Ligand steric and fluoroalkyl substituent effects on enchainment cooperativity and stability in bimetallic nickel(II) polymerization catalysts

FULL PAPER

DOI: 10.1002/chem.201200713

Ligand Steric and Fluoroalkyl Substituent Effects on Enchainment

Cooperativity and Stability in Bimetallic Nickel(II) Polymerization Catalysts

AHCTUNGTRENNUNG

Michael P. Weberski, Jr., Changle Chen, Massimiliano Delferro,* and Tobin J. Marks*^[a]

Abstract: The synthesis and characteri-

zation of two neutrally charged bimet-

allic Ni^IIethylene polymerization cata-

lysts, {2,7-di-[2,6-(3,5-di-methylphenyli-

mino)methyl]1,8-naphthalenediolato}-

and [2-tert-butyl-6-((2,6-(3,5-ditrifluoro-

methyl-phenyl)phenylimino)methyl)-

phenolato]-Ni^II-methyl-(trimethylphos-

co-monomer incorporation selectivity,

with bimetallic

(CH₃)FI²-Ni₂and

(CF₃)FI²-Ni₂enchaining approximately

three- and six-times more norbornene,

respectively, than monometallic

(CH₃)FI-Ni and (CF₃)FI-Ni. Addition-

ally,

(CH₃)FI²-Ni₂and (CF₃)FI²-Ni₂ex-

hibit significantly enhanced thermal

stability versus the less sterically en-

cumbered dinickel catalyst {2,7-di-[(2,6-

diisopropylphenyl)imino]-1,8-naphtha-

lenediolato}-bis-Ni^II-

AHCTUNGTRENNUNG

phine) [

lenes ranging from highly branched

M_w=1400 oligomers (91 methyl

branches per 1000C) to low branch

density M_w=92000 polyethylenes

ACHTUNGTNER(NUGN CF₃)FI-Ni], produce polyethy-

bis-Ni^II

(CH₃)FI²-Ni₂] and {2,7-di-[2,6-(3,5-di-

(methyl)(trimethylphosphine)

A

ACHTUNGTRENNUNG

[

N

G

ACHTUNGTRENNUNG

trifluoromethyl-phenylimino)methyl]-

1,8-naphthalenediolato}-bis-Ni^II-

(7 methyl branches per 1000C). In the

bimetallic catalysts, Ni···Ni cooperative

effects are evidenced by increased

product polyethylene branching in eth-

ylene homopolymerizations (~3ꢁ for

ACHTUNGTRENNUNG

[ACHTUNGTRENNUNG

N

A

The

A

N

pathway for bimetallic catalyst thermal

deactivation is shown to involve an un-

expected polymerization-active inter-

mediate, {2,7-di-[2,6-(3,5-di-trifluoro-

methyl-phenylimino)methyl]-1-hy-

droxy,8-naphthalenediolato-Ni^II-

A

U

Ni), as well as by enhanced norbornene

catalysts, these complexes along with

their monometallic analogues [2-tert-

butyl-6-((2,6-(3,5-dimethylphenyl)phe-

nylimino)methyl)-phenolate]-Ni^II-meth-

Keywords: bimetallic catalysts · co-

operative effects

· homogeneous

catalysis · nickel · polymerization

yl(trimethylphosphine)

[N

ACHTUNGTRNE(NUNG methyl)-(trimethylphosphine).

Introduction

Pronounced enchainment cooperativity effects between co-

valently linked group 4 metal centers in binuclear CGC

(constrained geometry catalyst) olefin polymerization cata-

lysts, such as C2-Zr₂and C1-Zr₂, have been reported from

this laboratory.^[1]These catalysts include significantly en-

hanced polyethylene branching and remarkably increased

co-monomer enchainment selectivity with respect to mono-

metallic analogues M₁(Scheme 1).^[1b,2]Note, some aspects of

these processes mimic binuclear metalloenzyme cooperative

effects in how substrates are selectively activated and con-

centrated.^[3–5]The proposed pathway by which these cata-

lysts produce novel macromolecular architectures involves

[a] Dr. M. P. Weberski, Jr., Dr. C. Chen, Dr. M. Delferro,

Prof. Dr. T. J. Marks

Department of Chemistry, Northwestern University

Evanston, Illinois 60208-3113 (USA)

Fax : (+1)847 491 2990

E-mail: m-delferro@northwestern.edu

t-marks@nortwestern.edu

Supporting information for this article is available on the WWW

under http://dx.doi.org/10.1002/chem.201200713: includes catalyst and

polymer characterization, crystallographic data for

ACHTUNGTRENNUNG

(CF₃)H₂FI²and

Scheme 1. Group 4 monometallic and bimetallic olefin polymerization

catalysts.

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secondary interactions between weakly basic monomer func-

a marked increase in activity over the corresponding FI-M

monometallic analogues (M=Ti, Zr; Scheme 1), is ob-

served. Interestingly, the Ti versus Zr reactivity patterns in

these bimetallic phenoxyiminato catalysts are very different

from those in the CGC systems, for example, FI²-Zr₂is

a more active ethylene polymerization catalyst than is FI²-

Ti₂.^[10a]

À

tionalities (e.g., C H, Ph) and the proximate active catalytic

centers, as suggested by low temperature H NMR spectros-

1

copy^[6]and DFT calculations (Figure 1).^[7]In group 4 mediat-

ed polymerizations, the magnitude of these cooperative ef-

fects scales approximately inversely with metal···metal dis-

tance.^[1b]

The area of group 10 olefin polymerization catalysis,^[11]in

particular Ni^IIcomplexes,^[12,13]has received much recent at-

tention^[14]since the pioneering discovery of bulky aryl-sub-

stituted cationic a-diimine Ni^IIand Pd^IIcatalysts by Broo-

khart and co-workers^[15](Scheme 2). These catalysts effect

the polymerization of ethylene at high rates and the copoly-

Scheme 2. Examples of Ni^IIolefin polymerization catalysts.

Figure 1. a) Schematic of proposed bimetallic catalyst–substrate activa-

tion/binding in ethylene-co-hexene polymerization catalysis mediated by

binuclear catalysts C2-M₂and C1-M₂; P¹, P², P³=polymer fragment.

b) DFT modeling of bimetallic 1-octene binding to the R,R diastereoiso-

mer of the C1-Zr₂dication. The agostic interaction with a 1-octene meth-

ylene group is circled.

merization of ethylene with polar co-monomers, such as

acrylates, vinyl ketones, and silyl-vinyl ethers.^[14d,j,8^,15d]De-

tailed mechanistic studies reveal that these catalysts produce

highly branched polyethylenes through sequences of rapid

b-H elimination and subsequent reinsertion, that is, “chain-

walking”.^[11i,16]Highly active, neutrally-charged Ni^IIphen-

oxy-iminato ethylene polymerization catalysts reported by

Grubbs^[8](Scheme 2) are tolerant toward polar solvents and

are competent to enchain polar-substituted norbornenes

into polyethylene backbones.

Recently, the scope of these cooperativity effects was ex-

tended from group 4 CGC to phenoxyiminato systems,

building on the mononuclear catalysts of Grubbs^[8]and

Fujita.^[9]Similar to the binuclear CGC catalysts, binuclear

group 4 phenoxyiminato-based FI²-M₂catalysts (M=Ti, Zr;

Scheme 1) display increased a-olefin co-monomer enchain-

ment selectivity in ethylene copolymerizations.^[10]Specifical-

ly, selectivity for 1-hexene, 1-octene, and highly encumbered

1,1-disubstituted cycloalkene enchainment, as well as

We recently reported that neutrally-charged mononuclear

Ni^IIcatalysts

N

ACHTUNGRTEN(NUNG CF₃)FI-Ni (Scheme 2) afford

AHCTUNGTRENNUNG

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Bimetallic Nickel(II) Polymerization Catalysts

FULL PAPER

92 kgmol^À1at 6.5-times the polymerization activity.^[17]From

1

2D ¹⁹F, H HOESY NMR spectroscopy and molecular mod-

eling it was argued that the remote ligand CF₃groups can

[18]

À

engage in C F···H C interactions

with hydrogen atoms

on the b-carbon of Ni-alkyl/polymeryl groups,^[9b,d,17,19]disfa-

voring conformers required to access the favorable syn-peri-

planar conformation preceding b-H elimination (Scheme 3).

This interaction yields catalysts that produce dramatically

higher M_wpolyethylenes with significantly less branching

than the non-fluorinated analogues.

Scheme 4. Proposed thermal deactivation pathway of bimetallic Ni^IIcata-

lyst FI²-Ni₂.

In related work, bimetallic nickel(II) catalyst FI²-Ni₂

(Scheme 2) was shown^[6,20]to increase polyethylene branch

formation as well as co-monomer enchainment selectivity,

including that of polar norbornenes and acrylates, over that

of monometallic FI-Ni. Nevertheless, FI²-Ni₂undergoes sig-

nificant thermal deactivation, forming a catalytically inactive

bis-ligated species on exposure to temperatures above 408C

(Scheme 4).^[6,20]

In an effort to better understand ligation effects on coop-

erativity and stability in this system, we report here the syn-

thesis and properties of new bimetallic Ni^IIphenoxyiminato-

based catalysts ACHTUNGTRENNUNG ACHUTNGTRENNUGN

(CH₃)FI²-Ni₂and (CF₃)FI²-Ni₂(Scheme 5)

that contain sterically encumbered and fluorocarbon-substi-

tuted polyaryl substituents. Among the interesting findings,

it is found that these bulky substituents significantly sup-

press catalyst deactivation through the redistribution path-

way shown in Scheme 4. Details of this deactivation path-

way are scrutinized here, and an unexpected monometallic

polymerization-active intermediate

(CF₃)FI²-Ni(OH) is

ACHTUNGTRENNUNG

identified and shown to contribute significantly to polyethy-

lene production at 508C. All evidence argues that the pre-

dominant deactivation pathway for bimetallic

Scheme 5. Bimetallic Ni^IIcatalysts investigated in this study.

(CH₃)FI²-Ni₂

ACHTUNGTRENNUNG

and

ACHTUNGTRENNUNG

(CF₃)FI²-Ni₂displaying significantly greater norbornene en-

ACHTUNGTRENNUNG

chainment selectivity than their monometallic counterparts.

À

rather reductive elimination of an Ni H functionality to

yield the corresponding protonated ligand and Ni⁰. Further-

more, we report that NiACHTUNTRGNEUNG(COD)₂functions here as a “non-in-

nocent” co-catalyst and is also capable of mediating ethyl-

ene polymerization in the presence of the free ligand liber-

Results

ated during ACHTUNGTRENNUNG AHCTUNRTGENNUGN CAHTNUGTRENNGUN

(CH₃)FI²-Ni₂, (CF₃)FI²-Ni₂and (CF₃)FI²-

Ni(OH) thermolysis. Finally, marked catalyst center···cata-

lyst center cooperative effects are observed in ethylene-co-

norbornene polymerizations, with

A principal goal of this study was to investigate ligand sub-

stituent steric and fluorocarbon effects on the polymeri-

zation cooperativity and chain transfer characteristics as

well as thermal stability of bi-

(CH₃)FI²-Ni₂and

ACHTUNGTRENNUNG

metallic Ni^IIethylene polymeri-

zation catalysts. Sterically en-

cumbered ligand terphenyl sub-

stituents are introduced with

the aim of possibly suppressing

intermolecular

redistribution

processes (Scheme 4) and as-

sessing the effects of bulky and

fluorocarbon

substituents

(Scheme 3). The ethylene poly-

merization behavior of the bi-

metallic catalysts

and

(CF₃)FI²-Ni₂, as well as

their corresponding monome-

(CH₃)FI²-Ni₂

ACHTUNGTRENNUNG

AHCTUNGTRENNUNG

Scheme 3. Newman projections illustrating how (ligand)F···H

conformation, which facilitates b-H elimination.

ACHTUNGTREN(NGNU alkyl) interactions disfavor the syn-periplanar

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M. Delferro, T. J. Marks et al.

tallic analogues

G

E

appropriate terphenyl amine (Scheme 6). The condensations

were carried out by using a Dean–Stark apparatus with a cat-

alytic amount of formic or p-toluenesulfonic acid, and pro-

ceeded slowly, presumably because of the steric encum-

brance of the terphenyl amine. The reactions proceed via

isolable half-condensation products (2),^[23]which react with

a second equivalent of amine, affording the product over

vestigated. Ethylene-co-norbornene polymerizations are

also conducted to investigate the nature of metal center···-

metal center cooperativity that these catalysts might display.

Specific attention is focused on the deactivation pathways

these bimetallic ethylene polymerization catalysts traverse

at elevated temperatures. A polymerization active inter-

mediate,

pathway of bimetallic catalyst

ene polymerizations when using catalyst

(CF₃)FI²-Ni(OH) accounts for a significant fraction of the

polyethylene production.

G

the course of 3 and 7 days for ACHTGUNTRENNUG ACTHUNGTRENNUNG

(CF₃)H₂FI²and (CH₃)H₂FI²,

respectively, in refluxing toluene. Both ligands are purified

1

by recrystallization from toluene/methanol. H NMR analy-

T

sis of ACHTUGNTRENNUG ACHTUNGTRENNUNG

(CH₃)H₂FI²and (CF₃)H₂FI²solutions left standing in

air for several days evidence significant hydrolytic decompo-

sition, yielding the corresponding half-condensation product

and 1 equiv free amine.^[24]Similar to the previously reported

Catalyst synthesis: The ligand reagent 2,7-diformyl-1,8-nap-

thalenediol (1) was obtained by a previously published syn-

thesis route,^[10,21]whereas the hindered terphenyl amines

were prepared by using Suzuki cross-coupling procedures.^[22]

The bimetallic ligands

thesized through condensation reactions between 1 and the

ACTHNUTRGNEUNG

phenoxyiminato bimetallic ligand H₂FI²,^[10]both (CH₃)H₂FI²

and ACHTNUTGRNEUNG

(CF₃)H₂FI²undergo dynamic structural rearrangement

processes (keto-amino/enol-imine tautomerism, Figure 2)^[25]

in solution that are sufficiently slow on the NMR time-

scale^[26]to resolve a single dissymmetric species below about

Scheme 6. Synthesis of bimetallic ligands ACTHNUGRTNENUG ACHUTNGTRENNUGN

(CH₃)H₂FI²and (CF₃)H₂FI².

1

Figure 2. Variable-temperature H NMR (400 MHz, 1,1,2,2,-tetrachloroethane) stack plot spectra for the keto-amine tautomerism in

N

lescenceꢀ808C).

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Bimetallic Nickel(II) Polymerization Catalysts

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808, with a rate constant (k_coal

)

of approximately 28 s^À1and

DG^°(353 K) of about 18 kcal

mol^À1, typical of such tautomer-

isms.^[27]The proposed solution

structure is consistent with the

solid-state molecular structure

(see below), and the spectral

coalescence temperature is not

significantly affected by the ter-

phenyl ring substituents.

The

disodium

salts

of

A

ACHTUNGTRENNUNG

prepared by stirring the free li-

gands with excess NaH in dry

THF for 2 days.^[28]The bimetal-

lic catalysts

(CF₃)FI₂-Ni₂are then prepared

ACHTUNGTRENNUNG

(CH₃)FI²-Ni₂and

ACHTUNGTRENNUNG

by treating the ligand disodium

salts with 2 equiv trans-NiClMe-

[29]

ACHTUNGTRENNUNG(PMe₃)₂in benzene and tolu-

(CF₃)FI²-Ni₂and (CF₃)H₂FI²to afford (CF₃)FI²-Ni(OH).

Scheme 8. Comproportionation reaction of ACHTNUGTRENNNUG ACHTUNRTGENNUNG ACHTGUNTRENNUGN

ene, respectively (Scheme 7).

The

ACHTUNGTRENNUNG

ceeds cleanly on stirring in benzene at room temperature,

overnight; however, the use of these conditions for the

ACHTUNGTRENNUNG

AHCTUNGTRENNUNG

A

ACHTUNGTRENNUNG

[29]

amounts of NiCl

N

U

ACHTUNGTRENNUNG

ucts. These can be minimized by slowly warming the reac-

tion mixture from À78 to 258C over a period of 7 h in tolu-

ACHTUNGTRENNUNG

ene. Monometallic catalysts ACHTNUTRGENNUG(CH₃)FI-Ni and ACHTUTGNREN(NUNG CF₃)FI-Ni

were prepared according to literature procedures.^[17]

Molecular structure of binucleating ligand (CF₃)H₂FI²:

Single crystals of ligand

(CF₃)H₂FI²were grown by slow

evaporation of a CDCl₃solution. A displacement ellipsoid

plot of

(CF₃)H₂FI²is shown in Figure 3. Selected bond dis-

tances and angles are included in the Figure caption.

In investigating any reactivity that bimetallic ligand

ACHTUNGTRENNUNG

(CF₃)H₂FI²might exhibit toward bimetallic Ni^IIcomplex

AHCTUNGTRENNUNG

2

¯

AHCTUNGTRENNUNG

À

O1 H1···O2 (1.65(5) ꢀ), and N2 H2···O2 (1.92(4) ꢀ),

which form two six-membered pseudo-rings.^[30]The distance

between phenol O2 atom and imine N2 atom (2.56(2) ꢀ) is

shorter than the average distance found in the Cambridge

Crystallographic Data Centre (CCDC) (2.67(1) ꢀ), whereas

the distance between phenol atom O1 and phenol atom O2

(2.52(3) ꢀ) is negligibly different from the average distance

(2.55(2) ꢀ) found in the CCDC.^[31]The solid-state structure

of ACTHNUTRGNEUNG

(CF₃)H₂FI²displays a dissymmetric orientation and tauto-

À

merization is evidenced by elongation of the C1 O1 and

À

C34 N2 distances. The tautomerization and hydrogen bond-

ing present in

(CF₃)H₂FI²are similar to that previously re-

ported in the less sterically encumbered bimetallic ligand,

H₂FI².^[10]The crystal packing is dominated by intermolecular

[18a,c–e]

À

C H···F C hydrogen bonds

at distances ranging from

À

2.49–2.52 ꢀ; these C H···F distances are typical of interac-

tions of this type.^[18a,c–e]

Scheme 7. Synthesis of bimetallic catalysts ACTHNUGRTNENUG ACHUTNGTRENNUGN

(CH₃)FI²-Ni₂and (CF₃)FI²-

Ni₂.

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M. Delferro, T. J. Marks et al.

shows the trimethylphosphine ligands to be positioned trans

to the imine functionalities; both Ni atoms in ACTHNUTRGNEUNG

(CF₃)FI²-Ni₂

adopt a distorted square-planar coordination geometry.

Around Ni1, atoms P1 and C1 are displaced +0.500(2) and

À0.324(3) ꢀ, respectively, from the Ni1/O1/N1 mean plane;

around Ni2, atoms P2 and C2 are displaced À0.559(2) and

+0.279(3) ꢀ, respectively, from the Ni2/O2/N2 mean plane.

Significant twisting of the Ni square planes is also observed

in ACTHNUTRGNEUNG

(CF₃)FI²-Ni₂(Figure 5). Around Ni1, the plane containing

À

the naphthalene backbone (PL 1=C9 C18) and the plane

containing Ni1 and the atoms directly bound to Ni1 (PL 2=

Ni1/O1/N1/C1/P1) display a dihedral angle of 19.11(5)8. The

dihedral angle between PL 1 and the mean plane defined by

Ni2 and the atoms directly bound to Ni2 (PL 3=Ni2/O2/N2/

C2/P2) is found to be 37.48(4)8, whereas the dihedral angle

between the two planes containing Ni1 and Ni2 (PL2 and

PL3, respectively) is 53.69(4)8.

Figure 3. ORTEP plot of the molecular structure of dinucleating ligand

(CF₃)H₂FI². Thermal ellipsoids are drawn at the 50% probability level.

Hydrogen atoms are drawn as arbitrarily small spheres. Selected bond

ACHTUNGTRENNUNG

Despite the distorted square-planar geometry in the solid

(CF₃)FI²-Ni₂and all other catalysts reported evidence

ACHTUNGTRENNUNG

À

distances (ꢀ) and angles (8): C1 O1 1.343(3); C9 O2 1.282(3); C2 C11

state,

diamagnetic NMR chemical shifts in solution. The Ni

À

1.460(4); C8 C34 1.390(4); C34 N2 1.323(4); C11 N1 1.278(4); aC2

À

C11 N1 122.2(3); aC8 C34 N2 123.2(3); aC1 C2 C11 N1 178.9(3);

À

ligand bond metrics (Ni O_phenol, Ni N_imine, Ni C_methyl, Ni

À

aC9 C8 C34 N2 À2.1(5).

P_phosphine, C=N_imine, C O_phenol, Figure 4, caption)^[32]are very

À

Molecular structure of binuclear precatalyst (CF₃)FI²-Ni₂:

similar in each Ni center in

(CF₃)FI²-Ni₂, and are also very

Single crystals of

tion of an n-hexane solution under N₂. A displacement ellip-

soid plot of

(CF₃)FI²-Ni₂is shown in Figure 4. Selected bond

distances and angles are included in the Figure caption.

Complex

(CF₃)FI²-Ni₂crystallizes with one-half of a mole-

A

similar to the previously reported structure of monometallic

ACHTUNGTRENNUNG

cule of n-hexane in the asymmetric unit (Z=2) in space

(CF₃)FI²-Ni₂

¯

group P1. The configuration about each Ni in

Figure 4. ORTEP plot of binuclear precatalyst ACTHNUTRGNEUNG

(CF₃)FI²-Ni₂. Thermal el-

lipsoids are drawn at the 50% probability level. H atoms and solvent

molecules are omitted for clarity. Selected bond distances (ꢀ) and angles

À

(8): Ni1···Ni2 5.8024(5); Ni1 C1 1.941(2); Ni2 C2 1.943(2); Ni1 P1

À

2.1528(7); Ni2 P2 2.1391(7); Ni1 N1 1.929(2); Ni2 N2 1.944(2); Ni1 O1

À

1.896(2); Ni2 O2 1.899(2); aN1 Ni1 C1 94.60(9); aN2 Ni2 C2

94.23(9); aC1 Ni1 P1 85.17(8); aC2 Ni2 P2 86.84(7); aP1 Ni1 O1

89.53(5); aP2 Ni2 O2 89.49(5); aO1 Ni1 N1 93.19(7); aO2 Ni2 N2

91.83(7); aN1 Ni1 P1 166.31(6); aN2 Ni2 P2 164.81(6); aO1 Ni1

À

(CF₃)FI²-Ni₂molecular core with H atoms, sol-

ACHTUNGTRENNUNG

À

Figure 5. a) View of the

vent molecules, and terphenyl groups omitted for clarity. b) Plane num-

bering scheme for the core structure of binuclear complex

(CF₃)FI²-Ni₂.

À

C1 167.61(9); aO2 Ni2 C2 169.76(9).

ACHTUNGTRENNUNG

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Bimetallic Nickel(II) Polymerization Catalysts

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Table 2. Ethylene polymerization data for experiments at 508C.^[a]

catalyst ACHTUNGTRENNUNG

(CF₃)FI-Ni,^[17]and are within the distance

range typical of square-planar salicylaldiminato Ni^II

complexes.^[32]In addition, these negligible differen-

Entry Catalyst

Polymer M_w

PDI^[b]

Total Me

per

Act.^[d]

yield [g] (ꢁ10³)^[b]

1000C^[c]

ces in lengths and angles between ACHTUNGTRNEUNG

(CF₃)FI²-Ni₂and

the salicylaldiminato Ni^IIcomplex family indicate

that the electron-withdrawing groups CF₃do not

significantly alter the electronic structure near the

Ni center through inductive effects, however, weak

fluorocarbon ligand–polymer product interactions

can affect the course of ethylene polymerization

(Scheme 3).^[17]As expected, the crystal packing of

1

2

3

4

5

6

7

8

N

3.042

0.293

0.640

3.040

0.515

0.490

0.360

7.9

11

5.1

6.4

6.9

1.7

2.2

2.9

1.8

2.0

1.5

1.7

40

47

45

63

57

99

98

460

22

48

456

193

7

[f]

1.8

27

0.03

880/6.1^[i]

6.2/1.8^[i]65

ACHTUNGTRENNUNG

(CF₃)FI²-Ni₂is dominated by intermolecular aro-

[a] All polymerizations carried out under constant 8.0 atm ethylene pressure with

5.0 mmol catalyst and 2.0 equiv NiACHTNUGTRNEUNG(COD)₂/Ni for 10 min in 50 mL toluene. Entries per-

[18a,c–e]

À

matic C H···F C hydrogen bonding

ces ranging from 2.51–2.52 ꢀ. The Ni1···Ni2 dis-

tance observed in

(CF₃)FI²-Ni₂is 5.8024(5) ꢀ, one

at distan-

formed in duplicate. [b] From GPC versus polystyrene standards in (gmol^À1). [c] By

¹H NMR assay. [d] kgpolymermol^À1[Ni]h^À1atm^À1. [e] Data from ref. [17]. [f] Polymeri-

zation carried out under constant 8.0 atm ethylene pressure with 5.0 mmol catalyst and

ACHTUNGTRENNUNG

1 equiv B

constant 8.0 atm ethylene pressure with 0.5 mmol catalyst and 2.0 equiv Ni

for 40 min in 50 mL toluene. [h] Polymerizations carried out with 40 mmol Ni

and 10 mmol

(CF₃)H₂FI²for 40 min in 25 mL toluene at 8.0 atm ethylene pressure.

[i] GPC trace exhibits bimodal molecular weight distribution.

ACHTUNGTRENNUNG

of the shortest Ni···Ni distances reported to date in

bimetallic neutrally charged Ni^IIcatalysts,^{[1a,6,14k,20,33]}

However, this is far longer than the sum of Ni

atomic van der Waals radii (3.26 ꢀ)^[34]and indicates

no significant chemical interaction. Note that this

value is significantly smaller than in previously re-

ACHTUNGTRENNUNG

AHCTUNGTRENNUNG

ported CGC-based bimetallic catalysts C1-Zr₂and C2-Zr₂

that have Zr···Zr distances of 7.392(3) and 8.671(3) ꢀ

(Scheme 1), respectively.^[2e]

At room temperature, bimetallic catalysts

and ACTHGUNTRNENUG

(CH₃)FI²-Ni₂display ethylene polymerization activities

(CF₃)FI²-Ni₂

ACHTUNGTRENNUNG

(21 and 9 kgpolymermol^À1[Ni]h^À1atm^À1, respectively;

Table 1, entries 2 and 4) similar to that previously reported

for FI²-Ni₂(7.1 kgpolymermol^À1[Ni]h^À1atm^À1).^[20]However,

ethylene polymerizations mediated by monometallic

Ethylene homopolymerization experiments: Complexes

A

E

U

ACHTUNGTREN(NUNG CF₃)FI-Ni, and

G

(CF₃)FI-Ni are significantly more rapid^[17]

ACHUTGTNNERNUG(CH₃)FI-Ni and ACHUTNGTRENNGUN

A

than in the case of the bimetallic catalysts. The microstruc-

tures of the polyethylenes produced by these catalysts vary

greatly depending on the ligand terphenyl substitution.

Thus, the polyethylenes produced by both methylterphenyl

scavenger/co-catalyst; relevant data are collected in Tables 1

and 2. In the absence of co-catalyst, negligible polyethylene

is obtained with the catalysts reported here. Typical ethylene

homopolymerization experiments were conducted with cata-

lyst (5 mmol) in toluene (50 mL) under a continuous ethyl-

ene pressure (8.0 atm) for 10 min by using conditions mini-

mizing mass transport and exotherm effects.^[1b,2d–g]The poly-

meric products were characterized by ¹H and ¹³C NMR

spectroscopy, and molecular weight by GPC with viscome-

try/refractive index detection versus a polystyrene standard.

catalysts [

weight, highly branched, grease-like materials (e.g., M_w=

1400; PDI=1.1 for (CH₃)FI-Ni; M_w=3800; PDI=2.0 for

(CH₃)FI²-Ni₂). In marked contrast, CF₃-substituted catalysts

(CF₃)FI-Ni and

(CF₃)FI²-Ni₂produce far higher molecular

weight polyethylenes (e.g., M_w=92000; PDI=2.4 for

(CF₃)FI-Ni) with appreciably less branching versus

(CH₃)FI²-Ni₂and

(CH₃)FI-Ni.

Monometallic

(CF₃)FI²-Ni(OH), when activated with Ni-

(COD)₂, is an active ethylene polymerization catalyst at

room temperature (Table 1, entry 5) and at 508C (Table 2,

entries 4 and 5). At room temperature,

(CF₃)FI²-Ni(OH) ex-

hibits four-times the activity and produces a significantly

lower M_wproduct polyethylene than bimetallic

(CF₃)FI²-Ni₂.

At 508C, the reactivity trends of these catalysts are similar,

with

(CF₃)FI²-Ni(OH) displaying 20.7-times greater activity

than bimetallic

(CF₃)FI²-Ni₂, and producing bimodal poly-

(CH₃)FI²-Ni₂] are low molecular

ACHUTGTNNERNUG(CH₃)FI-Ni and ACHUTNGTRENNGUN

AHCTUNGTRENNUNG

A

ACHTUNGTRENNUNG

AHCTUNGTRENNUNG

1

Polyethylene branch numbers were quantified by H NMR

A

ACHTUNGTRENNUNG

spectroscopy.^[33a,d,e,35]

ACHTUNGTRENNUNG

AHCTUNGTRENNUNG

Table 1. Ethylene polymerization data for experiments at room tempera-

ture.^[a]

AHCTUNGTRENNUNG

Entry Catalyst

Polymer M_w

PDI^[b]Total Me

(ꢁ10³)^[b]

yield [g] ACUTHGTNRNENUG per

Act.^[d]

AHCTUNGTRENNUNG

1000C^[c]

AHCTUNGTRENNUNG

1

2

3

4

5

N

1.661

0.280

0.253

0.120

0.546

92.0

25

1.4

3.8

11

3.0

2.4

1.1

2.0

2.3

7

250

21

91

9

AHCTUNGTRENNUNG

40

88

91

44

ethylenes with a high M_wshoulder (entry 4; Figure S22 in

the Supporting Information). Due to the high polymeri-

zation activity of ACTHNUTRGENNGU ACHTUGNTRENNUGN

(CF₃)FI²-Ni(OH) relative to (CF₃)FI²-Ni₂,

82

and in order to minimize mass transport and exotherm ef-

fects,^[1b,2d–g]polymerizations with ten-times lower catalyst

loading (entry 5, 0.5 mmole) were also used. In the present

study minimizing exotherms was critical since temperature

has a large influence on polymer M_w, and the polymer M_w

[a] All polymerizations carried out under constant 8.0 atm ethylene pres-

sure with 5.0 mmol catalyst and 2.0 equiv Ni(COD)₂/Ni for 10 min in

50 mL toluene. Entries performed in duplicate. [b] From GPC versus

polystyrene standards in (gmol^À1). [c] By ¹H NMR assay. [d] kgpolymer

mol^À1[Ni]h^À1atm^À1. [e] Data from ref. [17].

AHCTUNGTRENNUNG

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M. Delferro, T. J. Marks et al.

was used to probe the mechanism of bimetallic catalyst de-

composition (vide infra). Under these lower concentration

Similarly, when 258C polymerizations with the use of

ACHUTNGRENNUG CAHTUNGTRENNUGN

(CH₃)FI²-Ni₂and (CF₃)FI²-Ni₂are allowed to continue for

conditions, catalyst

A

2 h, GPC analysis shows that higher M_wpolyethylene begins

lower activity than in the previous experiment, but produces

a monomodal polyethylene. The nature of the polyethylenes

to form.^[36]In contrast, 258C polymerizations when using bi-

metallic catalysts ACTHNUGRTENNUG ACHUTNGTRENNGUN

(CH₃)FI²-Ni₂and (CF₃)FI²-Ni₂produce

obtained from

(CF₃)FI²-Ni₂have significant implications for the deactiva-

tion pathways of the bimetallic catalysts (vide infra). It will

be shown later that

(CF₃)FI²-Ni(OH) is the predominant

catalytically-active deactivation product of bimetallic

(CF₃)FI²-Ni₂.

All of the present terphenyl-substituted catalysts display

A

monomodal polyethylene when the polymerization time is

40 min. Investigations of the catalyst deactivation pathway

will be discussed below.

To better understand the role of the co-catalyst in these

polymerizations, ethylene polymerizations were conducted

ACHTUNGTRENNUNG

E

R

at 508C by using B

catalyst and

(CF₃)FI²-Ni₂as the catalyst (Table 2). Polymeri-

zations with B(C₆F₅)₃as co-catalyst are 2.2-times more

active than analogous Ni(COD)₂co-catalyzed polymeri-

zations, albeit with a significant decrease in product M_w(5.1

vs. 11 K). Additionally, the B(C₆F₅)₃co-catalyzed polymeri-

zations produce monomodal polyethylenes, whereas Ni-

(COD)₂co-catalyzed polymerizations produce bimodal

polyethylenes at 508C. Interestingly, it is found that Ni-

(COD)₂functions as a “non-innocent” co-catalyst. In the

presence of free ligand [ (COD)₂is capable

(CF₃)H₂FI²], Ni

ACHUTNGTRENU(NG C₆F₅)₃in place of NiACHTUNGTRENN(UGN COD)₂as the co-

AHCTUNGTRENNUNG

appreciable ethylene polymerization activity at 508C

(Table 2). In all cases, polyethylene molecular weights are

significantly depressed and branch densities increased com-

pared to room temperature polymerizations, except for

ACHTUNGTRENNUNG

AHCTUNGTRENNUNG

ACHTUNGTRENNUNG

(CH₃)FI²-Ni₂, for which the M_wand branch density remain

nearly the same as in the room temperature polymerization.

Catalyst thermal stability studies of the present bimetallic

ACHTUNGTRENNUNG

catalysts reveal that both

hibit falling ethylene polymerization activity over time

(Table 3, Figure 6), with catalyst

(CF₃)FI²-Ni₂exhibiting

greater stability at 508C than

(CH₃)FI²-Ni₂. The polyethy-

lenes produced by bimetallic catalysts

(CH₃)FI²-Ni₂and

(CF₃)FI²-Ni₂at 508C show bimodal GPC traces that can be

A

N

ACHTUNGTRENNUNG

A

ACHTUNGTRENNUNG

N

of polyethylene production at 508C (Table 2) with low activ-

ity. The polyethylene produced by the combination of Ni-

ACHTUTGNRENGU(N COD)₂and AHCTUTGNRNEN(GUN CF₃)H₂FI₂is bimodal, displaying two very dif-

ferent product polyethylene M_wvalues, 880 and 6.1 K. It will

N

R

C

attributed to the formation of catalytically competent deac-

tivation products (vide infra).

be shown that during the deactivation of the bimetallic cata-

lysts reported here, free ligand is liberated. The NiACHTUNGTRENNUNG(COD)₂

co-catalyst (typically used in excess) can then react with the

free ligand and contribute to polyethylene production at

508C.

Table 3. Ethylene polymerization data as a function of polymerization

time at 508C.^[a]

Catalyst

Time

[min]

Polymer

yield [g]

Activity^[b]

Ethylene-co-norbornene polymerization experiments: Ethyl-

ene+norbornene copolymerizations were carried out by

AHCTUNGTRENNUNG

A

10

20

40

60

90

0.360

0.293

0.406

0.506

0.533

0.693

0.546

0.799

0.545

1.077

27

22

15

19

10

13

6.8

10

4.5

9

using catalysts

(CF₃)FI-Ni with NiACHTUNGTRENNUNG

(CH₃)FI²-Ni₂, (CF₃)FI²-Ni₂,

ACHTUNGTRNEUNGN ACHTNUGTRENNUNG ACTUHNGTRENNUGN

ACHTUNGTRENNUNG

T

ACHTUNGTRENNUNG

ized in Table 4, with the norbornene content of the copoly-

ACHTUNGTRENNUNG

mers determined by ¹³C NMR spectroscopy.^[35c,37]Bimetallic

ACHTUNGTRENNUNG

catalyst ACTHNUTRGNEUNG

(CH₃)FI²-Ni₂introduces approximately three-times

ACHTUNGTRENNUNG

Table 4. Ethylene-co-norbornene copolymerization data.^[a]

Catalyst Polymer M_w

PDI^[c]Total Me Act.^[e]NB

yield

(ꢁ10³)^[c]

[g]

ACHTUNGTRENNUNG

[a] Polymerizations were out in 50 mL toluene under constant 8.0 atm

per

incor.^[f]

[%]

ethylene pressure at 508C with 5.0 mmol catalyst and with 2.0 equiv Ni-

1000C^[d]

ACHTUNGTRENNUNG .

(COD)₂/Ni. [b] kgpolyethylenemol^À1[Ni]h^À1atm^À1

A

0.979

0.064

0.133

0.063

68

2.9

2.8

1.7

2.2

21

44

79

93

150

0.6

20

0.6

<0.5

R

16

3.0

2.1

7.0

[b]

Ni₂

(CH₃)FI-

Ni^[a]

(CH₃)FI²-

E

3.4

4.5

AHCTUNGTRENNUNG

[b]

Ni₂

[a] Polymerizations carried out under constant 8.0 atm ethylene pressure

with 5 mmol catalyst, 225 equiv of norbornene, and 2 equiv Ni(COD)₂/Ni

ACHTUNGTRENNUNG

for 10 min in 50 mL toluene. [b] Polymerizations carried out under con-

stant 8.0 atm ethylene pressure with 10 mmol catalyst, 225 equiv of nor-

bornene, and 2.0 equiv NiACTHNUTRGNE(UGN COD)₂/Ni for 40 min in 50 mL toluene.

[c] From GPC versus polystyrene standards in (gmol^À1). [d] By ¹H NMR

Figure 6. Temporal characteristics of

merization activity at 508C.

(CH₃)FI²-Ni₂and

E

assay. [e] kgpolymermol^À1[Ni]h^À1atm^À1

¹³C NMR spectroscopy.^[37]

.

[f] Molar percentage from

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Bimetallic Nickel(II) Polymerization Catalysts

FULL PAPER

more norbornene than does monometallic analogue

creased steric repulsion in the latter catalysts. At 508C, ob-

A

served polymerization rates for CF₃-substituted terphenyl

A

catalysts ACTHNGURTENUNG ACHTUGNTNER(NUGN CF₃)FI-Ni are increased relative

(CF₃)FI²-Ni₂and

A

to room temperature polymerizations, indicating enhanced

À

A

thermal stability versus the CH₃substituted analogues. The

increased thermal stability of fluorinated catalysts

A

Ni₂and ACTHUNGTERNU(NG CF₃)FI-Ni may reflect suppression of b-H elimina-

À

respectively). In all cases, catalyst productivity is lower in

the ethylene-co-norbornene polymerizations than in analo-

gous ethylene homopolymerizations. The chain branch den-

sities and PDIꢃs of the ethylene-co-norbornene polymers are

similar to those of the corresponding ethylene homopoly-

mers.

tion via the aforementioned C F···H C interaction, since b-

H elimination has been shown to be a key step in the deacti-

vation of monometallic Ni^IIethylene polymerization cata-

lysts,^[38]and will also be shown to be important in the deacti-

vation of the present bimetallic catalysts (vide infra). Non-

fluorinated catalysts

vate rapidly at 508C. The thermal stability of

and

(CF₃)FI²-Ni₂was further investigated by conducting eth-

(CH₃)FI²-Ni₂and

ACHUTGTNRENNUG CAHTUNGTRENNUNG

AHCTUNGTRENNUNG

Catalyst deactivation experiments: The catalyst deactivation

ACHTUNGTRENNUNG

products arising from ethylene polymerizations when using

ylene polymerizations at 508C for varying reaction times

(Table 3, Figure 6). Although both bimetallic catalysts evi-

dence a fall in ethylene activity over time, CF₃-substituted

ACHTUNGTRENNUNG

(CH₃)FI²-Ni₂were investigated by analysis of the post-poly-

merization materials. Ethylene polymerizations were con-

ducted under continuous 8.0 atm ethylene pressure at 508C

for 50 min. After the desired run time, the reactor pressure

was reduced to 1.0 atm ethylene pressure and the volatiles

removed, in vacuo. ¹H NMR spectroscopic analysis of the

residue indicates formation of the free ligand in addition to

a large amount of black Ni⁰. The free ligand formed during

AHCTUNGTRENNUNG

(CF₃)FI²-Ni₂displays significantly higher thermal stability

than does ACTHNUTRGNEUNG

(CH₃)FI²-Ni₂. During ethylene polymerizations at

508C, all product polyethylene M_wvalues are depressed rel-

ative to 258C polymerizations, presumably reflecting more

favorable/entropically driven b-H elimination at higher tem-

peratures.

A

During attempts to identify the deactivation pathways

that these catalysts might undergo at elevated temperatures,

ethylene polymerizations were also conducted with

R

ACHTUNGTRENNUNG

Under the conditions investigated, no evidence of bis-ligated

products is observed.^[8,38]

ACHUTNGRENNUG CAHTUNGTRENNUNG

(CF₃)FI²-Ni₂at 508C by using B

AHCTUNGTRENNUNG

Discussion

AHCTUNGTRENNUNG

Ethylene homopolymerization: Several trends are evident

when the ethylene polymerization characteristics of

ACHTUNGTRENNUNG

A

E

N

G

ACHTUNGTRENNUNG

A

ACHTUNGTRENNUNG

A

E

as co-catalyst display monomodal GPC traces (Table 2,

entry 3); analogous polymerizations with the use of Ni-

significantly higher molecular weight relative to the methyl-

substituted terphenyl catalysts (M_w=92 vs. 1.4 K, respective-

N

ACHTUNGTRENNUNG(COD)₂

ly, for

G

ACHTUNGTRENNUNG

À

We have previously argued that weak C F···H C interac-

tions between CF₃substituents remote to the catalytic

ACHTUNGTRENNUNG

À

center and a C H unit on the growing polymer chain likely

engers by abstracting PMe₃, thus opening a Ni coordination

site for ethylene activation/-polymerization.^[8d]In the present

systems, two factors may be responsible for the co-catalyst

requirement: 1) PMe₃is significantly more basic^[40]than

PPh₃, which is typically used in catalyst systems that are

active in the absence of phosphine scavenger, and 2) the

prodigious steric encumbrance in these catalysts may

impede associative ligand exchange between coordinated

PMe₃and incoming ethylene.^[38b,41]

disfavor chain transfer in

N

syn-periplanar conformation generally thought to facilitate

b-H elimination (Scheme 3).^[17]For catalyst

(CH₃)FI-Ni, the

absence of such interactions favors the correct conformation

AHCTUNGTRENNUNG

À

for elimination. We expect similar C F···H C interactions

to be operative in

(CF₃)FI²-Ni₂and to be largely responsible

for the dramatic differences in M_wand branching character-

istics of the polyethylenes produced by

(CF₃)FI²-Ni₂versus

(CH₃)FI²-Ni₂. In terms of ethylene polymerization activity at

258C, mononuclear (CF₃)FI-Ni is 2.7-times more active than

(CH₃)FI-Ni, whereas binuclear

(CF₃)FI²-Ni₂is 2.3-times

more active than

(CH₃)FI²-Ni₂. At 258C, both mononuclear

ACHTUNGTRENNUNG

AHCTUNGTRENNUNG

ACHTUNGTRENNUNG

E

Catalyst cooperativity effects: Several groups have synthe-

sized and investigated the ethylene polymerization charac-

teristics of bimetallic neutrally charged Ni^IIcatalysts

(Scheme 9).^[1a,42]Where X-ray diffraction data are available,

Ni···Ni distances are large, typically from 7.41 to 7.77 ꢀ, and

A

ACHTUNGTRENNUNG

catalysts display higher ethylene polymerization activities

than do the bimetallic analogues, presumably reflecting in-

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M. Delferro, T. J. Marks et al.

Scheme 9. Examples of previously reported bimetallic neutrally charged Ni^IIpolymerization catalysts (A–J,^[1a]

K

^[42]).

reported cooperative effects are minimal.^[33a,b,d,42]In all of

tion (e.g., Figure 1), which are expected to be stronger than

[43]

À

the present 258C ethylene polymerizations (Table 1), bimet-

the proposed C F···H C interactions. At 508C, polyethy-

lene branch densities are increased for all catalysts (Table 2)

relative to 258C. In accord with this model, bimetallic

allic catalysts ACHTUNGTRENNUNG ACHUTNGTRENNUGN

(CH₃)FI²-Ni₂and (CF₃)FI²-Ni₂introduce sig-

nificantly greater polyethylene branch densities than do the

corresponding monometallic controls, presumably reflecting

AHCTUNGTRENNUNG

(CF₃)FI²-Ni₂displays significantly more branching than

À

favorable agostic polymer C H interactions between the

growing polymer chain and the second proximate metal

center, thus favoring branch formation (Scheme 10b).

monometallic ACHTNGUTERNNU(G CF₃)FI-Ni. At 508C, differences in branch

densities introduced by catalysts ACHTNGUTRENNUG ACHTUNGTRENNUNG(CH₃)FI-

(CH₃)FI²-Ni₂and

Ni are similar.

By conducting ethylene polymerizations with FI²-Ni₂over

a range of ethylene pressures,^[6]it was shown that the origin

of the branching in these bimetallic catalysts is likely the

same as in the monometallic analogues, that is, rapid “chain-

walking” b-H elimination/reinsertion sequences.^[38b]In the

In ethylene-co-norbornene polymerization experiments

catalyzed by

N

ACHTUNGTRENNUNG

display approximately 3–6-times greater selectivity for nor-

bornene enchainment than do their monometallic counter-

parts (Table 4). These results parallel our previously report-

ed bimetallic Ni^IIcatalyst, FI²-Ni₂(Scheme 2), which dis-

plays somewhat greater (~3ꢁ) norbornene selectivity than

its monometallic analogue.^[20]Lee and co-workers also re-

ported bimetallic Ni^IIsalicylaldimine catalysts that mediate

ethylene+polar norbornene copolymerization (Scheme 9,

G);^[33c]although X-ray structural characterization of these

catalysts was not reported, computational geometry optimi-

zations suggest Ni···Ni distances ranging from 6.24–9.40 ꢀ;

case of fluorocarbon-substituted catalysts

(CF₃)FI-Ni, polyethylene branching would also be affected

(CF₃)FI²-Ni₂and

ACHTUNGTRENNUNG

À

by the proposed C F···H C interactions, which would sup-

press b-H elimination and chain-walking (Scheme 3). Thus,

the marked increase in branch density in the polyethylenes

produced by bimetallic

lic (CF₃)FI-Ni likely reflects the proximate metal centers

and agostic C H···Ni interactions that favor branch forma-

(CF₃)FI²-Ni₂relative to monometal-

ACHTUNGTRENNUNG

À

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Bimetallic Nickel(II) Polymerization Catalysts

FULL PAPER

ethylene-co-norbornene polymerizations versus correspond-

ing ethylene polymerizations was observed previously in

neutrally charged Ni^IIcatalysts.^[14r]It is attributable to slug-

À

gish ethylene insertion into the severely encumbered Ni

norbornyl bond. Indeed, norbornene displays this type of

chelating p donation/agostic bonding in several Rh, Ru, and

Cu complexes (Scheme 11, A, B, and C, respectively).^[44]

Also, in norbornene homopolymerizations mediated by

monometallic cationic (allyl)Pd catalysts, such g-agostic spe-

cies were recently shown to be

a key intermediate

(Scheme 11, D), and were fully characterized by X ray dif-

fraction and NMR spectroscopy.^[45]

Catalyst deactivation: At 508C, all the catalysts reported

here, with the exception of ACHTNUTRGNEUN(G CF₃)FI-Ni, undergo decomposi-

tion to form black Ni⁰. The deactivation pathway for mono-

metallic neutrally charged nickel(II) phenoxyiminato cata-

lysts is thought to involve reductive elimination of alkane

À

through bimolecular [N,O]Ni H+[N,O]Ni alkyl reductive

elimination (Scheme 12).^[38a]

Scheme 10. a) Proposed secondary agostic interactions in bimetallic cata-

lysts that may influence b-H elimination/re-insertion kinetics and afford

À

increased chain branching. b) Proposed chelating p/agostic C H inter-

mediate facilitating increased norbornene incorporation in ethylene-co-

norbornene polymerizations mediated by catalysts

(CH₃)FI²-Ni₂and

ACHTUNGTRENNUNG

these catalysts were reported to incorporate 2–3-times more

polar-norbornene than a monometallic control. The greater

selectivity for norbornene enchainment relative to the mon-

onuclear catalysts reported here is consistent with the short-

er Ni···Ni distance, which—all other factors being equal—

would be expected to enhance catalyst center···catalyst

center cooperativity (Scheme 9).

Scheme 12. Proposed deactivation pathway for monometallic phenoxyi-

minato Ni catalysts.

An attractive enchainment pathway is one in which nor-

bornene p bonds to one Ni center and simultaneously binds

to the second Ni center via an agostic interaction

(Scheme 10b), thereby pre-organizing the monomer for en-

chainment (similar to the DFT-computed catalyst–octane in-

teraction of Figure 1). Note that the present results reveal

a significant decrease in copolymerization activity upon ad-

dition of the norbornene co-monomer. The reduced rate of

For monometallic catalysts

our observations agree with this proposed pathway

(Scheme 12). For bimetallic catalysts

(CH₃)FI²-Ni₂and

ACHTUGTNRENGUN(CH₃)FI-Ni and ACHTUNGTRNEN(UGN CF₃)FI-Ni,

AHCTUNGTRENNUNG

(CF₃)FI²-Ni₂-mediated ethylene polymerizations at 508C,

Ni⁰is observed visually, and free ligand formation by in situ

¹H NMR spectroscopy. A pathway consistent with Ni⁰, free

Scheme 11. Examples of Rh, Ru, Cu, and Pd norbornene complexes exhibiting g-agostic interactions.

Chem. Eur. J. 2012, 00, 0 – 0

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M. Delferro, T. J. Marks et al.

sponsible for the high M_wfrac-

tion, the ethylene polymeri-

zation properties of

Ni(OH) were investigated.

Complex

(CF₃)FI²-Ni(OH),

when activated with Ni(COD)₂,

(CF₃)FI²-

ACHTUNGTRENNUG

AHCTUNGTRENNUNG

ACHTUNGTRENNUNG

is an active ethylene polymeri-

zation catalyst at room temper-

ature and at 508C (Tables 2 and

3). At 258C,

exhibits four-times the activity

of bimetallic

(CF₃)FI²-Ni₂, and

at 508C, 20.7 greater activity

than bimetallic

(CF₃)FI²-Ni₂

under the same polymerization

conditions. Microstructural

analysis of the polyethylenes

produced by

(CF₃)FI²-Ni(OH)

ACHTUNGTRENNUNG

AHCTUNGTRENNUNG

indicates lower M_wpolyethy-

lene with similar branch num-

bers versus the polyethylenes

produced by ACTHNUTRGNEUNG

(CF₃)FI²-Ni₂. In

previous work, the effects of in-

stalling an intramolecular hy-

drogen bond directed toward

Scheme 13. Proposed thermal deactivation pathway for bimetallic catalysts ACTHNUGRTENNUG ACHUTNGTRENNGUN

(CH₃)FI²-Ni₂and (CF₃)FI²-Ni₂.

ligand, and our conclusion that the predominant chain trans-

fer pathway in these catalysts is b-H elimination^[17](yielding

À

Ni H), is shown in Scheme 13. Here, elimination of a grow-

À

ing polymer chain via b-H transfer yields a Ni H at one co-

ordination site (II), which undergoes reductive elimination

forming Ni⁰and one ligand O H group (IV). Repetition

À

then eliminates another Ni⁰moiety and free ligand (VII).

Investigation of the reaction between

(CF₃)H₂FI²and

ACHTUNGTRENNUNG

(CF₃)FI²-Ni₂(Scheme 8) confirms that liberated free ligand

VII indeed undergoes reaction with the dinickel complex,

forming 2 equiv monometallic Ni species IV (Scheme 13). A

roughly analogous deactivation pathway was proposed for

monometallic neutral Ni^IIanilinotroponate ethylene poly-

À

merization catalysts in which an Ni H group undergoes re-

ductive elimination yielding Ni⁰and free ligand.^[38b]At

Figure 7. Normalized GPC traces with viscometry detection of polyethy-

lenes derived from catalyst

(CF₃)FI²-Ni₂at 508C under 8.0 atm ethylene

508C, bimetallic catalysts ACHTUNTRGENNUG AHCTUNGTRENNGUN

(CH₃)FI²-Ni₂and (CF₃)FI²-Ni₂

AHCTUNGTRENNUNG

pressure, showing the appearance of a higher M_wpolyethylene fraction as

polymerization time is increased.

both produce polyethylene, which has a bimodal molecular

weight distribution by GPC. For both catalysts, the minor

component of the GPC trace is higher M_wpolyethylene. As

the polymerization time at 508C is increased, the proportion

of the higher M_wpolyethylene fraction increases (Figure 7).

This observation suggests the formation of a new catalytic

a polymerization-active Ni^IIcenter were investigated,^[14c]and

it was concluded that installing the hydrogen bond adjacent

to the Ni center leads to a more electron-deficient catalyst

as shown below; see also ref. [14c]), increasing ethylene

polymerization activity and depressing product polyethylene

M_w. Similar conclusions can be drawn here when the poly-

species during the deactivation of

(CF₃)FI²-Ni₂. In room temperature ethylene polymerizations

when using bimetallic

(CH₃)FI²-Ni₂and (CF₃)FI²-Ni₂, the

(CH₃)FI²-Ni₂and

ACHTUNGTRENNUNG

A

ACHTUNGTRENNUNG

product polymers display monomodal GPC traces if the

polymerization time is held to 40 min. However, when the

polymerization time is increased to 120 min, a high M_w

shoulder, reminiscent of the high M_wpolymer formed at

508C, appears.^[46]To determine if species IV might be re-

merization results for

compared. GPC analysis of the polyethylenes obtained at

508C from

(CF₃)FI²-Ni(OH) shows that this complex is not

responsible for the high M_wshoulder present in the GPC

(CF₃)FI²-Ni(OH) and (CF₃)FI²-Ni₂are

ACHUTGTNRENNUG CAHTUNGTRENNUGN

AHCTUNGTRENNUNG

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Bimetallic Nickel(II) Polymerization Catalysts

FULL PAPER

trace of the polyethylenes pro-

duced by

(CF₃)FI²-Ni₂at 508C.

However, the data (Figure 8)

suggest that the polyethylene

fraction that was observed in analogous polymerizations

G

when using Ni

observations, it appears likely that Ni

the formation of the high M_wpolymer in the polyethylenes

produced by

(CH₃)FI²-Ni₂and (CF₃)FI²-Ni₂at 508C. Keim

and Peuckert^[47]showed that Ni

(COD)₂undergoes reaction

with Ph₂PCH₂CO₂H, to yield the active ethylene oligomeri-

zation catalyst [P,O]Ni

(h³-C₈H₁₃). Indeed, in the presence of

other bidentate ligands with acidic hydrogen atoms, such as

ACHTUNGTRENNUNG

produced by

N

A

ACHTUNGTRENNUNG

is very similar to the major

polyethylene peak produced by

ACHTUNGTRENNUNG

AHCTUNGTRENNUNG

hexafluoroacetylacetone, NiACHTNUTRGNENG(U COD)₂is also active for ethyl-

ene oligomerization.^[48]Based on deuterium labeling experi-

ments, it was shown that the formation of the active catalyst

occurs by direct protonation of an electron-rich Ni-coordi-

nated alkene. Ni

ACHTUNGTRENNUNG

ylene polymerization catalyst in the presence of [HAHCTUNGTRENNUNG

[BACTHNUTRGNEUNG

(C₆F₅)₄]^À(an acid source) with amidodiphosphine ligand

{(Ar)₂P}₂NMe (PNP).^[49]Furthermore, Jordan and co-work-

ers concluded that the polymerization-active species is

[(PNP)Ni

of (PNP)Ni

(Scheme 14).^[49a]

A

(C₆F₅)₄]^À, generated by protonation

ACHTUNGTRENNUNG

A

with

[HACTHUNGTRENNUG ACHTUNGTRENNUNG

(Et₂O)₂]⁺[B(C₆F₅)₄]^À

Figure 8. Normalized GPC with viscometer detection of polyethylenes

derived from catalyst

vated with Ni(COD)₂, and

(C₆F₅)₃at 508C under constant 8.0 atm ethylene pressure.

ACHTUNGTRENNUNG

(CF₃)FI²-Ni(OH) (Table 2, entry 5, 0.5 mmol) acti-

A

(CF₃)FI²-Ni₂activated with Ni

ACHUTGTNERNNUG ACHTUNGTREN(NUGN COD)₂or B-

ACHTUNGTRENNUNG

Scheme 14. Formation of an active ethylene polymerization catalyst from

an L₂Ni(COD) complex.

AHCTUNGTRENNUNG

ACHTUNGTRENNUNG

G

In the pathway shown in Scheme 13, free ligand and Ni⁰

are produced during the deactivation of

(CH₃)FI²-Ni₂and

(CF₃)FI²-Ni₂activated by Ni

(COD)₂. The results above

show that Ni(COD)₂in the presence of a protic ligand can

afford active ethylene oligomerization/polymerization-active

species. Since Ni(COD)₂is used in excess in the polymeri-

zations reported here, free Ni(COD)₂is doubtless present.

To investigate any additional role Ni(COD)₂might play

G

ACHTUNGTRENNUNG

A

G

ACHTUNGTRENNUNG

AHCTUNGTRENNUNG

modal when the catalyst loading is low (0.5 mmol; Figure 8).

However, the deactivation pathway depicted in Scheme 13

suggests that

polyethylene similar to

ACHTUNGTRENNUNG

(CF₃)FI²-Ni(OH) should produce bimodal

ACHTUNGTRENNUNG

G

(other than phosphine abstraction) in these polymerizations,

that, due to the low catalyst concentration used in these

polymerizations, the amount of polyethylene produced by

reaction of free ligand, arising from deactivation of

reactions were also conducted at 508C by using a combina-

tion of the free

In situ reaction of ACTHNUTRGENNGU ACHTGNUTRENNNUG

(CF₃)H₂FI²ligand and Ni

ACHUTGTNRENNUG CAHTUNGTRENNUNG

(CF₃)H₂FI²and Ni

A

R

production of polyethylene with low activity (0.03 kg polye-

thylenemol^À1[Ni]h^À1atm^À1), and GPC analysis of the poly-

nent. Furthermore, when polymerizations are conducted at

higher catalyst loadings (5.0 mmol) a bimodal polyethylene

is obtained (Figure S22 in the Supporting Information) with

a high M_wshoulder similar to the GPC traces of the polyeth-

ethylenes produced by ACTHNUTRGENNUG ACHTUTGNREN(NUGN COD)₂reveals a bimo-

(CF₃)H₂FI²/Ni

dal behavior with one very high M_wcomponent (880 K)

with a large PDI (6.1), and one component with a M_wmore

typical of the systems investigated here (6.1 K). These re-

ylenes produced at 508C by

To help identify the species producing the high M_wpoly-

mer in polymerizations with

(CH₃)FI²-Ni₂and (CF₃)FI²-Ni₂

at 508C, ethylene polymerizations were performed by using

(CF₃)FI²-Ni₂with

(C₆F₅)₃as the co-catalyst at 508C

(CF₃)FI²-Ni₂(Figure 7).

ACHTUNGTRENNUNG

sults argue that Ni

(phosphine-scavenger), and that reaction of Ni

free ligand, generated during ACHTNUGTRENNUNG

(CH₃)FI²-Ni₂and

ACHTUNGTRENNUNG

A

U

ACHTUNGTRENNUNG

G

A

B

A

catalyst thermolysis at 508C, plausibly yields a catalytic spe-

cies accounting for the high M_wfraction in the product

GPCs from the bimetallic catalysts.^[50]Further support for

this hypothesis comes from the observation that the use of

(Table 2). In addition to approximately 2.2-times increase in

activity, GPC analysis of the polyethylenes obtained with

ACHTUNGTRENNUNG ACHTUNGTRENNUNG(C₆F₅)₃showed the absence of the high M_w

(CF₃)FI²-Ni₂+B

Chem. Eur. J. 2012, 00, 0 – 0

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M. Delferro, T. J. Marks et al.

high-vacuum sublimation (808C/10^À6Torr). The reagents trans-NiMeCl-

BACHTUNGTRENNUNG(C₆F₅)₃as a co-catalyst in place of NiACHTUNTGERN(NUGN COD)₂suppresses

the production of the high molecular weight fraction.

AHCTUNGTRENNUNG

(PMe₃)₂,^[29]2,7-diformyl-1,8-dihydroxynaphthalene (1),^[10a,21]and the ter-

phenyl amines^[22]were prepared according to literature procedures. Ni-

(COD)₂(COD=1,5-cyclooctadiene) was purchased from Strem; p-tolue-

nesulfonic acid monohydrate and formic acid were purchased from

Sigma–Aldrich. The monometallic catalysts (CH₃)FI-Ni and (CF₃)FI-Ni

were prepared according to literature procedures.^[17]

AHCTUNGTRENNUNG

Conclusion

A

ACHTUNGTRENNUNG

Two new sterically encumbered Ni^IIbimetallic ethylene

Physical and analytical measurements: NMR spectra were taken on

Varian Hg400 (400 MHz, ¹H; 100 MHz, ¹³C; 162 MHz, ³¹P; 376 MHz,

¹⁹F), Varian Ic 400 (400 MHz, ¹H; 100 MHz, ¹³C), Varian Inova 500

(500 MHz, ¹H), and a Bruker Avance III 500 (500 MHz, ¹H; 125 MHz,

¹³C) NMR spectrometers. Chemical shifts (d) for ¹H and ¹³C are refer-

enced to TMS, internal solvent resonances relative to TMS, and the poly-

mer CH₂backbone. Chemical shifts (d) for ³¹P and ¹⁹F are referenced to

the external standards 85% H₃PO₄and CFCl₃dissolved in CDCl₃, re-

spectively. NMR spectra of air-sensitive samples were acquired in Teflon

valve sealed J. Young NMR tubes. NMR analysis of polymers was carried

out in 1,1,2,2-[D₂]tetrachloroethane at 1208C with d1=10 s. Polymer

NMR spectra were assigned, and polyethylene branch numbers were cal-

culated, according to the literature procedures for polyethylene^[33a,d,e,35]

and ethylene-co-norbornene.^[37]Gel permeation chromatography (GPC)

was carried out in 1,2,4-trichlorobenzene (stabilized with 125 ppm BHT)

at 1508C on a Polymer Laboratories 220 instrument equipped with a set

of three PLgel 10 mm mixed-B LS columns with differential refractive

index and viscosity detectors. Molecular weights were determined

through universal calibration relative to polystyrene standards. Elemental

analyses were performed by Midwest Microlabs, Indianapolis, Indiana.

polymerization catalysts, ACHTUNTRGENNUG AHCTUNGTRENNGUN

(CH₃)FI²-Ni₂and (CF₃)FI²-Ni₂,

were synthesized and fully characterized. These catalysts are

active ethylene polymerization catalysts in the presence of

the phosphine scavengers/co-catalysts Ni

(C₆F₅)₃. Catalyst center···catalyst center cooperative effects

are observed in ethylene-co-norbornene polymerizations,

with bimetallic catalysts

(CH₃)FI²-Ni₂and (CF₃)FI²-Ni₂en-

chaining three- and six-times, respectively, more norbornene

than their monometallic analogues (CH₃)FI-Ni and (CF₃)FI-

Ni. The catalytic performance of

(CH₃)FI²-Ni₂and (CF₃)FI²-

ACHTUNGRTENN(UNG COD)₂or B-

ACHTUNGTRENNUNG

A

ACHTUNGTRENNUNG

A

ACHTUNGTRENNUNG

A

ACHTUNGTRENNUNG

Ni₂exhibits greater thermal stability than previous, less en-

cumbered Ni₂catalysts, and at 508C, all of the new catalysts

exhibit appreciable ethylene polymerization activity. How-

ever,

gradual deactivation at 508C. The deactivation pathway for

(CH₃)FI²-Ni₂and (CF₃)FI²-Ni₂was investigated, and key

ACHTUNGTRENNUNG(CH₃)FI-Ni, ACHTUNGTRENNUNG CAHTNUGTRENNUGN

(CH₃)FI²-Ni₂, and (CF₃)FI²-Ni₂evidence

A

ACHTUNGTRENNUNG

Synthesis of 2,7-diACTHUNRGTNE[NUG 2,6-(3,5-dimethylphenyl)]imino-1,8-dihydroxynaphtha-

À

steps are proposed to be the reductive elimination from Ni

lene, (CH₃)H₂FI₂: Under N₂, a Schlenk flask (100 mL) was charged with

activated molecular sieves (1.7 g), 0.241 g (1.12 mmol) of 2,7-diformyl-

1,8-dihydroxynaphthalene (1), 1.35 g (4.48 mmol) of 2,6-(3,5-dimethyl-

phenyl)aniline, benzene (35 mL), and formic acid (5 drops). The resulting

mixture was refluxed for 7 days during which time the reaction color

changed from orange to red. The reaction mixture was allowed to cool

and was then filtered to remove the sieves. The volatiles were next re-

moved from the filtrate, in vacuo, and the resulting dark red oil was tritu-

rated with methanol, affording an orange solid. The orange solid was

washed with diethylether, cooled to À108C, and filtered. This red solid

was recrystallized from a 1:9.5 mixture of toluene and methanol, afford-

ing 0.357 g (0.456 mmol, 41% yield) of microcrystalline red solid.

¹H NMR (500 MHz, CDCl₃, 258C, TMS): d=14.14 (s, OH), 13.47 (d,

NH), 8.50 (s, HC=N), 7.87 (d, NH-CH=C), 7.37 (s, Ar), 7.23–7.11 (m,

Ar), 7.08 (s, Ar), 7.05 (s, Ar), 7.02 (s, Ar), 6.82 (s, Ar), 6.77 (s, Ar), 6.42

(d, Ar), 6.22 (d, Ar), 2.33 (s, H₃C-Ar), 2.24 ppm (s, H₃C-Ar); ¹³C NMR

(125 MHz, CDCl₃, 258C, TMS): d=183.98, 163.68, 159.83, 158.12, 149.78,

141.38, 140.00, 138.78, 137.81, 136.96, 135.96, 133.62, 130.66, 129.57,

129.47, 128.25, 127.90, 127.01, 126.81, 123.68, 118.67, 116.72, 116.30,

115.65, 108.60, 21.31 ppm; elemental analysis calcd (%) for C₅₆H₅₀N₂O₂:

C 85.90, H 6.44, N 3.58; found: C 86.04, H 6.59, N 3.71.

H groups to form free (protonated) ligand and Ni⁰. An eth-

ylene polymerization-active intermediate ACTHNUTRGNEUNG

(CF₃)FI²-Ni(OH)

(IV in Scheme 13) in the deactivation process is identified as

that responsible for significant polyethylene production

when the bimetallic catalysts are utilized at 508C. The free

ligand formed in situ during bimetallic catalyst deactivation

can then undergo reaction with a dinickel species (I in

Scheme 13) to yield 2 equiv polymerization-active inter-

mediate

react with the Ni

ble of producing very high M_wpolyethylene, which is very

unusual for group 10 catalysts. In place of Ni(COD)₂, ethyl-

ene polymerizations co-catalyzed by B(C₆F₅)₃led to mono-

ACHTUNGTRENNUNG

AHCTUNGTRENNUNG

modal polyethylene production at higher activities.

Experimental Section

Synthesis of 2,7-diACTHUNTGRNEUNG[2,6-(3,5-di-trifluormethylphenyl)]imino-1,8-dihydroxy-

naphthalene, (CF₃)H₂FI²: A round-bottom flask (250 mL) was charged

with 0.709 g (3.28 mmol) of 2,7-diformyl-1,8-dihydroxynaphthalene (1),

3.90 g (7.54 mmol) of 2,6-(3,5-di-trifluoromethylphenyl)aniline, 62 mg

(0.33 mmol) of p-toluenesulfonic acid monohydrate, and toluene

(70 mL). The reaction mixture was refluxed by using a Dean–Stark trap

for 3 days. The solvent was then removed under reduced pressure, and

the resulting orange oil was triturated with methanol affording a red

solid. This solid was washed with methanol (20 mL) to remove the half-

condensation product. The excess aniline was then removed by recrystall-

izing the solid from a 1:9.5 mixture of toluene and methanol. This afford-

ed 3.04 g (2.50 mmol, 76% yield) of red solid. Crystals suitable for X-ray

analysis were obtained by slow evaporation of a CDCl₃solution of

Materials and methods: All manipulations of air-sensitive materials were

performed with rigorous exclusion of O₂and moisture in oven-dried

Schlenk-type glassware on a dual manifold Schlenk line, interfaced to

a high-vacuum line (10^À6Torr), or in a N₂-filled vacuum atmospheres

glove box with a high capacity recirculator (<1 ppm O₂). Argon (Airgas,

prepurified grade) was purified by passage through a supported MnO

oxygen-removal column and an activated Davison 4A molecular sieve

column. Ethylene (Airgas) was purified by passage through an O₂/mois-

ture trap (Matheson, model MTRP-0042-XX). Norbornene was dried

over sodium and transferred, in vacuo, to a Teflon-sealed storage flask.

Diethyl ether and tetrahydrofuran were distilled from Na/benzophenone

ketyl. Hydrocarbon solvents (benzene, n-pentane, n-hexane, toluene)

were vacuum transferred from Na/K alloy. [D₆]Benzene (Cambridge Iso-

tope Laboratories, 99+atom%D) was stored over Na/K alloy, in vacuo,

and vacuum transferred immediately prior to use. All other deuterated

solvents were used as received (Cambridge Isotope Laboratories, 99+

AHCTUNGTRENNUNG

(CF₃)H₂FI². ¹H NMR (500 MHz, CDCl₃, 258C, TMS): d=13.62 (d, NH),

13.32 (s, OH), 8.39 (s, HC=N), 7.92 (s, Ar), 7.74 (s, Ar), 7.57 (s, Ar), 7.51

(d, Ar), 7.40 (m, Ar), 7.02 (d, Ar), 6.83 (d, Ar), 6.50 (d, Ar), 6.24 ppm (d,

Ar); ¹³C NMR (125 MHz, CDCl₃, 258C, TMS): d=184.77, 163.91, 161.71,

157.36, 150.02, 142.44, 141.76, 139.62, 134.82, 134.11, 132.92, 132.65,

132.21, 131.52, 131.29, 130.98, 130.84, 130.54, 129.67, 129.19, 128.77,

atom%D). Tris(pentafluorophenyl)borane, B

ACHTNUGTNER(UNNG C₆F₅)₃, was a gift from Al-

bemarle Corporation (Baton Rouge, LA). The borane was purified by

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Bimetallic Nickel(II) Polymerization Catalysts

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128.38, 128.33, 125.44, 125.29, 124.58, 124.11, 122.40, 122.29, 121.93,

120.59, 118.15, 117.85, 115.94, 109.62, 21.56 ppm; ¹⁹F NMR (376 MHz,

CDCl₃, 258C): d=À63.41, À63.56 ppm; elemental analysis calcd (%) for

C₅₆H₂₆N₂F₂₄O₂: C 55.73, H 2.16, N 2.31; found: C 55.02, H 2.31, N 2.27.

Synthesis of {2,7-di-[2,6-(3,5-di-trifluoromethylphenylimino)methyl]-1,8-

naphthalenediolato}-bis-Ni^II-(methyl)(trimethylphosphine), (CF₃)FI²-Ni₂:

A

Schlenk flask (100 mL) was charged with 2.00 g (1.50 mmol) of

A

ACHTUNGTRENNUNG

Representative procedure for the synthesis of sodium salts (CH₃)FI²-Na₂

(150 mL) was added to this mixture via cannula at À788C. The reaction

mixture was allowed to stir at À788C for 15 min. The reaction mixture

was then warmed to À428C and stirred for 3.5 h after which time the re-

action mixture turned red. The reaction mixture was then placed in

a À108C water bath and stirred for 75 min. The resulting cerise-colored

reaction mixture was then allowed to warm to room temperature and

was stirred for an additional 3 h. The reaction mixture was then filtered

and the volatiles were removed from the filtrate, in vacuo. The solid ob-

tained next was triturated with n-pentane to yield 1.60 g (1.06 mmol,

73% yield) of red solid. Single crystals suitable for X-ray diffraction

were grown from the slow evaporation of an n-hexane solution in the

and (CF₃)FI²-Na₂: Under N₂, a Schlenk flask (100 mL) was charged with

2.66 g (2.19 mmol) of ACHTUNGTRENNUNG

(CF₃)H₂FI²and 0.210 g (8.75 mmol) of NaH. To

this was added dry THF (30 mL) via syringe. This red-orange mixture

was allowed to stir for 48 h. The reaction mixture was then filtered and

the volatiles were removed, in vacuo. The resulting red-orange solid was

washed with n-pentane (50 mL) and dried under high vacuum, overnight,

yielding 2.42 g (1.93 mmol, 88% yield) of orange solid.

1

glovebox. H NMR (500 MHz, [D₆]benzene, 258C, TMS): d=8.29 (s, 4H,

10-, 12-, 13-, and 14-H), 7.73 (s, 2H, 11- and 15-H), 7.68 (s, 2H, 21- and

24-H), 7.63 (s, 4H, 19-, 20-, 22-, and 23-H), 6.97–6.90 (m, 6H, 5-, 6-, 7-, 8-

3

4

, 9-, and 17-H), 6.80 (dd, J

18-H), 6.38 (d, ³J(H,H)=8.4 Hz, 2H, 3- and 4-H), 6.26 (d, ³J

(P,H)=9.9 Hz, 9H,

(P,H)=6.5 Hz, 6H, Ni-CH₃); ¹³C NMR (125 MHz,

ACHUTGTNREN(NUG H,H)=6.9 Hz, JACHTNUGTRENNUNG

N

ACHTUNGTRENNUNG

8.4 Hz, 2H, 1- and 2-H), 0.81 (d, ²J

A

PACHTUNGTRENNUNG

À1.36 ppm (d, ³J

ACHTUNGTRENNUNG

[D₆]benzene, 258C, TMS): d=170.15, 165.53, 150.16, 145.78, 142.76,

142.12, 134.45, 134.20, 133.79, 131.78, 131.51, 131.27, 130.88, 130.77,

125.87, 125.07, 124.97, 123.49, 122.90, 122.80, 120.94, 114.94, 13.28 (d, ¹J-

(P,C)=28.5 Hz,

P

(CH₃)₃), À13.61 ppm (d, ²J

ACHTUNGTREN(NUGN P,C)=44.6 Hz, Ni-CH₃);

³¹P NMR (162 MHz, [D₆]benzene, 258C): d=À9.46 ppm; ¹⁹F NMR

(376 MHz, [D₆]benzene, 258C): d=À62.89, À63.07 ppm; elemental analy-

sis calcd (%) for C₆₄H₄₈N₂F₂₄Ni₂O₂P₂: C 50.83, H 3.20, N 1.85; found: C

50.98, H 3.39, N 1.85.

Synthesis of {2,7-di-[2,6-(3,5-di-methylphenylimino)methyl]-1,8-naphtha-

lenediolato}-bis-Ni^II-(methyl)(trimethylphosphine), (CH₃)FI²-Ni₂: Dry

benzene (20 mL) was added to a flask containing 0.590 g (0.713 mmol) of

(CH₃)FI²-Na₂. This mixture was then added slowly via cannula to a ben-

ACHTUNGTRENNUNG

zene solution (30 mL) of 0.373 g (1.43 mmol) of trans-NiMeCl

An immediate red color change was observed. Due to the low solubility

of

(CH₃)FI²-Na₂in benzene, the reaction mixture was transferred via can-

nula back to the original

(CH₃)FI²-Na₂flask. The reaction mixture was

ACHTUNGTRNE(NUNG PMe₃)₂.

ACHTUNGTRENNUNG

AHCTUNGTRENNUNG

allowed to stir at room temperature, overnight. The reaction mixture was

then filtered and the filtrate was concentrated, in vacuo. Dry n-pentane

(15 mL) was then added via syringe, precipitating an orange solid. After

filtration and drying under high vacuum, 0.654 g (0.605 mmol, 85%) of

ACHTUNGTRENNUNG

A

ACHTUNGTRENNUNG

7.5 Hz, 2H, 16- and 18-H), 7.19, À7.12 (m, 6H, 8-, 17-, 19-, 20-, 22-, 23-

H), 6.82 (s, 2H, 11- and 15-H), 6.75 (s, 2H, 21- and 24-H), 6.66 (d, ³J-

Synthesis of {2,7-di-[2,6-(3,5-di-trifluoromethylphenylimino)methyl]-1-hy-

droxy-8-naphthalene-diolato}-Ni^II-(methyl)(trimethylphosphine),

(CF₃)FI²-Ni(OH): A Schlenk flask (25 mL) was charged with 0.240 g

3

A

N

H), 2.23 (s, 12H, Ar-CH₃), 2.12 (s, 12H, Ar-CH₃), 0.97 (d, ²J

ACHTUNGTRENNUNG

9.2 Hz, 18H, P

N

ACHTUNGTRENNUNG

(0.198 mmol) of ACTHNUTRGNENGU ACHTUGNTRENNUGN

(CF₃)H₂FI², 0.300 g (0.198 mmol) of (CF₃)FI²-Ni₂, and

¹³C NMR (125 MHz, [D₆]benzene, 258C, TMS): d=169.65, 166.07,

150.16, 144.82, 141.19, 141.19, 141.03, 137.61, 137.30, 137.27, 136.90,

133.80, 130.53, 130.32, 128.91, 128.85, 128.59, 128.35, 128.16, 127.97,

toluene (20 mL). The resulting red solution was then stirred at 508C,

overnight, after which the volatiles were removed, in vacuo, leaving a red

solid. The solid obtained was triturated with n-pentane and dried under

vacuum affording 0.401 g (0.294 mmol, 74% yield) of orange solid.

¹H NMR (500 MHz, [D₆]benzene, 258C, TMS): d=12.83 (s, 1H, OH),

8.31 (s, 1H, Ar-H), 8.09 (d, 1H, Ar-H), 7.91 (s, 4H, Ar-H), 7.89 (s, 4H,

Ar-H), 7.75 (s, 2H, Ar-H), 7.69 (s, 2H, Ar-H), 6.98–6.88 (m, 6H, Ar-H),

6.86 (s, 1H, Ar-H), 6.78 (d, 1H, Ar-H), 6.44 (d, 1H, Ar-H), 6.26 (d, 1H,

125.28, 124.08, 115.24, 113.49, 21.65, 13.89 (d, ¹J

G

ACHTUGNTERN(NUNG CH₃)₃,

À13.44 ppm (d, ²J

ACHTUNGTRENNUNG

[D₆]benzene, 258C): d=À10.42 ppm; elemental analysis calcd (%) for

C₆₄H₇₂N₂Ni₂O₂P₂: C 71.13, H 6.72, N 2.59; found: C 71.25, H 6.67, N,

2.60.

Ar-H), 0.54 (s, 9H, PACHTUNGTRENNUNG

(125 MHz, [D₆]benzene, 258C, TMS): d=167.88, 166.50, 162.56, 161.75,

150.53, 149.74, 142.44, 142.31, 141.62, 133.77, 132.26, 131.99, 131.86,

131.73, 131.60, 131.46, 131.33, 131.07, 130.97, 130.78, 130.74, 127.46,

127.30, 127.07, 126.71, 125.13, 125.08, 124.90, 122.96, 122.73, 121.25,

120.79, 120.50, 118.81, 116.86, 116.66, 115.93, 112.86, 12.37, À13.65 ppm;

³¹P NMR (162 MHz, [D₆]benzene, 258C): d=À12.06 ppm; ¹⁹F NMR

(376 MHz, [D₆]benzene, 258C): d=À63.11, À63.23 ppm; elemental analy-

sis calcd (%) for C₆₀H₃₇N₂F₂₄NiO₂P: C 52.85, H 2.73, N 2.05; found: C

52.62, H 2.78, N 2.13.

General procedure for ethylene polymerization experiments: In a typical

experiment, an oven-dried thick-walled glass pressure vessel (350 mL)

Chem. Eur. J. 2012, 00, 0 – 0

ꢂ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.chemeurj.org

&

15

&

ÞÞ

These are not the final page numbers!

M. Delferro, T. J. Marks et al.

was charged in the glovebox with Ni catalyst (5 mmol), 2.0 equiv Ni-

ACHTUNGTRENNUNG(COD)₂per Ni, dry toluene (50 mL), and a large magnetic stir bar. The

the supplementary crystallographic data for this paper. These data can be

obtained free of charge from The Cambridge Crystallographic Data

Centre via www.ccdc.cam.ac.uk/data_request/cif.

pressure vessel was then interfaced to a high-pressure line and the solu-

tion was degassed. The reactor was warmed to the desired temperature

by using a water or oil bath, and allowed to equilibrate for 5 min. With

rapid stirring, the reactor was then pressurized to 8.0 atm pressure ethyl-

ene, which was maintained during the course of the polymerization.

After the desired run time, the reactor was vented and the contents

poured into acidic methanol. The precipitated polymer was collected by

filtration, washed with methanol, and dried at 608C, overnight, under

high vacuum.

Acknowledgements

Financial support from DOE (grant 86ER13511) and NSF (grant CHE-

0809589) is gratefully acknowledged. We also acknowledge Albemarle

Corporation for the generous gift of BACHTNUTRGNE(UNG C₆F₅)₃. We thank Dr. C. Weiss,

General procedure for ethylene polymerization experiments with catalyst

(CF₃)FI²-Ni(OH) (Table 2, entry 4): An oven-dried thick-walled glass

pressure vessel (350 mL) was charged in the glovebox with 1 mL

Ms. J. McInnis, and Mr. S. Wobser for helpful discussions.

(0.5 mmol) of

2.0 equiv Ni(COD)₂per Ni, dry toluene (49 mL), and a large magnetic

(CF₃)FI²-Ni(OH),

a 0.5 mm dry toluene solution of ACTHUNTGRNUEGN

[1] For recent reviews on olefin polymerization catalysis with bimetallic

catalysts, see: a) M. Delferro, T. J. Marks, Chem. Rev. 2011 , 111 ,

245 0 –2 485; b) H. Li, T. J. Marks, Proc. Natl. Acad. Sci. USA 2006 ,

103 , 1529 5 –1 5302.

ACHTUNGTRENNUNG

stir bar. The pressure vessel was then interfaced to a high-pressure line

and the solution was degassed. The reactor was warmed to 508C by using

an oil bath, and allowed to equilibrate for 5 min. With rapid stirring, the

reactor was then pressurized to 8.0 atm pressure ethylene, which was

maintained during the course of the polymerization. After the desired

run time (40 min), the reactor was vented and the contents poured into

acidic methanol. The precipitated polymer was collected by filtration,

washed with methanol, and dried at 608C, overnight, under high vacuum.

[2] a) N. Guo, C. L. Stern, T. J. Marks, J. Am. Chem. Soc. 2008 , 130 ,

224 6 –2 247; b) S. Amin, T. J. Marks, J. Am. Chem. Soc. 2007 , 129 ,

293 8 –2 953; c) S. Amin, T. J. Marks, J. Am. Chem. Soc. 2006 , 128 ,

450 6 –4 507; d) H. Li, L. Li, D. J. Schwartz, M. V. Metz, T. J. Marks,

L. Liable-Sands, A. L. Rheingold, J. Am. Chem. Soc. 2005 , 127 ,

1475 6 –1 4768; e) H. Li, C. L. Stern, T. J. Marks, Macromolecules

2005 , 38 , 901 5 –9 027; f) H. Li, L. Li, T. J. Marks, Angew. Chem.

2004 , 116 , 504 5 –5 048; Angew. Chem. Int. Ed. 2004 , 43 , 493 7 –4 940;

g) N. Guo, L. Li, T. J. Marks, J. Am. Chem. Soc. 2004 , 126 , 654 2 –

6543; h) H. Li, L. Li, T. J. Marks, L. Liable-Sands, A. L. Rheingold,

J. Am. Chem. Soc. 2003 , 125 , 1078 8 –1 0789; i) L. Li, M. V. Metz, H.

Li, M.-C. Chen, T. J. Marks, L. Liable-Sands, A. L. Rheingold, J.

Am. Chem. Soc. 2002 , 124 , 1272 5 –1 2741.

General procedure for ethylene-co-norbornene polymerization experi-

ments: In a typical experiment, an oven-dried thick-walled glass pressure

vessel (350 mL) was charged in the glovebox with Ni catalyst (5.0 mmol),

2.0 equiv NiACHTUNGTRENNUNG(COD)₂per Ni, dry toluene (23.5 mL), and a large magnetic

stir bar. The pressure vessel was then interfaced to a high-pressure line

and the solution was degassed. The reactor was warmed to the desired

temperature by using a water or oil bath, and allowed to equilibrate for

5 min. The reactor was then pressurized to 1.0 atm ethylene pressure and

1.5 mL from a 0.74m norbornene solution in toluene was immediately in-

jected. The norbornene solution had been degassed and the aliquot was

taken under an atmosphere of purified ethylene. With rapid stirring, the

reactor was then pressurized to 8.0 atm ethylene pressure, which was

maintained during the course of the polymerization. After the desired

run time, the reactor was vented and the reaction mixture was poured

into acidic methanol. The precipitated polymer was collected by filtra-

tion, washed with methanol, and dried at 608C, overnight, under high

vacuum.

[3] a) L. R. Gahan, S. J. Smith, A. Neves, G. Schenk, Eur. J. Inorg.

Chem. 2009 , 274 5 –2 758; b) X. Cao, S. V. Antonyuk, S. V. Seethara-

man, L. J. Whitson, A. B. Taylor, S. P. Holloway, R. W. Strange, P. A.

Doucette, J. S. Valentine, A. Tiwari, L. J. Hayward, S. Padua, J. A.

Cohlberg, S. S. Hasnain, P. J. Hart, J. Biol. Chem. 2008 , 283 , 1616 9 –

´

16177; c) N. Mitic, S. J. Smith, A. Neves, L. W. Guddat, L. R. Gahan,

G. Schenk, Chem. Rev. 2006, 106, 3338–3363; d) C. Belle, J. L.

Pierre, Eur. J. Inorg. Chem. 2003 , 413 7 –4 146; e) M. J. Jedrzejas, P.

Setlow, Chem. Rev. 2001 , 101 , 60 7 –6 18; f) T. C. Bruice, S. J. S. Ben-

kovic, Biochemistry 2000 , 39 , 626 7 –6 274; g) E. Jabri, M. B. Carr,

R. P. Hausinger, P. A. Karplus, Science 1995 , 268 , 99 8 –1 004; h) V. K.

Yachandra, K. Sauer, M. P. Klein, Chem. Rev. 1996 , 96 , 292 7 –2 950.

[4] a) B. Bauer-Siebenlist, S. Decher, F. Meyer, Chem. Eur. J. 2005 , 11 ,

534 3 –5 352; b) J. P. Collman, R. Boulatov, C. J. Sunderland, L. Fu,

Chem. Rev. 2004 , 104 , 56 1 –5 88; c) R. Krishnan, J. K. Voo, C. G.

Riordan, L. Zahkarov, A. L. Rheingold, J. Am. Chem. Soc. 2003 ,

125 , 442 2 –4 423; d) T. C. Bruice, Acc. Chem. Res. 2002 , 35 , 13 9 –1 48;

e) D. P. OꢃBrien, R. M. N. Entress, A. C. Matthew, S. W. OꢃBrien, A.

Hopkinson, D. H. Williams, J. Am. Chem. Soc. 1999, 121, 5259–

5265; f) R. E. Carazo-Salas, G. Guarguaglini, O. J. Gruss, A. Segref,

E. Karsenti, L. W. Mattaj, Nature 1999, 400, 178–181; g) F. M.

Menger, Acc. Chem. Res. 1993 , 26 , 20 6 –2 12.

General procedure for analysis of ethylene polymerization deactivation

products: An oven-dried thick walled glass pressure vessel (350 mL) was

charged in the glovebox with 10.8 mg (10.0 mmol)

(40.0 mmol) Ni(COD)₂, dry toluene (25 mL), and a large magnetic stir

(CH₃)FI²-Ni₂, 11.0 mg

ACHTUNGTRENNUNG

bar. The pressure vessel was then interfaced to a high-pressure line and

the solution was degassed. The reactor was next warmed to 508C by

using an oil bath, and allowed to equilibrate for 5 min. With rapid stir-

ring, the reactor was then pressurized to 8.0 atm ethylene pressure, which

was maintained during the course of the polymerization. After 50 min

the reactor was vented to 1.0 atm ethylene pressure. The glass pressure

vessel was then interfaced to a Schlenk line and all volatiles were re-

moved, in vacuo. Air-free ¹H NMR (C₆D₆) analysis of the residue con-

firmed the formation of free ligand.

[5] a) H. Steinhagen, G. Helmchen, Angew. Chem. 1996 , 108 , 248 9 –

2492; Angew. Chem. Int. Ed. Engl. 1996 , 35 , 233 9 –2 342; b) D. E.

Wilcox, Chem. Rev. 1996 , 96 , 243 5 –2 458; c) N. Strꢄter, W. N. Lips-

comb, T. Klabunde, B. Krebs, Angew. Chem. 1996 , 108 , 215 8 –2 191;

Angew. Chem. Int. Ed. Engl 1996 , 35 , 202 4 –2 055.

X-ray crystal structure determinations of (CF₃)H₂FI², and

(CF₃)FI²-Ni₂:

ACHTUNGTRENNUNG

Intensity data for

N

U

on a Bruker AXS APEXII diffractometer equipped with a CCD area de-

tector by using graphite-monochromated Mo_Ka[l=0.7107 ꢀ,

[6] B. A. Rodriguez, M. Delferro, T. J. Marks, J. Am. Chem. Soc. 2009 ,

131 , 590 2 –5 919.

ACHTUNGTRENNUNG ACHTUNGTRENNUGN

(CF₃)H₂FI²] or Cu_Ka[l=1.5418 ꢀ, (CF₃)FI²-Ni₂] radiation. All data were

corrected for absorption by using an empirical correction. Structure solu-

tions and refinements were obtained by using SIR-92^[51]or SHELXS-

97^[52]with direct methods and were refined on F²with the use of full-

matrix least-squares techniques. All aromatic hydrogen atoms were re-

fined with a riding model. All non-hydrogen atoms were refined aniso-

tropically and hydrogen atoms were either located in the difference map

or were refined with a riding model. Crystallographic results are summar-

ized in Table S1 of the Supporting Information. CCDC-869747 [for

[7] A. Motta, I. L. Fragalaꢅ, T. J. Marks, J. Am. Chem. Soc. 2009 , 131 ,

397 4 –3 984.

[8] a) A. W. Waltman, T. R. Younkin, R. H. Grubbs, Organometallics

2004 , 23 , 512 1 –5 123; b) E. F. Connor, T. R. Younkin, J. I. Hender-

son, A. W. Waltman, R. H. Grubbs, Chem. Commun. 2003 , 227 2 –

2273; c) T. R. Younkin, E. F. Connor, J. I. Henderson, S. K. Frie-

drich, R. H. Grubbs, D. A. Bansleben, Science 2000 , 287 , 46 0 –4 62;

d) C. Wang, S. Friedrich, T. R. Younkin, R. T. Li, R. H. Grubbs,

D. A. Bansleben, M. W. Day, Organometallics 1998 , 17 , 314 9 –3 151.

ACHTUNGTRENNUNG ACHTUNGTRENNUGN

(CF₃)H₂FI²], -869748 [for 2-CH₃], and -869750 [for (CF₃)FI²-Ni₂], contain

&

16

&

www.chemeurj.org

ꢂ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Chem. Eur. J. 0000, 00, 0 – 0

ÝÝ

These are not the final page numbers!

Bimetallic Nickel(II) Polymerization Catalysts

FULL PAPER

[9] a) H. Makio, H. Terao, A. Iwashita, T. Fujita, Chem. Rev. 2011 , 111 ,

236 3 –2 449; b) M. Mitani, R. Furuyama, J.-I. Mohri, J. Saito, S. Ishii,

H. Terao, T. Nakano, H. Tanaka, T. Fujita, J. Am. Chem. Soc. 2003 ,

125 , 429 3 –4 305; c) S.-I. Ishii, R. Furuyama, N. Matsukawa, J. Saito,

M. Mitani, H. Tanaka, T. Fujita, Macromol. Rapid Commun. 2003 ,

24 , 45 2 –4 56; d) M. Mitani, J.-I. Mohri, Y. Yoshida, J. Saito, S. Ishii,

K. Tsuru, S. Matsui, R. Furuyama, T. Nakano, H. Tanaka, S.-I.

Kojoh, T. Matsugi, N. Kashiwa, T. Fujita, J. Am. Chem. Soc. 2002 ,

124 , 332 7 –3 336.

[10] a) M. R. Salata, T. J. Marks, Macromolecules 2009 , 42 , 192 0 –1 933;

b) M. R. Salata, T. J. Marks, J. Am. Chem. Soc. 2008 , 130 , 1 2 –1 3.

[11] a) D. Takeuchi, Dalton Trans. 2010 , 39 , 31 1 –3 28; b) A. Nakamura,

S. Ito, K. Nozaki, Chem. Rev. 2009 , 109 , 521 5 –5 244; c) E. Y. X.

Chen, Chem. Rev. 2009 , 109 , 515 7 –5 214; d) G. J. Domski, J. M.

Rose, G. W. Coates, A. D. Bolig, M. Brookhart, Prog. Polym. Sci.

2007 , 32 , 3 0 –9 2; e) J. Zhang, X. Wang, G. X. Jin, Coord. Chem. Rev.

2006 , 250 , 9 5 –1 09; f) J. Durand, B. Milani, Coord. Chem. Rev. 2006 ,

250 , 54 2 –5 60; g) V. C. Gibson, S. K. Spitzmesser, Chem. Rev. 2003 ,

103 , 28 3 –3 16; h) S. Mecking, Coord. Chem. Rev. 2000 , 203 , 32 5 –

351; i) S. D. Ittel, L. K. Johnson, M. Brookhart, Chem. Rev. 2000 ,

100 , 116 9 –1 204; j) L. S. Boffa, B. M. Novak, Chem. Rev. 2000 , 100 ,

147 9 –1 493; k) G. J. P. Britovsek, V. C. Gibson, D. F. Wass, Angew.

Chem. 1999 , 111 , 44 8 –4 68; Angew. Chem. Int. Ed. 1999 , 38 , 42 8 –

447.

1996 , 118 , 1166 4 –1 1665; f) L. K. Johnson, C. M. Killian, M. Broo-

khart, J. Am. Chem. Soc. 1995 , 117 , 641 4 –6 415.

[16] a) E. F. McCord, S. J. McLain, L. T. J. Nelson, S. D. Ittel, D. Tempel,

C. M. Killian, L. K. Johnson, M. Brookhart, Macromolecules 2007 ,

40 , 41 0 –4 20; b) L. Zhang, M. Brookhart, P. S. White, Organometal-

lics 2006 , 25 , 186 8 –1 874; c) A. E. Cherian, J. M. Rose, E. B. Lobkov-

sky, G. W. Coates, J. Am. Chem. Soc. 2005 , 127 , 1377 0 –1 3771; d) W.

Liu, M. Brookhart, Organometallics 2004 , 23 , 609 9 –6 107; e) M. D.

Leatherman, S. A. Svejda, L. K. Johnson, M. Brookhart, J. Am.

Chem. Soc. 2003 , 125 , 306 8 –3 081; f) A. C. Gottfried, M. Brookhart,

Macromolecules 2003 , 36 , 308 5 –3 100; g) L. H. Shultz, D. J. Tempel,

M. Brookhart, J. Am. Chem. Soc. 2001 , 123 , 1153 9 –1 1555; h) L. H.

Shultz, M. Brookhart, Organometallics 2001 , 20 , 397 5 –3 982; i) A. C.

Gottfried, M. Brookhart, Macromolecules 2001 , 34 , 114 0 –1 142;

j) D. J. Tempel, L. K. Johnson, R. L. Huff, P. S. White, M. Brookhart,

J. Am. Chem. Soc. 2000 , 122 , 668 6 –6 700; k) S. A. Svejda, L. K.

Johnson, M. Brookhart, J. Am. Chem. Soc. 1999 , 121 , 1063 4 –1 0635;

l) Z. Guan, P. M. Cotts, E. F. McCord, S. J. McLain, Science 1999 ,

283 , 205 9 –2 062.

[17] M. P. Weberski, Jr., C. Chen, M. Delferro, C. Zuccaccia, A. Mac-

chioni, T. J. Marks, Organometallics 2012 , 31 , 377 3 –3 789.

[18] a) H.-J. Schneider, Chem. Sci. 2012 , 3 , 138 1 –1 394; b) E. D’Oria, J. J.

Novoa, CrystEngComm 2008, 10, 423–436; c) K. Reichenbacher,

H. I. Suss, J. Hulliger, Chem. Soc. Rev. 2005, 34, 22–30; d) I. Hyla-

Kryspin, G. Haufe, S. Grimme, Chem. Eur. J. 2004 , 10 , 341 1 –3 422;

e) G. R. Desiraju, Acc. Chem. Res. 2002 , 35 , 56 5 –5 73; f) J. Parsch,

J. W. Engels, J. Am. Chem. Soc. 2002 , 124 , 566 4 –5 672; g) L. Shimo-

ni, H. L. Carrell, J. P. Glusker, M. M. Coombs, J. Am. Chem. Soc.

1994 , 116 , 816 2 –8 168.

[12] a) D. Guironnet, I. Goettker-Schnetmann, S. Mecking, Macromole-

cules 2009 , 42 , 815 7 –8 164; b) D. Guironnet, T. Friedberger, S. Meck-

ing, Dalton Trans. 2009 , 892 9 –8 934; c) D. H. Camacho, Z. Guan,

Macromolecules 2005 , 38 , 254 4 –2 546; d) D. H. Camacho, E. V. Salo,

J. W. Ziller, Z. Guan, Angew. Chem. 2004 , 116 , 185 7 –1 861; Angew.

Chem. Int. Ed. 2004 , 43 , 182 1 –1 825; e) Z. Guan, Chem. Eur. J. 2002 ,

8 , 308 6 –3 0902; f) S. Mecking, Angew. Chem. 2001 , 113 , 55 0 –5 57;

Angew. Chem. Int. Ed. 2001 , 40 , 53 4 –5 40.

[19] a) L.-C. So, C.-C. Liu, M. C. W. Chan, J. C. Y. Lo, K.-H. Sze, N. Zhu,

Chem. Eur. J. 2012 , 18 , 56 5 –5 73; b) H. M. Mçller, M. C. Baier, S.

Mecking, E. P. Talsi, K. P. Bryliakov, Chem. Eur. J. 2012 , 18 , 84 8 –

856; c) M. C. W. Chan, Chem. Asian J. 2008 , 3 , 1 8 –2 7; d) M. C. W.

Chan, S. C. F. Kui, J. M. Cole, G. J. McIntyre, S. Matsui, N. Zhu, K.-

H. Tam, Chem. Eur. J. 2006 , 12 , 260 7 –2 619; e) S. C. F. Kui, N. Zhu,

M. C. W. Chan, Angew. Chem. 2003 , 115 , 166 6 –1 670; Angew. Chem.

Int. Ed. 2003 , 42 , 162 8 –1 632.

[13] a) B. M. Boardman, G. C. Bazan, Acc. Chem. Res. 2009 , 42 , 159 7 –

1606; b) K. C. Gupta, A. K. Sutar, Coord. Chem. Rev. 2008 , 252 ,

142 0 –1 450; c) P. Kuhn, D. Semeril, D. Matt, M. J. Chetcuti, P. Lutz,

Dalton Trans. 2007 , 51 5 –5 28; d) F. Speiser, P. Braunstein, L. Saus-

sine, Acc. Chem. Res. 2005 , 38 , 78 4 –7 93; e) J. Heinicke, N. Peulecke,

M. Koehler, M. He, W. Keim, J. Organomet. Chem. 2005 , 690 , 244 9 –

2457; f) P. Braunstein, J. Organomet. Chem. 2004 , 689 , 395 3 –3 967.

[14] a) C. S. Popeney, C. M. Levins, Z. Guan, Organometallics 2011 , 30 ,

243 2 –2 452; b) D.-P. Song, Y.-X. Wang, H.-L. Mu, B.-X. Li, Y.-S. Li,

Organometallics 2011 , 30 , 92 5 –9 34; c) M. Delferro, J. P. McInnis,

T. J. Marks, Organometallics 2010 , 29 , 504 0 –5 049; d) C. Chen, S.

Luo, R. F. Jordan, J. Am. Chem. Soc. 2010 , 132 , 527 3 –5 284; e) D. H.

Camacho, Z. Guan, Chem. Commun. 2010 , 46 , 787 9 –7 893; f) A.

Berkefeld, H. M. Mçller, S. Mecking, Organometallics 2009 , 28 ,

404 8 –4 055; g) A. Berkefeld, M. Drexler, H. M. Mçller, S. Mecking,

J. Am. Chem. Soc. 2009 , 131 , 1261 3 –1 2622; h) S. Noda, A. Naka-

mura, T. Kochi, L. W. Chung, K. Morokuma, K. Nozaki, J. Am.

Chem. Soc. 2009 , 131 , 1408 8 –1 4100; i) C. Chen, S. Luo, R. F. Jordan,

J. Am. Chem. Soc. 2008 , 130 , 1289 2 –1 2893; j) P. Wehrmann, S.

Mecking, Organometallics 2008 , 27 , 139 9 –1 408; k) D. H. Leung,

J. W. Ziller, Z. Guan, J. Am. Chem. Soc. 2008 , 130 , 753 8 –7 539; l) B.

Korthals, I. Goettker-Schnetmann, S. Mecking, Organometallics

2007 , 26 , 131 1 –1 316; m) C. S. Popeney, D. H. Camacho, Z. Guan, J.

Am. Chem. Soc. 2007 , 129 , 1006 2 –1 0063; n) S. Luo, R. F. Jordan, J.

Am. Chem. Soc. 2006 , 128 , 1207 2 –1 2073; o) P. Wehrmann, S. Meck-

ing, Macromolecules 2006 , 39 , 596 3 –5 964; p) S. R. Foley, R. A.

Stockland, H. Shen, R. F. Jordan, J. Am. Chem. Soc. 2003 , 125 ,

435 0 –4 361; q) E. F. Connor, T. R. Younkin, J. I. Henderson, S.

Hwang, R. H. Grubbs, W. P. Roberts, J. J. Litzau, J. Polym. Sci. Part

A 2002 , 40 , 284 2 –2 854.

[20] B. A. Rodriguez, M. Delferro, T. J. Marks, Organometallics 2008 , 27 ,

216 6 –2 168.

[21] T. Glaser, I. Liratzis, Synlett 2004 , 73 5 –7 37.

[22] D. Meinhard, M. Wegner, G. Kipiani, A. Hearley, P. Reuter, S.

Fischer, O. Marti, B. Rieger, J. Am. Chem. Soc. 2007 , 129 , 918 2 –

9191.

[23] The half-condensation of

terized by X-ray diffraction. Please see the Supporting Information.

[24] Solution of

(CF₃)H₂FI²is less susceptible to hydrolysis than

(CH₃)H₂FI².

(CH₃)H₂FI²has been structurally charac-

ACHTUNGTRENNUNG

AHCTUNGTRENNUNG

[25] a) E. Malamidou-Xenikaki, S. Spyroudis, M. Tsanakopoulou, H.

Krautscheid, J. Org. Chem. 2007 , 72 , 50 2 –5 08; b) J. J. Charette,

H. E. De, J. Org. Chem. 1979 , 44 , 225 6 –2 262.

[26] J. L. Burdett, M. T. Rogers, J. Am. Chem. Soc. 1964 , 86 , 210 5 –2 109.

[27] a) H. Tanak, J. Phys. Chem. A 2011, 115, 13865–13876; b) S. Guieu,

A. K. Crane, M. J. MacLachlan, Chem. Commun. 2011 , 47 , 116 9 –

1171; c) D. Nedeltcheva, L. Antonov, J. Phys. Org. Chem. 2009 , 22 ,

27 4 –2 81; d) T. Dziembowska, M. Szafran, A. Katrusiak, Z. Rozwa-

dowski, J. Mol. Struct. 2009 , 929 , 3 2 –4 2; e) S. H. Alarcon, A. C. Oli-

vieri, D. Sanz, R. M. Claramunt, J. Elguero, J. Mol. Struct. 2004, 705,

1–9; f) A. Hetenyi, Z. Szakonyi, K. D. Klika, K. Pihlaja, F. Fueloep,

J. Org. Chem. 2003, 68, 2175–2182.

[28] The presence of coordinated THF molecules was confirmed by

¹H NMR spectrscopy.

[29] H. F. Klein, H. H. Karsch, Chem. Ber. 1972 , 105 , 262 8 –2 636.

[30] A. Filarowski, A. Koll, L. Sobczyk, Curr. Org. Chem. 2009, 13, 172–

193.

[31] a) G. M. Battle, F. H. Allen, J. Chem. Educ. 2012 , 89 , 3 8 –4 4;

b) R. A. Sykes, P. McCabe, F. H. Allen, G. M. Battle, I. J. Bruno,

P. A. Wood, J. Appl. Crystallogr. 2011 , 44 , 88 2 –8 86; c) F. H. Allen,

R. Taylor, Chem. Soc. Rev. 2004 , 33 , 46 3 –4 75.

[15] a) M. D. Leatherman, M. Brookhart, Macromolecules 2001 , 34 ,

274 8 –2 750; b) D. P. Gates, S. A. Svejda, E. Onate, C. M. Killian,

L. K. Johnson, P. S. White, M. Brookhart, Macromolecules 2000 , 33 ,

232 0 –2 334; c) S. Mecking, L. K. Johnson, L. Wang, M. Brookhart, J.

Am. Chem. Soc. 1998 , 120 , 88 8 –8 99; d) L. K. Johnson, S. Mecking,

M. Brookhart, J. Am. Chem. Soc. 1996 , 118 , 26 7 –2 68; e) C. M. Kill-

ian, D. J. Tempel, L. K. Johnson, M. Brookhart, J. Am. Chem. Soc.

Chem. Eur. J. 2012, 00, 0 – 0

ꢂ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.chemeurj.org

&

17

&

ÞÞ

These are not the final page numbers!

M. Delferro, T. J. Marks et al.

[32] The average distances found in the Cambridge Crystallographic

tallics 2009 , 28 , 372 7 –3 733; c) T. S. Thakur, G. R. Desiraju, J. Mol.

Struc. Theochem. 2007 , 810 , 14 3 –1 54; d) Y. Liu, M. G. B. Drew, Y.

Liu, J. Mol. Struc. Theochem. 2007 , 821 , 3 0 –4 1; e) S. Collins, T. Zie-

gler, Organometallics 2007 , 26 , 661 2 –6 623; f) E. Kogut, A. Zeller,

T. H. Warren, T. Strassner, J. Am. Chem. Soc. 2004 , 126 , 1198 4 –

11994; g) T. Tomita, T. Takahama, M. Sugimoto, S. Sakaki, Organo-

metallics 2002 , 21 , 413 8 –4 146; h) L. Fan, A. Krzywicki, A. Somogy-

vari, T. Ziegler, Inorg. Chem. 1994 , 33 , 528 7 –5 294; i) N. Koga, S.

Obara, K. Kitaura, K. Morokuma, J. Am. Chem. Soc. 1985 , 107 ,

710 9 –7 116.

À

Data Centre (CDC, Feb. 2012) are: Ni O_phenol=1.911; Ni N_imine

=

À

1.981; Ni C_methyl=1.935; Ni P_phosphine=2.198; C=N_imine=1.295; C

O

_phenol=1.299 ꢀ.

[33] a) Q. Chen, J. Yu, J. Huang, Organometallics 2007 , 26 , 61 7 –6 25;

b) D. Zhang, G.-X. Jin, Inorg. Chem. Commun. 2006 , 9 , 132 2 –1 325;

c) S. Sujith, D. J. Joe, S. J. Na, Y. Park, C. H. Choi, B. Y. Lee, Macro-

molecules 2005, 38, 10027–10033; d) T. Hu, L. Tang, X. Li, Y. Li, N.

Hu, Organometallics 2005 , 24 , 262 8 –2 632; e) D. Zhang, G. Jin, Or-

ganometallics 2003 , 22 , 285 1 –2 584; f) K. Kurtev, A. Tomov, J. Mol.

Catal. 1994, 88, 141–150.

[44] a) P. H. M. Budzelaar, N. N. P. Moonen, R. de Gelder, J. M. M.

Smits, A. W. Gal, Eur. J. Inorg. Chem. 2000 , 75 3 –7 69; b) D. B.

Brown, M. Cripps, B. F. G. Johnson, C. M. Martin, D. Braga, F. Gre-

pioni, Chem. Commun. 1996 , 142 5 –1 426; c) M. Pasquali, C. Floria-

ni, A. Gaetani-Manfredotti, A. Chiesi-Villa, J. Am. Chem. Soc.

1978 , 100 , 491 8 –4 919.

[34] A. Bondi, J. Phys. Chem. 1964 , 68 , 44 1 –4 51.

[35] a) J. C. Jenkins, M. Brookhart, Organometallics 2003 , 22 , 25 0 –2 56;

b) W. Liu, D. G. Ray, P. L. Rinaldi, Macromolecules 1999 , 32 , 381 7 –

3819; c) M. De Pooter, P. B. Smith, K. K. Dohrer, K. F. Bennett,

M. D. Meadows, C. G. Smith, H. P. Schouwenaars, R. A. Geerards, J.

Appl. Polym. Sci. 1991 , 42 , 39 9 –4 08.

[45] M. D. Walter, R. A. Moorhouse, S. A. Urbin, P. S. White, M. Broo-

khart, J. Am. Chem. Soc. 2009 , 131 , 905 5 –9 069.

[36] See the Supporting Information.

[37] a) N. Osamu, M. Hideki, S. Ryosuke, K. Toyoji, S. Toshifumi, J.

Polym. Sci. Part A 2008, 46, 7411–7418; b) T. Hasan, T. Ikeda, T.

Shiono, Macromolecules 2004 , 37 , 850 3 –8 509.

[38] a) A. Berkefeld, S. Mecking, J. Am. Chem. Soc. 2009 , 131 , 156 5 –

1574; b) J. C. Jenkins, M. Brookhart, J. Am. Chem. Soc. 2004 , 126 ,

582 7 –5 842.

[39] a) B. L. Durfey, T. M. Gilbert, Inorg. Chem. 2011 , 50 , 787 1 –7 879;

b) G. C. Welch, T. Holtrichter-Roessmann, D. W. Stephan, Inorg.

Chem. 2008 , 47 , 190 4 –1 906; c) P. A. Chase, M. Parvez, W. E. Piers,

Acta Crystallogr. E 2006 , 62 , o518 1 –o 518 3; d) B. Y. Lee, X. Bu,

G. C. Bazan, Organometallics 2001 , 20 , 542 5 –5 431; e) G. S. Hair,

R. A. Jones, A. H. Cowley, V. Lynch, Organometallics 2001 , 20 , 17 7 –

181.

[46] See the Supporting Information.

[47] M. Peuckert, W. Keim, Organometallics 1983 , 2 , 59 4 –5 97.

[48] B. Akermark, J. Martin, J.-E. Nystrom, S. Stromberg, M. Svensson,

K. Zetterberg, M. Zuber, Organometallics 1998, 17, 5367–5373.

[49] a) L. Lavanant, A.-S. Rodrigues, E. Kirillov, J.-F. Carpentier, R. F.

Jordan, Organometallics 2008 , 27 , 210 7 –2 117; b) N. A. Cooley, S. M.

Green, D. F. Wass, K. Heslop, A. G. Orpen, P. G. Pringle, Organo-

metallics 2001 , 20 , 476 9 –4 771.

[50] The GPC traces of the polyethylenes obtained from the in situ reac-

tion of

ethylene fraction that grows in as polymerization times are in-

creased where

(CF₃)FI²-Ni₂is the catalyst, do not overlap. Presuma-

(CF₃)H₂FI²/Ni

ACHUTGTNRENNUG CAHTUNGTREN(NUGN COD)₂and the high molecular weight poly-

AHCTUNGTRENNUNG

bly this is due to difficulties in matching exact polymerization condi-

tions. Nevertheless, the observation that the in situ combination of

[40] W. A. Henderson, C. A. Streuli, J. Am. Chem. Soc. 1960 , 82 , 579 1 –

5794.

A

ACHTUNGTRENNUNG

[41] F.-G. Fontaine, M.-A. Dubois, D. Zargarian, Organometallics 2001 ,

20 , 515 6 –5 161.

[42] M. R. Radlauer, M. W. Day, T. Agapie, J. Am. Chem. Soc. 2012 , 134 ,

147 8 –1 481.

ACHTUNGTRENNUNG

[51] A. Altomere, M. C. Burla, G. Camilla, G. Cascarano, C. Giacovazzo,

A. Gualiardi, G. Polidori, J. Appl. Crystallogr. 1994, 27, 435.

[52] G. Sheldrick, Acta Crystallogr. A 2008 , 64 , 11 2 –1 22.

À

[43] For DFT calculations of the agostic C H···Ni interaction, see

a) M. E. Evans, T. Li, W. D. Jones, J. Am. Chem. Soc. 2010 , 132 ,

1627 8 –1 6284; b) M. P. Mitoraj, A. Michalak, T. Ziegler, Organome-

Received: March 2, 2012

Published online: && &&, 0000

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Bimetallic Nickel(II) Polymerization Catalysts

FULL PAPER

Ni-ce cats: Two neutrally charged

bimetallic phenoxyiminato Ni^IIethyl-

ene polymerization catalysts are

reported. Significant Ni···Ni coopera-

tive effects are evidenced by increased

product polyethylene branching in eth-

ylene homopolymerizations and by

enhanced norbornene co-monomer

incorporation selectivity in ethylene–

norbornene copolymerization than

monometallic controls.

Homogeneous Catalysis

M. P. Weberski, Jr., C. Chen,

M. Delferro,* T. J. Marks* .. &&&& — &&&&

Ligand Steric and Fluoroalkyl

Substituent Effects on Enchainment

Cooperativity and Stability in Bimet-

allic Nickel(II) Polymerization

AHCTUNGTRENNCGUN atalysts

Chem. Eur. J. 2012, 00, 0 – 0

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Article Doi

Ligand steric and fluoroalkyl substituent effects on enchainment cooperativity and stability in bimetallic nickel(II) polymerization catalysts

DOI: 10.1002/chem.201200713

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Article abstract of DOI:10.1002/chem.201200713

Full text of DOI:10.1002/chem.201200713

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