Deactivation Pathways of Neutral Ni(II) Polymerization Catalysts

Supporting Information

Deactivation Pathways of Neutral Ni(II) Polymerization Catalysts

Andreas Berkefeld and Stefan Mecking*

University of Konstanz, Chair of Chemical Materials Science, Department of Chemistry, Universitiitsstrasse 10, D-78457 Konstanz, Germany

E-mail: stefan.mecking@uni-konstanz.de

General reactivity of neutral Ni(lI)-methyl complexes.

A 9.8 mM solution ofI-DMSO in CD2Ch was prepared at room temperature and stored at -30°C. In general, samples of I-DMSO in non coordinating solvents should not be kept at ambient temperatures for prolonged times since gradual decomposition to ethane occurs.

'n

NMR spectra were acquired at -60°C, -20°C, O°C, 25°C, 35°C and 45°C. Figure SI shows the

'n

NMR spectrum obtained at -20°C. In general, the line widths of the [(N,O)NiCH3(DMSO)] and [(N,O)NiCH3(DM SO )] resonances increased upon warming the sample to temperatures above 25°C. Furthermore, the resonance of free DMSO was observed to shift continuously from 2.55 ppm at T < O°C to 3.24 ppm at T > 25°C. The equilibrium constants KMe(T) ~ [l-DMSOltmni[l-DMSO]cis were determined directly from the NMR spectra by integration of the Ni(II)-CH3 resonances. Figure S2 depicts the plot of In(KMe(T)) versus liT, providing the reaction enthalpy and entropy from which the free enthalpy difference between the trans and the cis isomer ofI-DMSO was calculated for room temperature.

,...., \0 00 -

o -

i i

[(NO)N"(CH )(DMSO)] ^I

rans- , I 3

~

-HC=N- free [(N,O)Ni(CH_3)(DMSO)]

DMSO trans- eis-

trans- eis-isomer

*

~ '

eis-leN,O)N i(CH_{3 ) (}DMSO)]

•

_I ¹

.:

I

• 1

I I i

^{11 A &}

_loo ._

- -

8.0 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 -0.5 fl (ppm)

Figure SI. lH NMR spectrum ofI-DMSO in CD_2Cb(*) at -20°C.

ilH_~(7.98±0.09) kJ mar!

ss~(21±0.3) J mar! K! ilG_~(1.71±0.31) kJ mar!

-1,8 -2,0

+-...,~---.-~--.-~,....,---.~---.-~....-~,---.----r~

3,0 3,2 3,4 3,6 3,8 4,0 4,2 4,4 4,6 4,8 1/T*103K

-0,4

-0,6 -0,8

~ -1,0

f='~w -12

::;. '

E

@-1 4

~- ,

~

.E: -1,6

Figure S2. Vant Hoff plot of the equilibrium between the trans and cis isomer of I-DMSO in CD2Cbsolution at variable temperatures.

82

Second-order rates of exchange of free with coordinated DMSO were determined for the cis and trans isomer separately by variable temperature lH NMR spectroscopy.' A CD2CI2 solution ofI-DM80 (7.7 mM) was prepared, to which 2.3 equivalents of DMSO (17.6 mM) were added. Coalescence of the resonances of coordinated and free DMSO was observed at 10°C for the cisisomer and was estimated to occur at 40 to 45°C in case of the trans isomer. Second-order exchange rates at coalescence temperatures were calculated according to k(Tcoal.)exch..DMSO = }];'(!l0)/{2112'[DMSO]}

(!lo chemical shift difference between free and coordinated DMSO in Hz)2 Rate constants at temperatures where the exchange occurs slowly on the chemical shift time scale were determinedby comparison of peak widths at half heights of the resonances of coordinated DMSO in the presence and absence of excess DMSO according to k(T)exch.DMSO = }];'(!lv)/[DMSO] (Av difference in line width at half height of the resonance of coordinated DMSO in Hz in the presence and absence of free DMSO). Activation parameters of DMSO exchange were obtained from linear regression of Eyring plots, In(k(T)exch..DMso/T) vs. liT (Figure S3).

4,5

3,5

0:::

0

3,0

~.^2,5

~ .:y.@2,0

c;

1,5 1,0

0,5+----,-~-_,___~___,-~--,-~-,---~--,-~

3,2 3,4 3,6 3,8

1fT*103K

4,0 4,2

Figure 83. Eyring plots of temperature dependent rates of exchange of free (2.3 equivalents per Ni(II)- methyl) with coordinated DMSO for complex I-DM80, determinedby variable temperature

'n

^NMR

spectroscopy in CD2Ch.

Reactivity of I-DMSO towards methanol-da. Figure S4 depicts the IH NMR spectrum of a 17 mM solution of I-DMSO in methanol-d, (*) at 0° IH and ^l3C e H } NMR spectroscopic characterization of the resulting neutral Ni(II)-methy1 species was carried out at OCC to suppress the undesired methano1ysis reaction. IH NMR (CD30D, 400 MHz, OCC): (58.29 (br s, 4H, H15, 21, 23, 29); 8.12 (br s, 2H, H18, 26); 7.88 (d,4J H_H = 2.3 Hz, lH, H4); 7.66 (s, lH,H7); 7.54 (m, 3H, HlO, 11, 12); 7.17 (d,4J H_H = 2.3 Hz, lH, H6); 2.67 (s, 6H, DMSO); -1.28 (s, 3H, Ni-CH₃₎ ppm. l3c NMR (CD_30D, 100 MHz, OCC): (5 170.2 (C7); 163.9 (C2); 151.7 (C8); 150.9 (C4); 142.9 (C14, 22); 142.8 (C6); 134.5 (C9, 13); 132.9 (q, 2Jc_F= 33 Hz , C 16, 19,24,27); 132.1 (ClO, 12); 132.0 (C15,21,23,29); 128.4 (C11); 125.1 _{(q,I JC_F}= 273 Hz, C17, 20, 25, 28); 122.5 (q, 3JC_F= 4 Hz, C18, 26); 122.1 (Cl); 96 (C5); 73.1 (C3); 40.4 (DMSO); -14.0 (Ni-CH3) ppm.

DMSO

/

[(N,O)Ni(CH_3)(L)]

* ~

-HC=N-

*

, , , , , , ,

I

,

I I I

, , , , , , , ,

I

8.5 8.0 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 -1.0 f1(ppm)

Figure S4. Representative IH NMR spectrum of I-DMSO in methanol-d, (*) solution at OCC (L =

S4

A 15 mM methanol-d, solution was prepared from I-DMSOat room temperature in a glove box and the Nl\1R tube was sealed with a rubber septum. The sample was transferred to the prewarrued NMR probe and the decrease of the Ni(II)-CH3 resonance was monitored over four half life times. A first-order rate constant was deterruined from linear regression of a plot ofIn([Ni(II)-CH3lt/[Ni(II)-CH3lt~o)versus time (Figure S5). Dark red crystals separated from a light yellow methanol solution after the complete decomposition of the sample. An X-ray crystallographic analysis confirrued the forruation of the bis- chelated Ni(II) complex trans-[(N,O)2Ni] but the crystal quality was poor in order to perforru a detailed structural analysis of bond distances and angles. Unit cell parameters were deterruined as follows: Laue symmetry P-l, Z ⁼ 2; a = 11.3653(13)A; b = 11.8194(13) A; c = 21.682(2) A; a = 91.559(9)°; _~ =

90.275(9)°; Y = 97.874(9)°; V = 2883.9(6) A3

(STOE IPDS II Image plate diffractometer, Mo-Ka radiationA= 0.71073A)

o 0,0

~ J::~

«

^-0,5

z 6'

^-1,0

~~ J::~ -1,5

«

- -2,0

z 6'

z

c

4 -1 kCboCO,oo= (4.2±0.1)·10 s

10 20 30 40 50 60 70 80 90 100 time/ min

Figure S5. Representative first order plot of the time dependent decrease of the Ni(II)-CH3 resonance in methanol-d, solution at 40°C.

Characterization of Ni(II)-ethyl complex 2-DMSO.

Figure S6 depicts a representative

'n

NMR spectrum (25°C) of a 3: 1 mixture of Ni(II)-ethyl and Ni(II)-methyl (-1.19 ppm) complexes prepared from bubbling ethylene through a 14 mM solution of 1- DMSO in DMSO-d6 at 55°C for 45 minutes (cf. Experimental Section). The methylene and methyl protons of 2-DMSO are assigned as a (-0.42 ppm) and~ (-0.07 ppm), respectively. The rate of eis-trans isomerization of 2-DMSO was estimated from the 1H NMR spectra to be in the range of 2 -7 S-l. Figure S7 shows the enlargement of the aromatic region of the 1H NMR spectrum. The resonances of the aromatic protons 1- and 2-H4, 1- and 2-H6 and the imine resonances 2-H7 and l-H7 are assigned.

, " -

("", _0\

0 -T

-

residual C₂H4 0

_i

0

_i -

_I^,

.>: _...---

^2-butene

2-D l\ISO

,~

I-Dl\ISO

,

water

2-butene a

I -bU ~ .:

lJwV\A

\li lt ^lJ 'Ill

^\Iu.

""

_8.^I_{0 i.}

^,

_{5 i}^I_.O ^"~_6.5

^,

_6.0^{I JlI.} _5.5

^,

_5.0

^,

_~.

^{, ,}

_{5 ~.}

^,

_{O 3.5}^I

-

_3.0

^,

_2.5

^,

_2.0^I _1.5^I _1.0

^,

_0.5^I _0.0

^{, W}

_-0.5^I

^,

^~

f1(ppm)

Figure S6. lH NMR spectrum of a 3: 1 mixture of 2-DMSO and I-DMSO in DMSO-d₆ at 25°C, obtained from bubbling ethylene through a solution of I-DMSO.

S6

1'" <". 0 0 0 0\ 00 \0

1'"

-

^{0\ 00} ("'f"', ("#"', ("I")

00 00 ^{,... 1- 1- [...[...}

I I \ I .../ ~

2-H7 1-H7 1-H42-H4 1-H6 2-H6

"

8.30 8.20 8.10 8.00 i.90 i.80

n o

fl(ppm) i.60 i.50 i.-lO i.30

FigureS7. Expansion of the aromatic region of the IHNMR spectrum in Figure S6.

The alkane region of a IHNMR spectra of a sample containing 2d-DMSO and I-DMSO (1: I ratio) in the absence (top) and presence (bottom) of water(H20) after ea. 24 h at room temperature is shown in Figure S8. The formation of 1,l,1,2,2-pentadeuteropropane H3CCD2CD3, C2H6, CH4 and CH3D as the ultimate decomposition products of the neutral Ni(II)-alkyls is shown. A multiplet resonance at 0.74 ppm might correspond to ethane-e, the hydrolysis product of 2d-DMSO.

-ren en

o 0

I I

bottom:> 500 equiv H20

2JHD= 1.8Hz (CH3D)

0\1--

0 0\ I

0.90 0.85 0.80 O.i5 O.iO 0.65 0.60 0.55 0.50 0.-t5 0..f0 0.35 0.30 0.25 0.20 0.15 fl(ppm)

Figure S8. IHNMR spectrum (alkane region) showing the decomposition products from a mixture of the Ni(II)-alkyls 2d-DMSO and I-DMSO(l: 1) in DMSO-d6after 24 h at 25°C.

t-

~ ~ ^{000 M~ 00t-} ":^{\0 C'l}r-.

'"

r-.

eo M

c:i c:i c:i

c:i c:i c:i .-. C'l C'l

I I I i i I i i i

C_2H6

'/

0.4 -0.3 -1.2

fl(ppm)

-2.1

Figure S9. ¹H NMR spectrum showing the formation of the ultimate decomposition products ethane and methane from a mixture of Ni(II)-alkyls in the presence of the Ni(II)-hydride complex 3-PMe3 in DMSO-d6after 12 h at 25°C (chemical shifts 0 are assigned).

S8

The gradual formation of ethane was also observed from a neat sample of2-PMe3 in THF-ds solution, prepared in situ from 3-PMe3 with C2H4 at -lOoC, as depicted in Figure Slo. Notably, the chemical shifts of the Ni-ethyl fragment observed in THF-d, solution (T ⁼ -lOOC) differ from that in DMSO-d6

solution (T⁼ 25°C).

or, 00o

I

00

"<t

oI

[(N,O)Ni(CH2CH 3)(PMe3 ) ]

2-PMe₃

[(N,O)Ni(CH2CH 3)(PMe3 ) ]

2-PMe₃

I

[(N,O)Ni(H)(PMe_{3 ) ]} 3-PMe₃

~

.I . L

1.0 0.5 0.0 -0.7

f1(ppm)

-26.1

Figure SIO.IHNMR spectrum showing the formation of ethane from 2-PMe3 in THF-ds solution at- 1O°C(chemical shifts 8 are assigned).

NMR-Scale Experiments at Various Temperatures

24 mM 1-DMSO, 60 eq. O₂

°'

^{T = 55'C:}

'" C_2H4, to CsH^{6, 0} C_4Hs

+ [1-DMSO], x [2-DMSO]

.8-o

.~

*

^{0 0 0 0 0 0 0 c}

-E'" 1,0

+ +

+ '"^{r.J0 0 0 0 0 0}

++ $ ... +++++ + + +

:s

^{00 '"}

^+++++-1

c; 0,5 0 '" '"

><~ i~)()()()(lOUC)(lhc~ ~ ~ ~

^{)( )( )( >( 1I}

0,0 '" '"

o

^{2 4 6 8 10 12 14 16 18 20 22}

timet min

Figure S11. Typical time dependence of the conversion of I-DMSO into 2-DMSO, the consumption of ethylene and the evolution of propene and butenes in the presence of D20. Relative concentrations of all Ni(II)-alkyl species and olefins are normalized to I-DMSO = 1 at t = O. (24 mM I-DMSO in DMSO-d6,60 equiv. D20, T⁼ 55°C).

Kinetic analysis of ethane formation from I-DMSO.

Second-order rate constants of the bimolecular elimination of ethane from I-DMSO were determined from linear regression of plots of l/[l-DMSOlt-l/[l-DMSOlt~oversus time. Representative kinetic plots are shown in Figure S12. Error margins given are the estimated standard deviations (esd) calculated from the linear regression to the dataset. Since the reaction proceeds very slowly at 55°C only one half life time was followed, whereas at 80°C the reaction was monitored for 2 Yz half life times.

SlO

T k (T)*10³M-¹S-1 , Me-Me

lIE 80'C, 6.3+01

X 71'C, 3.7+0.1 + 54'C, 1.3+0.1

0,8 4,2

o

^1,7

~

C,

~

~

~

.--5C 3,3

o ~ q

2,5

~

~

~,

0,0

o

100 200 300 400 500 600 700 time/ min

Figure S12. Second-order plots of decomposition of I-DMSO to ethane monitored by

'n

NMR spectroscopy at variable temperatures in DMSO-d6solution.

Kinetic analysis of methane formation from I-DMSO and 3-PMe3.

Second-order rate constants of the bimolecular elimination of methane from I-DMSO and 3-PMe3 were determined from linear regressions of plots of 1/{[3-PMe3lt~o-[I-DMSOlt~o}*ln{[3-PMe3lt*[I- DMSOlt~o/{[3-PMe3lt~o*[I-DMSOlt}}versus time. Representative kinetic plots are shown in Figure S13. Error margins given are the estimated standard deviations (esd) calculated from the linear regression to the dataset, The reaction proceeds slowly for temperatures T < 20°e. Therefore, the decrease of I-DMSO was monitored for one half life time only. At temperatures T > 20⁰

e

^the

disappearance of I-DMSO was followed for two half life times. After ea. 2 half life times a strong broadening of all resonances was observed that limited the accuracy of the integration. A black precipitate, presumably Ni black, separated out from the reaction solution.