysis has been performed with the TopMod package43 by considering a cubical grid of a step size smaller than 0.1 bohr. The description of the ELF is based on strong physical arguments related to the Fermi hole.44 This function was first introduced by Becke and Edgecombe,33 and subsequently Savin’s interpretation based on terms of the kinetic energy excess due to Pauli repulsion45 supported the ELF calculation from Kohn-Sham orbitals. The topological partition of the ELF gradient field32,46 yields basins of attractors which can be considered as local chemical objects such as atomic cores, bonds and lone pairs. These basins are either core basins (C(A)) or valence basins (V(A)) where A is the atomic symbol of the element. V(A)s are characterized by their coordination number with a core basis (synaptic order).47 In addition, changes in control parameters which define the reaction pathway (nuclear coordinates and the electronic state) can produce different ELF topologies. According to the theory of dynamic systems it can be considered structurally stable if a small perturbation is possible only for control parameter values which are comprised into well-defined ranges; i.e., structural stability domains (SSDs) where all critical points are hyperbolic separated by catastrophic points where at least one critical point is non-hyperbolic. Along the reaction pathway, the chemical system proceeds from a given ELF-SSD to another by bifurcation catastrophes occurring at the turning points (TPs). Bifurcation catastrophes occurring at these turning points are identified according to Thom’s classification.34 Thus, a chemical reaction can be viewed as a sequence of elementary chemical processes characterized by a catastrophe. Only three types of bifurcation catastrophes have been found in chemical reactivity: (i) the fold catastrophe which corresponds to the creation or to the annihilation of two critical points of different parity; (ii) the cusp catastrophe which transforms one critical point into three (and vice versa) such as in the formation of or the breaking of a covalent bond; and (iii) the elliptic umbilic where the index of a critical point changes by a factor of two. The identification of TPs connecting ELF-SSDs along the reaction pathway allows a rigorous characterization of the sequence of electron pair rearrangements occurring during a chemical transformations such as multiple bond forming/breaking processes, the creation/annihilation of lone pairs, transformations of double bonds into single bonds or vice versa and other electronic rearrangements. The sequence of catastrophes occurring along the reaction pathway can be represented by the general formula introduced by Berski et al.48 N1-N2-FCSHEBP-N3 where N1 is the ordinal number of the analyzed sequence which can be omitted when only one reaction is considered; i.e. N1=1. The number of SSDs is represented by N2. FCSHEBP are symbols of catastrophes according to Thom’s classification; i.e., F = fold, C = cusp, S = swallow tail, H= hyperbolic umbilic, E = elliptic umbilic, B = butterfly and P = parabolic umbilic, and N3 represents ACS Paragon Plus Environment

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the end of the sequence (N3=0). In addition, the † superscript is utilized in those catastrophes where either the number of attractors or the synaptic order increases; e.g., F† corresponds to a fold-type catastrophe where a new attractor is created. The catastrophe symbol written in bold is used to mark a catastrophe which leads to the formation of a first covalent bond (e.g., F) 3. Results and Discussions 3.1 Energetic and Geometrical Parameters As a result of oxygen transfer to a nucleophilic substrate, the diperoxo compounds are transformed into monoperoxo species which can in principle oxidize another molecule of the substrate (or further oxidize the same molecule of the substrate). However, monoperoxo-molybdenum complexes are proven to be less reactive than their diperoxo counterparts,28,29,35,49-51 and therefore only diperoxo-promoted OAT reactions were considered in this work. In particular, the MoO(η2-O2)2OPH3 complex model has been selected as the representative of the diperoxo molybdenum complex. Dimethyl sulfide (DMS) and dimethyl sulfoxide (DMSO) were selected to represent sulfide and sulfoxide substrates, respectively. As previously reported by several theoretical studies regarding the oxidation of sulfides and olefins,5,28,30,49,51 the MoO(η2-O2)2-OPH3 complex has a Cs symmetry which contains a molybdenum atom surrounded by six oxygen atoms in nearly pentagonal-pyramidal geometry with two bidentate peroxo ligands and a –OPH3 group which lies within the distorted pentagonal plane while the oxo group (Mo=O) occupies the axial position. Peroxo groups are asymmetrically side-bound to the molybdenum atom in a η2 fashion.52,53 Optimized geometries calculated for MoO(η2-O2)2OPH3, S(CH3)2, SO(CH3)2, SO2(CH3)2, MoO2(η2-O2)OPH3 and the transition structures (TS1, TS2) for both processes under consideration (see Scheme 1) are depicted in Figure 1 with their respective main geometric parameters. The reaction channel for the OAT reaction involving a MoO(η2-O2)2OPH3 complex and DMS demands an energy barrier of 7.3 kcal/mol where a direct attack of the DMS on one of the peroxoOtrans oxygen atoms is observed. The attacked oxygen atom, O1, is transferred to the sulfur atom of the DMS molecule which affords the monoperoxo MoO2(η2-O2)OPH3 complex and DMSO by an exothermic process of 33.3 kcal/mol. In reaching TS1, the O1-O2 distance is elongated from 1.438 Å to 1.716 Å ([O1-O2] = 0.278 Å) whereas the O5-O6 peroxo group and the Mo-O3 bond are not significantly affected during the reaction, see Figure 1a. The bond distance between O1 and S atoms at TS1 is calculated to be 2.323 Å. After transferring the oxygen atom to the DMS molecule, the Mimoun complex is transformed into a dioxo-monoperoxo complex, MoO2(η2-O2)OPH3. The remaining peroxo group O5-O6, as well as the Mo-OPH3 distance are not significantly affected along ACS Paragon Plus Environment


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the reaction. For the OAT reaction involving MoO(η2-O2)2OPH3 and DMSO, the process occurs with an activation barrier of 9.3 kcal/mol which is slightly higher than the value calculated for MoO(η2O2)2OPH3 and DMS. In this process, the peroxo oxygen O1 of the Mimoun complex is transferred to the sulfur atom of the DMSO. In the corresponding transition structure, TS2, the O1-O2 distance is calculated to be 1.737 Å while the S-O1 distance is predicted to be 2.228 Å, see Figure 1b. The rest of the molecular structure does not change along the reaction. The process is calculated to be exothermic by 55.2 kcal/mol. 3.2 ELF Topological Analysis a) Topological analysis of stationary points and transition states The ELF topological domains of reactants, TS1 and products regarding the OAT reaction from MoO(η2-O2)2OPH3 to DMS (Channel I, Scheme 1a) are depicted in Figure 2 while their respective basin populations are summarized in Table 1 (2nd, 6th and 12th columns, respectively). Previously, we have carried out an extensive chemical bonding analysis of the Mimoun complex30 using the topological analysis of ELF and the electron density (QTAIM).54 The QTAIM analysis for the Mimoum complex suggests closed shell interactions between molybdenum and oxygen atoms (involving peroxo groups), high values of the electron density and positive Laplacian (2ρ(r)) values in their respective bond critical point (bcp) indicate an important covalent contribution in Mo-Oi bonds. In contrast, Mo=O bond is claimed to be a dative bond. On the other hand, considering the topological ELF analysis for the MoO(η2-O2)2OPH3 Mimoun complex, the absence of disynapic valence V(Mo,Oi=1-6) basins in the region of formal MoOi=1-6 bonds indicates a “closed shell” interaction of molybdenum and oxygen atoms.30 Likewise, a protocovalent type bond55-57 has been found for peroxo moieties (O1-O2; O5-O6) characterized by pairs of monosynaptic non-bonding V3(Oi=1,2) and V3(Oi=5,6) basins which have been localized in C(Oi=1,2,5,6) oxygen core attractor vicinities on lines joining oxygen nuclei. Regarding the OPH3 phosphine oxide ligand , O4 possesses three non-bonding Vi=1,2,3(O4) basins and a single disynaptic V(P,O4) basin which in correspondence to the P-O4 bond while three disynaptic V(P,H) basins have also been localized surrounding the C(P) core basin. Besides, O3 (oxo group) is found with a single monosynaptic V1(O3) basin surrounding the core C(O3) attractor which corresponds to three (formal) lone electron pairs. DMS is found with two disynaptic Vi=1,2(S,Ci) basins in correspondence to the formal S-Ci=1,2 bonds, whereas two monosynaptic Vi=1,2(S) have been localized enclosing the core C(S) attractor resembling the lone pairs of sulfur atom in a classical Lewis representation. Along the reaction pathway, the oxygen transfer entails some changes in the ELF topology. Thus, at TS1, the ACS Paragon Plus Environment

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protocovalent O1-O2 bond is already broken due to the annihilation of respective monosynaptic V3(Oi=1,2) basins while the pair of V1,2(S) basins which surround the core C(S) attractor remain. Interestingly, the rest of attractors of the system are not affected except for the non-bonding Vi=2,3(O4) monosynaptic basins which have been transformed into a single monosynaptic V(O4) basin due to the compactness of the valence shell of the O4 atom. Furthermore, no disynaptic basin has been localized between core C(Mo) and C(S) attractors along the reaction pathway which suggests that the DMS does not coordinate with the metal center at the TS1; these findings are in good agreement with the results reported by Di Furia et al.4,24 ELF topological domains of (MoO2(η2-O2)OPH3 and DMSO) products reveal that the pair of monosynaptic V1,2(O2) basins has been transformed into a single V(O2) basin which resembles the monosynaptic V(O3) basin and therefore indicates the conversion of a peroxo oxygen into an oxo oxygen. In addition, a disynaptic V(S,O1) basin has been found between core C(O1) and C(S) attractors which confirms the formal formation of the S-O1 bond. Corresponding ELF topological domains of reactants, TS and products related to Channel II (Scheme 1b) are depicted in Figure 3 while their corresponding basin populations are summarized in Table 2 (2nd, 6th and 12th columns, respectively). In this regard, the progress of the reaction also entails the annihilation of both monosynaptic V3(Oi=1,2) basins associated with the rupture of the protocovalent O1-O2 bond. At TS2, the DMSO moiety is still not affected by the close proximity of the O1 atom (see Figure 3) since the DMSO molecule retains the same number of ELF attractors as in separated reactants. Once the O1 has been transferred to DMSO, the corresponding sulfone, DMSO2, is formed. From an ELF standpoint, a new disynaptic V(S,O1) basin is observed between core C(O1) and C(S) attractors which represents the formation of the S-O1 bond. The annihilation of the monosynaptic V(S) basin occurs in the course of the reaction after TS2. Finally, non-bonding V1,2(O2) basins are transformed into a V(O2) basin which resembles the monosynaptic V(O3) basin and is in line with the conversion of the peroxo oxygen into an oxo oxygen. b) Topological description of reaction paths Basin populations along the IRC pathway for Channel I are summarized in Table 1. For convenience, hydrogen V(P,Hi) and V(S,Hi) basin populations have not been considered in this discussion. Moreover, due to the valence shell compactness of oxygen atoms, the overall population of V2,3(O4) basins has been considered instead of their internal reorganizations which permits a specific description of those ELF topological changes whose participation is more relevant for the reactive process. Thus, the energy profile of the reaction is depicted in Figure 4 (including seven different ELF-SSDs) while the reaction coordinate is traced from -12.0 to 18.4 amu1/2bohr.



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The first SSD (SSD-I) of the reaction path is characterized mainly by its low energetic cost. Along the SSD-I the system, only increments 1.6 kcal/mol (considering as reference separated reactants) whereas the principal geometrical changes is reflected by the lengthening of the O1-O2 distance whose increment along SSD-I cannot evoke any ELF topological change. At ≈ -3.16 amu1/2bohr, d(S-O1) = 2.765 Å and d(O1-O2) = 1.461, the first ELF topological change associated with a fold-type catastrophe is localized as result of the annihilation of the monosynaptic V3(O1) basin. In terms of the ELF topological analysis, it is the first indication of the O1-O2 bond breaking. Consequently, the overall population of non-bonding V1,2(O1) and V1,2,3(O2) basins have increased their populations in 0.10e and 0.17e, respectively, regarding separated reactants. Then the reaction along the SSD-II is short since it only involves four points on the IRC pathway with a total change in energy of 2.8 kcal/mol. The second ELF topological change is therefore associated with the annihilation of the monosynaptic V3(O2) basin (a fold-type catastrophe). This topological change is predicted to occur at ≈ 1.58 amu1/2bohr, d(O1-O2) = 1.520Å and d(S1-O1) = 2.554 Å connecting SSD-II and SSD-III. The annihilation of the monosynaptic V3(O2) basin causes an increase in the overall population of the monosynaptic V1,2(O1) and V1,2(O2) basins, and therefore, in terms of the ELF topology, evidence of the O1-O2 bond does not already exist at this point while the peroxo O5-O6 bond is not significantly affected by the progress of the reaction. TS1 is also found in SSD-III, but it is worth noting that from an ELF topological characterization, there is no evidence of the formation of the S-O1 bond yet. Thus, the OAT process is an asynchronous process since O1-O2 bond breaking and S-O1 bond formation do not occur at the same time. A similar behavior has also been found for the Mimoun-mediated olefin epoxidation processes previously studied by us.30 Furthermore, in the limit of the TS1 zone, populations of the non-bonding electron pairs of V1,2(O1) and V1,2(O2) basins have incremented their values along the reaction progress while the monosynaptic V2(S) basin population has depleted mainly in the vicinity of TS1. Interestingly, the loss of this charge density in the V2(S) basin is not transferred to the monosynaptic V1(S) basin but is distributed between the Mimoun complex and disynaptic Vi(S,C1,2) basins. Thus, the charge transfer to the Mimoun complex which is calculated from the ELF basin population is predicted to be small at TS1 (only 0.28e). The reaction progress for SSD-III entails an increase in energy of 2.9 kcal/mol until the TS1 is reached, and then it decreases by 1.2 kcal/mol when the system reaches the next bifurcation catastrophe point. The next ELF topological change occurs at ≈ 0.79 amu1/2bohr and d(S-O1)= 2.201Å which connects the SSD-III and SSD-IV. A fold-type catastrophe occurs due to the monosynaptic V2(S) attractor annihilation, and as consequence, the monosynaptic V1(S) basin increases its population up to 3.82e. Thus, for SSD-IV, there is a depletion of overall monosynaptic V1,2(O1) basin populations ACS Paragon Plus Environment

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whereas the disynaptic Vi(S,C1,2) basin populations gradually increase. The electronic density redistribution occurs principally in the surrounding atomic region of O1 and S atoms whereas the rest of the electronic density surrounding the Mimoun complex is not altered by the progress of the reaction. Once the system reaches the bifurcation point at the end of the SSD-IV, two new attractors, V(S,O1) and V4(O1), appear which correspond to two simultaneous fold-type catastrophes according to Thom´s classification. The bifurcation point which connects SSD-IV and SSD-V is localized at ≈ 2.78 amu1/2bohr and d(S-O1) = 1.910Å. The disynaptic V(S,O1) basin is located between C(S) and C(O1) core basins while the monosynaptic V4(O1) basin is localized on C(O1) and C(Mo) core basin lines. Certainly, from an ELF topological standpoint, this result is the first evidence for the establishment of a S-O1 chemical bond while the electron pairs in the valence shell of O1 change considerably due to the creation of the non-bonding V4(O1) basin. Basin populations of V(S,O1) and V4(O1) are predicted to be 0.70e and 0.58e, respectively. Thus, while V4(O1) and V(S,O1) basins are created, the monosynaptic V1(S) basin population decreases considerably which indicates that electron density flows from the sulfur valence shell to the S-O1 bond region and O1. In fact, the loss of electronic charge from the V1(S) basin is approximately the sum of V4(O1) and V(S,O1) basin populations when considering the last bifurcation point at ≈ 0.79 amu1/2bohr as a reference. Six points have been found on the IRC path along SSD-V which are related to a decrease of 24.5 kcal/mol. The next bifurcation point is localized at ≈ 5.16 amu1/2bohr and d(S-O1) = 1.564Å which connects SSD-V and SSD-VI and is associated with a fold-type catastrophe which corresponds to the annihilation of the non-bonding V4(O1) basin. The electron density is now distributed in two nonbonding V1(O1) and V2(O1) basins with population values of 4.80e and 1.48e, respectively, while the pairs of these non-bonding basins resemble the position of lone electron pairs in an oxygen atom of the DMSO. Note that the disynaptic V(S,O1) basin population increases as the reaction proceeds. Finally, the last ELF field topological change occurs by a cusp-type catastrophe which connects SSD-VI and SSD-VII and corresponds to a reorganization of monosynaptic V1,2(O2) basins into a single V(O2) basin. Valence electrons in O2 are reorganized; when the Mo=O2 bond is formed, its ELF topology is similar to the topology for the Mo=O3 moiety. Thus, the sequences in ELF topological changes are summarized in Scheme 2 which involve their respective catastrophes according to Thom’s classification. In summary, the process occurs first by O1-O2 bond breaking followed by a redistribution of sulfur atom lone pairs for a subsequent S-O1 bond formation. From a topological point of view, the breaking/forming process does not occur at the transition state zone as should be expected. Regarding the OAT reaction between MoO(η2-O2)2OPH3 and DMSO (Channel II), there are seven ELF SSDs along the IRC pathway and the reaction pathway is traced from -9.72 to 17.94 ACS Paragon Plus Environment


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amu1/2bohr (see Figure 5). ELF topological changes reveal differences in the mechanism regarding Channel I principally in the evolution of the charge transfer and redistribution of electron pairs after the transition state. Thus, the first ELF topological changes are also associated with the O1-O2 bond rupture before reaching the transition state; i.e., the annihilation of both monosynaptic V3(O1,2) basins. Two fold-type catastrophes occur successively which is unlike the reaction involving DMS where there are three points on the IRC pathway between the annihilation of the V3(O1,) and V3(O2) basins. Interestingly, the annihilation of the V3(O2) basin occurs almost at the same point in the reaction coordinate than reaction involving DMS; however, the partial energetic cost for the rupture of the O1O2 bond is slightly higher than the DMS reaction (5.7 kcal/mol for DMSO reaction vs. 4.4 kcal/mol for DMS).58 Note that the peroxo O1-O2 bond rupture occurs at ≈ -1.56 amu1/2bohr and d(S-O1) = 2.423Å. Thus, once the peroxo O1-O2 bond is broken, the system passes along the SSD-III and overcomes TS2; however, there is still no evidence for the formation of a S-O1 bond throughout SSDIII. On passing from Rx ≈ -1.56 amu1/2bohr to TS2, the V1(S) basin population decreases by 0.20e. Interestingly, the charge transfer from DMSO to the Mimoun complex at TS2 is calculated to be 0.25e which corresponds to the reduction of the V(S) basin population. Thus, along SSD-III, the energy increases in 3.5 kcal/mol until TS2 is reached; subsequently the energy decreases by 25.6 kcal/mol when a new bifurcation point is found at ≈ 3.12 amu1/2bohr and d(S-O1) = 1.810 Å. The bifurcation point which connects SSD-III and SSD-IV entails the creation of the monosynaptic V4(O1) basin; however, at this point there is no evidence of the creation of the S-O1 bond yet as seen in DMS reaction. Certainly the monosynaptic V1(S) attractor which surrounds the C(S) core basin remains and is directed on the line of C(O1) and C(S) core basins, but it might not be considered as a V(S,O1) disynaptic basin since the V(S) valence basin does not share a common boundary between the respective core basins, C(O1) and C(S) (see Figure 6). Moreover, the V(S) basin population decreases considerably to 1.36e, and the V4(O1) basin population is calculated to be 1.06e while the system reduces its energy in 20.3 kcal/mol for SSD-IV. The following ELF topological change which connects SSD-IV and SSD-V does not occur by the annihilation/creation of one (or more) basins as in previous bifurcations. SSD-V is characterized by a change in the monosynaptic V(S) basin synapicity which is transformed into the disynaptic V(S,O1) basin. The progress of the reaction entails the approach of the O1 towards the S atom while the charge density accumulated in V(S) basin remains until the core basin C(O1) is approached to the sulfur atom to transform this monosynaptic basin into a disynaptic one by means of a fold type of catastrophe. In terms of the ELF topological analysis, this result is the first evidence of the formation of the S-O1 bond. Furthermore, V4(O1) and V(S,O1) basin populations are calculated to be 1.70e and


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1.30e, respectively, at the bifurcation point. Once the S-O1 bond is formed, the charge density of the system is distributed to arrive at products. The next topological changes which lead to the last SSD-VI and SSD-VII first show the annihilation of V4(O1) (fold-type of catastrophe) and finally connect SSD-VI and SSD-VII which is observed as a reorganization of the monosynaptic V1,2(O2) basins into a single V(O2) basin (cusp-type catastrophe) and resembles the process for V(O3) which corresponds to the Mo=O3 moiety. ELF topological changes regarding the OAT between the Mimoun complex and DMSO are summarized in Scheme 3 where their respective catastrophes according to the Thom’s classification are displayed. In summary, the OAT concerning the Mimoun complex and DMSO first occurs by O1-O2 bond breaking, and then the monosynaptic V(S) basin is transformed into the V(S,O1) basin. From a topological point of view, note that the breaking/forming process does not occur at the transition state zone as is traditionally expected. c) Electronic Character of the Oxygen Transfer To address the electronic character (i.e., if the oxidant attacks the substrate in an electrophilic or nucleophilic manner) for the oxidation of sulfide and sulfoxide by Mimoun complexes, we have previously applied a CDA (charge decomposition analysis) on the corresponding transition structures.35, 51 Our results revealed that both processes (the OAT reaction from Mimoun complex to DMS or DMSO) occur with an electrophilic attack of the molybdenum peroxo complex on the organic substrate. Moreover, the oxidation of the sulfur group of DMS by the Mimoun complex is a more electrophilic process than the oxidation of the sulfinyl group of DMSO. Indeed, the ELF topological analysis cannot quantify the electronic character as the CDA does; however, ELF topological and CT analyses have previously been utilized to symbolize the electronic transfer in pericyclic reactions which suggests a graphical representation of curved arrows in Lewis structures as the reaction proceeds.59 Thus, this kind of representation can also be utilized to represent the electrophilic/nucleophilic character of the species. For example, as far as the OAT reaction toward the DMS is concerned, the nucleophilic character of DMS is reflected by the creation of a disynaptic V(S,O1) basin after the system reaches TS1. Indeed, in the vicinity of TS1 the annihilation of the monosynaptic V2(S) basin is observed (see Scheme 2 and Figure 4) while the charge density involved in the annihilation of this basin is concentrated mainly in the valence shell of the sulfur atom, V1(S), and is waiting for the approach of the O1 electrophilic center. When the O1 atom is sufficiently close to the DMS fragment, the ELF field undergoes a sudden topological change which is reflected by two simultaneous fold-type catastrophes; i.e., the creation of the valence V4(O1) and V(S,O1) basins. Certainly the creation of the ACS Paragon Plus Environment


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V(S,O1) basin evokes the classical Lewis arrows representation where the lone sulfur pair attacks the O1 electrophilic site. Actually, at the moment of the creation of the V(S,O1) basin, it might be interpreted as a dative bond which becomes a covalent bond as the reaction proceeds. Thus, the topological ELF field evolution agrees well with the electrophilic oxidant character of the Mimoun complex regarding sulfides. However, as far as the OAT reaction toward the DMSO is concerned, once the system reaches the TS2, the monosypnaptic V(S) basin which surrounds the C(S) basin remains until the O1 atom is sufficiently close to transform the monosynaptic V(S) basin into the disynaptic V(S,O1) basin. Thus, in response to the proximity of the O1 atom, the ELF field undergoes a sudden topological change which is reflected in a synapticity change in the monosynaptic V(S) basin. Certainly the approach of the O1 atom to the DMSO fragment towards the sulfur atom diminishing the nucleophilic character of the DMSO regarding the Mimoun complex, in addition to the depletion of the monosynaptic V(S) basin population before becoming a disynaptic basin. Consequently, the charge density concentrated in the valence shell of the sulfur atom does not increase until the O1 atom is sufficiently close for transfer charge density and therefore facilitates the formation of the S-O1 bond. 4. Conclusions The combined use of ELF and CT (i.e., BET analysis) is a useful tool for studying the mechanisms of chemical reactions through the characterization of the electron redistribution in the course of a given chemical reaction. The reaction mechanism for the OAT process from Mimoun complexes to sulfides and sulfoxides was rationalized in terms of chemical events that drive the chemical reaction. This study demonstrates an unprecedented insight into the mapping of electrons creating bonds while the bonds change and is a good guide to unravel the electronic structure along reaction pathways. The results can be summarized as follows: i) The OAT process involving the oxidation sulfides and sulfoxides is an asynchronous process where O1-O2 bond breaking and S-O1 bond formation processes do not occur simultaneously; ii) a rupture of the peroxo O1-O2 bond breaking process occurs, and then a rearrangement of the lone pairs of the sulfur atom and a subsequent formation of the S-O1 bond occurs; and iii) an insight into the nucleophilic and electrophilic character of both dimethyl sulfide and dimethyl sulfoxide are provided.


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5. Acknowledgements This work is supported by Generalitat Valenciana for the Prometeo /2009/053 project, Spanish Ministry Ministerio de Economíay Competitividad for project CTQ-2012-36253-C03-01, the Spanish–Brazilian program (PHB2009-0065-PC) for their financial support and Fundación BancaixaUniversitat Jaume I (UJI) for project P1.1B2010-10. P.G-N acknowledges the postdoctoral grant provided by CNPq. F.R.S. thanks to São Paulo Research Foundation, FAPESP (grant 2009/01628-8). The authors are also grateful to the Servei d’ Informatica, Universitat Jaume I.

6. Author Information Corresponding author* E-mail: [email protected]. Telephone: +34 964728083. Fax: +34 964728066 E-mail: [email protected] 7. References (1) Das, S. P.; Boruah, J. J.; Chetry, H.; Islam, N. S. Selective Oxidation of Organic Sulfides by Mononuclear and Dinuclear Peroxotungsten (VI) Complexes. Tetrahedron Lett. 2012, 53, 1163-1168. (2) Holland, H. L. Chiral Sulfoxidation by Biotransformation of Organic Sulfides. Chem. Rev. 1988, 88, 473-485. (3) Ballistreri, F. P.; Tomaselli, G. A.; Toscano, R. M.; Conte, V.; Di Furia, F. Application of the Thianthrene 5-oxide Mechanistic Probe to Peroxometal Complexes. J. Am. Chem. Soc. 1991, 113, 6209-6212. (4) Bonchio, M.; Conte, V.; Deconciliis, M. A.; Di Furia, F.; Ballistreri, F. P.; Tomaselli, G. A.; Toscano, R. M. The Relative Reactivity of Thioethers and Sulfoxides toward Oxygen-Transfer Reagents: the Oxidation of Thianthrene 5-oxide and Related Compounds by MoO5HMPT. J. Org. Chem. 1995, 60, 4475-4480. (5) Deubel, D. V.; Frenking, G.; Gisdakis, P.; Herrmann, W. A.; Rösch, N.; Sundermeyer, J. Olefin Epoxidation with Inorganic Peroxides. Solutions to Four Long-Standing Controversies on the Mechanism of Oxygen Transfer. Acc. Chem. Res. 2004, 37, 645-652. (6) Luisa Ramos, M.; Justino, L. L. G.; Burrows, H. D. Structural Considerations and Reactivity of Peroxocomplexes of V(V), Mo(VI) and W(VI). Dalton Trans. 2011, 40, 4374-4383. (7) Mimoun, H. Oxygen-Transfer from Inorganic and Organic Peroxides to Organic Substrates: A Common Mechanism. Angew. Chem. Int. Ed. 1982, 21, 734-750. (8) Mimoun, H.; De Roch, I. S.; Sajus, L. New Molybdenum-6 and Tungsten-6 PeroxyComplexes. Bull. Soc. Chim. Fr. 1969, 1481-1492. (9) Mimoun, H.; Roch, I. S. D.; Sajus, L. Olefin Epoxidation by Covalent Molybdenum Peroxide Complexes. Tetrahedron 1970, 26, 37-50. (10) Dickman, M. H.; Pope, M. T. Peroxo and Superoxo Complexes of Chromium, Molybdenum, and Tungsten. Chem. Rev. 1994, 94, 569-584. (11) Herbert, M.; Montilla, F.; Alvarez, E.; Galindo, A. New Insights into the Mechanism of Oxodiperoxomolybdenum Catalysed Olefin Epoxidation and the Crystal Structures of Several OxoPeroxo Molybdenum Complexes. Dalton Trans. 2012, 41, 6942-6956. (12) Das, S.; Bhowmick, T.; Punniyamurthy, T.; Dey, D.; Nath, J.; Chaudhuri, M. K. Molybdenum(VI)-Peroxo Complex Catalyzed Oxidation of Alkylbenzenes with Hydrogen Peroxide. ACS Paragon Plus Environment


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Tetrahedron Lett. 2003, 44, 4915-4917. (13) Maiti, S. K.; Malik, K. M. A.; Gupta, S.; Chakraborty, S.; Ganguli, A. K.; Mukherjee, A. K.; Bhattacharyya, R. Oxo- and Oxoperoxo-Molybdenum(VI) Complexes with Aryl Hydroxamates: Synthesis, Structure, and Catalytic Uses in Highly Efficient, Selective, and Ecologically Benign Peroxidic Epoxidation Of Olefins. Inorg. Chem. 2006, 45, 9843-9857. (14) Piquemal, J.-Y.; Halut, S.; Brégeault, J.-M. Novel Distorted Pentagonal-Pyramidal Coordination of Anionic Oxodiperoxo Molybdenum and Tungsten Complexes. Angew. Chem. Int. Ed. 1998, 37, 1146-1149. (15) Salles, L.; Piquemal, J. Y.; Thouvenot, R.; Minot, C.; Bregeault, J. M. Catalytic Epoxidation by Heteropolyoxoperoxo Complexes: From Novel Precursors or Catalysts to a Mechanistic Approach. J. Mol. Catal. A-Chem 1997, 117, 375-387. (16) Jorgensen, K. A. Transition Metal Catalyzed Epoxidations. Chem. Rev. 1989, 89, 431-458. (17) Bandyopadhyay, R.; Biswas, S.; Guha, S.; Mukherjee, A. K.; Bhattacharyya, R. Novel OxoPeroxo Molybdenum (VI) Complexes Incorporating 8-Quinolinol: Synthesis, Structure and Catalytic uses in the Environmentally Benign and Cost-Effective Oxidation Method of Methyl Benzenes: Ar(CH3)n (n=1, 2). Chem. Commun. 1999, 1627-1628. (18) Ballistreri, F. P.; Barbuzzi, E. G. M.; Tomaselli, G. A.; Toscano, R. M. Multiplicity of Reaction Pathways in the processes of Oxygen Transfer to Secondary Amines by Mo(VI) and W(VI) Peroxo Complexes. J. Org. Chem. 1996, 61, 6381-6387. (19) Biradar, A. V.; Kotbagi, T. V.; Dongare, M. K.; Umbarkar, S. B. Selective N-Oxidation of Aromatic Amines to Nitroso Derivatives using a Molybdenum Acetylide Oxo-Peroxo Complex as Catalyst. Tetrahedron Lett. 2008, 49, 3616-3619. (20) Luan, Y.; Wang, G.; Luck, R. L.; Yang, M.; Han, X. Oxidation of Alcohols with Hydrogen Peroxide Catalyzed by Molybdenum (VI)-Peroxo Complex under Solvent Free Conditions. Chem. Lett. 2007, 36, 1236-1237. (21) Basak, A.; Barlan, A. U.; Yamamoto, H. Catalytic Enantioselective Oxidation of Sulfides and Disulfides by a Chiral Complex of Bis-Hydroxamic Acid and Molybdenum. Tetrahedron-Asymmetr. 2006, 17, 508-511. (22) Batigalhia, F.; Zaldini-Hernandes, M.; Ferreira, A. G.; Malvestiti, I.; Cass, Q. B. Selective and Mild Oxidation of Sulfides to Sulfoxides by Oxodiperoxo Molybdenum Complexes Adsorbed onto Silica Gel. Tetrahedron 2001, 57, 9669-9676. (23) Bortolini, O.; Di Furia, F.; Modena, G.; Seraglia, R. Metal Catalysis in Oxidation by Peroxides. Sulfide Oxidation and Olefin Epoxidation by Dilute Hydrogen-Peroxide Catalyzed by Molybdenum and Tungsten Derivatives under Phase-Transfer Conditions. J. Org. Chem. 1985, 50, 2688-2690. (24) Campestrini, S.; Conte, V.; Di Furia, F.; Modena, G.; Bortolini, O. Metal Catalysis in Oxidation by Peroxides. Electrophilic Oxygen-Transfer from Anionic, Coordinatively Saturated Molybdenum Peroxo Complexes. J. Org. Chem. 1988, 53, 5721-5724. (25) Keilen, G.; Benneche, T.; Gaare, K.; Undheim, K. Peroxymolybdenum Complexes in Sulfide to Sulfone Oxidations. Acta Chem. Scand. 1992, 46, 867-871. (26) Khurana, J. M.; Agrawal, A.; Kumar, S. Oxidation of Chalcogenides using the Peroxo Complex of Molybdenum MoO(O-2)(2)(H2O)(hmpa), hmpa = hexamethylphosphoramide. J. Brazil Chemi. Soc. 2009, 20, 1256-1261. (27) Sharpless, K. B.; Townsend, J. M.; Williams, D. R. Mechanism of Epoxidation of Olefins by Covalent Peroxides of Molybdenum(VI). J. Am. Chem. Soc. 1972, 94, 295-296. (28) Deubel, D. V.; Sundermeyer, J.; Frenking, G. Mechanism of the Olefin Epoxidation Catalyzed by Molybdenum Diperoxo Complexes: Quantum-Chemical Calculations give an Answer to a LongStanding Question. J. Am. Chem. Soc. 2000, 122, 10101-10108. (29) Di Valentin, C.; Gisdakis, P.; Yudanov, I. V.; Rosch, N. Olefin Epoxidation by Peroxo Complexes of Cr, Mo, and W. A Comparative Density Functional Study. J. Org. Chem. 2000, 65, 2996-3004. (30) Berski, S.; Sensato, F. R.; Polo, V.; Andrés, J.; Safont, V. S. Olefin Epoxidation by ACS Paragon Plus Environment

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Molybdenum Peroxo Compound: Molecular Mechanism Characterized by the Electron Localization Function and Catastrophe Theory. J.Phys. Chem. A 2011, 115, 514-522. (31) Krokidis, X.; Noury, S.; Silvi, B. Characterization of Elementary Chemical Processes by Catastrophe Theory. J.Phys. Chem. A 1997, 101, 7277-7282. (32) Silvi, B.; Savin, A. Classification of Chemical-Bonds based on Topological Analysis of Electron Localization Functions. Nature 1994, 371, 683-686. (33) Becke, A. D.; Edgecombe, K. E. A Simple Measure of Electron Localization in Atomic and Molecular-Systems. J. Chem. Phys. 1990, 92, 5397-5403. (34) Thom, R. Structural Stability and Morphogenesis; An Outline of a General Theory of Models; W. A. Benjamin: Reading, Mass., 1975 (35) Sensato, F. R.; Custodio, R.; Longo, E.; Safont, V. S.; Andres, J. Sulfide and Sulfoxide Oxidations by Mono- and Diperoxo Complexes of Molybdenum. A Density Functional Study. J. Org. Chem. 2003, 68, 5870-5874. (36) Gaussian 09, Revision B.01, Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson et al. Gaussian, Inc., Wallingford CT, 2009. (37) Becke, A. D. A New Mixing of Hartree-Fock and Local Density-Functional Theories. J. Chem. Phys. 1993, 98, 5648. (38) Becke, A. D. Density-Functional Exchange-Energy Approximation with Correct AsymptoticBehavior. Phys Rev A 1988, 38, 3098-3100. (39) Frisch, M. J.; Pople, J. A.; Binkley, J. S. Self-Consistent Molecular-Orbital Methods. Supplementary Functions for Gaussian-Basis Sets. J. Chem. Phys. 1984, 80, 3265-3269. (40) Ahlrichs, R.; May, K. Contracted All-Electron Gaussian Basis Sets for Atoms Rb to Xe. Phys. Chem. Chem. Phys. 2000, 2, 943-945. (41) Deubel, D. V. Ethylene Epoxidation with Tungsten Diperoxo Complexes: Is Relativity the Origin of Reactivity? J. Phys. Chem. A 2001, 105, 4765-4772. (42) Li, J.-L.; Mata, R. A.; Ryde, U. Large Density-Functional and Basis-Set Effects for the DMSO Reductase Catalyzed Oxo-Transfer Reaction. J. Chem. Theory Comput. 2013, 9, 1799-1807. (43) Fukui, K. A Formulation of Reaction Coordinate. J.Phys. Chem. 1970, 74, 4161-4163. (44) Fukui, K. The Path of Chemical Reactions: The IRC Approach. Acc. Chem. Res. 1981, 14, 363-368. (45) Noury, S.; Krokidis, X.; Fuster, F.; Silvi, B. Computational Tools for the Electron Localization Function Topological Analysis. Comput. Chem.1999, 23, 597-604. (46) McWeeny, R. Some Recent Advances in Density Matrix Theory. Rev. Mod. Phys. 1960, 32, 335-369. (47) Savin, A.; Jepsen, O.; Flad, J.; Andersen, O. K.; Preuss, H.; Vonschnering, H. G. Electron Localization in Solid-State Structures of the Elements: The Diamond Structure. Angew. Chem. Int. Ed. 1992, 31, 187-188. (48) Haussermann, U.; Wengert, S.; Hofmann, P.; Savin, A.; Jepsen, O.; Nesper, R. Localization of Electrons in Intermetallic Phases Containing Aluminum. Angew. Chem. Int. Ed. 1994, 33, 2069-2073. (49) Silvi, B. The Synaptic Order: A Key Concept to Understand Multicenter Bonding. J. Mol. Struct.-Theochem 2002, 614, 3-10. (50) Berski, S.; Andres, J.; Silvi, B.; Domingo, L. R. New Findings on the Diels-Alder Reactions. An Analysis Based on the Bonding Evolution Theory. J.Phys. Chem. A 2006, 110, 13939-13947. (51) Deubel, D. V.; Sundermeyer, J.; Frenking, G. Olefin Epoxidation with Transition Metal Eta(2)-Peroxo Complexes: The Control of Reactivity. Eur. J. Inorg. Chem. 2001, 1819-1827. (52) Yudanov, I. V.; Di Valentin, C.; Gisdakis, P.; Rosch, N. Olefin Epoxidation by Mono and Bisperoxo Complexes of Mo(VI): A Density Functional Model Study. J. Mol. Catal. A-Chem 2000, 158, 189-197. (53) Sensato, F. R.; Custodio, R.; Longo, E.; Safont, V. S.; Andres, J. Why do Peroxomolybdenum Complexes Chemoselectively Oxidize the Sulfur Centers of Unsaturated Sulfides And Sulfoxides? A DFT Analysis. Eur. J. Org. Chem. 2005, 2406-2415. ACS Paragon Plus Environment


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(54) Sensato, F. R.; Cass, Q. B.; Longo, E.; Zukerman-Schpector, J.; Custodio, R.; Andres, J.; Hernandes, M. Z.; Longo, R. L. Molecular Structure of the Molybdenum Oxo-Diperoxo Compound MoO(O-2)(2)(OPy)(H2O): A Computational and X-Ray Study. Inorg. Chem. 2001, 40, 6022-6025. (55) Sensato, F. R.; Custodio, R.; Cass, Q. B.; Long, E.; Hernandes, M. Z.; Longo, R. L.; Andres, J. The use of the Generator Coordinate Method for Designing Basis Set. Application to Oxo-Diperoxo Molybdenum Complexes. J. Mol. Struct.-Theochem 2002, 589, 251-264. (56) Bader, R. F. W. Atoms in Molecules: A Quantum Theory; Clarendon Press Oxford: New York, 1990 (57) Llusar, R.; Beltran, A.; Andres, J.; Noury, S.; Silvi, B. Topological Analysis of Electron Density in Depleted Homopolar Chemical Bonds. J. Comput. Chem. 1999, 20, 1517-1526. (58) Sambrano, J. R.; Gracia, L.; Andres, J.; Berski, S.; Beltran, A. A Theoretical Study on the Gas Phase Reactions of the Anions NbO3-, NbO5-, and NbO2(0H)(2)(-) with H2O and O-2. J.Phys. Chem. A 2004, 108, 10850-10860. (59) Shaik, S.; Danovich, D.; Silvi, B.; Lauvergnat, D. L.; Hiberty, P. C. Charge-Shift Bonding: A Class of Electron-Pair Bonds that Emerges from Valence Bond Theory and is Supported by the Electron Localization Function Approach. Chem-Eur. J. 2005, 11, 6358-6371. (60) The energetic cost for the rupture of the O1-O2 bond was calculated as follows: E(at the annihilation of the V3(O2) basin)- E(at separated reactants) (61) González-Navarrete, P.; Andrés, J.; Berski, S. How a Quantum Chemical Topology Analysis Enables Prediction of Electron Density Transfers in Chemical Reactions. The Degenerated Cope Rearrangement of Semibullvalene. J.Phys. Chem. Lett. 2012, 3, 2500-2505. (62) These calculations have been performed using a MDF 28-electron relativistic effective core potential (ECP) for Mo atom, while the remaining 14 valence electrons were treated with the ccpVTZ-PP basis set. 6-311+(2df,2p) basis set has been used for the rest of the atoms. The activation barrier have been predicted to be 6.78 kcal/mol and 8.93 kcal/mol for TS1 and TS2, respectively.


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FIGURE CAPTIONS

Figure 1. Optimized structures for the Mimoun complex, transition states, DMS, DMSO and DMSO2. Bond distances are in angstrom.

Figure 2. Snapshots of ELF localization domains for reactants (Mimoun complex and DMS), transition structure TS1 and products (monoperoxo complex and DMSO).

Figure 3. Snapshots of ELF localization domains for reactants (Mimoun complex and DMSO), transition structure TS2 and products (monoperoxo complex and DMSO2).

Figure 4. IRC path with marked SSDs obtained from the BET analysis for the OAT reaction between Mimoun complex and DMS.

Figure 5. IRC path with marked SSDs obtained from the BET analysis for the OAT reaction between Mimoun complex and DMSO. Figure 6. ELF contour at the SSD-IV in the C(Mo)-C(O1)-C(S) plane.



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TABLE CAPTIONS

Table 1. Integrated electron populations of the ELF basins for the reaction of Mimoun complex and DMS. [a] First point on the IRC path. [b] Last point on the IRC path. Table 2.Integrated electron populations of the ELF basins for the reaction of Mimoun complex and DMSO. [a] First point on the IRC path. [b] Last point on the IRC path.


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Figure 1. Optimized structures for the Mimoun complex, transition states, DMS, DMSO and DMSO2. Bond distances are in angstrom.



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Scheme 1


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Figure 2. Snapshots of ELF localization domains for reactants (Mimoun complex and DMS), transition structure TS1 and products (monoperoxo complex and DMSO).



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Figure 3. Snapshots of ELF localization domains for reactants (Mimoun complex and DMSO), transition structure TS2 and products (monoperoxo complex and DMSO2).


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-5250.34 TS1

-5250.36

Total Energy (Hartree)

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-5250.38

I

II

III

IV

V

VI

VII

-5250.4

-5250.42

-5250.44 -12

-10

-8

-6

-4

-2

0

2

4

6

Reaction Coordinate (amu

1/2

8

10

12

14

16

18

bohr)

Figure 4. IRC path with marked SSDs obtained from the BET analysis for the OAT reaction between Mimoun complex and DMS.

F

F

F ϯ F ϯ

F

Scheme 2


F

C


-5325.56 TS2 -5325.58

Total Energy (Hartree)

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

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-5325.6

I

II

III

IV

V

VI

VII

-5325.62

-5325.64

-5325.66

-5325.68 -10

-8

-6

-4

-2

0

2

4

6

8

10

12

14

16

18

Reaction Coordinate (amu1/2 bohr)

Figure 5. IRC path with marked SSDs obtained from the BET analysis for the OAT reaction between Mimoun complex and DMSO.

Figure 6. ELF contour at the SSD-IV in the C(Mo)-C(O1)-C(S) plane.


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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


F

F

F

F

V1(O2) C(O2)

C(Mo)

V1(O7) C(O ) 7 V2(O7) V(S,O7) V1(O1) C(O1) V2(O1)

C(C2) V(S,C2) C(S) V(S,C1)

V(S,O1)

C(C1)

Scheme 3


F

C


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

Table 1. Integrated electron populations of the ELF basins for the reaction of Mimoun complex and DMS. SSD SSD-I SSD-II SSD-III SSD-IV SSD-V SSD-VI SSD-VII 2 species MoO(η O2)2OPH3 + DMS [a] TS1 [b] MoO2(η2O2)OPH3 + DMSO basin V1(O1) 3.13 3.13 3.19 3.26 3.27 3.29 3.05 4.80 4.71 4.42 3.26 V2(O1) 3.10 3.11 3.14 3.21 3.25 3.26 2.95 1.48 1.56 1.86 3.17 V3(O1) 0.23 0.22 V1(O2) 3.14 3.15 3.17 3.37 3.38 3.42 3.57 3.42 7.04 7.02 7.03 V2(O2) 3.12 3.12 3.16 3.25 3.35 3.39 3.40 3.60 V3(O2) 0.27 0.26 0.37 V1(O3) 7.00 7.01 7.02 7.03 7.06 7.06 7.08 7.09 7.08 7.11 7.07 V1(O4) 1.26 1.27 1.27 1.31 1.39 1.43 1.49 1.46 1.46 1.48 1.18 V2(O4) + 4.82 4.84 4.81 4.78 4.71 4.66 4.61 4.64 4.63 4.59 4.90 V3(O4) V(P,O4) 1.59 1.60 1.60 1.61 1.60 1.61 1.62 1.60 1.60 1.63 1.59 C(Mo) 38.53 38.49 38.48 38.47 38.43 38.44 38.45 38.47 38.47 38.46 38.49 V1(O6) 3.14 3.13 3.14 3.12 3.13 3.13 3.14 3.14 3.14 3.13 3.11 V2(O6) 3.10 3.11 3.12 3.13 3.13 3.13 3.16 3.17 3.16 3.16 3.16 V3(O6) 0.23 0.23 0.22 0.23 0.25 0.25 0.26 0.26 0.26 0.25 0.18 V1(O5) 3.14 3.15 3.15 3.15 3.13 3.14 3.11 3.10 3.10 3.10 3.14 V2(O5) 3.12 3.10 3.10 3.10 3.12 3.13 3.16 3.16 3.15 3.15 3.19 V3(O5) 0.27 0.26 0.26 0.26 0.26 0.25 0.25 0.25 0.25 0.28 0.25 V1(S) 2.23 2.23 2.22 2.21 2.26 3.82 2.72 2.34 2.31 2.30 2.19 V2(S) 2.21 2.22 2.18 2.12 1.77 V(S,C1) 1.65 1.63 1.64 1.65 1.71 1.76 1.83 1.85 1.85 1.85 1.86 V(S,C2) 1.65 1.63 1.64 1.65 1.72 1.76 1.83 1.85 1.85 1.85 1.86 V(S,O1) 0.70 1.26 1.31 1.29 1.27 V4(O1) 0.58 distance d(S-O1) 3.622 2.765 2.554 2.323 2.201 1.910 1.564 1.526 1.534 1.494 Rx -11.96 -3.16 -1.58 0.0 0.79 2.78 5.16 7.03 18.37 -

[a] First point on the IRC path. [b] Last point on the IRC path.


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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


Table 2.Integrated electron populations of the ELF basins for the reaction of Mimoun complex and DMSO. SSD species

SSD-I MoO(η2O2)2OPH3 + DMSO

[a]

SSD-II

SSD-III TS

SSD-IV

SSD-V

SSD-VI

basin V1(O1) V2(O1) V3(O1) V1(O2) V2(O2) V3(O2) V1(O3) V1(O4) V2(O4) + V3(O4)

3.13 3.10 0.23 3.14 3.12 0.27 7.00 1.26 4.82

3.14 3.12 0.22 3.15 3.13 0.26 7.00 1.25 4.85

3.18 3.18 3.34 3.24 0.13 7.01 1.27 4.82

3.28 3.20 3.35 3.27 7.01 1.29 4.80

3.24 3.30

V(P,O4) C(Mo) V1(O6) V2(O6) V3(O6) V1(O5) V2(O5) V3(O5) V1(S) V(S,C1) V(S,C2) V(S,O1) V4(O1) V1(O7) V2(O7) V(O7,S)

1.59 38.53 3.14 3.10 0.23 3.14 3.12 0.27 2.19 1.86 1.86 3.26 3.17 1.27

1.59 38.48 3.14 3.12 0.24 3.15 3.11 0.26 2.28 1.84 1.84 3.35 2.88 1.40

1.60 38.46 3.13 3.13 0.24 3.16 3.11 0.26 2.22 1.86 1.86 3.31 2.90 1.42

distance d(S-O1) Rx

-

3.168 -9.72

2.475 -1.94

3.38 3.35 7.06 1.38 4.71

2.99 2.54 3.62 3.40 7.06 1.46 4.62

3.03 1.73 3.81 3.23 7.07 1.44 4.66

4.06 2.12 4.23 2.85 7.05 1.40 4.71

4.11 2.08 7.08 7.04 1.40 4.67-

4.89 1.27 7.05 7.08 1.38 4.70

3.16 2.93 7.03 7.07 1.18 4.90

1.61 38.45 3.13 3.13 0.24 3.15 3.11 0.26 2.20 1.86 1.86 3.34 2.86 1.41

1.60 38.43 3.13 3.13 0.25 3.14 3.12 0.26 2.00 1.88 1.90

1.62 38.45 3.10 3.16 0.25 3.14 3.15 0.26 1.36 1.98 1.98 1.06 3.11 3.02 1.50

1.59 38.46 3.15 3.15 0.25 3.08 3.17 0.27 2.01 2.01 1.56 3.22 2.87 1.69

1.62 38.46 3.13 3.16 0.25 3.10 3.15 0.27 2.01 2.01 1.55 3.33 2.74 1.70

1.62 38.46 3.11 3.16 0.27 3.10 3.14 0.25 2.01 2.01 1.55 3.13 2.93 1.70

1.59 38.49 3.11 3.16 0.18 3.14 3.19 0.25 2.01 2.01 1.69

4.26 1.87 1.44

1.60 38.46 3.14 3.15 0.26 3.09 3.12 0.26 2.00 2.00 1.30 1.70 3.16 3.01 1.58

2.423 -1.56

2.228 0.0

1.810 3.12

1.641 4.30

1.479 6.23

1.459 8.89

1.472 17.94

-

[a] First point on the IRC path. [b] Last point on the IRC path.


SSD-VII [b] MoO2(η2O2)OPH3 + DMSO2

3.10 2.99 1.69


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

Graphic Table of Content ELF + TC

Oxygen Atom Transfer

Where and how the breaking/forming processes take place.


Page 28 of 28

Oxygen Atom Transfer Reactions from Mimoun Complexes to Sulfides

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