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Thiaphosphiranes and Their Complexes: Systematic Study on Ring Strain and Ring Cleavage Reactions Arturo Espinosa Ferao*,† and Rainer Streubel*,‡ †

Departamento de Química Orgánica, Facultad de Química, Universidad de Murcia, Campus de Espinardo 30100 Murcia, Spain Institut für Anorganische Chemie der Rheinischen Friedrich-Wilhelms-Universität Bonn, Gerhard-Domagk-Strasse 1, 53121 Bonn, Germany

‡

S Supporting Information *

ABSTRACT: A computational study on energies and geometries of a representative set of thiaphosphirane derivatives 1a−e and their W(CO)5 (W) and BH3 (B) complexes is reported. A particular focus was put on ring-opening reactions of κP- (2) and κS-complex isomers (3). Concerning the ring strain energy, a general trend was observed for compounds 1a,d, 2Wa,d, and 2Ba,d: (i) substituted rings are less strained than the parent compounds, and (ii) κP-complexation with a W(CO)5 group (2Wa,d) significantly increases the ring strain (5.63 and 4.38 kcal/mol) which is exceeded in the case of κP-BH3 complexation (2Ba,d) (7.14 and 7.22 kcal/mol). To unveil the thermal endocyclic bond weakness, a variety of bond strength related descriptors such as bond distance, relaxed force constants k0, Bader’s quantitative theory of atoms-in-molecules parameters such as the electron density ρ(r) and its Laplacian at bond critical points, and several bond order quantities (Wiberg bond index, Mayer bond order, and Löwdin bond order) were calculated. Heterolytic ring-opening reactions were investigated, revealing some general trends: (i) the strongest donor substituent at carbon significantly lowers relative energies for both the P−C and C−S bond cleavage products as well as the corresponding transition states, (ii) κP-complexes are more stable than the corresponding κS-complexes, for cyclic and acyclic species, and (iii) P-to-S haptotropic shifts in P−C bond cleavage products are disfavored processes, whereas it is more favored for C−S bond cleavage products. Other rearrangement products, being within energetic reach, were located on the potential energy surface. Two deserve particular mention as one stems from a combined H2 elimination and C−S bond cleavage of 2Bb and the other represents a first case of peribicyclic reaction leading to 7B′.

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oxaphosphiranes12,13 and azaphosphiridines14 became easily accessible using the versatile Li/Cl phosphinidenoid complex methodology, thus enabling intense studies on closed- and open-shell chemistry of the CPO and CPN rings.15 It is worth mentioning that studies related with the theoretical exploration of the potential energy surface (PES) of these ring systems have provided valuable information about relative stabilities of isomers, ring strain energies, and, very interestingly, to eventual bond weakening upon simple transformations such as protonation, complexation, one-electron oxidation, and/or reduction.13,15 On the other hand, transition-metal complexes possessing ligands with a 1,2-dipole bonding motif possess a wellestablished chemistry, especially in Wittig-ylides 16 and “umpoled” phosphaalkenes.17 Albeit examples of complexes with 1,3-dipolar ligands such as I18 and II19 (Scheme 1) are scarce, they paved the path to new coordination chemistry. The intermediacy of 1,3-dipole complexes III,20 formal products of P−C bond cleavage in oxaphosphirane complexes, has also been reported,21 while complexes IV formally derived from C−

INTRODUCTION Saturated three-membered heterocycles such as oxiranes and aziridines display a reactivity dominated by relief of ring strain through ring opening reactions (ROR) and are used, e.g., in ring opening polymerizations (ROPs).1 This makes them highly versatile building blocks in synthetic organic chemistry and is illustrated by their industrial use in the large-scale production of poly(ethylene glycols)2 and polyamines.3 In principle, the same should hold for the largely underdeveloped,4 heavier secondrow analogues such as phosphiranes5 and thiiranes,6 but no applications have been established so far.7 The latter is in stark contrast to detailed investigations of ROPs of cyclophosphazenes.8 Even more scarce is the knowledge about threemembered phosphorus heterocycles possessing a PIII center and one more heteroatom and, hence, differently polarized ring bonds. Whereas unligated oxaphosphiranes, having a CPO ring (standing for a three-membered ring constituted by a C, a P, and a O atom) and a PIII center, are completely unknown, the chemistry of azaphosphiridines9 and thiaphosphiranes,10 having CPN and CPS rings, respectively, is still largely underdeveloped, and only diphosphiranes,11 having a CP2 ring, have been investigated in greater detail. Recently, pentacarbonyl metal complexes of group 6 elements (Cr, Mo, W) of © XXXX American Chemical Society

Received: June 1, 2016

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DOI: 10.1021/acs.inorgchem.6b01322 Inorg. Chem. XXXX, XXX, XXX−XXX

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Inorganic Chemistry

[SD(60,MWB)] effective core potential (ECP) was used.31 In all optimizations and energy evaluations, the latest Grimme’s semiempirical atom-pairwise correction (DFT-D3 methods), taking into account the major part of the contribution of dispersion forces to the energy, was included.32 Harmonic frequency calculations verified the nature of the computed species as minima or transition state (TS) structures, featuring none or only one negative eigenvalues, respectively. Moreover, all TS structures were confirmed by intrinsic reaction coordinate (IRC) calculations. From these geometries, all reported electronic data were obtained by means of single-point (SP) calculations using the same functional as well as the more polarized def2-TZVPP33 basis set. Reported energies were corrected for the zero-point vibrational term at the optimization level and obtained by means of the recently developed near linear scaling domain-based local pair natural orbital (DLPNO) method34 to achieve coupled cluster theory with single−double and perturbative triple excitations (CCSD(T)).35 For comparative purposes, local correlation schemes of type local pair natural orbital (LPNO) for high level single reference methods, such as coupled electron-pair approximation (CEPA),36 here the slightly modified NCEPA/1 version37 implemented in ORCA, was used, as well as the spin-component scaled second-order MöllerPlesset perturbation theory (SCS-MP2) level38 and the double-hybridmeta-GGA functional PWPB95,39 together with the D3 correction (PWPB95-D3). All electronic properties including bond strength related parameters were computed at the B3LYP/def2-TZVPP level, except the relaxed force constants, k0, that were obtained at the optimization level by inversion of the Hessian matrix and appropriate units conversion of the reciprocal of the resulting diagonal elements. Equivalent results can be obtained with Grunenberg’s Compliance software.40 The topological analysis of the electronic charge density, ρ(r), within Bader’s Atoms-In-Molecules (AIM) methodology41 was conducted using the AIM2000 software.42 Electric charges were obtained from the natural bond orbital (NBO) population analysis.43

Scheme 1. Reported Stable or Transient Metal Complexes With 1,3-Dipolar Ligands

O bond cleavage were claimed as intermediates22 in P,C,O-cage complex formation or ring expansion in oxaphosphirane complexes. Only recently, the first stable derivative of IV was firmly established including an X-ray structure.23 Very early attempts to access thiaphosphirane complexes via a thermal terminal phosphinidene complex transfer reaction failed due to a facile decomplexation of the thiaphosphirane ligand,24 thus revealing a rather weak P−M bond but also a remarkable thermal stability of the unligated thiaphosphirane. In a more recent study on the reactivity of a Li/Cl phosphinidenoid complex toward thiocarbonyl compounds, it was revealed that the thiaphosphirane complexes were not obtained as (expected) final products. Instead, products arising from a P−C bond cleavage of transient thiaphosphirane complexes were obtained.25 In the case of thiobenzophenone, a subsequent P−C cyclization involving a phenyl ortho C atom yields a bicyclic benzo[c]-1,2-thiaphospholane ligand system V (Scheme 2), in analogy to reactions with benzophenone.26 Scheme 2. Reported Products Derived from Transient Thiaphosphirane Tungsten Complexes

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RESULTS AND DISCUSSION Ring Strain. The ring strain energy (RSE) is a useful parameter for describing ring cleavage reactivity in small rings. Reported values,44 obtained by evaluation of isodesmic reactions with G3 and CBS-APNO computational methods, for simple cyclopropanes (calculated: 27.4−28.2 kcal/mol; experimental: 27.5 kcal/mol45 for the parent compound), oxiranes (27.1−28.1 kcal/mol), aziridines (27.5−28.0 kcal/ mol), thiiranes (17.6−18.2 kcal/mol), and phosphiranes (19.4−20.0 kcal/mol) reveal, as a general trend, that threemembered heterocycles containing one-third row element such as S or P possess lower RSEs than their second row homologues (containing O or N) or the carbocyclic analogue cyclopropane. Most likely this is due to the more diffuse orbitals required for bonding of the larger S and P atoms, thus leading to a more compliant character compared to O, N, or C. Three-membered heterocycles containing P and one secondrow heteroatom such as O or N display RSEs (calculated: ca. 23.5 kcal/mol for both the parent oxaphosphirane15a and azaphosphiridine15b) lying roughly at halfway between those of oxirane or aziridine and phosphirane. A rather low RSE value should be therefore expected if two-third-row heteroelements are present in a three-membered heterocycle, as in the case of the CPS ring in thiaphosphiranes; a computational study10e was conducted on the substituent effects on relative stabilities of valence isomers, i.e., thiaphosphiranes and alkylidene(thio)phosphoranes. Here, homodesmotic reactions,46 similar to those used for evaluating RSEs of azaphosphiridine and oxaphosphirane derivatives,13,15,23,47 were employed to compute RSEs for six different thiaphosphiranes including their pentacarbonyltungsten(0) and borane κP-complexes (Scheme 3). For every formal

Interestingly, the reaction with thiourea led to the formation of complex VI in which, apparently, a haptotropic P → S metal shift was involved. Stimulated by these singular reports on thiaphosphirane complexes, we became interested to shed more light on the bonding and reactivity of this class of coordination compounds. Herein, a computational study on energies and geometries of a representative set of thia phosphirane derivatives 1a−e and their W(CO)5 (W) and BH3 (B) complexes is reported (Figure 1). A particular focus was put on ring-opening reactions of κP(2) and κS-complex isomers (3).

Figure 1. Thiaphosphirane derivatives included in this study.

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EXPERIMENTAL SECTION

Computational Details. Quantum chemical calculations were performed with the ORCA electronic structure program package.27 All geometry optimizations were run in redundant internal coordinates with tight convergence criteria, in the gas-phase and using the B3LYP28 functional together with the RIJCOSX algorithm29 and the Ahlrichs’ segmented def2-TZVP basis set.30 For W atoms the B


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Inorganic Chemistry

case of phosphirane and thiirane. In addition, some general trends can be observed: (i) substituted (R = Me) systems are less strained than parent (R = H) compounds, (ii) Pcomplexation with a W(CO)5 group (2Wa,e) significantly increases the ring strain, and (iii) this strain being even enhanced by P-BH3 complexation. As a result, the most strained P-BH3 derivatives (2Ba,e) are only as strained as phosphirane or thiirane. Furthermore, it was recently shown that much less computationally demanding Lagrange kinetic energy at the ring critical point (RCP), G(r), correlates with RSEs within related systems,48 and has been successfully applied to analyze strain in the other three-membered CPO and CPN rings.13,23,47 As expected, G(r) values (Table 1) show the same trends as RSE for changes in functionalization at P (E) within a set of derivatives of this substitution pattern (R/R′). Moreover this computationally inexpensive parameter can be used to obtain a rapid insight into strain of larger systems. For instance, the G(r) values for 3,3-bis(dimethylamino)-2methylthiaphosphirane (1e, 6.59 × 10−2 au) and its tungsten (2We, 7.04 × 10−2 au) or boron complex (2Be, 6.97 × 10−2 au) enables establishing a decrease in ring strain with regard to the parent (R,R′ = H,H) or trimethylsubstituted (R,R′ = Me,Me) derivatives, while keeping the tendency of strain increase upon complexation. Endocyclic Bond Strengths. The computed strain in the above studied systems underlines the inherent tendency of these cyclic compounds to undergo ring opening reactions (ROR). Hence, the next step was trying to determine which of the three different endocyclic bonds should be more easily cleaved regardless of the presence or not of inducing reagents or, in other words, to identify the order of thermal endocyclic bond weakness. With this aim, a variety of bond strength related descriptors, including bond distance, have been computed for all three endocyclic bonds of three representative termini (a, d, and e) of thiaphosphirane (1) and its P-tungsten (2W) and borane (2B) complexes (Table 2). Among these descriptors, the relaxed force constants k0, obtained from the compliance matrix method,49 have received much attention in recent years as a measure of bond strength in a variety of bonding situations40b,50 including organophosphorus deriva-

Scheme 3. Homodesmotic Reactions Used to Compute RSEs in Thiaphosphirane Derivativesa

a

The bonds used for the calculation of acyclic bond strength parameters are represented in bold.

endocyclic bond cleavage homodesmotic reaction, the type and number of bonds and valencies of all atoms are conserved at both sides of the equation so that their contributions cancel out and the only remaining one is due to ring strain. Collected RSE values (Table 1) are the average for all three different ring bond Table 1. Computed RSEa and G(r)b Values for Selected Thiaphosphirane Derivatives R,R′ 1a 2Wa 2Ba 1d 2Wd 2Bd

H,H H,H H,H Me,Me Me,Me Me,Me

E W(CO)5 BH3 W(CO)5 BH3

RSE

G(r)

13.75 19.48 20.89 10.05 14.43 17.27

6.59 7.11 7.49 6.67 7.18 7.50

a

Obtained at the DLPNO-CCSD(T)/def2-TZVPP(ecp)//B3LYPD3/def2-TZVP(ecp), in kcal/mol. bObtained at the B3LYP-D3/ def2-TZVPP(ecp)//B3LYP-D3/def2-TZVP(ecp), in au × 102.

cleavage processes. The reagents used to perform the homodesmotic P−C and P−S bond cleavage were chosen so that the final products had the same structure. The RSE computed for parent thiaphosphirane (1a) is lower than in the

Table 2. Computed Bond Strength Related Parameters for Thiaphosphiranes (1) and Their P-Complexes (2)

d (Å)

k0 (mdyn/Å)

WBI

ρ(r) × 102 (au)

−1/4∇2(ρ(r)) × 102 (au)

G(r) × 102 (au)

P−S P−C C−S P−S P−C C−S P−S P−C C−S P−S P−C C−S P−S P−C C−S P−S P−C C−S

1a

1d

1e

2Wa

2Wd

2We

2Ba

2Bd

2Be

2.126 1.841 1.817 2.302 2.622 2.469 0.997 0.976 1.035 11.68 15.11 17.23 2.56 3.55 5.37 4.85 10.17 6.48

2.127 1.847 1.848 2.587 3.149 2.182 0.965 0.914 0.982 11.73 15.47 16.46 2.69 5.31 4.46 4.79 14.12 6.11

2.128 1.890 1.862 2.277 1.699 1.507 0.949 0.876 0.968 11.82 14.61 16.27 3.02 5.85 4.38 4.63 6.76 5.87

2.099 1.811 1.840 2.263 2.932 2.303 0.949 0.948 1.016 12.44 16.14 16.53 3.45 4.00 4.61 5.03 11.19 6.19

2.099 1.825 1.874 2.277 2.652 1.831 0.929 0.885 0.963 12.55 16.26 15.69 3.61 4.54 3.69 4.88 10.87 5.84

2.100 1.876 1.895 2.270 1.665 1.065 0.928 0.839 0.934 12.67 15.30 15.31 4.07 6.99 3.44 4.74 6.48 5.55

2.076 1.797 1.851 2.587 3.149 2.182 0.967 0.953 1.013 13.04 16.56 16.18 4.03 2.66 4.22 5.07 13.04 6.08

2.077 1.810 1.890 2.567 2.904 1.668 0.949 0.892 0.953 15.21 16.70 13.10 3.24 4.27 4.31 5.69 11.74 5.06

2.068 1.841 2.016 2.475 2.340 0.200 0.966 0.862 0.808 13.64 16.00 12.02 5.29 4.83 0.32 5.00 10.21 5.00

C


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Inorganic Chemistry tives.25,46,51 Also three different bond order magnitudes were collected: the widespread used Wiberg bond index (WBI),52 as well as Mayer bond order (MBO),53 and Löwdin bond order (LBO)54 (see the Supporting Information for the latter two). Finally, some magnitudes derived from Bader’s quantitative theory of atoms-in-molecules (QTAIM)41 such as the electron density ρ(r), its Laplacian and the Lagrangian of the kinetic energy density G(r) at bond critical points (BCP) were included. The lowest values displayed in general for the relaxed force constant k0 at the C−S bond must be understood in terms of higher flexibility (compliance upon elongation/compression) of this particular bond, but no other clear-cut tendencies were observed. When dealing with three different bonds of different polarization and involving atoms of differrent size (one second-row and two-third-row elements), comparing the corresponding bond distances within a ring is not informative at all, but still allows comparison of the same type of bond along a series of different compounds. Thus, while the P−S distance is quite uniform, specially upon variation of only the Pand C-substituents, the invariance presumably indicating stability, a large variation is observed for the C−S bonds where a significant enlargement occurs along the series 1 < 2W < 2B and along the substitution pattern a < d < e. In the case of the P−C bond a similar enlargement trend is observed on substitution a < d ≪ e, but the bond length decreases in the order 1 > 2W > 2B. The WBI (as well as LBO, see the Supporting Information) uniformly points to the P−C bond as the weakest of all three endocyclic bonds (except in 2Be where indicates that C−S is weaker than P−C). The electron density at BCP, ρ(r), has limited utility because it indicates the lowest values for the P−S bond, as expected for the interaction between two-third-row elements using diffuse orbitals for binding, in comparison with the other two bonds between a second- and a third-row element. The only exceptions are the remarkably low ρ(r) values displayed by the C−S bonds in 2Bd and 2Be, indicative of significantly weak bonding situations. Similarly, no clear tendencies were observed by the Laplacian of the electron density, therefore indicating no remarkable variations of the ionic character of the bonds. Comparison with bond strength related parameters in the corresponding acyclic species could provide valuable information concerning weakening of all or specific endocyclic bonds when belonging to small ring (strained) systems. With this aim some of the above-mentioned descriptors were computed for all three types of bonds (P−S, P−C, and C−S) in acyclic species resulting from homodesmotic ring opening reactions (see Scheme 3), averaged values for compounds originated from 1a,d and 2a,d being collected in Table 3. By comparing data in Tables 2 and 3, as a general trend, the WBI shows a systematic strengthening of the P−C bond on ring formation except for 1e and 2We (see the Supporting Information for incremental values). On the contrary, a systematic decrease of the electron density evaluated at the C−S BCPs points to a weakening of this bond in cyclic structures. Interestingly, although there is no previous report in this line to the best of our knowledge, ring formation entails a remarkable systematic decrease of the Laplacian of the electron density, as well as a significant increase of the Lagrange of the kinetic energy density (except for the P−C bonds in 1e and 2We), the latter shown to be related with ring strain when

Table 3. Averaged Computed Bond Strength Related Parameters for Acyclic Products Arising from Homodesmotic P−C and C−S Bond Cleavage in Thiaphosphiranes 1a,d and Their P-Complexes 2a,d WBI

ρ(r) × 102 (au)

−1/4∇2(ρ(r)) × 102 (au)

G(r) × 102 (au)

P−S P−C C−S P−S P−C C−S P−S P−C C−S P−S P−C C−S

1

2W

2B

1.027 0.884 0.975 13.00 15.36 17.26 4.97 6.67 6.39 3.95 7.07 4.93

0.994 0.851 0.976 13.51 15.94 17.30 5.74 7.38 6.46 3.86 7.26 4.95

0.996 0.853 0.983 14.55 16.31 16.56 6.04 7.42 6.52 4.07 7.90 4.72

computed at the RCP (vide supra); this might be tentatively ascribed to a kinetic instability of these bonds due to strain. Ring-Opening Pathways and Metal Shifts. RORs were studied according to the equations shown in Scheme 4 by Scheme 4. Expected ROR Pathways in Azaphosphiridines 1 and Their P- (2) and S-Metal Complexes (3), as Well As Possible Haptotropic P-to-S Metal Shifts

cleavage of one of the two weakest endocyclic bonds, P−C and C−S, in agreement with the results of the previous section, and only for termini a-c and e as representative cases. The results are collected in Table 4. In general, uncomplexed thiaphosphiranes 1 undergo thermodynamically and kinetically more favored C−S than P−C ring cleavage, which can be understood in terms of a most favorable stabilization of the negative charge at the most electronegative S atom. The C−S bond cleavage occur over low TS barriers for C-amino-substituted derivatives 1c,e, although only in the case of 1c the process is exergonic. P−C bond cleavage follows a conrotatory stereochemistry; for only the parent compound 1a it is the slightly kinetically preferred cleavage path, although both processes have high energy barriers for both 1a and 1b. In the case of κP-tungsten complexes 2W, C−P cleavage is also conrotatory; C−S cleavage is always thermodynamically favored, much more than in the corresponding uncomplexed derivatives 1, Moreover C−S bond cleavage is also the kinetically preferred path, except for the unsubstituted terminus 2Wa. The C−S ring cleavage is exergonic for the CD


Article

Inorganic Chemistry Table 4. Computed (DLPNO-CCSD(T)/def2-TZVPP) ZPE-Corrected Energetics (kcal/mol) for ROR in Scheme 4 a b c e 34.29 30.83 0.40 4.71 6B

a b c e a

TS1→4

1

30.84 28.75 6.62 19.39

40.80 41.15 19.76 20.52

0.00 0.00 0.00 0.00 8W

TS2W→6W

6W a b c e

4

2W

39.02 39.92 12.50 10.79 TS2B→6B

36.35 18.05d 17.10 4.20 b

0.00 0.00 0.00 0.00 2B

41.07 39.93

0.00 0.00

14.28

0.00 c

TS2W→7W 44.27 37.36 2.68 3.63 TS2B→7B 51.55 39.62 1.40

7W a

TS1→5

TS3W→8W b

40.71 43.20b 16.14 27.38 8B

5.51 14.19a −13.90 −4.19 7B −9.84 −3.73e 0.00 −3.00 e

42.95 40.03 30.99 29.86

5

47.46 40.63 7.47 7.25 3W

55.06 54.77

7.58 8.65

8.50 9.30 −6.87 5.09 TS3W→9W

9W

46.05 42.25

19.31c 19.83 −8.00 −3.77 9B

TS3B→8B

3B

TS3B→9B

52.55 50.81

2.72 4.57

39.66 34.11

1.18f 3.95g 8.62 3.09

d

Structure 7W′. Structure 8W′. Structure 9W′. Fragmentation into thioacetone and H2P-BH2. eStructure 7B′. fFragmentation into phosphaalkene and HS-BH2. gStructure 9B′ by loss of H2.

a bicyclic path it should be named as peribicyclic. Conversely the process for aminosubstituted derivatives has extremely low TS energies; indeed 2Bc was not located as a minimum on its PES because it spontaneously opens up to the most stable C−S bond cleavage product 7Bc that was taken as a reference for the calculation of relative energies in this series. P−C Bond cleavage in 2Bb was accompanied by C−S bond cleavage, thus resulting in fragmentation into thioacetone and H2P-BH2.55 κS-Complexes 3 also display different behavior for unsubstituted or alkyl-substituted compounds (3Wa,b and 3Ba,b) on one hand and amino-substitution at the ring C atom (3Wc,e and 3Bc,e) on the other hand. The former are moderately less stable than the corresponding P-complexes and preferentially undergo C−S bond ring cleavage. In the case of 3Wa the C−S bond cleavage affords the PS side-on complex 9W′, whereas for both complexes 3Wa,b P−C cleavage results in the formation of the CS side-on complex 8W′. The C−S cleavage is even slightly exergonic in the case of borane complexes 3Ba,b, yielding either fragmentation into CH2PH and HS-BH2 for 3Ba, or additional elimination of H2 (9B′) for 3Bb. The latter turns out to be an interesting process, not only because its relation to H2 storage, but also because it furnishes an attractive S-bridged P/B-FLP new species 9B′(P···B 3.069 Å) that will deserve further investigation. The S-complexes of C-aminosubstituted thiaphosphiranes 3Wc,e and 3Bc,e were not located at their respective PES, and only the C−S and P−C bond cleavage products were found as energy minima. Phosphorus-to-sulfur haptotropic shifts from all P-complexes 2, 6, and 7 (Scheme 5) were found to proceed through low to moderate energy barriers within the range 14.07−30.40 kcal/ mol (Table 5), although most of them amounts to ca. 20 kcal/ mol. In three out of four cases in which the complexes 3 do not

aminosubstituted derivatives 2Wc,e, as expected due to the stabilization of the positive charge at C by the neighboring electron-donating N atoms, and leads to side-on complexes 7W′ (Scheme 5) in the case of the other two 2Wa,b derivatives. Scheme 5. Other Products Arising from P−C or C−S Ring Cleavage in Some Thiaphosphirane Derivatives

P-Borane complexes 2B behave similarly affording exergonically the C−S bond cleavage product. Again the unsubstituted (2Ba) and C-methyl substituted complex (2Bb) follow a high-energy C−S cleavage path affording the product of subsequent P-to-C migration of the boryl moiety with simultaneous B-to-P prototropy (7B′). According to the located TS structure (see the animation of the imaginary frequency in the TS(2Bb7B′b).avi file at the Supporting Information) this seems to be an unusual case of complex pericyclic shift engaging six σ electrons in the starting structure and leading to a 4σ + 2π electron system in the final species. As this rearrangement involves a synchronic (concerted) movement of electrons along

Table 5. Computed (DLPNO-CCSD(T)/def2-TZVPP) ZPE-Corrected Energetics (kcal/mol)a for Haptotropic Shifts Depicted in Scheme 4 a b c e a

TS6W→8W

TS2W→3W

TS7W→9W

53.37 47.94 28.97 41.02

23.56 24.26

34.96 33.42 12.84 15.27

TS2W→9W

27.74 21.13

TS6B→8B

TS2B→3B

49.42

18.38 19.53

45.05 44.24

TS7B→9B

TS2B→9B

30.40 24.51

22.41

Relative to the same reference complexes as in Table 4. E


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Inorganic Chemistry

Figure 2. Computed (DLPNO-CCSD(T)/def2-TZVPPecp) ZPE-corrected relative energy profile for reactions depicted in Scheme 5 for two important substitution cases (a and b). From all depicted minimum energy structures the reaction paths to the left and right correspond to P−C and C−S bond cleavage processes, respectively.

exist as minima, the haptotropic P-to-S shifts in 2 lead to the C−S cleaved product 9. From the results depicted in Tables 3 and 4, the b and e series were chosen for display in Figure 2a,b, to illustrate the differences. All of them are shown in the following order (from left to right): minima corresponding to the unligated thiaphosphirane (1), P- and S-tungsten(0) complexes (2W and 3W), and then the corresponding borane complexes (2B and 3B). From these minima, the reaction paths to the left correspond to P−C bond cleavage processes, while C−S bond cleavage path are shown on the right side. In addition, the P-toS haptotropic shifts connect the corresponding pairs of structures 2/3, 6/8, and 7/9. Apparently the strongest donor substituent at the carbon exerts significant lowering of relative energies for both the P−C and C−S bond cleavage products as well as the corresponding TSs. As a further general trend, Pcomplexes are more stable than the corresponding S-complexes, for cyclic and acyclic species. P-to-S haptotropic shifts in P−C bond cleavage products are disfavored processes from the thermodynamic (e.g., 6 Wb → 8 Wb) and/or the kinetic (e.g., 6We → 8We) points of view, whereas it is a more favored process for C−S bond cleavage products. Noteworthy is the relatively low barrier for the transformation 7We → 9We (Figure 2) that would account for the formation of compound VI (Scheme 2, R = CHTms2), experimentally observed previously.24 Complex 7We results from the exergonic very low barrier C−S bond cleavage in 2We, which in turn could be the expected product in the reaction between tetramethylthiourea and a Li/Cl phosphinidenoid complex. Alternatively the latter reaction could proceed via displacement of the chlorine atom at phosphorus affording complex 6We (using the P-methyl model analogue) that would undergo very exergonic low-barrier P−C cyclization to 2We.

The alternative direct P-to-S shift with concomitant C−S cleavage in 2We proceeds with slightly higher energy barrier than the rate-limiting step in the 2We → 7We → 9We transformation. A similar conversion of borane complexes (2Be → 9Be) is expected to be an endergonic and one-step process and preferred over the two-step mechanism (2Be → 7Be → 9Be). Worth mentioning is that for a set of 71 values (see Table S2), the DLPNO-CCSD(T) with the standard def2-TZVPP(ecp) used along this work, performed nicely in relation to the highest quality def2-QZVPP(ecp), according to the low rootmean-square deviation (RMSD) displayed (0.20 kcal/mol). For a wider set of 93 nonzero values (see Tables SI 1−6), within the results obtained with the def2-TZVPP(ecp) basis set, the LPNO-NCEPA1 method performed most accurately (RMSD = 0.19 kcal/mol) in relation to DLPNO-CCSD(T), whereas among the less computationally demanding methods, PWPB95-D3 (RMSD = 0.55 kcal/mol) and even B3LYP-D3 (RMSD = 0.53 kcal/mol) clearly outperformed SCS-MP2 (RMSD = 0.65 kcal/mol).

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The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.6b01322. Comparison of energetics at different computational methods; energies and Cartesian coordinates for all computed structures (PDF) Movie: with the animation of the imaginary frequency in TS(2Bb-7B′b) (AVI) F


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(12) (a) Ö zbolat, A.; von Frantzius, G.; Marinas Pérez, J.; Nieger, M.; Streubel, R. Strong Evidence for a Transient Phosphinidenoid Complex. Angew. Chem., Int. Ed. 2007, 46, 9327−9330. (b) Albrecht, C.; Bode, M.; Pérez, J. M.; Daniels, J.; Schnakenburg, G.; Streubel, R. First examples of oxaphosphirane pentacarbonylchromium(0) and -molybdenum(0) complexes: synthesis, structures and reactions. Dalton Trans. 2011, 40, 2654−2665. (c) Pérez, J. M.; Klein, M.; Kyri, A. W.; Schnakenburg, G.; Streubel, R. First examples of spirooxaphosphirane complexes. Organometallics 2011, 30, 5636− 5640. (d) Streubel, R.; Klein, M.; Schnakenburg, G. Probing the group tolerance of a Li/Cl phosphinidenoid complex using alkenyl substituted aldehydes. Organometallics 2012, 31, 4711−4715. (13) Albrecht, C.; Schneider, E.; Engeser, M.; Schnakenburg, G.; Espinosa, A.; Streubel, R. Synthesis and DFT Calculations of Spirooxaphosphirane Complexes. Dalton Trans. 2013, 42, 8897−8906. (14) (a) Fankel, S.; Helten, H.; von Frantzius, G.; Schnakenburg, G.; Daniels, J.; Chu, V.; Müller, C.; Streubel, R. Novel access to azaphosphiridine complexes and first applications using broensted acid-induced ring expansion reactions. Dalton Trans. 2010, 39, 3472− 3481. (b) Streubel, R.; Villalba Franco, J. M.; Schnakenburg, G.; Espinosa Ferao, A. Reactivity of terminal phosphinidene versus Li/Cl phosphinidenoid complex in cycloaddition chemistry. Chem. Commun. 2012, 48, 5986−5988. (15) (a) Krahe, O.; Neese, F.; Streubel, R. The quest for ringopening of oxaphosphirane complexes: a coupled cluster and density functional study of CH3PO isomers and their Cr(CO)5 complexes. Chem. - Eur. J. 2009, 15, 2594−2601. (b) Espinosa, A.; Streubel, R. Computational studies on azaphosphiridines or how to effect ringopening processes via selective bond activation. Chem. - Eur. J. 2011, 17, 3166−3178. (c) Espinosa, A.; Gómez, C.; Streubel, R. Single Electron Transfer-Mediated Selective endo- and exocyclic Bond Cleavage Processes in Azaphosphiridine Chromium(0) Complexes: A Computational Study. Inorg. Chem. 2012, 51, 7250. (d) Espinosa, A.; Streubel, R. Exocyclic bond cleavage in oxaphosphirane complexes? Chem. - Eur. J. 2012, 18, 13405. (16) (a) Kreissl, F. R.; Held, W. Zur umsetzung von diphenylcarbenpentacarbonylwolfram(0) mit trimethylphosphin. J. Organomet. Chem. 1975, 86, C10−C12. (b) Kreissl, F. R.; Held, W. Neuartige Phosphor-Ylid-Komplexe des Wolframs. Chem. Ber. 1977, 110, 799− 804. (17) (a) Hahn, F. E.; Le Van, D.; Moyes, M. C.; von Fehren, T.; Fröhlich, R.; Würthwein, E.-U. Unusual Formation of an Azaphospholene from 1,3,4,5-Tetramethylimidazol-2-ylidene and Di(isopropyl)aminophosphaalkyne. Angew. Chem., Int. Ed. 2001, 40, 3144−3148. (b) Tran Huy, N. H.; Donnadieu, B.; Bertrand, G.; Mathey, F. Umpolung of Electrophilic Terminal Phosphinidene Complexes by Interaction with Nucleophilic Carbenes. Chem. Asian J. 2009, 4, 1225−1228. (18) Facchin, G.; Mozzon, M.; Michelin, R. A.; Ribeiro, M. T. A.; Pombeiro, A. J. L. Chemistry and electrochemistry of phosphoniumfunctionalized isocyanide and derived carbene and indole complexes of Group 6 transition-metal carbonyls. J. Chem. Soc., Dalton Trans. 1992, 2827−2835. (19) (a) Gudat, D.; Nieger, M.; Schrott, M. Synthese und Charakterisierung stabiler Bis(phosphonio)isophosphindolylium-Carbonylmetallate und eines kationischen Bis(phosphonio)isophosphindolylium-Gold-Komplexes. Chem. Ber. 1995, 128, 259− 266. (b) Gudat, D.; Nieger, M.; Schrott, M. A novel coordination mode for cationic phosphorus pπ systems: μ2-bridging coordination of a bis(phosphonio)isophosphindolium cation. J. Chem. Soc., Chem. Commun. 1995, 1541−1542. (c) Gudat, D.; Schrott, M.; Bajorat, V.; Nieger, M.; Kotila, S.; Fleischer, R.; Stalke, D. [Bis(phosphonio)isophosphindolide]silver complexes. Chem. Ber. 1996, 129, 337−345. (d) Gudat, D.; Nieger, M.; Schrott, M. Reactions of Bis(triphenylphosphonio)isophosphindolide Salts with Mercury(II) Compounds: Coordination Induced Addition and Oxidation Reactions and Synthesis of a Monomeric 1:1 Complex of the Type [R2(R′O)P]HgBr2. Inorg. Chem. 1997, 36, 1476−1481. (e) Gudat, D.; Holderberg, A. W.; Korber, N.; Nieger, M.; Schrott, M. Bis-

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Corresponding Authors

*(A.E.F.) Fax: +34 868 884149. Tel.: +38 868887489. E-mail: [email protected]. *(R.S.) Fax: +49 228 739616. Tel.: +49 228 735345. E-mail: r. [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS Financial support by the Deutsche Forschungsgemeinschaft (DFG STR 411/36-1) and the Cost Action cm1302 “Smart Inorganic Polymers” (SIPs) is gratefully acknowledged; A.E.F. wishes also to thank the computation centre at Servicio de ́ Cálculo Cientifico (SCC - University of Murcia) for their technical support and the computational resources used.

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REFERENCES

(1) Gilchrist, T. L. Heterocyclic Chemistry, 2nd ed.; Longman: Harlow, 1992. (2) For instance, see Kubisa, P. Hyperbranched polyethers by ringopening polymerization: Contribution of activated monomer mechanism. J. Polym. Sci., Part A: Polym. Chem. 2003, 41, 457−468. (3) For instance, see: Stewart, I. C.; Lee, C. C.; Bergman, R. G.; Toste, F. D. Living Ring-Opening Polymerization of N-Sulfonylaziridines: Synthesis of High Molecular Weight Linear Polyamines. J. Am. Chem. Soc. 2005, 127, 17616−17617. (4) Phosphorus-Carbon Heterocyclic Chemistry: The Rise of a New Domain; Mathey, F., Ed.; Pergamon Press: Amsterdam, 2001. (5) Mathey, F. Chemistry of 3-membered carbon-phosphorus heterocycles. Chem. Rev. 1990, 90, 997−1025. (6) (a) Zoller, U. In Small Ring Heterocycles. Part 1. Aziridines, Azirines, Thiiranes, Thiirenes; Hassner, A., Ed., John Wiley & Sons Inc.: New York, 1983; Chapter 3. (b) Chew, W.; Harpp, D. N. Recent Aspects of Thiirane Chemistry. Sulfur Rep. 1993, 15, 1−39. (7) For a recent example of phosphirane-mediated polymerization, see Tebaldi de Sordi, M. L.; Ceschi, M. A.; Petzhold, C. L.; Muller, A. H. E. Controlled Radical Polymerization of 2,3-Epithiopropyl Methacrylate. Macromol. Rapid Commun. 2007, 28, 63−71. (8) McWilliams, A. R.; Dorn, H.; Manners, I. New Inorganic Polymers Containing Phosphorus. Top. Curr. Chem. 2002, 220, 141− 167. (9) (a) Niecke, E.; Seyer, A.; Wildbredt, D.-A. Valenzisomerisierung eines Imino(methylen)phosphorans zu einem 1,2λ3-Azaphosphiridin: Eine neuartige Umlagerung im Phosphorsystem. Angew. Chem. 1981, 93, 687−688. (b) Dufour, N.; Caminade, A.-M.; Majoral, J.-P Unexpected synthesis of a 1,2λ3azaphosphoridine. Tetrahedron Lett. 1989, 30, 4813−4814. (10) (a) Niecke, E.; Wildbredt, D.-A. Methylenethioxophosphoranes and 1,2-λ5-thiaphosphirans. J. Chem. Soc., Chem. Commun. 1981, 72− 73. (b) Appel, R.; Casser, C. [2 + n]-Cycloadditionen des [Bis(trimethylsilyl)methylen]-[(trimethylsilyl)ethinyl]phosphans. Chem. Ber. 1985, 118, 3419−3423. (c) Maurer, S.; Jikyo, T.; Maas, G. Unexpected Thermal Reactivity of Phosphirano-[1,2]thiaphosphole P−W(CO)5 Complexes. Eur. J. Org. Chem. 2009, 2009, 2195−2207. (d) Turcheniuk, K. V.; Rozhenko, A. B.; Shevchenko, I. V. Synthesis and Some Chemical Properties of a 1,2λ3σ3-Thiaphosphirane. Eur. J. Inorg. Chem. 2011, 2011, 1762−1767. (e) Turcheniuk, K. V.; Rozhenko, A. B. (σ3,λ5)-phosphoranes versus (σ3,λ3)-thiaphosphiranes: Quantum chemical investigation of products of phosphaalkene sulfurization. J. Comput. Chem. 2012, 33, 1023−1028. (11) (a) Baudler, M.; Glinka, K. Contributions to the chemistry of phosphorus. 218. Monocyclic and polycyclic phosphines. Chem. Rev. 1993, 93, 1623. (b) Bourissou, D.; Bertrand, G. Diphosphoruscontaining unsaturated three-membered rings: Comparison of carbon, nitrogen, and phosphorus chemistry. Top. Curr. Chem. 2002, 220, 1− 25. G


Article

Inorganic Chemistry phosphonio-isophosphindolide Copper Complexes. Z. Naturforsch., B: J. Chem. Sci. 1999, 54, 1244−1252. (20) (a) Streubel, R.; Ostrowski, A.; Wilkens, H.; Ruthe, F.; Jeske, J.; Jones, P. G. Unexpected Intramolecular Reactions of Intermediate Phosphacarbonyl Ylide Tungsten Complexes. Angew. Chem., Int. Ed. Engl. 1997, 36, 378−381. (b) Inubushi, Y.; Tran Huy, N. H.; Ricard, L.; Mathey, F. The reaction of electrophilic terminal phosphinidene complexes with benzophenone and fluorenone: The unexpected formation of six- and eight-membered heterocycles. J. Organomet. Chem. 1997, 533, 83−86. (21) Similar 1,3-dipole intermediates with other element units E instead of oxygen were reported. For examples with E = NR, see (a) Vlaar, M. J. M.; Valkier, P.; de Kanter, F. J. J.; Schakel, M.; Ehlers, A. W.; Spek, A. L.; Lutz, M.; Lammertsma, K. Addition of a Phosphinidene Complex to CN Bonds: P-Ylides, Azaphosphiridines, and 1,3-Dipolar Cycloadditions. Chem. - Eur. J. 2001, 7, 3551− 3557. (b) Vlaar, M. J. M.; Valkier, P.; Schakel, M.; Ehlers, A. W.; Lutz, M.; Spek, A. L.; Lammertsma, K. C−N Bond Insertion of a Complexed Phosphinidene into a Bis(imine) − A Novel 2,3Sigmatropic Shift. Eur. J. Org. Chem. 2002, 2002, 1797−1802. (c) For a modern theoretical description of 1,3-dipolar cycloadditions, see Grimme, S.; Mück-Lichtenfeld, C.; Würthwein, E.-U.; Ehlers, A. W.; Goumans, T. P. M.; Lammertsma, K. Consistent Theoretical Description of 1,3-Dipolar Cycloaddition Reactions. J. Phys. Chem. A 2006, 110, 2583−2586. (22) Streubel, R.; Murcia-García, C.; Schnakenburg, G.; Espinosa Ferao, A. Transient terminal phosphinidene oxide complexes − key intermediates in the formation of O,P,C-cages from oxaphosphirane complexes. Organometallics 2015, 34, 2676−2682. (23) (a) Villalba Franco, J. M.; Sasamori, T.; Schnakenburg, G.; Espinosa Ferao, A.; Streubel, R. Going for strain: synthesis of the first 3-imino-azaphosphiridine complexes and their surprising conversion into oxaphosphirane complex valence isomers. Chem. Commun. 2015, 51, 3878−3881. (b) Villalba Franco, J. M.; Schnakenburg, G.; Sasamori, T.; Espinosa Ferao, A.; Streubel, R. Substrate stimuliresponsive FLP-type reactivity − first insights. Chem. - Eur. J. 2015, 21, 9650−9655. (24) Streubel, R.; Neumann, C. Dual reaction behaviour of an in-situ generated nitrilium phosphane-ylid complex towards carbon-sulfur πsystems. Chem. Commun. 1999, 499−500. (25) Streubel, R.; Faßbender, J.; Schnakenburg, G.; Espinosa Ferao, A. Formation of transient and stable 1,3-dipole complexes with P,S,C and S,P,C ligand skeletons. Organometallics 2015, 34, 3103−3106. (26) (a) Klein, M.; Schnakenburg, G.; Espinosa Ferao, A.; Streubel, R. Rearrangement and deoxygenation of 3,3′-bis(2-pyridyl) oxaphosphirane complexes. Dalton Trans. 2016, 45, 2085−2094. (b) MurciaGarcía, C.; Espinosa Ferao, A.; Schnakenburg, G.; Streubel, R. CPh3 as a functional group in P-heterocyclic chemistry: elimination of HCPh3 in the reaction of P-CPh3 substituted Li/Cl phosphinidenoid complexes with Ph2CO. Dalton Trans. 2016, 45, 2378−2385. (27) Neese, F. ORCA - An ab initio, DFT and semiempirical SCF-MO package, Version 3.0.2; Max Planck Institute for Bioinorganic Chemistry: D-45470 Mülheim/Ruhr, 2012; http://www.cec.mpg.de/ forum/portal.php. Neese, F. The ORCA program system. WIREs Comput. Mol. Sci. 2012, 2, 73−78. (28) (a) Becke, A. D. Density-functional thermochemistry. III. The role of exact exchange. J. Chem. Phys. 1993, 98, 5648−5652. (b) Lee, C. T.; Yang, W. T.; Parr, R. G. Development of the Colle-Salvetti correlation-energy formula into a functional of the electron density. Phys. Rev. B: Condens. Matter Mater. Phys. 1988, 37, 785−789. (29) Neese, F.; Wennmohs, F.; Hansen, A.; Becker, U. Efficient approximate and parallel Hartree-Fock and hybrid DFT calculations. A ’chain-of-spheres’ algorithm for the Hartree-Fock exchange. Chem. Phys. 2009, 356, 98−109. (30) (a) Schäfer, A.; Huber, C.; Ahlrichs, R. Fully optimized contracted Gaussian basis sets of triple zeta valence quality for atoms Li to Kr. J. Chem. Phys. 1994, 100, 5829−5835. (b) Weigend, F.; Ahlrichs, R. Balanced basis sets of split valence, triple zeta valence and

quadruple zeta valence quality for H to Rn: Design and assessment of accuracy. Phys. Chem. Chem. Phys. 2005, 7, 3297−3305. (31) Andrae, D.; Haeussermann, U.; Dolg, M.; Stoll, H.; Preuss, H. Energy-adjusted ab initio pseudopotentials for the second and third row transition elements. Theor. Chim.Acta 1990, 77, 123−141. ECP parameters for W [SD(60,MWB)] have been obtained from Turbomole basis set library at ftp://ftp.chemie.uni-karlsruhe.de/pub/ basen/. ECP basis sets for W [def2-TZVP]: Weigend, F.; Ahlrichs, R. Balanced basis sets of split valence, triple zeta valence and quadruple zeta valence quality for H to Rn: Design and assessment of accuracy. Phys. Chem. Chem. Phys. 2005, 7, 3297−3305. (32) Grimme, S.; Antony, J.; Ehrlich, S.; Krieg, H. A consistent and accurate ab initio parametrization of density functional dispersion correction (DFT-D) for the 94 elements H-Pu. J. Chem. Phys. 2010, 132, 154104−19. (33) Schäfer, A.; Huber, C.; Ahlrichs, R. Fully optimized contracted Gaussian basis sets of triple zeta valence quality for atoms Li to Kr. J. Chem. Phys. 1994, 100, 5829−5835. (34) Riplinger, C.; Sandhoefer, B.; Hansen, A.; Neese, F. Natural triple excitations in local coupled cluster calculations with pair natural orbitals. J. Chem. Phys. 2013, 139, 134101−134113. (35) Pople, J. A.; Head-Gordon, M.; Raghavachari, K. Quadratic configuration interaction. A general technique for determining electron correlation energies. J. Chem. Phys. 1987, 87, 5968−5975. (36) (a) Neese, F.; Wennmohs, F.; Hansen, A. Efficient and accurate local approximations to coupled-electron pair approaches: An attempt to revive the pair natural orbital method. J. Chem. Phys. 2009, 130, 114108. (b) Neese, F.; Hansen, A.; Wennmohs, F.; Grimme, S. Accurate theoretical chemistry with coupled pair models. Acc. Chem. Res. 2009, 42, 641−648. (37) Wennmohs, F.; Neese, F. A comparative study of single reference correlation methods of the coupled-pair type. Chem. Phys. 2008, 343, 217−230. (38) (a) Grimme, S. Improved second-order Møller−Plesset perturbation theory by separate scaling of parallel- and antiparallelspin pair correlation energies. J. Chem. Phys. 2003, 118, 9095−9102. (b) Grimme, S.; Goerigk, L.; Fink, R. F. Spin-component-scaled electron correlation methods. WIREs Comput. Mol. Sci. 2012, 2, 886− 906. (39) (a) Goerigk, L.; Grimme, S. Efficient and Accurate DoubleHybrid-Meta-GGA Density FunctionalsEvaluation with the Extended GMTKN30 Database for General Main Group Thermochemistry, Kinetics, and Noncovalent Interactions. J. Chem. Theory Comput. 2011, 7, 291−309. (b) Goerigk, L.; Grimme, S. A thorough benchmark of density functional methods for general main group thermochemistry, kinetics, and noncovalent interactions. Phys. Chem. Chem. Phys. 2011, 13, 6670−6688. (40) Compliance 3.0.2; http://www.oc.tu-bs.de/Grunenberg/. (a) Brandhorst, K.; Grunenberg, J. Efficient computation of compliance matrices in redundant internal coordinates from Cartesian Hessians for nonstationary points. J. Chem. Phys. 2010, 132, 184101. (b) Brandhorst, K.; Grunenberg, J. How strong is it? The interpretation of force and compliance constants as bond strength descriptors. Chem. Soc. Rev. 2008, 37, 1558−1567. (41) (a) Bader, R. F. W. In Atoms in Molecules: A Quantum Theory; Oxford University Press: Oxford, 1990. (b) Bader, R. F. W. A quantum theory of molecular structure and its applications. Chem. Rev. 1991, 91, 893−928. (c) Matta, C. F.; Boyd, R. J. In The Quantum Theory of Atoms in Molecules; Matta, C. F.; Boyd, R. J., Eds., Wiley-VCH: New York, 2007; pp 1−34. (42) (a) Biegler-König, F.; Schönbohm, J. AIM2000 v. 2.0, 2002; http://www.aim2000.de/. Biegler-König, F.; Schönbohm, J.; Bayles, D. AIM2000A Program to Analyze and Visualize Atoms in Molecules. J. Comput. Chem. 2001, 22, 545−559. (b) Biegler-Kö nig, F.; Schönbohm, J. Update of the AIM2000-program for atoms in molecules. J. Comput. Chem. 2002, 23, 1489−1494. (43) (a) Reed, A. E.; Weinhold, F. Natural bond orbital analysis of near-Hartree−Fock water dimer. J. Chem. Phys. 1983, 78, 4066−4073. (b) Reed, A. E.; Weinstock, R. B.; Weinhold, F. Natural population H


Article

Inorganic Chemistry analysis. J. Chem. Phys. 1985, 83, 735−746. Using the NBO 5.9 code: Glendening, E. D.; Badenhoop, J. K.; Reed, A. E.; Carpenter, J. E.; Bohmann, J. A.; Morales, C. M.; Weinhold, F. Theoretical Chemistry Institute, University of Wisconsin, Madison, WI, 2001. (44) Morgan, K.; Ellis, K. A.; Lee, J.; Fulton, A.; Wilson, S. L.; Dupart, P. S.; Dastoori, R. Thermochemical Studies of Epoxides and Related Compounds. J. Org. Chem. 2013, 78, 4303−4311. (45) Wiberg, K. B. The Concept of Strain in Organic Chemistry. Angew. Chem., Int. Ed. Engl. 1986, 25, 312−322. (46) (a) Wheeler, S. E.; Houk, K. N.; Schleyer, P. v. R.; Allen, W. D. A Hierarchy of Homodesmotic Reactions for Thermochemistry. J. Am. Chem. Soc. 2009, 131, 2547−2560. (b) Wheeler, S. E. Homodesmotic Reactions for Thermochemistry. WIREs Comput. Mol. Sci. 2012, 2, 204−220. (47) Espinosa, A.; de las Heras, É.; Streubel, R. Oxaphosphiraneborane complexes: Ring strain and migratory insertion reactions. Inorg. Chem. 2014, 53, 6132−6140. (48) Bauzá, A.; Quiñonero, D.; Deyà, P. M.; Frontera, A. Estimating ring strain energies in small carbocycles by means of the Bader’s theory of ‘atoms-in-molecules’. Chem. Phys. Lett. 2012, 536, 165−169. (49) (a) Decius, J. C. Compliance matrix and molecular vibrations. J. Chem. Phys. 1963, 38, 241−248. (b) Jones, L. H.; Ryan, R. R. Interaction coordinates and compliance constants. J. Chem. Phys. 1970, 52, 2003−2004. (c) Baker, J. A critical assessment of the use of compliance constants as bond strength descriptors for weak interatomic interactions. J. Chem. Phys. 2006, 125, 014103. (50) Büschel, S.; Jungton, A.-K.; Bannenberg, T.; Randoll, S.; Hrib, C. G.; Jones, P. G.; Tamm, M. Secondary interactions in phosphanefunctionalized group 4 cycloheptatrienyl-cyclopentadienyl sandwich complexes. Chem. - Eur. J. 2009, 15, 2176−2184. (51) von Frantzius, G.; Espinosa Ferao, A.; Streubel, R. Coordination of CO to low-valent phosphorus centres and other related P-C bonding situations. A theoretical case study. Chem. Sci. 2013, 4, 4309− 4322. (52) Wiberg, K. B. Application of the pople-santry-segal CNDO method to the cyclopropylcarbinyl and cyclobutyl cation and to bicyclobutane. Tetrahedron 1968, 24, 1083−1096. (53) (a) Mayer, I. Charge, bond order and valence in the ab initio SCF theory. Chem. Phys. Lett. 1983, 97, 270−274. (b) Mayer, I. Bond order and valence: Relations to Mulliken’s population analysis. Int. J. Quantum Chem. 1984, 26, 151−154. (c) Mayer, I. Bond orders and valences in the SCF theory: A comment. Theor. Chim. Acta 1985, 67, 315−322. (d) Mayer, I. In Modelling of Structure and Properties of Molecules; Maksic, Z. B.Ed.; John Wiley & Sons: New York, 1987. (e) Bridgeman, A. J.; Cavigliasso, G.; Ireland, L. R.; Rothery, J. The Mayer bond order as a tool in inorganic chemistry. J. Chem. Soc., Dalton Trans. 2001, 2095−2108. (54) (a) Lö wdin, P.-O. On the Non-Orthogonality Problem Connected with the Use of Atomic Wave Functions in the Theory of Molecules and Crystals. J. Chem. Phys. 1950, 18, 365−375. (b) Löwdin, P.-O. On the nonorthogonality problem. Adv. Quantum Chem. 1970, 5, 185−199. (c) Szabo, A.; Ostlund, N. S. Modern Quantum Chemistry. Introduction to Advanced Electronic Structure Theory; Dover Publications: Mineola, NY, 1989. (55) Bailey, J. A.; Pringle, P. G. Monomeric phosphinoboranes. Coord. Chem. Rev. 2015, 297−298, 77−90.

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