ISSN 0012-5008, Doklady Chemistry, 2006, Vol. 409, Part 2, pp. 139–141. © Pleiades Publishing, Inc., 2006.Original Russian Text © M.G. Voronkov, E.A. Grebneva, O.M. Trofimova, N.F. Chernov, A.I. Albanov, N.N. Chipanina, 2006, published in Doklady Akademii Nauk, 2006,Vol. 409, No. 6, pp. 779–781.

139

In the course of study of the C–Si bond cleavage inphenyltrifluorosilane (PTS) with the aim of using PTSin the synthesis of organoelement compounds [1–6],we studied the reaction of PTS with 2-aminoethanoland its

N-

methyl- and

N

,

N

-dimethyl derivatives. Previ-ously, we found that the reaction of protodesilylation ofPTS with 8-hydroxyquinoline or 8-mercaptoquinolineleads to new intracomplex heterocyclic compounds,(N Si) 8-(trifluorosiloxy)quinoline or (N Si)8-(trifluorosilylthio)quinoline, containing a pentacoor-dinated silicon atom [3] (reaction 1):

(1)

We also showed that the reaction of PTS with 2-amino-ethanol and its

N-

methyl and

N

,

N

-dimethyl derivativesalso involves the cleavage of the Ph–Si bond to give ben-zene and (N Si) trifluoro(2-aminoethoxy)silane (

I

),(N Si) trifluoro(2-methylaminoethoxy)silane (

II

), or(N Si) trifluoro(2-dimethylaminoethoxy)silane (

III

),containing a pentacoordinated silicon atom.

N

Y + C6H6

SiF3N

YH + C6H5SiF3

Y = O, S

(2)

H

Si FF

FO

N

H2 – n Men

F

SiF

FO

N

H2 – n Men

n = 0 (I), 1 (II), 2 (III) (A)

(I–III)

C6H6 +C6H5SiF3 + HOCH2CH2NH2 – nMen

We assume that the process begins with the coordi-nation of the silicon atom of PTS to the nitrogen atomof

β

-aminoalcohol, which is followed by the formationof the four-centered transition complex

A

; finally ben-zene is eliminated to produce intracomplex compounds

I

–

III

, containing a five-membered coordination ringclosed by the intramolecular N Si donor–acceptorbond.

Compounds

I

–

III

are colorless crystalline solidswith a slight amine odor (Table 1).

It was reported earlier that the reaction of PTS withtrimethyl(2-aminoethoxy)silane and trimethyl(2-methyl-aminoethoxy)silane gave rise to the cleavage of theSi

−

F bond, whereas the C–Si bond remained intact [7].We found that, in agreement with these data, the previ-ously unknown reaction of PTS with trimethyl(2-dimeth-ylaminoethoxy)silane also occurs as a transsilylationreaction accompanied by the cleavage of the Si–F bondand the elimination of trimethylfluorosilane to yield intra-complex (N Si) phenyldifluoro(2-dimethylamino-

The Unusual Reaction of Phenyltrifluorosilane with 2-Aminoethanol and Its

N

-Methyl Derivatives

Academician

M. G. Voronkov, E. A. Grebneva, O. M. Trofimova,N. F. Chernov, A. I. Albanov, and N. N. Chipanina

Received March 22, 2006

DOI:

10.1134/S0012500806080040

Favorskii Institute of Chemistry, Siberian Division, Russian Academy of Sciences, ul. Favorskogo 1, Irkutsk, 664033 Russia

CHEMISTRY

140

DOKLADY CHEMISTRY

Vol. 409

Part 2

2006

VORONKOV et al.

ethoxy)silane (

IV

), containing a pentacoordinated sili-con atom (reaction 3):

(3)

When an excess of trimethyl(2-dimethylaminoeth-oxy)silane is used, phenyldifluorobis(2-dimethylami-

C6H6SiF3 Me3SiOCH2CH2NMe2+ PhF2SiOCH2CH2NMe2

+ Me2NCH2CH2O( )2SiPhF Me3SiF.+(V)

(IV)

noethoxy)silane (

V

) forms along with compound

IV

.Compound

IV

is a colorless crystalline solid with aslight amine odor, while compound

V

is a colorless liq-uid (Table 1).

The composition and structure of compounds

I

–

V

was confirmed by multinuclear

1

H,

13

C,

19

F, and

29

SiNMR (Tables 2, 3) and IR spectroscopy.

The intramolecular donor–acceptor interaction ofnitrogen and silicon atoms is known to change theparameters of

19

F and

29

Si NMR spectra as comparedwith the structurally related compounds of tetrahedralsilicon: the shielding of the silicon atom increases, theresonance of fluorine atoms is shifted downfield, andthe

29

Si–

19

F spin coupling constant decreases [8]. Table 3shows that the above variations in NMR spectralparameters are observed for compounds

I

–

V

. The sig-nals in the

29

Si NMR spectra of compounds

I

,

III

,

IV

,and

V

show an upfield shift by ~22, ~10, and ~2 ppm incomparison with F

3

SiOEt, F

2

Si(OEt)Ph, andFSi(OEt)

2

Ph, respectively [6], and their chemical shiftsdecrease with the number of Si–F bonds. The strengthof the intramolecular N Si coordination bond in themolecules of compounds

I

–

V

decreases in the samesequence.

Table 1.

Intracomplex compounds of 2-aminoethanol and its

N

-methyl and

N

,

N

-dimethyl derivatives (

I

–

V

)

Compound Yield, %

T

m

,

°

C Molecular formula

Found, wt %Calculated, wt %

C H F N

I

73 98–99 C

2

H

6

NOF

3

Si

II

78 180–183 C

3

H

8

NOF

3

Si

III

65 173–175 C

4

H

10

NOF

3

Si

IV 85 143–145(2)* C10H15NOF2Si

V 80 160(5)* C14H25N2O2FSi

* Boiling point is given, °C (P, mmHg).

16.8216.55------------- 4.67

4.17---------- 39.32

39.26------------- 9.50

9.65----------

22.8422.63------------- 5.53

5.06---------- 35.11

35.80------------- 8.48

8.80----------

27.7327.57------------- 5.90

5.74---------- 32.40

32.74------------- 8.09

8.04----------

51.7651.92------------- 6.06

6.54---------- 16.23

16.43------------- 6.36

6.06----------

55.4755.97------------- 8.56

8.39---------- 6.02

6.32---------- 9.06

9.32----------

Table 2. Parameters of 1H and 13C NMR spectra for compounds I–V (CDCl3, 25°C)

CompoundδH, ppm (J, Hz) δC, ppm

NMe NCH2 OCH2 NMe NCH2 OCH2

I – 2.83 t (5.2) 3.56 t – 41.65 58.29

II 2.47 s 2.84 t (5.2) 3.59 t 33.83 51.51 57.32

III 2.65 s 2.97 t (5.6) 3.66 t 43.45 56.12 59.22

IV 2.24 s 2.45 t (5.6) 3.61 t 44.49 58.59 61.28

V 2.21 s 2.53 t (6.1) 3.96 t 45.59 60.66 61.65

Table 3. Parameters of 29Si and 19F NMR spectra for com-pounds I–V and model alkoxyfluorosilanes [6] (CDCl3, 25°C)

Compound δSi, ppm δF, ppm JSi–F, Hz

I –125.81 –117.42 208.0II – –117.44 –III –126.0 –117.35 207.70IV –77.45 –138.16 248.90V –63.0 –141.88 259.50F3SiOEt –104.10 –158.12 182.0F2Si(OEt)Ph –67.0 –140.90 265.0FSi(OEt)2Ph –61.50 –142.40 262.0

DOKLADY CHEMISTRY Vol. 409 Part 2 2006

THE UNUSUAL REACTION OF PHENYLTRIFLUOROSILANE 141

As compared with the above compounds of tetraco-ordinated silicon (F3SiOEt, F2Si(OEt)Ph, andFSi(OEt)2Ph), the 19F chemical shift in the 19F NMRspectra of compounds I–III, IV, and V is shifted down-field by ~41, ~3, and ~0.5 ppm, respectively; i.e., itdecreases with the number of fluorine atoms, whichindicates that the N Si donor–acceptor interactionin the molecules of compounds IV and V is muchweaker. The close values of the 19F and 29Si NMR spec-tral parameters for compounds I and III indicate thatthe appearance of methyl groups at the nitrogen atomdoes not entail marked strengthening of the coordina-tion N Si bond.

The 29Si–19F spin coupling constants in the NMRspectra of compounds IV and V are ~16 and ~2 Hzlower than those in the model compounds F2Si(OEt)Phand FSi(OEt)2Ph, respectively. The change in 29Si–19Fspin coupling constants in compounds I and III isanomalous. This seems to result from the previouslyrevealed [9] inverse relationship between the 1JSi–F val-ues and the electronegativity of the substituent X inF3SiX molecules (1JSi–F decreases when the electroneg-ativity increases). Therefore, the 1JSi–F value for trifluo-roethoxysilane is relatively low, whereas the increase inthe coordination number of silicon to five leads to aslight increase rather than a decrease in 1JSi–F. Thechange in the averaged 1JSi–F in the presence of intramo-lecular coordination to the silicon atom is caused by thebalance between 1 and 1 . The first parame-ter decreases while the second one increases (owing toa change in s character) the averaged spin coupling con-stant. Thus, the contribution of 1 prevails for tri-fluorosilanes, where a carbon atom is the fourth substit-uent, whereas 1 prevails for trifluoroalkoxysi-lanes. Thus, for example, in passing from fluorotri-ethoxysilane to fluorosilatrane, there is no contributionfrom 1 and 1JSi–F decreases by 68 Hz.

The Si–F stretching vibration bands in the IR spec-tra of compounds I–III correspond to the trigonal-bipy-ramidal environment of the silicon atom with nitrogenand fluorine atoms in the axial positions. The spectra ofcompounds I–III show the bands of stretching vibra-tions of the axial bonds ν Si–Fax at 720 (I and II) and730 cm–1 (III) and the bands of antisymmetric and sym-metric stretches of the equatorial bonds ν Si−Feq

JSi–FaxJSi–Feq

JSi–Fax

JSi–Feq

JSi–Feq

(νas and νs) at 990 and 886 cm–1 (I), 930 and 870 cm–1

(II), and 970 and 880 cm–1 (III), respectively. The spec-tra of compounds I–V show the lack of bands of Si–Fantisymmetric stretches at 940 cm–1 typical for thecompounds of tetrahedral silicon and also confirm thepentacoordination of the silicon atom in these mole-cules.

Thus, the protodesilylation reaction of PTS with2-aminoethanol and its N-methyl and N,N-dimethylderivatives is a promising method for the synthesis ofnew types of intracomplex organosilicon compoundscontaining a pentacoordinated silicon atom.

ACKNOWLEDGMENTS

This work was supported by INTAS (project no. 03–51–4164) and the Presidential program “Leading Sci-entific Schools” (grant no. NSh-4575.2006.3).

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