This article was downloaded by: [University of Saskatchewan Library]On: 29 September 2014, At: 20:46Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registeredoffice: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK

Phosphorus, Sulfur, and Silicon and theRelated ElementsPublication details, including instructions for authors andsubscription information:http://www.tandfonline.com/loi/gpss20

Theoretical Conformational Analysisof Cyclic Organophosphorus andOrganosilicon CompoundsYana A. Vereshchagina a b , Denis V. Chachkov c , Eleonora A.Ishmaeva a , Aisylu A. Gazizova d & Gulnaz R. Fattakhova da Kazan Federal University , Kazan , Russiab Kazan State Technological University , Kazan , Russiac Kazan Scientific Center of Russian Academy of Sciences , Kazan ,Russiad Institute Neftepromkhim , Kazan , RussiaPublished online: 25 Apr 2011.

To cite this article: Yana A. Vereshchagina , Denis V. Chachkov , Eleonora A. Ishmaeva , AisyluA. Gazizova & Gulnaz R. Fattakhova (2011) Theoretical Conformational Analysis of CyclicOrganophosphorus and Organosilicon Compounds, Phosphorus, Sulfur, and Silicon and the RelatedElements, 186:4, 830-837, DOI: 10.1080/10426507.2010.525767

To link to this article: http://dx.doi.org/10.1080/10426507.2010.525767

PLEASE SCROLL DOWN FOR ARTICLE

Taylor & Francis makes every effort to ensure the accuracy of all the information (the“Content”) contained in the publications on our platform. However, Taylor & Francis,our agents, and our licensors make no representations or warranties whatsoever as tothe accuracy, completeness, or suitability for any purpose of the Content. Any opinionsand views expressed in this publication are the opinions and views of the authors,and are not the views of or endorsed by Taylor & Francis. The accuracy of the Contentshould not be relied upon and should be independently verified with primary sourcesof information. Taylor and Francis shall not be liable for any losses, actions, claims,proceedings, demands, costs, expenses, damages, and other liabilities whatsoever orhowsoever caused arising directly or indirectly in connection with, in relation to or arisingout of the use of the Content.

This article may be used for research, teaching, and private study purposes. Anysubstantial or systematic reproduction, redistribution, reselling, loan, sub-licensing,systematic supply, or distribution in any form to anyone is expressly forbidden. Terms &

Conditions of access and use can be found at http://www.tandfonline.com/page/terms-and-conditions

Dow

nloa

ded

by [

Uni

vers

ity o

f Sa

skat

chew

an L

ibra

ry]

at 2

0:46

29

Sept

embe

r 20

14

Phosphorus, Sulfur, and Silicon, 186:830–837, 2011Copyright C© Taylor & Francis Group, LLCISSN: 1042-6507 print / 1563-5325 onlineDOI: 10.1080/10426507.2010.525767

THEORETICAL CONFORMATIONAL ANALYSISOF CYCLIC ORGANOPHOSPHORUSAND ORGANOSILICON COMPOUNDS

Yana A. Vereshchagina,1,2 Denis V. Chachkov,3

Eleonora A. Ishmaeva,1 Aisylu A. Gazizova,4

and Gulnaz R. Fattakhova4

1Kazan Federal University, Kazan, Russia2Kazan State Technological University, Kazan, Russia3Kazan Scientific Center of Russian Academy of Sciences, Kazan, Russia4Institute Neftepromkhim, Kazan, Russia

Abstract The structure of some six- and eight-membered phosphorus and silicon heterocycleswas established by the method of dipole moments and density functional theory calculations.There are two necessary conditions for the feasibility of the transannular interaction in theseheterocycles: (1) the favorable disposition of the donor and acceptor centers in a molecule and(2) the presence of the substituents with the considerable polarizing effect at the heteroatom.

Keywords Density functional theory; dipole moments; organophosphorus compounds;organosilicon compounds; transannular interaction

INTRODUCTION

The spatial structure of some six- and eight-membered heterocyclic systems of phos-phorus and silicon has been studied by various physical methods.1–3 However, interest inthese compounds has not decreased. In the last 10 years, a search for new polyfunctionalheterocyclic systems of phosphorus and silicon that present theoretical interest and canhave useful properties has been conducted.4–6

We can observe the variety of conformational behavior and electronic interactions insuch structures, namely, intramolecular transannular (donor–acceptor) bonds, for exampleS→P, S→Si, N→Si, and so on.

RESULTS AND DISCUSSION

Recently, we have carried out theoretical conformational analysis of the number ofsix- and eight-membered cyclic organophosphorus and organosilicon compounds by thequantum chemical method DFT B3LYP/6–31G(d).

Received 30 July 2010; accepted 14 September 2010.This work was supported by Russian Foundation for Basic Research (grants 10-03-00098 and 10-03-08211).Address correspondence to Yana A. Vereshchagina, Kazan Federal University, Kremlevskaya St., 18, Kazan

420008, Russia. E-mail: yavereshchagina@yahoo.com

830

Dow

nloa

ded

by [

Uni

vers

ity o

f Sa

skat

chew

an L

ibra

ry]

at 2

0:46

29

Sept

embe

r 20

14

THEORETICAL CONFORMATIONAL ANALYSIS 831

The theoretical conformational analysis of 4-oxo-5,6-benzo-1,3,2-dioxaphosphorina-nes 1–4 (Scheme 1) showed that a conformer with the axial orientation of exocyclic sub-stituent X is preferred for all compounds.7 The quantum chemical calculations adequatelydescribe the polarity of the examined compounds. The results of the experimental and cal-culated dipole moments for salicylphosphite 2 can testify to strong intramolecular electroninteractions.

1 X = H; 2 X = Cl; 3 X = N=C=O; 4 X = NEt2

O

O

O

P X

Scheme 1

Our study of the spatial structure of 4-substituted 1,4-heterophosphinanes 5–7(Scheme 2) showed that the preferred conformation of 1,4-thia- and silaphosphinaneswith tetra-coordinated phosphorus atom is a chair form with the axial orientation of theP Y bond and the equatorial orientation of the phenyl group.8 The determined mutualorientation of the phenyl ring and the P Se group in the phosphinanes 5, 6 assumes anoverlap of their π -systems, but the absence of the exaltation between the obtained and cal-culated dipole moments testifies against any essential electronic interactions. The dihedralangle between the lone pair of electrons at the phosphorus atom and the phenyl substituentis 53◦ in the 7 conformer with the equatorial phenyl, but the interaction between them isnot realized as well. In solution, the conformational behavior of 1,4-heterophosphinaneswith tetra-coordinated phosphorus atom is analogous to that of the phosphinanes systems.The introduction of a second heteroatom (oxygen, sulfur, or silicon) to the fourth positionof a heterocycle does not affect the preferred axial orientation of the P Y bond and theequatorial orientation of the phenyl group; the latter is also kept in the trivalent derivative.8

P

XPh

Y

5 X = S, Y = Se; 6 X = SiMe2, Y = Se; 7 X = SiMe2, Y = lone pair of electrons

Scheme 2

We have determined polarity and structure of [4.4.4.0]1,6 tricyclotetradecane deriva-tives 8–15 (Scheme 3) in benzene solution by the method of dipole moments and quantumchemical calculations.9 The considerable exaltation (0.93–1.7 D) between the experimen-tal and the values calculated by the additive scheme dipole moments is observed for allcompounds, and this tendency remains for the theoretical moments also. It indicates thepresence of transannular N→Si bonding in compounds 8–15. We can conclude that in theexamined silatranes, there is the transannular N→Si interaction, in which the nitrogen andsilicon atoms, as well as the oxygen atoms located adjacent to the silicon atom, participate.Substitution of the five-membered semi-rings in the framework of 1-organylsilatranes10

Dow

nloa

ded

by [

Uni

vers

ity o

f Sa

skat

chew

an L

ibra

ry]

at 2

0:46

29

Sept

embe

r 20

14

832 Y. A. VERESHCHAGINA ET AL.

for the six-membered semi-rings with planar fragments does not affect their structures insolution—they are endo-structures with transannular N→Si bonding.

Me

R

SiO

N

R1

O

Me

R

O

Me

R1

23

8 R = Me, R1 = Me

9 R = Me, R1 = CH2Cl

10 R = Me, R1 = CH=CH2

11 R = Me, R1 = CH2-C6H5

12 R = Me, R1 =

13 R = t-Bu, R1 = Me

14 R = t-Bu, R1 = CH2Cl

15 R = t-Bu, R1 = C6H5

N

CH2CH2

Scheme 3

For the first time, we have determined the polarities11 of 1,3,2-dioxasilocins 16–24(Scheme 4). The eight-membered 1,3,2-dioxasilocins 20–24 are the model compounds fora study of reactions of nucleophilic substitution at the silicon atom.

X

O OSi

R3R4

R2

R1

R2

R1X

O OSiR2

R 1

R 2

R1

16 R1 = R2 = R3 = R4 = Me, X = CHCH2SMe 19 R1 = R2 = Me, X = CHCH2SMe

17 R1 = R2 = t-Bu, R3 = R4 = Me, X = CHCH2SMe 23 R1 = R2 = t-Bu, X = S

18 R1 = R2 = Me, R3 = R4 = Ph, X = CHCH2SMe

20 R1 = R2 = t-Bu, R3 = H, R4 = Me, X = S

21 R1 = Me, R2 = t-Bu, R3 = R4 = Me, X = S

22 R1 = Me, R2 = t-Bu, R3 = CH=CH2, R4 = Ph, X = S

24 R1 = R2 = Me, R3 = Me, R4 =Ph, X = S=O

Scheme 4

The planar unsaturated fragments in the 4, 5 and 7, 8 positions of 1,3,2-dioxasilocinsfix their geometry while retaining a possibility for the existence of the boat-chair (BC),boat-boat (BB), and twisted boat (TB) conformations of a heterocycle (Scheme 5).12

BC BB TB

Scheme 5

According to the quantum chemical calculations (Table 1), the boat-chair confor-mation of a heterocycle of compound 16 is energetically preferred in a gas phase. The

Dow

nloa

ded

by [

Uni

vers

ity o

f Sa

skat

chew

an L

ibra

ry]

at 2

0:46

29

Sept

embe

r 20

14

THEORETICAL CONFORMATIONAL ANALYSIS 833

Table 1 Relative energies, theoretical, and calculated by additive scheme dipole moments of conformers of 16(µexp = 2.88 D)

Conformer �E, kcal mol−1 µtheor, D µcalc, D

16а BC 0 2.10 2.4416b BC 0 2.10 2.2816c TB 1.92 0.92 1.3916d TB 2.47 1.52 2.1716e BC 4.21 1.07 1.1516f TB 5.87 1.96 1.52

comparison of the obtained data leads to a conclusion that compound 16 exists as theconformational equilibrium of the forms 16a–d with the preference of the boat-chair con-formation 16a (Figure 1). The Csp

3 S and Csp3 Н bonds are gauche-arranged in these

forms. The analysis of the obtained data (Table 2) indicates that compounds 17–19 exist as

Figure 1 Conformers of Silocin 16 by the B3LYP/6–31G∗ calculation.

Dow

nloa

ded

by [

Uni

vers

ity o

f Sa

skat

chew

an L

ibra

ry]

at 2

0:46

29

Sept

embe

r 20

14

834 Y. A. VERESHCHAGINA ET AL.

Table 2 Relative energies, theoretical and calculated by additive scheme dipole moments of conformers of 17(µexp = 2.58 D), 18 (µexp = 2.61 D), and 19 (µexp = 2.66 D)

Conformer �E, kcal mol−1 µtheor, D µcalc, D

17a BC 0 1.93 2.3117b BC 0 1.93 2.5617c TB 0.40 1.02 1.6517d TB 1.17 1.75 2.4117e BC 3.97 0.77 0.5517f TB 4.77 2.16 1.6118а BC 0 2.09 2.1718b BC 0 2.09 2.3018c TB 1.20 1.61 2.2418d TB 1.35 0.79 0.5718e BC 4.13 1.19 1.5418f TB 4.72 2.16 1.8019а BC 0 2.16 2.5119b BC 0 2.16 2.5319c TB 1.19 1.70 2.1519d TB 1.58 1.72 2.8719e TB 5.17 1.90 1.53

the conformational equilibrium of the boat-chair and twisted boat forms with the preferenceof the first ones, and the gauche-orientation of the Csp

3 S and Csp3 Н bonds is preferred

for these forms as well as for silocin 16. Thus, the presence of the planar fragments in theexamined eight-membered cycles 16–19 does not change the conformational picture of thecyclic part of a molecule, and the number of possible conformers decreases.

The comparison of the experimental dipole moment of silocin 20 with the theoreticaland calculated moments of its conformers leads to a conclusion that there is the confor-mational equilibrium between 20a and 20b forms (Table 3). This conclusion is in a goodagreement with the energetical parameters shown in Table 3. The boat-boat conformation20a, in which exocyclic methyl group at the silicon atom has the equatorial arrangement,is energetically preferred.

In crystal, the eight-membered heterocyclic compounds 21 and 23 have the boat-boat conformation according to the X-ray data.13,14 Also, we have examined the boat-chair

Table 3 Relative energies, theoretical, calculated by additive scheme dipole moments and distances rteor (S . . . Si)of conformers of 20 (µexp = 2.16 D), 21 (µexp = 1.47 D), 22 (µexp = 1.85 D), 23 (µexp = 1.77 D), 24 (µexp =5.10 D)

Conformer �E, kcal mol−1 µtheor, D µcalc, D rtheor (S . . . Si), Å

20a BB 0 1.65 1.62 3.01920b BB 0.96 1.26 2.10 3.13321a BB 0 0.93 1.54 3.07922a TB 0 0.83 0.93 3.12422b TB 1.35 1.15 1.19 3.10122c TB 1.62 1.26 0.94 3.09223a BB 0 1.21 1.96 3.01424a BC 0 5.84 5.14 —24b BC 0.41 5.24 4.77 —

Dow

nloa

ded

by [

Uni

vers

ity o

f Sa

skat

chew

an L

ibra

ry]

at 2

0:46

29

Sept

embe

r 20

14

THEORETICAL CONFORMATIONAL ANALYSIS 835

conformation. The comparison of the experimental dipole moments of silocins 21 and 23with the calculated values indicates that, in solution, these compounds have the boat-boatconformation as well (Table 3). Note that the boat-boat conformation is favorable for therealization of S→Si interaction because the distance between the sulfur and silicon atoms(Table 3) is smaller than the sum of their Van der Waals radii (3.90 Å), and the geometricalparameters14 are the evidence of some planarization of the geometry of the silicon atom.However, the absence of any meaningful exaltation between the experimental and calculateddipole moments of compounds 21 and 23 indicates that, in solution, transannular interactionbetween the spatially separated donor sulfur atom and acceptor silicon atom is absent, incontrast to the conclusion drawn for these compounds in the crystal.13,14

It should be noted that the favorable spatial arrangement of the donor and acceptorcenters in a heterocycle is the necessary but insufficient condition for the feasibility oftransannular interaction in it. Previously, it was convincingly shown that the presence ofthe substituents with the considerable polarizing effect at the element (silicon, phosphorus,carbon, or others) is necessary. Thus, transannular interactions N→P, N→Si, or P→Si areabsent in 1,3,2,6-dioxasilaazacyclooctanes despite the favorable crown conformation.3,15

This is evident from the absence of exaltation of the dipole moments as well as the data ofNMR spectroscopy and theoretical calculations. Kemme and Bleidelis16 have establishedthe absence of transannular bonding for azadioxasilocin Ph2Si(OCH2CH2)2NPh, thoughthe geometrical parameters of its cycle (the crown conformation, N . . .Si distance—3.08Å—is smaller than the sum of their Van der Waals radii) are favorable for the feasibility oftransannular interaction as well.

The heterocycle in silocin 22 has the boat-boat conformation with the axial orientationof the exocyclic phenyl group according to the X-ray data.17 The twisted boat form of 22 ispreferred according to the quantum chemical calculations; the exocyclic phenyl substituentis axial, and the Si CPh and C C bonds eclipse each other. The presence of exaltationbetween the experimental and calculated dipole moments of silocin 22 (Table 3) indicatesthe feasibility of the transannular interaction S→Si in this compound. The distance betweenthe sulfur and silicon atoms in compound 22 (Table 3) is smaller than the sum of their Vander Waals radii, and does not contradict this conclusion. Apparently, the substitution ofthe methyl groups at the silicon atom for the phenyl and vinyl radicals, which have thegreater polarizing effect (greater electronegativity), promotes the transannular interactionS→Si. Thus, the analysis of the obtained data leads to a conclusion that, in solution,silocin 22 exists as the conformational equilibrium of the twisted boat forms 22a–22c withthe preference of the axial orientation of the phenyl fragment at the silicon atom, whichpromotes the transannular interaction S→Si.

In crystal, silocin 24 has two conformers with the different orientation of the exo-cyclic substituents at the silicon atom, according to the X-ray data.18 The eight-memberedheterocycle of both conformers has the boat-chair conformation with the equatorial S Obond. We have also examined the conformations boat-boat (syn-form) and boat-chair withthe axial orientation of the S O bond. The analysis of the data in Table 3 shows that, in so-lution, there is the conformational equilibrium of forms 24a and 24b with the considerablepreference for 24a conformation, in which the endocyclic group S O is equatorial and theexocyclic phenyl group is axial.

Thus, the experimental and theoretical conformational analysis of the eight-membered 1,3,2-dioxasilocins 16–24 with the planar fragments have shown that, insolution, these compounds exist as the conformational equilibrium between the boat-chair,boat-boat, and twisted boat forms. The preference of either conformation is determined by

Dow

nloa

ded

by [

Uni

vers

ity o

f Sa

skat

chew

an L

ibra

ry]

at 2

0:46

29

Sept

embe

r 20

14

836 Y. A. VERESHCHAGINA ET AL.

the presence of unsaturated planar fragments in the 4, 5 and 7, 8 positions and the natureof the atom in the 6 position of a heterocycle, as well as the substituents not only at thesilicon but also at the opposite atom of a heterocycle (carbon, sulfur).

For all examined compounds, the theoretical results are in a good agreement with theexperimental data obtained.

For the feasibility of transannular interaction in a heterocycle, there are two necessaryconditions: (1) the favorable disposition of the donor and acceptor centers in a molecule(for example, the boat-boat conformation) and (2) the presence of the substituents with theconsiderable polarizing effect at the element atom (silicon, phosphorus, carbon, or others).

EXPERIMENTAL

The experimental values of dipole moments were determined in benzene at 20 ◦Con an IDM-2 instrument according to the procedure.19 Benzene was purified using thestandard procedure.20 Quantum chemical calculations were carried out by the GAUSSIAN03 program21 at the B3LYP level of the hybrid density functional theory with the 6–31G(d)basis set. All calculations were performed in the Kazan Branch of the Joint SupercomputerCenter of Russian Academy of Sciences (http://wt.knc.ru).

REFERENCES

1. Litvinov, I. A.; Kataeva, O. N.; Naumov, V. A.; Arshinova, R. P.; Arbuzov, B. A. Izv. Akad. NaukSSSR, Ser. Khim. 1987, 1985–1988.

2. Kataeva, O. N.; Litvinov, I. A.; Naumov, V. A.; Anonimova, I. V. Izv. Akad. Nauk SSSR. Ser.Khim. 1989, 1273–1278.

3. Zyablikova, T. A.; Ishmaeva, E. A.; Kataev, V. E.; Vereshchagina, Ya. A.; Bazhanova, Z. G.;Il’yasov, A. V.; Terent’eva, S. A.; Pudovik, M. A. Russ. J. Gen. Chem. 2004, 74, 1171–1177.

4. Burke, L. P.; De Bellis, A. D.; Fuhrer, H.; Meier, H.; Pastor, S.; Rihs, G.; Rist, G.; Rodebaugh,R. K.; Shum, S. P. J. Am. Chem. Soc. 1997, 119, 8313–8323.

5. Rashidi-Randjbar, P.; Khorama-Zad, A.; Roohi, M. Phosphorus, Sulfur Silicon Relat. Elem.2000, 159, 229–238.

6. Yoshida, M.; Goto, M.; Nakanishi, F. Inorg. Chem. Commun. 2000, 3, 59–61.7. Vereshchagina, Ya. A.; Chachkov, D. V.; Ishmaeva, E. A. Russ. J. Org. Chem. 2003, 39,

1367–1368.8. Vereshchagina, Ya. A.; Ishmaeva, E. A.; Gazizova, A. A.; Chachkov, D. V.; Voronkov, M. G.

Phosphorus, Sulfur Silicon Relat. Elem. 2008, 183, 452–455.9. Ishmaeva, E. A.; Timosheva, A. P.; Gazizova, A. A.; Chachkov, D. V.; Vereshchagina, Ya. A.;

Kataev, V. E.; Timosheva, N. V. Phosphorus, Sulfur Silicon Relat. Elem., 2009, 184, 1406–1412.10. Ishmaeva, E. A.; Samarina, O. A.; Dyakov, V. M.; Voronkov, M. G.; Pudovik, A. N. Dokl. Akad.

Nauk SSSR 1975, 222, 876–878.11. Vereshchagina, Ya. A.; Timosheva, A. P.; Ishmaeva, E. A.; Timosheva, N. V. Zhurn. Org. Khim.

2009, 45, 1440.12. Litvinov, I. A.; Struchkov, Yu. T.; Arbuzov, B. A.; Arshinova, R. P.; Ovodova, O. V. Zh. Strukt.

Khim. 1984, 25, 118–122.13. Day, R. O.; Prakasha, T. K.; Holmes, R. R. Organometallics, 1994, 13, 1285–1293.14. Prakasha, T. K.; Srinivasan, S.; Chandrasekaran, A.; Day, R. O.; Holmes, R. R. J. Am. Chem.

Soc. 1995, 117, 10003–10009.15. Zyablikova, T. A.; Ishmaeva, E. A.; Kushnikovskii, I. A.; Kudyakov, N. M.; Patsanovskii, I. I.;

Kushikovskaya, I. K.; Vereshchagina, Ya. A.; Il’yasov, A. V.; Voronkov, M. G. Russ. J. Gen.Chem. 1999, 69, 1120–1126.

Dow

nloa

ded

by [

Uni

vers

ity o

f Sa

skat

chew

an L

ibra

ry]

at 2

0:46

29

Sept

embe

r 20

14

THEORETICAL CONFORMATIONAL ANALYSIS 837

16. Kemme, A. А.; Bleidelis, J. J. Dokl. Org. Kristallokhim., Akad. Nauk SSSR. 1978, 75.17. Timosheva, N. V.; Prakasha, T. K.; Chandrasekaran, A.; Day, R. O.; Holmes, R. R. Inorg. Chem.

1996, 35, 3614–3621.18. Chandrasekaran, A.; Day, R. O.; Holmes, R. R. Organometallics 1996, 15, 3182–3188.19. Vereshchagin, A. N.; Grozina, L. A. Teor. Eksp. Khim. 1968, 4, 361–366.20. Weissberger, A.; Proskauer, E.; Riddick, J. A.; Toops, E. Organicheskie Rastvoriteli [Organic

Solvents]; Inostrannaya Literatura: Moscow, 1958; p. 519.21. Frisch, M. J., et al. GAUSSIAN 03; Gaussian Inc.: Pittsburgh, PA, 2003.

Dow

nloa

ded

by [

Uni

vers

ity o

f Sa

skat

chew

an L

ibra

ry]

at 2

0:46

29

Sept

embe

r 20

14