Supporting Information

© Wiley-VCH 2008

69451 Weinheim, Germany

1

Supporting information

Isoprene Polymerization with Yttrium Amidinate Catalysts: Switchingthe Regio- and Stereoselectivity by Addition of AlMe3

Lixin Zhang, Masayoshi Nishiura, Masahiro Yuki, Yi Luo, and Zhaomin Hou*

Organometallic Chemistry Laboratory, RIKEN (The Institute of Physical and Chemical Research), Hirosawa 2-1, Wako, Saitama

351-0198, Japan

Experimental Section

General Procedure and Materials. All manipulations were performed under a dry and oxygen-free nitrogen or

argon atmosphere using Schlenk techniques or an Mbraun glovebox. Argon and nitrogen were purified by being passed

through a Dryclean column (4 A molecule sieves, Nikka Seiko Co.) and a Gasclean GC-RX column (Nikka Seiko Co.).

The nitrogen in the glovebox was constantly circulated through a copper/molecular sieves (4 A) catalyst unit. The

concentration of the oxygen and moisture in the glovebox was always kept below 0.1 ppm (monitored by an Mbraun

O2/H2O Combi-Analyzer). THF, Et2O, Toluene, and hexane were distilled from sodium/benzophenone ketyl, degassed

by the freeze-pump-thaw method, and dried over fresh Na chips and stored in the glovebox. Monochlorobenzene was

distilled with CaH2, and degassed by the freeze-pump-thaw method. Isoprene (Junsei Chemical Co., Ltd.) was dried by

stirring with CaH2 for 48 hours, and distilled under reduced pressure before use. YCl3 was purchased from Strem.

CH3C6H4NMe2-o was purchased from Tokyo Chemical Industry Co., LTD and used without purification.

[Ph3C][B(C6F5)4] (A) was purchased from Tosohchem Corporation and used without purification. AlMe3 and AlEt3,

(1M toluene solution), AliBu3 (1M hexane solution) were bought from Kanto Chemical Co. Inc.. The deuterated

solvents (such as THF-d8, Toluene-d8, C6D6) were obtained from Cambridge Isotope and dried by sodium chips.

Y(CH2C6H4NMe2-o)31 and N,N´-bis(2,6-diisopropylphenyl)benzamidine (NCNdippH)2 ligand were prepared according to

literature procedures. 1H and 13C NMR spectra of polymers were recorded using TMS as internal standard on a JNM

EX-400 in CDCl3 at room temperature. The NMR spectra of air and moisture sensitive compounds were recorded by

using of J. Young valve NMR tube (Wilmad 528-JY) on a JNM EX-400 in C6D6. The weight-average molecular weight

(Mw), the number-average molecular weight (Mn), and the molecular weight distribution (Mw/Mn) of the polymers were

measured by means of gel permeation chromatography on TOSOH HLC-8220 GPC (Column: Super HZM-H×3) at

2

40 °C using THF as eluent (the flowing rate is 0.35 mL/min) against polystyrene standards. DSC was performed on SII

NanoTechnology EXSTAR6220 DSC at a heating rate of 10 °C/min under N2 atmosphere.

Synthesis of (NCNdipp)Y(CH2C6H4NMe2-o)2 (1): A n-hexane (10 mL) solution of NCNdippH (0.344 g, 0.781 mmol)

was added slowly dropwise via glass pipette to a toluene (6 mL) solution of Y(CH2C6H4NMe2-o)3 (0.384 g, 0.781

mmol), and stirred overnight to give a bright pale yellow solution. All volatiles were removed under vacuum. The

resulting pale yellow powder was washed with cold hexane quickly, and then dried up. 0.529 g (85%) of

(NCNDipp)Y(CH2C6H4NMe2-o)2 (1) was obtained. Crystals suitable for X-ray analysis were obtained by recrystallization

in toluene/hexane at -30 °C. Anal. Calcd for C49H63N4Y: C, 73.85; H, 7.97; N, 7.03. Found: C, 73.61; H, 7.95; N, 7.27.

1H NMR (400 MHz, RT, C6D6): δ 7.25 (br s, 1H, Ph), 7.10−7.03 (m, 8H, Ar), 6.94−6.90 (m, 2H, Ar), 6.62-6.54 (m, 8H,

Ar), 4.21 (br m, 2H, −CHMe2), 3.04 (br m, 2H, −CHMe2), 2.33 (br m, 12H, −CH2C6H4NMe2), 2.11 (br s, 2H,

−CH2C6H4NMe2), 1.90 (br s, 2H, −CH2C6H4NMe2), 1.59 (br m, 12H, −CHMe2), 0.91 (br m, 6H, −CHMe2), 0.11 (br m,

6H, −CHMe2). 13C NMR (100 MHz, RT, C6D6): δ 172.99 (s, NCN), 144.69 (s, Ar), 144.06 (s, Ar), 142.25 (s, Ar),

141.29 (s, Ar), 133.80 (s, Ar), 131.59 (d, J = 2 Hz, Ar), 130.746 (s, Ar), 128.89 (s, Ar), 128.79 (s, Ar), 128.27 (s, Ar),

127.89 (s, Ar), 127.65 (s, Ar), 126.84 (d, J = 2 Hz, Ar), 124.73 (br s, Ar), 124.38 (s, Ar), 123.40 (br s, Ar), 120.20 (s,

Ph), 118.47 (s, Ar), 47.19 (d, JY-C = 15 Hz, −CH2C6H3NMe2-o), 45.49 (br s, −CH2C6H3NMe2-o), 29.87 (br s, −CHMe2),

27.76 (br s, −CHMe2), 24.78 (br s, −CHMe2), 22.97 (br s, −CHMe2). 1H NMR (400 MHz, 70 °C, C6D6): δ 7.06−7.01 (m,

9H, Ar), 6.89 (t, 2H, J = 7 Hz, Ar), 6.64−6.54 (m, 8H, Ar), 3.59 (br m, 4H, −CHMe2), 2.36 (s, 12H, −CH2C6H4NMe2),

1.78 (s, 4H, −CH2C6H4NMe2), 1.45−0.39 (br m, 24H, −CHMe2). 13C NMR (100 MHz, 70 °C, C6D6): δ 173.33 (s, NCN),

145.08 (s, Ar), 144.57 (s, Ph), 142.94 (s, Ar), 141.89 (s, Ar), 132.18 (s, Ar), 132.15 (s, Ar), 131.14 (m, Ar), 129.12 (m,

Ar), 128.42 (s, Ar), 128.35 (s, Ar), 128.08 (s, Ar), 127.89 (s, Ar), 127.09 (s, Ar), 126.98 (s, Ar), 124.71 (br m, Ar),

124.32 (br m, Ar), 120.49 (s, Ph), 118.64 (s, Ar), 47.60 (d, JY-C = 15 Hz, −CH2C6H3NMe2-o), 46.01 (s,

−CH2C6H3NMe2-o), 29.11 (br s, −CHMe2), 24.43 (br s, −CHMe2), 23.70 (s, −CHMe2).

Synthesis of (NCNdipp)Y[(μ−Me)2AlMe2]2 (2): A toluene (10 mL) solution of complex 1 (0.10 g, 0.125 mmol) was

added dropwise via a glass pipette to a toluene solution (6 mL) of AlMe3 (0.627 mmol, 1M, 0.63 mL), and stirred 10

min to give a bright pale yellow solution. All volatiles were removed under vacuum. The resulting pale yellow powder

was recrystallized in hexane at -30 °C, removed the small amount of mother solution part and then dried up. 0.071 g

(80%) crystalline pale yellow (almost colorless) solid of (NCNdipp)Y[(μ-Me)2AlMe2]2 (5) was obtained. Anal. Calcd for

3

C39H63Al2N2Y: C, 66.65; H, 9.04; N, 3.99. Found: C, 66.99; H, 9.00; N, 4.15. 1H NMR (400 MHz, RT, C6D6): δ

6.99-6.95 (m, 8H, Ar), 6.54-6.52 (m, 3H, Ar), 3.29 (m, 4H, −CHMe2), 1.26 (d, J = 3 Hz, 12H, −CHMe2), 0.79 (d, J = 3

Hz, 12H, −CHMe2), 0.01 (s, 24H, [AlMe4]-). 1H NMR (400 MHz, -60 °C, C7D8): δ 7.14-6.89 (m, 8H, Ar), 6.44 (m, 3H,

Ar), 3.21 (m, 4H, −CHMe2), 1.26 (d, J = 3 Hz, 12H, −CHMe2), 0.77 (d, J = 3 Hz, 12H, −CHMe2), 0.02 (s, 24H,

[AlMe4]-). 13C NMR (100 MHz, RT, C6D6): δ 177.30 (s, NCN), 141.61 (s, Ph), 141.45 (s, Ar), 131.02 (s, Ar), 130.27 (s,

Ar), 127.37 (s, Ar), 125.87 (s, Ar), 124.68 (s, Ar), 29.19 (s, −CHMe2), 25.64 (s, −CHMe2), 23.82 (s, −CHMe2), 2.64 (s,

[AlMe4]-).

A Typical Procedure for the Polymerization of Isoprene Catalyzed by 1/[Ph3C][B(C6F5)4] (run 4, Table 1): In a

glovebox, a magnetic stir bar was placed in a 100 mL flask, to which a dropping funnel was attached. Isoprene (1.022 g,

15.0 mmol), NCNdippY(CH2C6H4NMe2-o)2 (1) (0.016g, 0.020 mmol), and C6H5Cl (8 mL) were charged into the flask. A

C6H5Cl solution (2 mL) of [Ph3C][B(C6F5)4] (A) (0.018 g, 0.020 mmol) was charged to the dropping funnel. The

reaction apparatus was moved outside and placed in a cooling bath (–10 °C). After 10 min, the C6H5Cl solution of

[Ph3C][B(C6F5)4] was dropped into the mixture of 1 and isoprene under rapid stirring. After the mixture was stirred at

–10 °C for 20 minutes, methanol was injected to terminate the polymerization. The reaction mixture was poured into a

large quantity (200 mL) of methanol containing a small amount of hydrochloric acid and butylhydroxytoluene (BHT) as

a stabilizing agent under stirring. The precipitated polymer was isolated by decantation, cut into small pieces, washed

with methanol, and then dried under vacuum at 60 °C to a constant weight to afford 1.021 g of 3,4-polyisoprene

(~100 % yield).

A Typical Procedure for the Polymerization of Isoprene Catalyzed by 1/[Ph3C][B(C6F5)4]/AlMe3 (run 13, Table

1): In a glovebox, a magnetic stir bar was placed in a 100 mL flask, to which a dropping funnel was attached. Isoprene

(1.022 g, 15.0 mmol), NCNdippY(CH2C6H4NMe2-o)2 (1) (0.016g, 0.020 mmol), a hexane solution (0.10 mmol, 0.1 mL,

1.0 M) of AlMe3 and C6H5Cl (7 mL) were charged into the preweighted flask. A C6H5Cl solution (3 mL) of

[Ph3C][B(C6F5)4] (A) (0.018 g, 0.020 mmol) was charged to the dropping funnel. The reaction apparatus was moved

outside and placed in a cooling bath (–10 °C). After 10 min, the C6H5Cl solution of [Ph3C][B(C6F5)4] was dropped into

the mixture of 1, AlMe3 and isoprene under rapid stirring. After the mixture was stirred at –10 °C for 60 minutes,

methanol was injected to terminate the polymerization. The reaction mixture was poured into a large quantity (200 mL)

of methanol containing a small amount of hydrochloric acid and butylhydroxytoluene (BHT) as a stabilizing agent

4

under stirring. The precipitated polymer was isolated by decantation, washed with methanol, and then dried under

vacuum at 60 °C to a constant weight to afford 0.838 g of 1,4-cis-polyisoprene 82 % yield).

Hf

n

34

125

Hb

Ha Hc

He

HdHfHf

Hf

Hd and He

Hc Ha and Hb

Figure S1. 1H NMR spectrum of the 91% 3,4-polyisoprene obtained at RT in CDCl3 at room temperature ( run 3

in Table 1).

5

5

4

n

34

125

Hb

Ha Hc

He

HdHfHf

Hf

2

31

Figure S2. 13C NMR spectrum of the 91% 3,4-polyisoprene obtained at RT in CDCl3 at room temperature ( run 3

in Table 1).

Hf

n

34

125

Hb

Ha Hc

He

HdHfHf

Hf

Hd and He

Hc Ha and Hb

Figure S3. 1H NMR spectrum of the 99.5% isotactic 3,4-polyisoprene in CDCl3 at room temperature (run 5 in Table 1).

6

Figure S4. 13C NMR spectrum of the 99.5% isotactic 3,4-polyisoprene in CDCl3 at room temperature (run 5 in

Table 1).

5

n

34

125

Hb

Ha Hc

He

HdHfHf

Hf 4

3 2 1

Hc

nHa

Hb

Hc

HcHc

Hd

Ha'Hb'

Ha,Hb,Ha’,Hb’

1,4-cis-polyisoprene

Hd

3,4-polyisoprene

Figure S5. 1H NMR spectrum of the 98% 1,4-cis-polyisoprene in CDCl3 at room temperature (run 13 in Table 1).

7

Figure S6. 13C NMR spectrum of the 98% 1,4-cis-polyisoprene in CDCl3 at room temperature (run 13 in Table 1).

5

4 1 3

n1

2 3

4

52

8

-1

1

3

5

7

9

11

13

15

8 10 12 14 16

Elution time (min)

Inte

nsi

ty (m

V)

Figure S7. GPC profile of isotactic 3,4-polyisoprene obtained in run 5, Table 1.

-1

4

9

14

19

24

29

8 10 12 14 1

Elution time (min)

Inte

nsi

ty (m

V)

6

Figure S8. GPC profile of 1,4-cis polyisoprene obtained in run 13, Table 1.

9

-3500

-2500

-1500

-500

500

1500

2500

3500

-50 0 50 100 150 200

Temperature (Cel)

DS

C (

mV

)

Figure S9. DSC chart of isotactic 3,4-polyisoprene obtained in run 5, Table 1.

-2500

-2000

-1500

-1000

-500

0

500

1000

1500

2000

2500

-110 -90 -70 -50 -30 -10 10 30 50

Temperature (Cel)

DS

C (

mV

)

Figure S10. DSC chart of 1,4-cis polyisoprene obtained in run 13, Table 1.

10

X-ray Crystallographic Analysis. A crystal was sealed in the thin-wall glass capillary under a microscope in the

glove box. Data collections were performed at –100 °C on a Bruker SMART APEX diffractometer with CCD area

detector using graphite-monochromated Mo Kα radiation (λ= 0.71069 Å). The determination of crystal class and unit

cell was carried out by SMART program package. The raw frame data were processed using SAINT and SADABS to

yield the reflection data file. The structure was solved by using SHELXTL program. Refinement was performed on F2

anisotropically by the full-matrix least-squares method for all the non-hydrogen atoms. The analytical scattering factors

for neutral atoms were used throughout the analysis. Except for the hydrogen atoms on C1 and C2 atoms of 2, hydrogen

atoms were placed at the calculated positions and included in the structure calculation without further refinement of the

parameters. The hydrogen atoms on C1 and C2 atoms of 2 were located by difference Fourier syntheses and their

coordinates and isotropic parameters were refined. The residual electron densities were of no chemical significance.

CCDC 657217 (complex 1) and 657218 (complex 2) contain the supplementary crystallographic data for this paper.

These data can be obtained free of charge via www.ccdc.cam.ac.uk/conts/retrieving.html (or from The Cambridge

Crystallographic Data Centre, 12, Union Road, Cambridge CB2 1EZ, UK; fax: (+44)-1223-336033; or

deposit@ccdc.cam.ac.uk).

Figure S11. ORTEP structure of 1 (thermal ellipsoids at 30% level; hydrogen atoms are omitted for clarity).

11

Figure S12. ORTEP structure of 2 (thermal ellipsoids at 30% level; hydrogen atoms are omitted for clarity).

Computations

The geometry optimizations followed by analytic frequency calculations were performed with two-layer

ONIOM(b3lyp:uff) method[3] planted in Gaussion 03.[4] For high level, 6-31G* basis was used for C, N and H atoms,

and the Lan2DZ basis set together with LanL2DZ effective core potential[5] was used for Y atom. The division of the

layers is shown in Figure S13, in which the reactive part of the cationic species (in red) was included in model system

treated at high layer (B3LYP[6]) calculation. The remained parts (in black) were included in low layer treated by

universal force field (UFF) molecular mechanics method.[7] The monomer molecule was included in high layer for the

calculations of coordination complexes. No symmetry restriction was used during all the calculations. The optimized

alkyl cationic species and coordination complex were confirmed to be minima (no imaginary frequencies).

The selected geometrical parameters of optimized cationic Y alkyl complexes are shown in Figure S14, which

indicates that the tridentate coordination mode are retained in the cationic species. In the [(NCN)YCH2C6H4NMe2]+

cation, there is an agostic interaction between Y and the NMe2 group (Y···NMe2 distance of 2.46 Å).

The optimized structure of isoprene–[(NCN)YCH2C6H4NMe2]+ π–complex is shown in Figure S15 together with

complexation energies. Attempts to locate 1,4-coordination (for 1,4-insertion) complexes were unsuccessful because of

the steric repulsion of the isopropyl groups. This may be one reason why such catalyst system catalytically offers

3,4-polyisoprene.

The optimized 3D structures of the [(NCN)YCH2C6H4NMe2]+ cation and the isoprene–[(NCN)YCH2C6H4NMe2]+

π–complex are shown in Figure S16 and Figure S17, respectively.

12

N N

Y

R

R = CH2C6H4NMe2

Figure S13. The divisions of layers in Y alkyl cationic species: red part for the high layer and black-part for the low

layer.

Y

CH2

C1

N1 N22.36

2.30 2.31

1.35 1.34

Y-C1 = 2.72 Å∠N1C1N2 = 112.4°∠N1YN2 = 58.0°∠YN1N2C1 = 157.8°

N

1.47

2.46

1.48

Figure S14. Optimized alkyl cationic species [(NCN)YCH2C6H4NMe2]+ (bond length in Å and angles in degree.

Y

CH2

C

N N

2.85

2.282.44

N

1.48

2.47

1.48

3.20

-19.2/-19.1/-6.2

Figure S15. The optimized isoprene–[(NCN)Y(CH2C6H4NMe2)]+ π–complexes (4,3-coordination) and its complexation

energy. The complexation energies (ΔE/ΔH/ΔG in kcal/mol) are relative to separate bare cation and isoprene.

13

Figure S16. The optimized 3D structure of [(NCN)Y(CH2C6H4NMe2)]+ cation. The selected geometrical data is shown

in Figure S14.

Figure S17. The optimized 3D structure of isoprene–[(NCN)Y(CH2C6H4NMe2)]+ π–complexes. The double bonds are

not shown. The selected geometrical data is shown in Figure S15.

14

References.

[1] S. Harder, Organometallics 2005, 24, 373−379.

[2] S. Ogata, A. Mochizuki, M. –A. Kakimoto, Y. Imai, Bull. Chem. Soc. Jpn. 1986, 59, 2171−2177.

[3] (a) R. D. J. Froese, K. Morokuma, Chem. Phys. Lett. 1999, 305, 419–424; (b) R. D. J. Froese, K. J. Morokuma, Phys. Chem. A

1999, 103, 4580–4586; (c) T. Vreven, K. Morokuma, J. Chem. Phys. 1999, 111, 8799–8803; (d) T. Vreven, K. Morokuma, J. Phys.

Chem. A 2002, 106, 6167–6170; (e) F. Maseras, K. Morokuma, J. Comput. Chem. 1995, 16, 1170–1179.

[4] M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A. Robb, J. R. Ch eeseman, Jr., J. A. Montgomery, T. Vreven, K. N.

Kudin, J. C. Burant, J. M. Millam, S. S. Iyengar, J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G.. Scalmani, N. Rega, G.. A.

Petersson, H. Nakatsuji, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H.

Nakai, M. Klene, X. Li, J. E. Knox, H. P. Hratchian, J. B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R. E.

Stratmann, O. Yazyev, A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, P. Y. Ayala, K. Morokuma, G. A. Voth, P. Salvador, J.

J. Dannenberg, V. G. Zakrzewski, S. Dapprich, A. D. Daniels, M. C. Strain, O. Farkas, D. K. Malick, A. D. Rabuck, K.

Raghavachari, J. B. Foresman, J. V. Ortiz, Q. Cui, A. G. Baboul, S. Clifford, J. Cioslowski, B. B. Stefanov, G. Liu, A. Liashenko,

P. Piskorz, I. Komaromi, R. L. Martin, D. J. Fox, T. Keith, M. A. Al-Laham, C. Y. Peng, A. Nanayakkara, M. Challacombe, P. M.

W. Gill, B. Johnson, W. Chen, M. W. Wong, C. Gonzalez, and J. A. Pople, Gaussian 03, Revision C.02, Gaussian, Inc.,

Wallingford CT, 2004.

[5] (a) P. J. Hay, W. R. Wadt, J. Chem. Phys. 1985, 82, 270–283; (b) W. R. Wadt, P. J. Hay, J. Chem. Phys. 1985, 82, 284–298; (c) P. J.

Hay, W. R. Wadt, J. Chem. Phys. 1985, 82, 299–310.

[6] (a) A. D. Becke, Phys. Rev. A 1988, 38, 3098–3100; (b) C. Lee, W. Yang, R. G. Parr, Phys. Rev. B 1988, 37, 785–789.

[7] A. K. Rappé, C. J. Casewit, K. S. Colwell, W. A., III Goddard, W. M. Skiff, J. Am. Chem. Soc. 1992, 114, 10024–10035.

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