Coordination of Halide and Chalcogenolate Anions to Heavier 1,2,5

Aug 5, 2014 - †Institute of Organic Chemistry, ‡Institute of Chemical Kinetics and Combustion, and §Institute of Inorganic Chemistry, Russian Aca...
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Coordination of Halide and Chalcogenolate Anions to Heavier 1,2,5Chalcogenadiazoles: Experiment and Theory Nikolay A. Semenov,† Anton V. Lonchakov,‡,∥ Nikolay A. Pushkarevsky,§,⊥ Elizaveta A. Suturina,‡,∥,& Valery V. Korolev,‡ Enno Lork,# Vladimir G. Vasiliev,† Sergey N. Konchenko,§,⊥ Jens Beckmann,*,# Nina P. Gritsan,*,‡,∥ and Andrey V. Zibarev*,†,∥,$ †

Institute of Organic Chemistry, ‡Institute of Chemical Kinetics and Combustion, and §Institute of Inorganic Chemistry, Russian Academy of Sciences, 630090 Novosibirsk, Russia ∥ Department of Physics and ⊥Department of Natural Sciences, National Research University-Novosibirsk State University, 630090 Novosibirsk, Russia # Institute for Inorganic Chemistry, University of Bremen, 28359 Bremen, Germany $ Department of Chemistry, National Research University-Tomsk State University, 634050 Tomsk, Russia S Supporting Information *

ABSTRACT: New products of coordination of anions X− (X = F, I, PhS) to the Te atom of 3,4-dicyano-1,2,5-telluradiazole (1) were synthesized in high yields and characterized by X-ray diffraction (XRD) as the salts [(Me2N)3S]+[1-F]− (9), [K(18crown-6)]+[1-I]− (10), and [K(18-crown-6)]+[1-SPh]−·THF (11), respectively. In the crystal lattice of 10, I atoms are bridging between two Te atoms. The bonding situation in anions of the salts 9−11 and some other adducts of 1,2,5chalcogenadiazoles (chalcogen = S, Se, Te) and anions X− (X = F, Cl, Br, I, PhS) was studied using DFT, QTAIM, and NBO calculations, for 9−11 in combination with UV−vis, IR/Raman, and MS-ESI techniques. In all cases, the nature of the coordinate bond is negative hyperconjugation involving the transfer of electron density from X− to the heterocycles. The energy of the bonding interaction varies in a range from ∼30 kcal mol−1 comparable with energies of weak chemical bonds (e.g., internal N−N bond in organic azides) to ∼86 kcal mol−1 comparable with an energy of the C−C covalent bonds. The thermodynamics of the anions’ coordination to 1 and their Se and S congeners was also studied by quantum chemical calculations. The general character of this reaction and favorable thermodynamics in the case of heavier chalcogens (Se, Te) were established. Comparison with available data on acyclic analogues, i.e. the chalcogen diimines RNXNR, reveals that they also coordinate various anions but in addition reactions across XN (X = S, Se, Te) double bonds. Attempts to prepare the anion [1TePh]− led to disintegration of 1. The only unambiguously identified product was a rather rare tellurocyanate that was characterized by XRD and elemental analysis as the salt [K(18-crown-6)]+[TeCN]− (13).

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associate through secondary bonding interactions.1c,6,11 Significantly, the Mg(II) complexes of tetrakis(1,2,5telluradiazolo)porphyrazine and tribenzoporphyrazine with one fused 1,2,5-telluradiazole ring were synthesized to be the first Te-containing phthalocyanine analogues. It was found that the introduction of Te atom(s) produces strong effects on the spectral, redox, and conductivity properties of porphyrazines with annulated chalcogenodiazole ring(s).12 Very recently, the ability of 1,2,5-telluradiazoles to coordinate anions to Te atoms was discovered. Particularly, with 3,4dicyano-1,2,5-telluradiazole (1; Chart 1) and anions X− (X = Cl, Br) adducts [1-X]− and [1-X2]2− were obtained as pyridinium salts and characterized by XRD (2 and 3,

INTRODUCTION Chalcogenadiazoles (chalcogen = S, Se, Te), particularly 1,2,5chalcogenadiazoles and their fused derivatives, feature nontrivial heteroatom reactivity together with impressive diversity of molecular and electronic structures and properties of compounds.1−6 These heterocycles are of interest not only for fundamental research but also for various actual or potential applications in the field of materials science and agricultural chemistry (the relevant literature is too abundant to be cited completely; for selected publications see refs 7−9 and 10, respectively, and references therein). In contrast to the well-developed chemistry of 1,2,5thia(selena)diazoles,1a,b,2−4 that of their Te congeners is still in its infancy.1c,5−7,11 To date, 1,2,5-telluradiazoles have been mostly studied as building blocks in the design and synthesis of supramolecular structures because of their propensity to © 2014 American Chemical Society

Received: June 17, 2014 Published: August 5, 2014 4302

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Chart 1. Structures of Compounds 1−13

Scheme 1. Synthesis of Compounds 9−11 by Interaction of Compound 1 with Anions F−, I− and [PhS]−, Respectively

with PhS− compound 7 was reduced into the stable radical anion (RA).14 Additionally, a weakly bonded complex between 1 and the neutral electron donor pyridine (Py) was synthesized and structurally defined by XRD as 1·2Py (8; Chart 1).5 According to the XRD data, the lengths of Te−X (X = Cl, Br) coordinate bonds15 in the salts 2 and the Se−X (X = SPh) bond in the salt 5 are ca. 0.5 Å longer than the sums of the corresponding covalent radii but ca. 1 Å shorter than the sums

respectively; Chart 1).5 A similar reaction was also observed for the Se congener of compound 1 (4; Chart 1) and anion PhS−, and the product was isolated and characterized by XRD as [K(18-crown-6)]+[4-SPh]− (5; Chart 1).13 In contrast, the S congener of compounds 1 and 4 (6; Chart 1) did not interact with PhS−.13 For the cocrystal of pyridinium chloride with bicyclic selenadiazolo-thiadiazole (7; Chart 1) no interaction between Cl− and either the Se or S atom was observed, whereas 4303

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Figure 1. XRD structures of compounds 9−11 (ellipsoids at the 50% probability level; for 10, a fragment of the infinite I−Te−I−Te chain is shown; for 11, the coordination to K by the THF molecule is not shown). Selected bond lengths (Å) and bond angles (deg): 9, Te−F 2.132(2), Te−N 2.011(2) and 2.076(2), F−Te−N 81.62(9); 10, Te−I 3.3905(10) and 3.4196(9), Te−N 2.024(7), K···I 3.593(2), I−Te−I 104.53(2), Te−I−Te 139.18(2); 11, Te−S 2.6884(10), Te−N 2.0150(24) and 2.0995(27), N−K 2.9112(26), S−Te−N 84.270(74).

Scheme 2. Interaction of Compound 1 with Anion [PhTe]−

namics in the case of heavier chalcogens (Se, Te) were established. Attempts to prepare the salt [K(18-crown-6)]+[1-TePh]− from 1 and the anion [PhTe]− used in the form of the salt [K(18-crown-6)]+[PhTe]− (12; Chart 1), however, failed and provided only one unambiguously XRD-identified product: namely, the salt [K(18-crown-6]+[TeCN]− (13; Chart 1). It should be noted that previous studies of the reactivity of 1,2,5-chalcogenadiazoles (chalcogen = S, Se, Te) toward anions (charged nucleophiles) are rather limited.1−6 It is only known that the reaction between 1,2,5-thia(selena)- and 2,1,3benzoselenadiazoles and organolithium (RLi) or organomagnesium (RMgBr) reagents (i.e., C-centered anions) results in the opening of the heterocycle with formation of the corresponding diimines and R−X−R (X = S, Se).17 With 2,1,3benzoselenadiazoles this reaction was recommended as a convenient method for the synthesis of R−Se−R (R = Alk, Ar).17a The products of anion coordination to the chalcogen atoms were not reported.

of the corresponding van der Waals (VdW) radii. QTAIM analyses of the anions of salts 2 and 5 in the gas phase reveal closed-shell interactions, while NBO analyses indicate negative hyperconjugation featuring transfer of electron density from lone-pair MOs of X− in σ*-antibonding MOs of the chalcogen−nitrogen bonds of 1,2,5-chalcogenadiazoles as the main course of forming these adducts.5,13 Conceptually, these findings belong to a broader field of donor−acceptor (D-A) chemistry involving heavy chalcogens which has recently received much attention.11,16 To clarify how general the coordination of anions to the Te atom of 1,2,5-telluradiazoles might be, in the present work the interaction of compound 1 with X− (X = F, I, PhS) was investigated. The new salts [(Me2N)3S]+[1-F]−, [K(18-crown6)]+[1-I]−, and [K(18-crown-6)]+[1-SPh]−·THF (9−11, respectively; Chart 1) were synthesized in high yields and characterized by XRD. The bonding situation in the salts 9−11, as well as thermodynamics of the anion formation, was studied by quantum chemical calculations. Additionally, the bonding situation and thermodynamics for a number of putative adducts of 1,2,5-chalcogenadiazoles with a series of anions were also analyzed. In all cases, the nature of the coordinate bond is negative hyperconjugation between chalcogenadiazoles and X− featuring transfer of electron density from anion to the heterocycles. The general character of the coordination of anions to 1,2,5-chalcogenadiazoles and favorable thermody-

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RESULTS AND DISCUSSION Preparation and XRD Characterization of Compounds. In this work, the reaction of 3,4-dicyano-1,2,5telluradiazole (1) with four anions X− (X = F, I, PhS, PhTe) was studied. With the anions F−, I−, and [PhS]− taken in the form of salts of cations [(Me2N)3S]+ and [K(18-crown-6)]+, 4304

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distance in salt 13 (Figure 2) is elongated in comparison with 1.07(1) Å found for the salt [PPN]+[TeCN]−.21d This can be attributed to N···K interactions in the salt 13 (Figure 2) having no analogy in the salt [PPN]+[TeCN]−. Previously, both thiophenolate7a,c,13,22 and iodide23 were used as reducing agents for transformation of a number of 1,2,5-thia(selena)diazoles and their TCNQ-fused derivatives into stable RAs, i.e. in reactions featuring complete CT from D to A, in contrast to the reactions presented in Scheme 1 for which the CT is incomplete. One might expect that for the same anion X− (X = I, PhS) completeness of the CT correlates with the gas-phase electron affinity (EA) of 1,2,5-chalcogenadiazole derivatives. Indeed, a comparison of the first adiabatic EAs of 1,2,5-chalcogenadiazoles from (U)B3LYP/6-31+G(d) calculations7a reveals the following: compound 6 (EA = 1.84 eV) does not interact with [PhS]− 13 and compounds 4 (1.94 eV) and 1 (2.10 eV) coordinate [PhS]− to their chalcogen atoms with formation of anionic adducts (ref 13 and this work), whereas compound 7 (2.19 eV) and its S congener (2.14 eV) become reduced into their RAs.13,22 With the anion I−, compound 1 (2.10 eV) forms an anionic adduct (Scheme 1), whereas bis[1,2,5]thiadiazolotetracyanoquinonodimethane (EA = 3.47 eV) transforms into its RA.23 This anion addition vs reduction to RA dichotomy13 should be taken into account in future work. Spectroscopy and Thermodynamics of the Adducts under Study. It was previously demonstrated that the UV−vis spectrum of salt 5 (Chart 1) is characterized by an intense CT absorption band in the visible region associated with its anion [4-SPh]−. Using UV−vis spectroscopy, the equilibrium constants K and the Gibbs free energies for the reaction of adduct formation in MeCN and THF were measured.13 The anion [1-SPh]− (salt 11, Chart 1) has a very similar UV−vis spectrum which was very well reproduced by timedependent DFT calculations with the double-hybrid B2PLYP functional24 known to perform well for the calculations of CT transitions.25 According to the calculations, two electronic transitions are responsible for the long-wavelength band (Figure 3A), and both are composed of electron promotions from the HOMO and HOMO-1 of the anion of 11 onto its LUMO (Figure 3B; Table S2, Supporting Information). The

the target products 9−11, respectively, were obtained in high isolated yields (Scheme 1) and their structures were confirmed by XRD (Figure 1; Table S1, Supporting Information). With the anion [TePh]−, disintegration of 1 was unexpectedly observed, with the only identified product being the salt [K(18crown-6)]+[TeCN]− (13) (see below). In contrast to other X− halide salts (9, X = F; 2,5 X = Cl, Br) in the crystalline state of salt 10 the I and Te atoms are connected in an alternating manner with two slightly different Te···I distances (Figure 1) to form infinite chains along the c axis (Figure S1, Supporting Information). It should be noted that Te···I interactions have attracted much attention recently,18 as they are structurally directing and responsible for a great structural diversity.18a According to the ESI-MS data, individual anions [1-X]− (X = F, I, SPh) exist not only in the crystalline state but also in MeCN solutions of 9−11. For salts 9 and 11 only the anions [1-F]− and [1-SPh]− were observed, but for salt 10 the anions [1-I]− and [I]− were detected, which indicates dissociation of [1-I]− into components. An equilibrium constant (K) cannot be estimated from these data; it should only be noted that intensity of peak [I]− is higher than that of peak [1-I]− (Figure S2, Supporting Information). The values of K in MeCN and CH2Cl2 solutions were measured using UV−vis spectroscopy (see Spectroscopy and Thermodynamics of the Adducts under Study). According to quantum chemical calculations (see below), there is a partial charge transfer (CT) from X− onto the heterocycle in 9−11, and in this aspect the corresponding anions [1-X] − can be considered as D-A or CT systems. In the case of an interaction between heterocycle 1 and anion [PhTe]− taken in the form of the specially prepared salt [K(18crown-6)]+[PhTe]− (12; Scheme 2, Figure 2),19 the only

Figure 2. XRD structures of compounds 12 and 13 (ellipsoids at the 30% probability level). Selected bond distances (Å) and bond angles (deg): 12, Te−C1 2.115(4), Te···K 3.513(1), K···O 2.782(3)− 2.902(4), C−Te−K 101.3; 13, Te−C 2.031(5), C−N 1.148(6), N···K 3.6164(10), K···O 2.774(3)−2.844(3).

unambiguously identified product was salt [K(18-crown6)]+[TeCN]− (13; Scheme 2), isolated in low yield, whose structure was established by XRD (Figure 2; Table S1, Supporting Information) and elemental analysis.20 Salts of the anion [TeCN]− are known only from the late 1960s as being isolable from their solutions only in the case of weakly polarizable, bulky countercations such as [Alk4N]+, [Ph4As]+, or bis(triphenylphosphoranylidene)ammonium, [PPN]+. For example, the salt [K]+[TeCN]− decomposed quickly with elimination of elemental tellurium when its isolation was attempted.21 In salt 13, the anion is linear, as in the salt [PPN]+[TeCN]− studied by XRD earlier.21d The Te−C bond distances are practically the same, whereas the C−N bond

Figure 3. (A) UV−vis spectra of 1 (dotted curve) and 11 (solid curve) in MeCN. The vertical bars indicate the positions and oscillator strengths ( f, right axis) of the electronic transitions calculated for the anion of 11 (i.e., [1-SPh]−) at the B2PLYP/def2-TZVP (with ECP for Te) level in MeCN. (B) HOMO, HOMO-1, and LUMO of [1-SPh]− calculated at the same level of theory. 4305

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Figure 4. (A) Experimental IR spectra of salt 11 in KBr (spectrum 1) and in polyethylene (spectrum 1a), and spectrum calculated for the optimized ion pair [K(18-crown-6)]+[1-SPh]− at the B3LYP/def2-TZVP (with ECP for Te) level (spectrum 2). (B) Experimental Raman spectrum of 11 (spectrum 1) and that calculated at the B3LYP/def2-TZVP level for the ion pair (spectrum 2). The scaling factor 0.97 was used for both calculated spectra28 (see also Figure S3, Supporting Information).

underestimation of the relative intensities of Raman lines in the 100−800 cm−1 region for salt 10. The Te−F stretching vibration of the anion [1-F]− contributes mainly to the intense band at νexp 362 cm−1 (νcalc 426 cm−1; the band is marked with an asterisk in Figure S4; see also Figure S6, Supporting Information). A small contribution of the Te−I stretch was revealed for the vibration modes with νcalc 113.5 cm−1 (Figures S5 and S6, Supporting Information). An attempt was made to measure the equilibrium constant K and the Gibbs free energy for the anion [1-SPh]− formation in solution using UV−vis spectroscopy. In contrast to the previous case of [4-SPh]−,13 addition of the parent 1 (having only weak absorption in the visible region at its short-wave end) to the THF and MeCN solutions of salt 11 has no noticeable influence on the long-wavelength absorption (Figure 3). These observations indicate that in both solutions and in the range of concentrations employed (≥3 × 10−5 M) the equilibrium is shifted completely to the adduct [1-SPh]−. Thus, only the lower limit of the equilibrium constant and the upper limit of the Gibbs free energy of adduct [1-SPh]− formation can be estimated as K ≥ 108 M−1 s−1 and ΔGo ≤ −11 kcal mol−1, respectively. Experimental and calculated UV−vis spectra of anions [1-F]− (salt 9) and [1-I]− (salt 10) are presented in Figure S7 and Table S4 (Supporting Information). Formation of the anion [1F]− is characterized by a small bathochromic shift (∼20 nm) of the visible and near-UV bands in the spectrum of heterocycle 1. Spectral changes are more pronounced upon formation of anion [1-I]− (Figure S4 and Table S4, Supporting Information). Using UV−vis spectroscopy we were able to measure the constant K for the formation of the [1-I]− anion in MeCN and CH2Cl2 solutions (Figures S8 and S9, Supporting Information). As in the case of the anion [4-SPh]−, the value of K is significantly reduced in the polar MeCN solution (Table 1). In the previous paper13 we estimated by DFT calculations with B97-D and M06-2X functionals the ΔG° value for formation of anion [1-SPh]− from 1 and [PhS]−. It turned out that the results obtained underestimate the absolute ΔG° value. In this paper, we used for calculations a more advanced version of dispersion correction, namely the B97-D3 method.31 As for UV−vis spectra calculations, two approaches, namely the effective core potentials for heavy atoms and full-electron DKH2 procedure,32 were employed. The Se−S and Te−S bond lengths predicted at the B97-D3 level using both approaches

LUMO is completely localized on the heterocycle, while the HOMO and HOMO-1 are localized mainly on the Ph−S fragment and Te−S bonding region. Therefore, the longwavelength band is indeed a CT band. The full-electron calculations with a DKH2 relativistic Hamiltonian gave very similar results (Table S2, Supporting Information). Calculations with a meta-GGA M06 functional also reproduce the long-wavelength absorption band fairly well. As expected, calculations with the conventional B3LYP functional significantly underestimate the energies of the CT transitions,26 whereas those with the BH&HLYP functional overestimate them (Table S3, Supporting Information). Experimental IR and Raman spectra of 11 were assigned on the basis of calculations performed for optimized structure of the ion pair [K(18-crown-6)]+[1-SPh]− by the B3LYP method,27 known to be very well established for the calculation of IR frequencies.28 The agreement of the experimental and theoretical IR/Raman spectra is very good (Figure 4). The Te− S stretching vibration of the anion [1-SPh]− contributes mainly −1 −1 (νmax to a weak band at νmax exp 239 cm calc 255 cm ; the bands are marked with an asterisk in Figure 4; see also Figure S3, Supporting Information). Compounds featuring a Te−S covalent bond, for example Ar−Te−S−Ar,29 are known but cannot be used as references, however, since they were not characterized by IR/Raman techniques in the needed spectral range. Previously,13 using the same combination of experimental and theoretical approaches, it was found that the Se−S stretching vibration of the anion [4-SPh]− of salt 5 contributes mainly to the IR band at 165 cm−1. The difference observed now for the E−S stretching modes of anions [4-SPh]− and [1SPh]− (E = Se, Te, respectively) reflects the prominent difference in the energies of the corresponding bonds E−S (see below) and therefore in their force constants. Thus, chalcogens in the anions under discussion do not behave as pseudoisotopes of each other as they do in some other cases of isostructural and isoelectronic chalcogen derivatives, making possible the empirical assignment of molecular vibrations they are involved in.30 The IR and Raman spectra of salts 9 (anion [1-F]−) and 10 (anion [1-I]−) were also recorded and calculated (Figures S4 and S5, Supporting Information). Figures S4 and S5 demonstrate that calculations reproduce fairly well the experimental spectra, the only exception being the tremendous 4306

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The results of Table 3 demonstrate that experimental coordinate E−X bond distances are longer than the sums of the corresponding covalent radii35,36 by ca. 0.07 Å (Te−F) to 0.71 Å (Te−I) and shorter than the sums of the corresponding VdW radii35,37 by ca. 1.40 Å (Te−F) to 0.65 Å (Te−I). A comparison of Tables 2 and 3 shows that the gas- and liquidphase optimizations lead to similar values of E−X bond lengths for the anions of salts 2, 5, and 9−11, although the bond lengths of Te with halogens (Cl, Br, and I) are noticeably shorter (by ca. 0.1 Å) in the gas phase. The gas-phase values are in worse agreement with XRD experiment, and indeed, the difference can be mainly attributed to the influence of the crystal field.5 It is also seen that calculations reproduce fairly well the ∠N−E−X bond angles for the anions of salts 2, 5, and 9−11. The experimental ∠N−E−X bond angles for the anions under study (165−175°) are within the same range as was determined previously for the intramolecular E···X secondary bonding interactions in structurally related compounds (Chart 2, ∠Y−E−X = 160−180°).34 Of interest are not only anions of salts 2, 5, and 9−11 but also similar derivatives of Se (4) and S (6) congeners of telluradiazole 1. For all proposed anions, the minima on the potential energy surfaces (PES) were located and bonding energies were calculated (Table 3). According to the calculations, coordinate E−X bonds are longer than the sums of the corresponding covalent radii by ca. 0.02 Å (Te−F) to 0.82 Å (S−I) and shorter than the sums of the corresponding VdW radii by ca. 1.40 Å (Te−F) to 0.61 Å (S−I). Overall, the i ratio rcalc E···X/∑rVdW varies between 0.59 (Te−F) and 0.84 (S−I) for the whole set of the compounds discussed (Table 3). The results of Table 3 show that the energy of bonding interaction (Eb) vary in a very wide range, and the lower values of ∼30 kcal mol−1 coincide with the energies of weak chemical bonds (e.g., internal N−N bond in organic azides),38 while the upper value of 86 kcal mol−1 is close to an energy of the C−C covalent bonds.39 As expected, the energy of the bonding interaction Eb increases for the same X in the order S, Se, and Te. In turn, for the same chalcogen, the value of Eb increases in the order I, Br, S, Cl, and F, and for all chalcogens the ratio of highest and smallest bonding energies is ca. 2.2−2.4. The energy of the E−X bonding interaction correlates with the difference between the E−X bond length and the sum of the covalent radii of E and X (Δr = ∑ricov − rE−X), and dependence of Eb on Δr is well described by an exponential function with characteristic value Δr0 = 0.43 ± 0.05 Å (Figure 5). We also performed QTAIM analysis of the electron density distribution obtained in the gas-phase calculations at the B97-

Table 1. Values of Equilibrium Constants (Kexp) and Gibbs Free Energies (ΔG°exp) of the Reaction of Adduct Formation Measured by UV−Vis Spectroscopy adduct [4-SPh]

solvent −

[1-SPh]− [1-I]−

THF CH3CN THF CH3CN CH2Cl2 CH3CN

Kexp, L mol−1 (7.4 ± (3.0 ± ≥108 ≥108 (6.8 ± (1.5 ±

ΔG°exp, kcal mol−1

1.0) × 10 0.6) × 103 4

1.4) × 105 0.2) × 103

−6.6 ± 0.1 −4.7 ± 0.1 ≤−11.0 ≤−11.0 −8.0 ± 0.2 −4.3 ± 0.1

are similar and are in reasonable agreement with the XRD data (Figure 1, Table 2). It is also seen that calculations at the B97D3/def2-TZVP level with the COSMO solvation model33 accurately predict the thermodynamics of formation of the anions [4-SPh]− (salt 5)13 and [1-SPh]− (salt 11) in THF solution. The same procedures were employed to optimize structures and to estimate formation thermodynamics for other anions isolated in the forms of salts (Table 2). It is seen that Te−X bond lengths (X = halogen) predicted at both levels of theory are also in reasonable agreement with XRD data. Previously, optimization of the [1-Cl]− adduct in the gas phase at the MP2 level led to pronounced underestimation of the Te−Cl bond length as 2.623 Å, and this was attributed to the influence of the crystal field.5 It is also evident that the DKH2-B97-D3/TZVPDKH calculations slightly underestimate exothermicity of the adduct formation in comparison to the B97-D3/def2-TZVP calculations. However, both types of calculations lead to qualitatively similar results, namely, they predict the following sequence of thermodynamic stability of adducts under study: [1-F]− ≫ [1-Cl]− ≥ [1-SPh]− ≥ [1-Br]− > [4-SPh]− ≥ [1-I]−. Bonding Situation in the Isolated and Putative Adducts. Currently, both bonding and nonbonding interactions involving Te atoms are under active experimental and theoretical study (see, for example, refs 1, 5, 6, 11, 13, 16, 18, and 34 and references cited therein). Particularly, for some Te− X bonds (X = S, Se, I) Pauling bond orders were calculated.18b To get a deeper insight into the bonding nature, the energies of bonding interactions (ΔEb and ΔEcb; eqs 1 and 2 in Experimental and Computational Details) were calculated for the adducts of 1,2,5-chalcogenadiazoles 1, 4, and 6 (Chart 1) with a series of anions X− (X = PhS, F, Cl, Br, I) in the gas phase (Table 3). Additionally, QTAIM analysis was performed for the optimized structures of adducts.

Table 2. Calculated Enthalpies and Gibbs Free Energies of the Adduct Formation in THF Solution (ΔH° and ΔG° in kcal mol−1) and Calculated and Experimental E···X Distances (E = S, Se, Te; X = S, F, Cl, Br, I) B97-D3b

r(E−X), Å adducta −

[1-SPh] [4-SPh]− [1-F]− [1-Cl]− [1-Br]− [1-I]−

DKH2-B97-D3c

bond E···X

B97-D3b

DKH2-B97-D3b

XRD

ΔH°

ΔG°

ΔH°

ΔG°

Te−S Se−Sd Te−F Te−Cle Te−Bre Te−I

2.727 2.691 2.122 2.747 2.962 3.214

2.727 2.691 2.128 2.764 2.965 3.256

2.688 2.722 2.132 2.80−2.86e,f 3.019 3.391, 3.420g

−26.2 −18.1 −38.5 −21.8 −17.8 −10.4

−14.3 −6.6 −33.1 −16.7 −12.8 −5.7

−22.1

−10.1

−32.6 −14.6 −9.7 −8.6

−27.3 −9.5 −4.7 −3.9

a For compound numbering, see Chart 1. bB97-D3/def2-TZVP with ECP for Te and I in THF. cDKH2-B97-D with DKH-TZVP basis set in THF; the calculations were not performed for [4-SPh]− since the anion does not contain heavy atoms. dXRD data of ref 13. eXRD data of ref 5. fDifferent counterions and polymorphs. gTwo values for bridging anions I−.

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Table 3. Gas-Phase Calculated and Experimental E−X Bond Lengths (Å) and N−E−X Bond Angles (deg) (E = Te, Se, S; X = S, F, Cl, Br, I), Calculated Energies of Bonding Interactions Eb and Ecb (kcal mol−1) for the Adducts of 1 (E = Te), 4 (E = Se), and 6 (E = S) with Anions X−, and the Sums of Covalent (∑ricov)35,36 and VdW (∑riVdW)35,37 Radii of Atoms E and X

r(E−X), ∠N−E−X anion

B97-D3 −

[1-SPh] [4-SPh]− [6-SPh]− [1-F]− [4-F]− [6-F]− [1-Cl]− [4-Cl]− [6-Cl]− [1-Br]− [4-Br]− [6-Br]− [1-I]− [4-I]− [6-I]− a

2.738, 2.683, 2.789, 2.080, 1.989, 1.925, 2.651, 2.609, 2.650, 2.854, 2.817, 2.889, 3.095, 3.084, 3.171,

a

166.2 176.1 112.8b 167.5 175.2 179.0 170.2 178.7 165.0 170.9 179.9 109.7b 171.0 179.7 109.0b

XRD

B97-D3a ∑ricov

2.688, 166.0 2.722, 175.2 2.132, 164.5

2.859, 172.4

2.982−3.110,c 165.1−167.9c

3.391, 3.420; 172.4, 169.1d

(∑ricov

2.37 2.18 2.04 2.06 1.87 1.73 2.34 2.15 2.01 2.49 2.30 2.16 2.68 2.49 2.35

− r)

(0.37) (0.50) (0.75) (0.02) (0.12) (0.20) (0.31) (0.46) (0.64) (0.36) (0.52) (0.73) (0.42) (0.59) (0.82)

∑riVdW

(∑riVdW

3.86 3.70 3.60 3.53 3.37 3.27 3.81 3.65 3.55 3.91 3.75 3.65 4.04 3.88 3.78

(1.12) (1.02) (0.81) (1.4) (1.38) (1.34) (1.16) (1.04) (0.90) (1.06) (0.93) (0.76) (0.96) (0.80) (0.61)

− r)

i rcalc E···X/∑rVdW

Eb

Ecb

0.71 0.73 0.78 0.59 0.59 0.60 0.70 0.72 0.75 0.73 0.75 0.79 0.77 0.79 0.84

50.1 39.1 31.7 86.2 72.1 61.2 54.2 42.3 33.0 46.3 35.4 29.1 39.8 29.8 25.0

48.9 37.3 29.5 78.4 63.5 53.6 51.6 39.4 27.5 45.3 34.0 27.3 40.0 29.4 24.4

B97-D3/def2-TZVP with ECP for Te and I. bThe optimized geometry is nonplanar. cTwo polymorphs were isolated.5 dSee Figure 1.

As expected,41 the higher ρb value corresponds to a higher energy of the bonding interaction, although there is an inverse relationship for a series of strongly bound adducts with F− (Figure S10, Supporting Information). Recently, the |Vb|/Gb ratio was proposed to be a good reliable indicator to classify bonding interactions: viz., the covalent bonds are characterized by |Vb|/Gb > 2, the bonding interactions with |Vb|/Gb < 1 are noncovalent in nature, and a partially covalent bonding was proposed in the intermediate case (1 < |Vb|/Gb < 2).42 It is also clear that the ratio |Vb|/Gb > 1 corresponds to the negative total energy density, Hb. Data of Table 4 demonstrate that bonding interactions for all but the [6-I]− anions belong to the intermediate case; thus, they are partially covalent. A fairly good linear correlation (r = 0.96) between the bonding energy and the discussed indicator is observed, with the only exception of the most strongly bound anion [1-F]− (Figure 6). This correlation indicates that the increase of Eb is due in part to the shared (or covalent) interactions. Data of Table 4 show that adduct formation is accompanied by CT from the anion to the heterocycle. It is well-known that the CT delocalization leads to a significant reduction of the energy.43 Calculations predict that the value of CT is within 0.32−0.52e for the Mulliken protocol and 0.29−0.44e for the NBO protocol. The results of NBO analysis43 are presented in Table 5 (the delocalization effects were semiquantitatively estimated within the second-order perturbation theory using the NBO6 program) and illustrated for the case of anion [1-F]− in Figure 7 that displays pairs of interacting localized MOs of this anion. According to the perturbative estimations, the main contribution to the delocalization effect (∼86%) comes from the interaction of the MOs presented in the upper row (Figure 7, Table 5). As a rule, only the main contribution is considered in the analysis; however, we also took into account two much smaller contributions (Figure 7, middle and bottom rows). The same procedure was applied to estimate the delocalization effects upon formation of the isolated and

Chart 2. Compounds Structurally Related to Anions of Salts 2, 5, and 9−11

Figure 5. Dependence of the energy of the E−X bonding interaction Eb on the difference between the E−X bond length and the sum of covalent radii of atoms E and X.

D3/def2-TZVP level (with ECP for Te and I). For all anions under study, BCPs lying between E and X atoms were localized and their topological descriptors were calculated (Table 4). It is seen that for all adducts the electron densities at BCP (ρb) are very low (0.024−0.053 au), with the only exception for adducts with fluoride (ρb ≈ 0.1). Furthermore, all values of a Laplacian of electron density (∇2ρb) at the BCPs are positive. Values of ρb < 0.1 au and relatively small and positive values of ∇2ρb are typical of closed-shell (i.e., predominantly electrostatic) interactions.40 4308

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Table 4. QTAIM Topological Descriptors (Electron Density ρb and Its Laplacian ∇2ρb, Ellipticity of Electron Density ηb, Electron Localization Function ELF at BCPs, Potential Vb, Kinetic Gb, and Full Electronic Hb Energy Densities) of BCPs of E− X Bonds (E = Te, Se, S; X = S, F, Cl, Br, I) of the Anion and Values of CT ΔQ from X− onto the Heterocycle upon Hypercoordinate Anion Formation Calculated using Mulliken (ΔQMul) and NBO (ΔQNBO) Protocolsa anionb −

[1-SPh] [4-SPh]− [6-SPh]− [1-F]− [4-F]− [6-F]− [1-Cl]− [4-Cl]− [6-Cl]− [1-Br]− [4-Br]− [6-Br]− [1-I]− [4-I]− [6-I]−

ρb

∇2ρb

Hb

Vb

|Vb|/Gb

ηb

ΔQMul

ΔQMul(E)/ΔQMul(X)

ΔQNBO

0.043 0.040 0.033 0.093 0.099 0.106 0.053 0.049 0.041 0.042 0.038 0.032 0.034 0.029 0.024

0.072 0.092 0.076 0.255 0.177 0.167 0.076 0.090 0.092 0.059 0.07 0.061 0.044 0.051 0.043

−0.006 −0.004 −0.002 −0.029 −0.039 −0.042 −0.010 −0.006 −0.003 −0.006 −0.003 −0.001 −0.003 −0.001 −0.0003

−0.031 −0.030 −0.022 −0.121 −0.122 −0.126 −0.039 −0.035 −0.030 −0.026 −0.023 −0.018 −0.018 −0.015 −0.011

1.292 1.111 1.048 1.315 1.470 1.500 1.345 1.207 1.111 1.300 1.150 1.125 1.200 1.071 1.000

0.427 0.408 0.169 0.106 0.219 0.265 0.243 0.269 0.223 0.267 0.290 0.045 0.298 0.315 0.023

0.52 0.46 0.41 0.47 0.47 0.47 0.45 0.39 0.33 0.43 0.36 0.33 0.42 0.34 0.32

0.43/−0.40 0.33/−0.42 0.38/−0.45 0.56/−0.53 0.43/−0.53 0.34/−0.53 0.50 /−0.55 0.40/−0.61 0.35/−0.67 0.49/−0.57 0.40/−0.64 0.35/−0.67 0.46/−0.58 0.39/−0.66 0.39/−0.68

0.44 0.41 0.37 0.30 0.32 0.33 0.36 0.33 0.28 0.36 0.32 0.29 0.39 0.32 0.29

a Values of ρb and ∇2ρb are given in in e/a03 and e/a05, respectively; Vb and Hb at BCPs are given in au. bThe electron densities were calculated in the gas phase at the B97-D3/def2-TZVP level of theory (with ECP for Te and I).

Figure 6. Correlation between the energy of the E−X bonding interaction Eb and the ratio of potential (Vb) and kinetic (Gb) electronic energy densities at BCPs. The black dot corresponds to the anion [1-F]−.

Figure 7. Interacting localized MOs of the anion [1-F]−: two lone pair MOs of the F atom, two σ*-antibonding MOs of the heterocycle, and their overlay.

Table 5. Calculated Energies Eb of Bonding Interactions and the Second-Order Perturbative Estimates E(2) of the D−A Interactions in the NBO Basis for the Adducts (kcal mol−1) Eb

adduct −

[1-SPh] [4-SPh]− [1-F]− [4-F]− [6-F]− [1-Cl]− [4-Cl]− [6-Cl]− [1-Br]− [4-Br]− [1-I]− [4-I]−

50.1 39.1 86.2 72.1 61.2 54.2 42.3 33.0 46.3 35.4 39.8 29.8

E(2) n→σ*

E(2) n→σ′*

E(2) n′→σ*

∑31E(2) i

29.0 44.4 48.9 40.3 32.4 28.5 13.0 26.7 22.6 22.0 16.9

3.0 13.8 7.4 5.3 6.2 1.7 7.3 4.3 1.0 3.2 0.5

3.6 11.6 10.3 9.0 5.2 4.0 2.0 4.1 3.1 2.9 1.9

35.6 59.8 56.6 54.6 43.8 34.2 22.3 35.1 26.7 28.1 19.3

putative adducts (Table 5). Unfortunately, we were unable to estimate this effect in the case of anion [1-SPh]− due to its inability to separate into two interacting units. For all other anions similar to the case of [1-F]−, the perturbative delocalization effects estimated as the sum ∑31E(2) made the i main contribution to the bonding interaction (Table 5). Thus, we can conclude that the negative hyperconjugation featuring transfer of electron density from the lone pair MOs of anions X− onto σ*-antibonding MOs of the chalcogen−nitrogen bonds of 1,2,5-chalcogenadiazoles is the main course of forming the coordinate E−X bonds. This description agrees with the Alcock model suggested for secondary bonding interactions between atoms of heavy p-block elements and atoms with lone pairs.44 Note that a good linear relationship is observed between Eb and discussed second-order perturbative estimates (∑E(2)) of the D-A interactions (r = 0.96; Figure S11A, Supporting Information).

a

a Other calculations were not performed, due to the inability of [1SPh]− to separate into two interacting units.

4309

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Figure 8. Gibbs free energies calculated at the B97-D3/def2-TZVP level of theory for formation of halide adducts of heterocycles 1 (green), 4 (brown), and 6 (yellow), with one (left) and two halides (right), in THF solution.

is predicted for Se and S congeners of [1-Cl]− and [1-Br]− and also for [1-I]−. Thus, these calculations are in agreement with experimental results of this paper and ref 5, and they also predict the possibility of synthesizing and isolating adducts of heterocycles 4 and 6 with anions F−, Cl−, and Br−.

The CT can be also estimated using the localized MOs and second-order perturbation theory: 1

ΔQ =

∑ Ei(2)Δε

■

3

where Δε is the energy difference between the interacting orbitals.43 Thus, it is expected that the correlation should exist between the bonding energy and CT for adducts under study. Indeed, the tendency of stronger E−X bonding for the larger CT (ΔQMul) does really exist, although the linear correlation is poor (r = 0.77; Figure S11B, Supporting Information). Thermodynamics of the Putative Adducts in THF Solution. In the previous sections, to analyze the bonding situation we used the results of gas-phase calculations (Tables 3−5). The thermodynamics in solution was analyzed only for anions isolated in the form of salts (Table 2). In this section, the results of calculations for anions in solution, including putative ones, are discussed. For a number of adducts, the QTAIM topological descriptors were also obtained using the electron density calculations in THF solution (Table S5, Supporting Information). A comparison of the results of Table 4 and Table S5 (Supporting Information) shows that values of descriptors obtained in two types of calculations are similar, although all absolute values obtained for the solution-phase densities are noticeably smaller (by about 10−20%). The destabilization effect of the solvation on the CT from the anion onto neutral heterocycle due to the adduct formation is obvious and leads to small back transfer. Structure optimization for the THF solutions was performed not only for putative adducts of 4 and 6 with one halogen anion but also for all heterocycles (1, 4, 6) with two halogen anions. Optimized E−X bond lengths are presented in Table S6 (Supporting Information). In all cases, introducing a second halogen anion leads to elongation of the E−X bonds due to electrostatic repulsion of negative charges. The same trend was observed experimentally for adducts of 1 with Cl− and Br− anions.5 Structure optimization was followed by the calculations of the adduct formation thermodynamics (ΔG° and ΔH°). Results of these calculations are visualized in Figure 8 for ΔG° and Figure S12 (Supporting Information) for ΔH°. Results of the calculations predict (Figure 8, left) that for the fluoride anion the equilibrium in THF solution is completely shifted to the adduct form. The equilibrium is predicted to be completely shifted to the adduct also in the case of [1-Cl]− and [1-Br]− anions. Detection of both adducts and free heterocycles

CONCLUSIONS New complexes between 3,4-dicyano-1,2,5-telluradiazole (1) and the anions X− (X = F, I, PhS) were synthesized and characterized by XRD as the salts [(Me2N)3S]+[1-F]− (9), [K(18-crown-6)]+[1-I]− (10), and [K(18-crown-6)]+[1-SPh]−· THF (11), respectively. The bonding situation in the anions of salts 9−11, as well as the thermodynamics of their formation, was studied by quantum chemical calculations employing a number of various approaches. In all cases, the nature of the coordinate bond15 was found to be negative hyperconjugation between 1 and X− featuring transfer of electron density from the latter onto the former. Previously, the same was also observed for halide adducts 2 (X = Cl, Br) and thiophenolate adduct 5.5,13 It follows from calculated thermodynamics of coordination of the anions X− to chalcogen atoms of 1,2,5-chalcogenadiazoles that S derivatives may also be involved, at least in the case of compound 4 and X = F. Therefore, the general character of the coordination of anions to 1,2,5-chalcogenadiazoles (chalcogen: S, Se, Te) may be expected. Indeed, very recently the adducts [K(18-crown-6)]+[1-SePh]−·THF and [K]+[1-SeCN]− were synthesized and characterized by XRD (good solubility of KSeCN in THF excluded using 18-crown-6).61 The study of isomeric heterocycles, e.g. 1,2,3-chalcogenadiazoles,62 is of interest in this context. Obviously, anions other than halides and chalcogenolates are also of interest. The aforementioned synthesis of [K]+[1SeCN]− shows that pseudohalides can also be involved in the chemistry under discussion.61 On the other hand, the known reactivity of C-nucleophiles (in the form of organolithum or organomagnesium reagents)17 toward S and Se congeners of 1,2,5-telluradiazoles is different from that discussed in this paper for the latter, as it features the opening of the heterocycle with formation of the corresponding diimines and organyl chalcogenides (chalcogen: S, Se). Therefore, there is at least one reaction route in the 1,2,5chalcogenadiazole−anion reaction system in addition to the reduction of the heterocycle into a RA and anion complex formation with the chalcogen atom. 4310

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In the discussed adducts, the CT from the anions X− onto heterocycles is moderate enough, except for adduct 11. An interesting challenge is whether the full CT from D onto A moieties of these adducts is possible, transforming their heterocyclic moieties into corresponding RAs, e.g. under light irradiation. Together with the continuing synthesis of new adducts, this can be one of directions for further research in the field.63 In the context of synthesis of new adducts, it should be noted that anions having additional coordination sites are of special interest. Among them, N-heterocyclic chalcogenolates, for example [HetX]− (Het = pyridin-2-yl, pyrimid-2-yl; X = S, Se, Te)64 and their O congeners, seem especially promising. Importantly, for acyclic analogues of 1,2,5-chalcogenadiazoles, i.e. the compounds RNXNR (X = S,65 Se,66 Te67), coordination of anions to the chalcogen atoms was also observed. In the case of X = S, the anions [RS(NR)2)]− can be prepared by reaction with practically any organometallics, and in the products the C-centered anion R− is coordinated to the S atom.68 For organolithium and organomagnesium compounds, RLi and RMgBr, this reaction was suggested to be used in their quantitative analysis.69 O-centered anions from metal alkoxides, as well as fluoride from CsF, also coordinate the S atom of RNSNR with formation of the corresponding anions.70 With X = Se, Te, the acyclic derivatives are inherently unstable (X = Se; although, with some exceptions)66 or/and dimerized (X = Te).1c,67 Nevertheless, the dianions [X(NR)3]2− were synthesized from RNXNR (X = Se, Te) and lithium amides LiHNR.66c,67b The same is also true for X = S.68 In contrast to the title reaction, however, these reactions proceed as addition reactions across the XN (X = S, Se, Te) double bonds. This difference, at least in part, may be associated with the fact that 1,2,5-chalcogenadiazoles are 6-π-electron heteroaromatics whereas their acyclic analogues RNXNR (X = S, Se, Te) are 4-π-electron heterocumulenes.

■

gas at 190 °C at a flow rate of 4 L min−1. The nebulizer pressure was set to 1.0 bar. Sample solutions were infused into the ESI source by an LC Agilent 1200 instrument at FIA mode (flow injection analysis, 10 μL at a flow rate of MeCN of 0.1 mL min−1). In all cases, isotopic distributions in the experimental mass spectra were in good agreement with theoretical simulations. Syntheses. Interaction of 1 with [(Me2N)3S]+[Me3SiF2]− (TAS-F). Synthesis of [(Me2N)3S]+[1-F]− (9). At −196 °C, MeCN (10 mL) was condensed into a mixture of 1 (0.170 g, 0.73 mmol) and TAS-F (0.198 g, 0.72 mmol). The reaction mixture was warmed to 20 °C, and diethyl ether (20 mL) was added to precipitate excess 1. The solution was filtered, and the filtrate was evaporated under vacuum. The residue was washed with diethyl ether and dried under vacuum. Salt 9 was obtained in quantitative yield in the form of orange plates: yield 0.293 g (98%). Single crystals suitable for XRD were obtained by crystallization from MeCN. Anal. Found for C10H18FN7STe (414.97): C, 29.03; H, 4.38; F, 4.62; N, 23.47; S, 7.74. Calcd: C, 28.94; H, 4.37; F, 4.58; N, 23.63; S, 7.73. NMR, δ: 1H, 2.88 (s); 13C, 138.3 (Chet), 119.4 (CN), 37.6 (CH3); 19F, 92; 125Te, 2180. ESI-MS, negative-ion base peak m/z 252.917 (calculated for [C4N4FTe]−, 252.917); positive-ion base peak m/z 164.120 (calculated for [C6H18N3S]+ 164.122). IR (KBr) ν, cm−1: 2852 w, 2814 w, 2221 m, 2169 vw, 2106 vw, 1708 vw, 1670 w, 1604 w, 1525 m, 1487 m, 1469 m, 1446 m, 1409 w, 1373 m, 1269 m, 1240 m, 1199 m, 1153 w, 1083 w, 1060 w, 1035 w, 943 vs, 914 s, 825 w, 783 w, 713 s, 686 m, 667 m, 650 m, 563 m, 516 w, 435 vw. Raman, ν, cm−1: 2220 vs, 1488 w, 1436 vw, 1376 w, 1236 vw, 1089 vw, 913 vw, 688 vw, 673 vw, 647 w, 538 vw, 519 vw, 471 vw, 440 vw, 423 vw, 292 vw, 174 vw, 127 vw. Interaction of 1 with [K(18-crown-6)]+[I]−. Synthesis of [K(18crown-6)]+[1-I]− (10). At ambient temperature, a solution of KI (0.058 g, 0.35 mmol) and 18-crown-6 (0.093 g, 0.35 mmol) in THF (15 mL) was added dropwise to a stirred solution of 1 (0.081 g, 0.35 mmol) in THF (10 mL). The orange-red reaction solution was filtered and evaporated to ∼one-third of its initial volume under reduced pressure, and 10 mL of pentane was condensed into it at −196 °C. The twolayer system obtained was kept at ambient temperature until mutual diffusion of solvents ceased (∼1 week), the solvents were removed with a syringe, and the residue was dried under vacuum. Salt 10 was obtained in the form of large orange prisms suitable for XRD, 0.155 g (67%). Anal. Found for C16H24IKN4O6Te (661.99): C, 29.19; H, 3.78, I 19.32, K 5.96; N, 8.32. Calcd: C, 29.03; H, 3.65, I 19.17, K 5.91; N, 8.46. NMR, δ, 1H, 3.50 (s), 3.36 (s); 13C, 141.1 (Chet), 119.7 (CN), 69.7 (CH2); 15N, 416 (Nhet), 256 (CN); 125Te, 2409. ESI-MS, negative-ion base peaks: lower-intensity peak m/z 360.823 (calculated for [C4N4TeI]−, 360.824), higher intensity peak m/z 126.905 (calculated for [I]−, 126.905); positive-ion base peak m/z 303.121 (calculated for [C12H4KO6]+ 303.120). IR (KBr) ν, cm−1: 3445 vw, 2907 m, 2893 m, 2868 m, 2820 w, 2793 w, 2743 vw, 2706 vw, 2687 vw, 2226 w, 1474 w, 1456 w, 1369 w, 1350 m, 1285 w, 1250 m, 1107 vs, 962 m, 837 w, 687 vw, 563 w, 532 vw. Raman, ν, cm−1: 2954 w, 2940 w, 2920 w, 2911 w, 2893 w, 2875 w, 2843 w, 2807 w, 2724 vw, 2697 vw, 2229 vs, 1484 w, 1476 vw, 1369 w, 1272 vw, 1244 vw, 1147 vw, 1069 vw, 873 vw, 710 m, 654 m, 562 vw, 468 w, 375 w, 297 vs, 188 vw, 154 vw. Interaction of 1 with [K(18-crown-6)]+[PhS]−. Synthesis of [K(18crown-6)]+[1-SPh]−·THF (11) and Solvent-Free [K(18-crown-6)]+[1SPh]−. At −60 °C, a solution of 1 (0.120 g, 0.52 mmol) in THF (5 mL) was added dropwise to a stirred solution of [K(18-crown6)]+[PhS]− (0.214 g, 0.52 mmol) in THF (15 mL). The red reaction solution was warmed to 20 °C, stirred for 30 min, filtered, and evaporated under reduced pressure to a volume of ∼5 mL, and 10 mL of pentane was condensed into it at −196 °C. The two-layer system obtained was kept at ambient temperature until mutual diffusion of solvents ceased, and the solvents were decanted. Salt 11 was obtained in the form of large red prisms suitable for XRD. Salt 11 was washed with hexane and dried under vacuum, which led to transformation of the sample into a crystalline powder due to loss of

EXPERIMENTAL AND COMPUTATIONAL DETAILS

General Procedures. Compound 1,5 tris(dimethylamino)sulfonium difluorotrimethylsilicate (TAS-F),45 and [K(18-crown6)]+[PhS]− 22 were prepared by known procedures, and 18-crown-6 was obtained from Aldrich. Solvents were dried under argon with an MBraun SPS-800 device. The syntheses described below were performed under argon using common Schlenk, glovebox, and vacuum-line techniques. Analyses for C, H, N, and S were performed with CHNS-Analyzer Euro EA 3000 and for K with an Agilent Technologies 4100 MP-AES microwave plasma-atomic emission spectrometer. Analyses for F were carried out by standard spectrophotometric methods with the La complex of alizarin complexone. Spectral Measurements. 1H and 13C NMR spectra were measured with a Bruker DRX-500 instrument and 15N and 125Te NMR spectra with a Bruker AV-600 instrument at frequencies of 500.13, 125.77, 60.85, and 189.85 MHz, respectively, for solutions in [D6]DMSO; chemical shifts (δ) are given with respect to Me4Si (1H, 13 C), NH3 (liquid) (15N), and Me2Te (125Te). UV−vis spectra were obtained with a Shimadzu UV-2401PC spectrophotometer for MeCN or THF solutions. IR spectra were recorded in KBr and polyethylene pellets using Lumex-Siberis Infralum FT-801 and Bruker Vertex FT-IR spectrometers, respectively. Raman spectra of polycrystalline samples of the salts were taken with a Bruker Optics microscope-Raman spectrometer Senterra (λex 785 nm, I = 100 mJ s−1). LC-MS data were obtained with a Bruker Daltonik micrOTOF-Q hybrid quadrupole time-of-flight mass spectrometer equipped with electrospray ionization (ESI) sources. Nitrogen was used as a drying 4311

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solvate THF. The solvent-free salt [K(18-crown-6)]+[PhS]− was obtained in a yield of 0.227 g (68%). Anal. Found for C22H9KN4O6STe (solvent-free) (644.25): C, 40.85; H, 4.46, K 5.90; N, 8.71; S, 4.71. Calcd: C, 41.01; H, 4.54, K 6.07; N, 8.70; S, 4.98. NMR, δ: 1H, 7.40 (dt, J1 = 7 Hz, J2 = 2 Hz), 7.16 (tt, J1 = 7.6 Hz, J2 = 1.6 Hz), 7.02 (tt, J1 = 7.6 Hz, J2 = 1.3 Hz), 3.59 (s); 13C, 144.7 (Car-S), 139.2 (Chet), 133.7 (CHpara), 128.2 (CHorto), 123.0 (CHmeta), 119.7 (CN), 69.5 (CH2); 15N, 430 (Nhet), 256 (CN); 125 Te, 2076. ESI-MS, negative-ion base peak m/z 342.934 (calculated for [C10H5N4STe]−, 342.930); positive-ion base peak m/z 303.123 (calculated for [C12H4KO6]+ 303.120). IR (KBr) ν, cm−1: 2899 m, 2824 w, 2745 vw, 2218 w, 1971 vw, 1576 w, 1493 vw, 1470 w, 1452 w, 1433 w, 1379 w, 1350 m, 1285 w, 1250 w, 1236 w, 1105 vs, 1022 w, 959 m, 837 w, 743 w, 696 w, 554 vw, 528 vw. Raman, ν, cm−1: 2218 vs, 1577 w, 1493 w, 1472 vw, 1432 vw, 1378 m, 1272 vw, 1126 vw, 1084 w, 1023 vw, 998 w, 867 vw, 829 vw, 700 vw, 679 vw, 635 w, 537 vw, 469 vw, 422 vw, 355 vw, 283 vw, 232 vw, 166 w, 125 vw. Compound [K(18-crown-6)]+[PhTe]− (12) and Its Interaction with 1. Isolation of [K(18-crown-6)]+[TeCN]− (13). (a) At −196 °C, THF (60 mL) was condensed into a mixture of PhTeTePh46 (1.687 g, 4.1 mmol), KC847 (1.300 g, 9.6 mmol), and 18-crown-6 (2.311 g, 8.7 mmol). The reaction mixture was warmed to 20 °C and stirred for 1 h before it was filtered under argon. The light yellow filtrate was kept at −20 °C for 3 days, the solution was decanted, and the residue was dried under vacuum. Salt 12 (0.565 g) was obtained as large yellow prisms suitable for XRD. Into the decanted solution was condensed 60 mL of pentane at −196 °C, and the two-layer system obtained was kept at 20 °C until mutual diffusion of solvents ceased. The solvents were decanted, the residue was dried under vacuum, and another crop of 12 (0.289 g) was obtained. The combined yield of salt 12 was 0.854 g (19%). Contact with the atmosphere led to rapid decomposition. Anal. Found for C18H29KO6Te (508.12).: C, 42.40; H, 5.80. Calcd: C, 42.55; H, 5.75. NMR, δ: 1H, 7.65 (dd, J1 = 8.2 Hz, J2 = 1.2 Hz), 6.75 (tt, J1 = 7.6 Hz, J2 = 1.2 Hz), 6.65 (tt, J1 = 7.6 Hz), 3.59 (s) (CH2); 13C, 142.3 (CHpara), 126.6 (CHorto), 120.6 (CHmeta), 115.9 (Car-Te), 69.6 (CH2); 125Te, 40. (b) At 20 °C, a solution of 12 (0.152 g, 0.3 mmol) in THF (15 mL) was added dropwise to a stirred solution of 1 (0.068 g, 0.3 mmol) in of THF (5 mL). The black reaction mixture was stirred for additional 30 min and evaporated under reduced pressure to a volume of ∼5 mL, and 10 mL of pentane was condensed into it at −196 °C. The twolayer system obtained was kept at 20 °C until mutual diffusion of solvents ceased. The solvents were decanted, and the residue was dried under vacuum. Compound 13 was obtained in the form of long black needles suitable for XRD: yield 0.025 g. Anal. Found for C13H24KNO6Te (453.03): C, 34.44; H, 5.28; N, 2.96. Calcd: C, 34.16; H, 5.29; N, 3.06. Crystallographic Analysis. The data for 9−13 were collected at 173 ± 2 K on a Bruker P4 diffractometer using Mo Kα radiation (λ = 0.71073 Å). The structures were solved by direct methods using the SHELX program,48 and all non-hydrogen atoms were refined unisotropically (Table S1, Supporting Information). The obtained structures were analyzed with the PLATON49 and MERCURY50 programs. Crystallographic data (excluding structure factors) for the structures in this paper have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication nos. CCDC (9, CCDC-1002778; 10, CCDC-1002779; 11, CCDC-1002780; 12, CCDC-1002781; 13, CCDC-1002782). Copies of the data can be obtained, free of charge, on application to the CCDC, 12 Union Road, Cambridge CB2 1EZ, U.K. (fax, +44-(0)1223-336033; e-mail, [email protected]). Quantum Chemical Calculations. The geometries of 1, 4, and 6 and their adducts with the anions X− (X = PhS, F, Cl, Br, I) were optimized at the B97-D3 level of theory.31 The Becke−Johnson damping function was used in all dispersion-corrected calculations,51 which were carried out using two approaches. First, the def2-TZVP basis set52 with effective core potentials for heavy atoms Te and I was employed. In addition, relativistic calculations using the second-order Douglas−Kroll−Hess method (DKH2)32 and full-electron DKH-TZV

basis set52 were performed. The Grimme geometrical counterpoise (gCP) correction scheme was used to semiempirically treat the basis set superposition error (BSSE) effects.53 The energy of the bonding interaction (Eb) was calculated as the difference between the energy of the adduct and the sum of the energies of the heterocycle and anion using eq 1, where Ead, Ehet, and Ean are electronic energies of the adduct, heterocycle, and anion in their optimized geometries. The energies of bonding interaction corrected for the BSSE and zero point energies (ZPE) (Ecb) were calculated with eq 2. E b = − (Ead − E het − Ean)

(1)

E bc = E b + E BSSE + ΔEZPE

(2)

Optimization of the geometries of heterocycles and adducts was also performed in the solvent (THF or MeCN) at the same levels of theory (B97-D3 and DKH2-B97-D3). In both types of calculations, the COSMO solvation model33 was applied. The calculated energies after outlying charge correction were used to calculate enthalpies and Gibbs free energies of adduct formation. Note that the standard state for the calculations of the Gibbs free energy was chosen to be a 1 M solution. In the case of DKH2-B97-D3 calculations, the optimization of the structure was followed by additional single-point calculations, as the one-center approximation was used in the geometry optimization.54 In turn, the thermochemical corrections were obtained from the gasphase optimization/frequency calculations at the B97-D3/def2-TZVP or DKH2-B97-D3/DKH-TZV levels of theory without gCP correction. More accurate single-point energies were also calculated using the double-hybrid B2PLYP-D3 functional55 with the same def2TZVP basis set. All quantum chemical calculations were performed using the ORCA suit of programs (version 3.0.0).54 The resolution-of-the-identity approximation (RI) was used to speed up the GGA computations.56 The RIJCOSX approximation was used to speed up computations with hybrid and double-hybrid functionals.57 To reveal the nature of the Te···X bonding interactions, a QTAIM analysis has been performed.58 The B97-D3/def2-TZVP densities were used in QTAIM calculations. QTAIM calculations and graphics were produced using the Multiwfn program (version 3.2).41 CT from the anion onto the heterocycle (ΔQ) upon adduct formation was evaluated from the atomic charges calculated using Mulliken (ΔQMul) and NBO37 (ΔQNBO) protocols. In addition, NBO analysis43 was performed using the NBO6 program.59 The strength of D-A interactions in the case of NBO analysis was determined by the second-order perturbation energy (ΔE(2) da ) calculated using eq 3, where Φd, Φa and εd, εa are the NBO MOs of D and A and their energies, respectively, nd is the occupation number of the MO of D, and F̂ is a Fock operator. (2) ΔEda = nd

̂ a ⟩2 ⟨Φd|F |Φ εd − εa

(3) 54

With the ORCA suit of programs, the UV−vis and IR/Raman spectra of the products were also calculated. The UV−vis spectra of adducts in their XRD geometries were calculated by time-dependent (TD) DFT26 at different levels of theory. The hybrid BH&HLYP,27 double-hybrid B2PLYP,24,56 and meta-GGA M0660 methods, as well as a conventional B3LYP procedure,27 were used in the calculations. The full-electron relativistic TD DKH2-B2PLYP and DKH2-M06 methods were also employed. The IR/Raman spectra were calculated by the B3LYP method.27

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ASSOCIATED CONTENT

S Supporting Information *

Figures, tables, and CIF and xyz files giving XRD, ESI-MS, IR/ Raman, UV−vis, and DFT data for the studied compounds together with calculated geometries of studied compounds (xyz 4312

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file). This material is available free of charge via the Internet at http://pubs.acs.org.

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Suturina, E. A.; Chulanova, E. A.; Kuratieva, N. V.; Bogomyakov, A. S.; Irtegova, I. G.; Vasilieva, N. V.; Konstantinova, L. S.; Gritsan, N. P.; Rakitin, O. A.; Ovcharenko, V. I.; Konchenko, S. N.; Zibarev, A. V. Inorg. Chem. 2013, 52, 6654. (c) Pushkarevsky, N. A.; Lonchakov, A. V.; Semenov, N. A.; Lork, E.; Buravov, L. I.; Konstantinova, L. S.; Silber, T. G.; Robertson, N.; Gritsan, N. P.; Rakitin, O. A.; Woollins, J. D.; Yagubskii, E. B.; Zibarev, A. V. Synth. Met. 2012, 162, 2267. (d) Zibarev, A. V.; Mews, R. Selenium and Tellurium Chemistry: From Small Molecules to Biomolecules and Materials; Woollins, J. D., Laitinen, R. S., Eds.; Springer: Berlin, 2011; pp 123−149. (8) (a) Watanabe, M.; Goto, K.; Shibahara, M.; Shinmyozu, T. J. Org. Chem. 2010, 75, 6104. (b) Watanabe, M.; Goto, K.; Fujitsuka, M.; Tojo, S.; Majima, T.; Shinmyozu, T. Bull. Chem. Soc. Jpn. 2010, 83, 1155. (9) (a) Chen, W.; Zhang, Q.; Salim, T.; Ekahana, S. A.; Wan, X.; Sum, T. C.; Lam, Y. M.; Hon Huan, A. C.; Chen, Y.; Zhang, Q. Tetrahedron 2014, DOI: 10.1016/j.tet.2014.01.026. (b) Uchiyama, S.; Kimura, K.; Gota, C.; Ukabe, K.; Kawamoto, K.; Inada, N.; Yoshikara, T.; Tobita, S. Chem Eur. J. 2012, 18, 9552. (c) Ellinger, S.; Graham, K. R.; Shi, P.; Farley, R. T.; Steckler, T. T.; Brookins, R. N.; Taranekar, P.; Mei, J.; Padilha, L. A.; Emsley, T. R.; Hu, H.; Webster, S.; Hagan, D. J.; Van Stryland, E. W.; Schanze, K. S.; Reynolds, J. R. Chem. Mater. 2011, 23, 3805. (d) Fang, F.; Xu, B.; Jiang, B.; Fu, H.; Chen, X.; Cao, A. Chem. Commun. 2005, 1468. (e) Akhtaruzzaman, M.; Kamata, N.; Nishida, J.; Ando, S.; Tada, H.; Tomura, M.; Yamashita, Y. Chem. Commun. 2005, 3183. (10) (a) Wang, G.; Phan, L. T.; Or, Y. S.; Qiu, Y. L.; Niu, D.; Peng, Y.; Busuyek, M.; Wang, Y.; Nakajima, S. WO/2006/119313, 2006. (b) Nederski, W.; Osswald, M.; Dorsch, D.; Schmitges, C. J.; Wilm, C.; Christadler, M. DE 196 09 597, 2002. (c) Yoshida, Y.; Matsuda, K.; Sasaki, H.; Matsumoto, Y.; Matsumoto, S.; Tawara, S.; Takasugi, H. Bioorg. Med. Chem. 2000, 8, 2317. (d) Fujiwara, M.; Kodama, E. N.; Okamoto, M.; Tokuhisa, K.; Ide, T.; Hanasaki, Y.; Katsuura, K.; Takayama, H.; Aimi, N.; Mitsuya, H.; Shigeta, S.; Konno, K.; Yokota, T.; Baba, M. AntiViral Chem. Chemother. 1999, 10, 315. (e) Kochansky, J. P.; Cohen, C. F.; Lusby, W. R.; Svoboda, J. A.; Feldmesser, J.; Wright, F. C. J. Agr. Entomol. 1988, 5, 131. (11) (a) Cozzolino, A. F.; Britten, J. F.; Vargas-Baca, I. Cryst. Growth Des. 2006, 6, 181. (b) Cozzolino, A. F.; Vargas-Baca, I.; Mansour, S.; Mahmoudkhani, A. H. J. Am. Chem. Soc. 2005, 127, 3184. (12) Stuzhin, P. A.; Mikhailov, M. S.; Yurina, E. S.; Bazanov, M. I.; Koifman, O. I.; Pakhomov, G. L.; Travkin, V. V.; Sinelshchikova, A. A. Chem. Commun. 2012, 48, 10135. (13) Suturina, E. A.; Semenov, N. A.; Lonchakov, A. V.; Bagryanskaya, I. Yu.; Gatilov, Yu. V.; Irtegova, I. G.; Vasilieva, N. V.; Lork, E.; Mews, R.; Gritsan, N. P.; Zibarev, A. V. J. Phys. Chem. A 2011, 115, 4851. (14) Bagryanskaya, I. Yu.; Gatilov, Yu. V.; Gritsan, N. P.; Ikorskii, V. N.; Irtegova, I. G.; Lonchakov, A. V.; Lork, E.; Mews, R.; Ovcharenko, V. I.; Semenov, N. A.; Vasilieva, N. V.; Zibarev, A. V. Eur. J. Inorg. Chem. 2007, 4751. (15) IUPAC. Compendium of Chemical Terminology, 2nd ed. (the Gold Book); McNaught, A. D., Wilkinson, A., Eds.; Blackwell Scientific Publications: Oxford, U.K., 1997. (16) (a) Dutton, J. L.; Ragogna, P. J. Inorg. Chem. 2009, 48, 1722. (b) Dutton, J. L.; Ragogna, P. J. Selenium and Tellurium Chemistry: From Small Molecules to Biomolecules and Materials; Woollins, J. D., Laitinen, R. S., Eds.; Springer: Berlin, 2011; pp 179−199. (17) (a) Rykowski, Z.; Sczesna, E. Polish J. Chem. 1989, 63, 307. (b) Neidlein, R.; Knecht, D.; Gieren, A.; Ruiz-Perez, C. Z. Naturforsch., B 1987, 42, 84. (c) Bertini, V.; Lucchesini, F.; De Munno, A. Synthesis 1982, 681. (18) (a) Beckmann, J.; Bolsinger, J.; Spandl, J. J. Organomet. Chem. 2008, 693, 957. (b) Robertson, S. D.; Chivers, T.; Tuononen, H. M. Inorg. Chem. 2008, 47, 10634. (c) On binary Te−I compounds, see: Greenwood, N. N.; Earnshaw, A. Chemistry of the Elements; Butterworth-Heinemann: Oxford, U.K., 1997. (19) It should be noted that compared to ubiquitous phenolates, [ArO]−, and common thiophenolates [ArS]−, the knowledge on their

AUTHOR INFORMATION

Corresponding Authors

*E-mail for J.B.: [email protected]. *E-mail for N.P.G.: [email protected]. *E-mail for A.V.Z.: [email protected]. Present Address &

Max Planck Institute for Chemical Energy Conversion, 45470 Mülheim an der Ruhr, Germany.

Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The authors are grateful to Mr. Peter Brackmann for his participation in the XRD measurements and to the Deutsche Forschungsgemeinschaft (project BE 3716/3-1), the Presidium of the Russian Academy of Sciences (project 8.14), the Siberian Branch of the Russian Academy of Sciences (project 13), and the Ministry of Education and Science of the Russian Federation (project of Joint Laboratories of Siberian Branch of the Russian Academy of Sciences and National Research Universities) for financial support of various parts of this work. N.A.S. and E.A.S. are grateful to the Russian Foundation for Basic Research (project 14-03-31653). E.A.S. is grateful to the Russian Academy of Sciences for the Golden Medal with Premium for Graduates 2011 and appreciates support from the Ministry for Education and Science of the Russian Federation (project 14.132.21.1451), the Dynasty Foundation, the Mikhail Prokhorov Foundation, and the International Scientific Charitable Foundation named after K. I. Zamaraev. A.V.L. thanks the Russian Foundation for Basic Research (project 1203-31534) and the Ministry for Education and Science of the Russian Federation (project 14.132.21.1471) for support.

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heavier congeners [ArTe]− is still scarce. To the best of our knowledge, the only aryltellurolate characterized by XRD before compound 12 was [K(18-crown-6)]+[2,4,6-i-Pr3C6H2Te]−: (a) Englich, U.; Ruhlandt-Senge, K. Coord. Chem. Rev. 2000, 210, 135. (b) Bonasia, P. J.; Arnold, J. J. Chem. Soc., Chem. Commun. 1990, 1299. (20) One can think that the anion [TeCN]− results from decay of the target anion [1-TePh]−. Importantly, formation of [TeCN]− was observed by ESI-MS in reaction of telluradiazole 1 not only with [PhTe]− (this work) but also with [PhO]− (Semenov, N. A.; Vasiliev, V. G.; Beckmann, J.; Zibarev, A. V. Unpublished results, 2014). These findings suggest that the anion [TeCN]− originates from the heterocyclic part of the [1-TePh]− containing the fragment Te−N− C. One can speculate that the fragment eliminates from [1-TePh]− in the form of anion [TeNC]− whose further isomerization via cyclic transition state gives the anion [TeCN]−. In this case byproducts X in Scheme 2 might be NC−CN and PhTeCN. The latter is known to be unstable toward further transformation in PhTeTePh.. (21) (a) Downs, A. W. Chem. Commun. 1968, 1290. (b) Austad, T.; Sogstad, J.; Kjell, A. Acta Chem. Scand. 1971, 25, 331. (c) Spencer, H. K.; Lakshmikantham, M. V.; Cava, M. P. J. Am. Chem. Soc. 1977, 99, 1470. (d) Foust, A. S. Chem. Commun. 1979, 414. (e) Jones, C. H. W.; Sharma, R. D. Organometallics 1987, 6, 1419. (22) Ikorskii, V. N.; Irtegova, I. G.; Lork, E.; Makarov, A. Yu.; Mews, R.; Ovcharenko, V. I.; Zibarev, A. V. Eur. J. Inorg. Chem. 2006, 3061. (23) Yamashita, Y.; Mikai, Y.; Miyashi, T.; Saito, G. Bull. Chem. Soc. Jpn. 1988, 61, 483. (24) Grimme, S.; Neese, F. J. Chem. Phys. 2007, 127, 154116. (25) Di Meo, F.; Trouillas, P.; Adamo, C.; Sancho-Garcia, J. C. J. Chem. Phys. 2013, 139, 164104. (26) Dreuw, A.; Head-Gordon, M. Chem. Rev. 2005, 105, 4009. (27) (a) Becke, A. D. J. Chem. Phys. 1993, 98, 1372. (b) Becke, A. D. J. Chem. Phys. 1993, 98, 5648. (c) Lee, C.; Yang, W.; Parr, R. G. Phys. Rev. B 1988, 37, 785. (28) Cramer, C. J. Essentials of Computational Chemistry: Theories and Models; Wiley: Chichester, England, 2004; pp 334−342. (29) Piette, J. L.; Pardon, M. C.; Weber, R.; Baiwir, E. M.; Liabres, G. Bull. Soc. Chim. Belg. 1986, 95, 247. (30) (a) Makarov, A. Yu.; Tersago, K.; Nivesanond, K.; Blockhuys, F.; Van Alsenoy, C.; Kovalev, M. K.; Bagryanskaya, I. Yu.; Gatilov, Yu. V.; Shakirov, M. M.; Zibarev, A. V. Inorg. Chem. 2006, 45, 2221. (b) Zibarev, A. V.; Beregovaya, I. V. Rev. Heteroat. Chem. 1992, 7, 171. (c) Fugaeva, O. M.; Zibarev, A. V.; Korobeinicheva, I. K.; Furin, G. G. J. Mol. Struct. 1990, 218, 169. (d) Zibarev, A. V.; Fugaeva, O. M.; Miller, A. O.; Konchenko, S. N.; Korobeinicheva, I. K.; Furin, G. G. Khim. Geterotsikl. Soedin. 1990, 1124 (in Russian); Chem. Abstr. 114, 100927. (31) (a) Grimme, S. J. Comput. Chem. 2006, 27, 1787. (b) Grimme, S.; Antony, J.; Ehrlich, S.; Krieg, H. J. Chem. Phys. 2010, 132, 154104. (32) Hess, B. A.; Marian, C. M.; Wahlgren, U.; Gropen, O. Chem. Phys. Lett. 1996, 251, 365. (33) Sinnecker, S.; Rajendran, A.; Klamt, A.; Diedenhofen, M.; Neese, F. J. Phys. Chem. A 2006, 110, 2235. (34) (a) Mukherjee, A. J.; Zade, S. S.; Singh, H. B.; Sunoj, R. B. Chem. Rev. 2010, 110, 4357. (b) Vargas-Baca, I.; Chivers, T. Phosphorus, Sulfur Silicon Relat. Elem. 2000, 164, 207. (c) VargasBaca, I.; Chivers, T. Main Group Chem. 1999, 7, 6. (35) URL: http://periodictable.com/Elements/034/data.html. (36) Cordero, B.; Gomez, V.; Platero-Prats, A. E.; Reves, M.; Echeverria, J.; Cremades, E.; Barragan, F.; Alvarez, S. Dalton Trans. 2008, 2832. (37) Mantina, M.; Chamberlin, A. C.; Valero, R.; Cramer, C. J.; Truhlar, D. G. J. Chem. Phys. A 2009, 113, 5806. (38) Nitrenes and Nitrenium Ions; Falvey, D. A., Gudmundsdottir, A. D., Eds.; Wiley: Hoboken, NJ, 2013. (39) Blanksby, S. J.; Ellison, G. B. Acc. Chem. Res. 2003, 36, 255. (40) (a) Bader, R. F. W.; Essen, H. J. Chem. Phys. 1983, 80, 1943. (b) Bone, R. G. A.; Bader, R. F. W. J. Phys. Chem. 1996, 100, 10892. (41) Lu, T.; Chen, F. J. Comput. Chem. 2012, 33, 580.

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dx.doi.org/10.1021/om5006403 | Organometallics 2014, 33, 4302−4314