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Late Metal Catalysts

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Olefin Polymerizations Catalyzed by Late
Transition Metal Complexes
Maurice Brookhart
University of North Carolina
Polyolefins
P o lye th yle n e ,
CH2
P o lyp ro p yle n e , C H 3 C H
CH
CH2
CH2
CH2
P o ly styre n e ,
6 x 10
n
n
10
3 x 10
n
1 x 10
10
lb s /yr
lb s/yr
10
lb s /yr
Total : 100 billions / year
16lbs / person on Earth / year !
• Inexpensive monomers
• Little waste in production
• Attractive physical properties, long term stabilities
Polymer Microstructure — Key to Properties
Polypropylene
H 3C
iso ta ctic
H 3C
H 3C
H 3C
H 3C
H
H
H
H
H
Tm = 160В°C
Stereoregular
Tm = 165В°C
syn d io ta ctic
Completely amorphous
a ta ctic
Polyethylene
High Density PE (HDPE) Tm= 136В°C
Linear Low Density PE (LLDPE)
R
R
Tm = 115~130В°C
Low Density PE (LDPE) Tm= 105~115В°C
Polyolefins Primarily Produced via
Metal-Catalyzed Processes
Catalyst Structures Control:
— polymer microstructures
— polymer molecular weights, molecular weight distributions
— comonomer incorporation
Early Metal Catalysts (Ti, Zr, Cr)
iso ta ctic p o lyp ro p yle n e
syn d io ta ctic p o lyp ro p yle n e
a ta ctic p o lyp ro p yle n e
Late Metal Catalysts (Pd, Ni, Co)
O
O
O
O
a lte rn a tin g C O /
co p o lym e r
h ig h % crysta llin ity
Ph
Ph
Ph
syn d io ta ctic p o lystyre n e
Ph
Ph
Ph
o
Tm ~ 250 C
General Mechanism for Polymer Formation
In itia tio n
L nM
H
L nM
m ig ra to ry
H
L nM
in s e rtio n
C h a in G ro w th (R P )
L nM
m ig ra to ry
L nM
L nM
in se rtio n
e tc
C h a in tra n sfe r (R C T )
L nM
L nM
L nM
P
H H
P
пЃў -H
e lim .
+
L nM
L nM
P
H
H
ne w ch ain s ta rts
e tc.
LnM
R P > > R C T = > H ig h P o lym e r
R P ~ R C T = > S h o rt C h a in s (o lig o m e rs)
R P < R C T = > O n ly C 4
Olefin Polymerizations Using Late Metal
Catalysts (Ni, Pd)
Why Late Metals ?
1. Potentially different enchainment mechanisms =>
new microstructures
2. Less oxophilic — functional group compatible
G
G
G
But…
1. Normally lower insertion barriers
2. Chain transfer competitive with propagation =>
dimers, short chain oligomers
α–Diimine Based Catalysts
R
R
R'
A
R = H , M e , a ce n a p h th yl
R'
N
M
R'
i
N
H 3C
R ' = - P r, -M e , a ryl, h a lo g e n
R'
CF3
so lv.
A
=
B
4
M = N i, P d
CF3
в– High molecular weight polymers with unique microstructures from:
в—Џ ethylene
● α – olefins
в—Џ cyclopentene
в—Џ trans-1,2-disubstituted olefins
в– Copolymers of ethylene with certain polar vinyl monomers
Catalysts Modeled on α–Diimine Systems
R
N
R
Ph
Ar
R
N
N
N
P
M
X
R
Ar
M
X
R
R
M M AO
D a u g u lis, B ro o k h a rt
M = Fe, C o
B e n n e tt
S m a ll, B ro o k h a rt
G ib s o n
R
R
N
N
M
R
G
R
M = N i, P d
R
R
R
N
N
N
N
N
O
Ni
R
G ru b b s
J o h n s o n (D u P o n t)
R
R
M
R
M = N i, P d
N
O
K illia n (E a s tm a n )
Ni
R
H ic k s , J e n k in s , B ro o k h a rt
Polyethylene
lin e a r P E
n
E a rly M e ta l C a ta ly sts
se m ic rysta llin e
H ig h D e n sity P E , H D P E
T m ~ 1 3 6 В°C
T i (IV ), Z r (IV ), C r/S iO 2
1 -1 0 % in c o rp o ra tio n , L L D P E
o
R
R
R
Tm = ~ 115 - 130 C
+
M n > 10
R
a m o rp h o u s P E
R
N
N
Pd
R
h yp e rb ra n ch e d ,
R
S o lv
R'
5
3 0 В°C
~ 5 0 0 T O /h r
~ 1 0 0 b ra n ch e s / 1 0 0 0 C 's
5
M n 10 - 10
R
Tm: 25В° - 135В° C
R
N
N
Ni
R
R
3 0 В°C
6
Br
Br
/ E t 2 A lC l
6
~ 1 -3 x 1 0 T O /h r
5 - 8 0 b ra n ch e s / 1 0 0 0 C 's
in cre a sin g [C 2 H 4 ] d e cre a se s b ra n ch in g
in cre a sin g T in c re a se s b ra n ch in g
Poly (α–Olefins)
E a rly M e ta l C a ta lysts
R
1 ,2 -in se rtio n
R
R
R
R
R
R
+
"ch a in -stra ig h te n e d " (1 , 3 e n ch a in m e n t)
Ar
N
N
Ar
M
c h a in -stra ig h te n e d , p rim a rily C 1 , C 4 b ra n c h e s
(1 ,6 e n ch a in m e n t)
1,2–Disubstituted Olefins
cis-1 ,3 e n ch a in m e n t
R
Ar
R
N
+
A-
N Ar
M
X
Y
ch a in
stra ig h te n in g
1 ,3 in se rtio n
Mechanistic Studies
Generation of Cationic Alkyl Complexes
R
R
R
N
X
M
N
X
R
2 R 'M g X
N
M = Pd
sta b le a t 2 5 В°C
CH3
M
N
CH3
M = Ni
sta b le o n ly b e lo w
ca . -2 0 В°C
R ' = -C H 3
-C H 2 C H 3
-C H 2 C H 2 C H 3
-C H 2 C H (C H 3 ) 2
N
CH3
M
N
CH3
H (O E t 2 ) 2
+
E t2 0
B A r' 4
-
+
N
CH3
M
N
O E t2
B A r' 4
-
1H, 13C
NMR Studies – Pd(II)
+
Ar
Me
N
N
Me
N
C 2 H 4 (e xce s s)
Pd
+
Ar
Pd
C D 2 C l2
O E t2
-8 0 В°C
Ar
N
Ar
-3 0 В°C
k1
+
Ar
p o ly
N
N
Pd
N
Ar
c a ta ly s t
re s tin g sta te
+
Ar
Pd
k p , -3 0 В°C
N
Ar
Insertion Kinetics – Ni(II)
+
Ar
N
Ni
C D C l2 F
O E t2
Ar
+
Ar
Pr
N
-7 0 В°C
R
N
Ni
Ar
+
Ar
Ni
k su b . in se rt.
N
Ar
-8 0 В°C
k 1 st in se rtio n
N
Ar
N
Me
N
2 . -1 1 0 В°C
Ni
+
Ar
-1 3 0 В°C
Me
N
1. 20 eq C 2H 4
Activation Barriers to Insertion (ethylene)
пЃ„G
(1 st in se rtio n )
пЃ„G
(su b se q . in se rtio n s)
+
Me
N
o
1 3 .6 kca l/m o l (-8 1 C )
Ni
o
1 4 .0 kca l/m o l (-7 2 C )
N
+
N
Me
o
Pd
1 8 .4 kca l/m o l (-2 0 C )
N
пЃ„пЃ„G
‡
o
1 8 .6 kca l/m o l (-2 0 C )
(P d -N i) ca . 5 kca l/m o l
Mechanistic Model
in se rtio n
in se rtio n
R'
N
N
R
R
M
M
N
N
M
N
m e th yl b ra n ch
re stin g sta te
N
e th yl b ra n ch
tu rn o ve rlim itin g
R
N
R
N
M
N
R
M
N
H
N
R'
N
M
N
M
N
"ch a in ru n n in g "
Blocking of Axial Coordination Sites
Chain Transfer Mechanisms
(1 ) A s s o c ia tiv e D is p la c e m e n t (re ta rd e d b y b lo c k in g a x ia l p o s tio n s )
N
N
N
M
N
+
R
M
H
H
R
(2 ) C h a in T ra n s fe r to M o n o m e r (s u g g e s te d b y Z ie g le r c a lc u la tio n s )
H 3C
N
N
Ni
Ni
H 3C
N
H 3C
N
N
H
Ni
H 3C
N
Mechanistic Model
in se rtio n
in se rtio n
R'
N
N
R
R
M
M
N
N
M
N
m e th yl b ra n ch
re stin g sta te
N
e th yl b ra n ch
tu rn o ve rlim itin g
R
N
R
N
M
N
R
M
N
H
N
R'
N
M
N
M
N
"ch a in ru n n in g "
Formation of Agostic Ethyl Complex
B A r' 4
H (O iP r 2 ) 2 B A r' 4
N
Pd
C D C l 2 F , -8 0
N
o
C
C H 3C H 3
1
13
Hc
Hc
C
2
t, J H H = 1 6 H z
1
JCH = 67 H z
C пЃ¤ 3 8 .5 p p m
JCH = 153 Hz
Hb
C
Pd
пЃ¤ -8 .9 p p m
1
H пЃ¤ пЂ 2 .2 p p m
Hb
Ha
1
13
1
H пЃ¤ пЂ 1 .4 p p m
C пЃ¤ 1 9 .3 p p m
JCH = 155 H z
N
Pd
N
H
(-1 3 0
o
C)
Dynamics of Agostic Ethyl Complex
Hc
N
Hc
*
Pd
N
Hb
N
HпЃЎ
= 7 .1 k c a l/m o l
HпЃў
Ni
HпЃў
N
HпЃў
-1
k = 1 7 0 s , 1 6 В°C
пЃ„G
‡
HпЃЎ
Ni
Ni
HпЃў
HпЃў
N
N
HпЃў
Hc
C
HпЃЎ
N
N
o
Hc
Ha
N
Ha
-1
‡
*
Pd
k = 1 4 5 0 s , -1 0 8
пЃ„G
Hb
N
Pd
Hb
Ha
N
Hb
*
= 1 4 .0 k c a l/m o l
N
HпЃЎ
HпЃў
Cationic Metal Alkyl Intermediates –
Ethylene Trapping Experiments
N
+
H (O E t 2 ) 2 B A r' 4
Pd
-
N
N
Pd
-8 0 В°C
N
N
Pd
H
1
N
-6 5 В°C
20
N
(via re ve rs ib le
Pd
Pd
-8 0 В°C
N
N
1
H
N
20
-2 5 В°C
in s e rtio n
(se ve ra l 1 0 0 1 ,2 sh ifts p rio r to in se rtio n )
lo s s o f C 2 H 4 )
Cationic Metal Alkyl Intermediates –
Ethylene Trapping Experiments
N
N
Ni
N
X
Ni
N
-8 0 В°C
-8 0 В°C
N
N
Ni
N
Ni
N
e tc .
e tc .
n o e q u ilib ra tio n
p rio r to in s e rtio n
Mechanistic Model
in se rtio n
in se rtio n
R'
N
N
R
R
M
M
N
N
M
N
m e th yl b ra n ch
re stin g sta te
N
e th yl b ra n ch
tu rn o ve rlim itin g
R
N
R
N
M
N
R
M
H
N
H
N
R'
N
M
N
M
H
N
H
"ch a in ru n n in g "
Commercial Copolymers of Ethylene and Polar
Vinyl Monomers
в—Џ Radical Initiation
в—Џ High temperatures, very high ethylene pressure
C O 2M e
O Ac
C O 2B u
CN
C O 2H
C O 2H
S i(O M e ) 3
Examination of Pd and Ni Diimine Catalysts for
Copolymerizations of Ethylene and:
OR
1.
O
O
2.
O
R
OR
3.
Si
OR
OR
Problems Connected with
G
Copolymerization
1. Monomer Binding through the Functional Group
R
L
M
R
L
+
M
G
L
L
G
2. ОІ-Elimination of G
R
L
M
L
R
L
L
M
M
G
L
R
G
L
G
3. Weak Competitive Binding of
R
L
G
M
M
+
L
R
L
+
L
G
G
K >> 1
4. Strong Chelate Formation Following Insertion
R
L
L
in sertion
M
L
G
iso m erizatio n
L
M
L
G
M
L
G
K << 1
5. High Barrier to Insertion of Open Chelate
G
L
M
G
R
L
in s e rtio n
M
s lo w
‡
R
пЃ„G1
R
пЃ„G2
L
L
L
M
R
L
in se rtio n
M
fa s t
L
L
пЃ„G1
‡
>
пЃ„G2
‡
‡
Examples: G = -CN ; -Br, -Cl
CH3
N
CN
CH3
N
Pd
Pd
N
N
O E t2
NC
Itte l, J o h n so n , B ro o kh a rt, C h e m . R e v . 2 0 0 0
CH3
N
X = B r, C l
N
Pd
Pd
N
X
S e n , e t. a l. 2 0 0 2
Jo rd a n , e t. a l. 2 0 0 3
N
N
пЃў пЂ­ e lim пЂ®
Pd
X
N
N
X
X
Pd
N
N
Pd
X
N
2+
Ethylene / Acrylate Copolymerization - Pd
C O 2C H 3
CH3
N
o
Pd
C H 2 C l2 , T = 3 5 C
N
NCCH3
P (C 2 H 4 ) = 2 a tm
M A = 2 5 v o l%
C O 2C H 3
T O F = ca . 1 0 0 T O /h (slo w !)
B ra n ch e d C o p o lym e r
6 m o l% M A in co rp o ra tio n
1 0 3 b ra n ch e s/1 0 0 0 C
M e th yl A c ry la te In se rtio n
O
OCH3
o
N
-8 0 C
Pd
N
CH3
2 ,1 -in se rtio n
O
N
o
-6 0 C
Pd
OCH3
N
OCH3
O
N
Pd
N
O
N
Pd
N
o
-3 0 C
OCH3
Mechanism of Copolymerization
O
OCH3
2 ,1 -in s.
пЃ„G
‡
= 1 6 kca l/m o l
N
N
O
+ C 2H 4
N
-C 2 H 4
N
Pd
Pd
N
OCH3
P
re a rra n g e m e n t
Pd
N
K ~ 0 .0 2 M
P
re stin g sta te
O
-1
P
OCH3
2 5 В°C
in se rtio n
N
пЃ„G
Pd
ch a in g ro w th
N
O
ch a in ru n n in g
P
OCH3
‡
~ 1 8 kca l/m o l
Examination of Pd and Ni Diimine Catalysts for
Copolymerizations of Ethylene and:
OR
1.
O
O
2.
O
R
OR
3.
Si
OR
OR
Ethylene / Alkoxy Vinyl Silane Copolymers
Versipol Group - DuPont
R'
ra n d o m co p o lym e r
R'
S i(O R ) x R 'y
R ''
N
N
M
R' R
/
lin e a r to h ig h ly b ra n ch e d
R ''
2 5 - 1 2 0 В°C
L R'
u p to 3 2 m o l%
co m o n o m e r in co rp o ra tio n
P E co p o lym e r
6 0 0 p si C 2 H 4 , 6 0 В°C
N
M e 3S i
1 0 M e b ra n ch e s / 1 0 0 0 C
N
Ni
S iM e 3
0 .4 2 m o l% sila n e
5 vo l%
S i(O E t) 3
to lu e n e
5 e q . B (C 6 F 5 ) 3
5 e q . L iB (C 6 F 5 ) 4
T m = 1 2 1 В°C
M n = 2 5 .5 K , M w /M n = 2 .9
1 1 0 kg P E / g m N i
Vinyl Alkoxy Silane Insertion Chemistry -
N
N
Ni
Me
O E t2
S i(O E t)(M e ) 2
C D 2 C l2
-6 0 В°C
2
n o пЃЁ -a lke n e
c o m p le x e s
o b se rv e d
N
N
S i(O E t)(M e ) 2
N
Ni
N
Ni
O
O
Si
Et
15%
2 ,1 in se rtio n
Et
Si
85%
1 ,2 in se rtio n
Evidence for Reversible C2H4 Coordination
N
N
N
Ni
+ C 2H 4
O
Et
N
Ni
C D C l2 F
Si
пЃ¤ 4 .5 9
пЃ¤ 3 .9 6
E tO
Si
K e q c a . 0 .0 3 5 M
-1
, -1 2 0 В°C
пЃ¤ 4 .6 8
пЃ¤ 3 .7 3
Advantages of Vinyl Alkoxy Silane
Comonomers
1. Insertion barriers of vinyl alkoxy silanes into Pd-R and
Ni-R bonds are similar to ethylene insertion barriers.
2. Chelates resulting from vinyl alkoxy silane insertions
are readily opened with ethylene.
3. Open chelates readily insert ethylene.
4. Relative binding affinities favor ethylene, but not to a
prohibitive extent.
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