Molecular Properties

243 Pages·1977·5.075 MB·English

by  Eishun Tsuchida, Hiroyuki Nishide (auth.)

Contents
Polymer-Metal Complexes and Their
Catalytic Activity
E. ADIHCUST and H. EDIHSIN
Strain Energy Density Functions of
Rubber Vulcanizates from Biaxial Extension
.S ATABAWAK and H. IAWAK 98
ESCA Applied to Polymers
D. T. KRALC 521
Polymer Separation and Characterization
by Thin-Layer Chromatography
H. IKAGANI 981
Author Index Volumes 1-24 239
Polymer-Metal Complexes and TChaetiarl ytic
Activity
Eishun Tsuchida and Hiroyuki Nishide
Department of University, Waseda Chemistry, Polymer Tokyo 160, Japan
Table of stnetnoC
I. Introduction . . . . . . . . . . . . . . . . . . . . 2
II. Formation and Structure of Pendant.Type Polymer-Metal Complexes 7
A. Pendant-Type Polymer-Co(III) and -Cr(IIIC)o mplexes . . . . . 7
B. Structures of Polymer-Heme Complexes . . . . . . . . . . 14
C. Polymerization of Coordinated Monomer . . . . . . . . . . 21
HI. Formation and Stability of Polymer Chelates . . . . . . . . . 24
A. Formation and Stability of Intra-Polymer Chelates of Cu(II) 24
B. Complexation of Metal Ions on Crosslinked Polymer Ligands 30
C. Resolution of a-Amino Acidsby Chiral Polymer Complexes 36
IV. Reactivity of Polymer-Co(Ill) Complexes . . . . . . . . . . 38
A. Electrostatic Effect of Polymer-Co(III) Complexes . . . . . . . 39
B. Hydrophobic Interaction . . . . . . . . . . . . . . . 43
C. Influence of Conformational Change of Ligand Chain. . . . . . 44
V. Reaction of Polymer-Heine Complexes with Molecular Oxygen. 45
A. Oxygenation of Polymer-Heme Complexes . . . . . . . . . 46
B. Immobilization of Heine on Polymer Matrixes . . . . . . . . 49
C. Pseudo-Allosteric Effect of Poly(L-lysine) Heme Complex . . . . 55
VI. ReactionsC atalyzed by Polymer-Metal Complexes . . . . . . . . 60
A. Oxidative Reactions . . . . . . . . . . . . . . . . . 61
B. Reductive Reactions . . . . . . . . . . . . . . . . . 63
C. Hydrolysis . . . . . . . . . . . . . . . . . . . . 65
VII. Phenol Oxidation Catalyzed by Polymer-Cu Complexes . . . . . . 66
A. Oxidative Polymerization Catalyzed by Polymer.Cu Complexes 67
B. Elementary Reactions of Phenol Oxidation . . . . . . . . . 71
C. Coordination Step of Substrate to Polymer-Cu Catalysts . . . . . 73
D. Effects of Polymer Ligands on the Electron.Transfer Step . . . . 75
VIII. Conclusion and Further Studies . . . . . . . . . . . . . . 82
IX. References . . . . . . . . . . . . . . . . . . . . . 84
2 E. Tsuchida and H. Nishide
1. Introduction
A polymer-metal complex is composed of a synthetic polymer and metal ions. Its
synthesis represents an attempt to give an organic polymer inorganic functions.
Catalytically active polymers can be obtained by inducing a metal complex to cata-
lyze a reaction with a polymer backbone, and it is reasonable to assume that the
metal complex bound to the polymer will show a specific type of catalytic behav-
ior, reflecting the properties of the polymer chain. Indeed, many synthetic polymer-
metal complexes have been found to exhibit high catalytic efficiency. On the other
hand, it has been shown that in metalloenzymes such as oxidase and hemoglobin,
where a metal complex is the active site, the macromolecular protein part plays a
significant role, or even controls the reactivity of the metal complex. Thus, research
on the catalytic activity of polymer-metal complexes has attracted considerable
interest, which has increased in recent years.
A wide variety of investigations have been carried out on polymeric metal com-
plexes; these include studies of semiconductivity, thermostability, redox reactions,
collection of metal ions, biomedical effects, and so on. The polymeric metal com-
plexes are classified into the following groups:
(A) polymer-metal complexes
f I I I I I
/ ..L L.. L .-L L..
I I 1 I l / ...- -" .
L L L L L + M ~ r M "M Schemel
,, "L L" L ""L "L
"-- I I I I I
I I I I I
1 I I l I L......L L L......"L
L L L L L + M ~ M" M Scheme 2
/ L ":'L L / L "L
1 i ! I l .............
(B) coordinate polymers
i i 1
, , LrL L ¢L\
f-L-,~ rE-,, /-L-N + M ~ L : L :: ...... -- Scheme3
L L L L L L M M"' M"
I [ I I I
I I 1 [ [ L L L L L
L L L L L + ('~ ----"~" ~M~ : Q~.~: : 4 Scheme
I I I I i
L L L L L L
! = : : : : : Scheme 5
L L ..-L. N fL. .... .--L. N fL. .... --L N fL. .... .
6 Scheme
L~---~L + M -''--4~ :..Lfl'------~E.M..~L.~--'~E..M..L.~-~E.M. '
lateM-remyloP sexelpmoC dna Activity Catalytic Their 3
(C) poly(metal-phthalocyanine) type
I I I I I I I I
--.L L L .......... L -L--L L--L
I J l
+ M or L' + M "'""~:"-~'"i;'" ....""t:'" "M "M"" ""M"' ""t:: "'M"" "" emehcS 7
--'L L ....L .......... L
1 I t I 1 I I I
L = coordinating atom or group; M = metal ion
Polymer-metal complexes, represented by Schemes 1 to 5, are defined as com-
plexes composed of a polymer ligand and metal ions in which the metal ions are
attached to the polymer ligand by a coordinate bond. Here a polymer ligand is un-
derstood to be a polymeric substance that contains coordinating groups or atoms
(mainly N, O, and S), obtained by the polymerization of monomers containing co-
ordinating sites, or by the chemical reaction between a polymer and a low-molecu-
lar-weight compound having coordinating ability. Typical polymer ligands previously
reported are listed in Table I. When a polymer ligand is mixed directly with a metal
ion, which generally has four or six coordinate bonding hands, a polymer-metal
complex is formed. This may be of the intra-polymer chelate type (Scheme 1) or of
the inter-polymer chelate type (Scheme 2). Complex formation proceeds via
Scheme 3, where the polymer backbone contains multidentate ligands, such as the
iminodiacetic acid group, or acts as a carrier for low-molecular-weight mu!tidentate
ligands; many so-called chelating resins fit this scheme. The polymer-metal com-
plexes represented by Schemes 1 to 3 have chelating structures in their polymer
ligands and are therefore called polymer chelates. The pendant-type polymer-metal
complex( Scheme 4) is formed by the reaction of a polymer ligand with a stable
metal complex, the central metal ion of which has already been masked with low-
molecular-weight ligands except for one coordinate site that remainvsa cant, .g.e
metalloporphyrins, or cobaltic chelates. A polymer-metal complex is also obtained
by polymerizing a monomeric metal complex (Scheme 5).
Scheme 6 represents polymers. coordinate A low.molecular-weight compound
with multidentate groups on both ends of the molecule grows into a linear polymer
with metal ions, and the polymer chain is composed of coordinate bonds. The par.
quetlike polymer complexes, poly(metal-phthalocyanine) and poly(metal-tetracyano-
ethylene), are classified into Scheme 7. They are formed by inserting metal ions into
planar-network polymerso r by causing a low.molecular-weight ligand derivative to
react with a metal salt and a condensation reagent.
This article deals with the polymer-metal complexes (Schemes 1-5), because
they have the following merits in comparison with other polymeric metal complexes.
.)i( Metal ion and ligand site can be chosen for study without restrictions. (ii) It is not
difficult to control the molecular weight of a polymer complex and to modify the
structure of a polymer ligand(.i ii) The polymerc omplex si soluble in both aqueous
and nonaqueous solvent. (iv) It possible is to change the ratio of the organic polymer
part to the inorganic metal complex part. This explains why the polymer often af-
fects the behavior of the metal complex.
3
~_~
I (CH2)4 1 NH 2 ~_~ C--C--CH II El
-NH-CH-CO- ' N--OH
--CH2--CH-- HO--N
~_~
! CH2 I NR2 CH-- I
--cHeerio-- --CHz--CH-- ~ ~_o~:_~ © =CH HO --CH ........... I COOH COOH
--CO-- _~_~_
--CH2--CH--
CH2NHCH2CH~NR2 ~ R i C- I COOH
ligands --CH~--¢H-- --NH--CHcH2[
~CH2--
polymer
of _~_ HO N
units -- 2-
NH9 © -°H CH=N OH
ligands Repeating --CH2--CH 1 -- NHCH2CH --CH~--CH-- -C~ --CH2--CH--
polymer
groups
Typical ~NH, ~N of -OH
1. base
2,
Table Coordinating Amines -NH Nitrogen heterocyclic compounds Schiff ~C=N- Alcohols carboxylic acids -COOH
o o
I OH
I C--NH II O , C=S I
--NH--N-- --NH--N--
--N--CH2--CH2--
CH2COOH
--CH2--CH-- I O I C=O ' I SH
2 I SH
--CH2--CH-- 2
' O I CH2--CH--CH2
"N(CH2COOH)
II 2
0 N(CH2COOH)2 "~ CH I O-CH2PO(OH) CH2 I
--R--C--CH2--C--R-- II O -- CH2 -- CH2~ --CH2--CH-- ~) CH2--SH
3 --CH2--CH--
--CH
II
O
--CH2--C
R I I C II O CH2N(CH2COOH)~ I SH
© O=P(Ott)2
--CH2--C-- --CH2--CH-- --CH2--CH-- --CH2--CH--
acids
2
amides
~C=O
Ketones esters, Aminopoly- carboxylic acids Phosphonic -PO(OH) Thiols -SH
6 .E adihcusT dna .H edihsiN
It is the purpose of this article to discuss whether or not there are any differ-
ences betweent he chemical reactivity of a polymer-metal complex and that of the
corresponding monomeric complex. Although various extensive investigations on
polymer-metaclo mplexes have been reported, most of these complexes are too
complicated to be discussed quantitatively due to the nonuniformity of their struc-
ture. These compounds include not only "complexes of macromolecules" but also
the structurally labile "metal complex". Before detailed information can be obtained
about the properties of polymer-metal complexes, and especially about the reactivity
and catalytic activity of polymer-metal complexes, their structure must be elucidated.
A polymer-metal complex having a uniform structure may be defined as follows;
(i) the structure within the coordination sphere is uniform, i.e. the species and the
composition of the ligand and its configuration are identical in any complex unit
existing in the polymer-metal complex;
(ii) the primary structure of the polymer ligand is known.
If the structure within the coordination sphere is identical in a polymer complex
and a monomeric complex, their reactivity ought to be the same even though the
complex is bound to a polymer chain. However, it is clear that the reactivity is some-
times strongly affected by the polymer ligand that exists outside the coordination
sphere and surrounds the metal complex. The effects of polymer ligands will be dis-
cussed in the text under the following two terms: (1) the steric effect, which is
determined by the conformation and density of the polymer-ligand chain, and (2)
the special environment constituted by a polymer-liganddo main. To illustrate these
effects, the followinqgu estions will be discussed:
(i) When metal complexes attach to a polymer ligand at high concentrations, are
the stability and the reactivity of the complexes changed?
(ii) In a rigid polymer do the attached metal complexes, at low concentrations,
behave virtually as in a solution at infinite dilution?
(iii) A polymer ligandi n solution may be extended or densely coiled up, or
sometimes helically structured. Does the conformation of the ligand chain influence
the reactivity?
(iv) Are there any differences between the chelate formation of a polymer-ligand
chain and that of the individual monomeric ligand?
(v) Because polymer-metal complexes are poly(electrolyte)s, an electrostatic
effect is predominant in the reactions of ionic species.
(vi) A metal complex in an aqueous solution may be occluded by a hydrophobic
polymer matrix, and this hydrophobic microenvironment affects reactivity.
These discussions will embrace homogeneous solutions of polymer-metal com-
plexes. Of course one of the important advantages offered by the use of a polymer
ligand, especially a crosslinked polymer ligand, in catalysis is the insolubilization of the
attached complexes; the insolubility of the polymer catalyst makes it verye asy to
separate from the other components of the reaction mixture. Several polymer-metal
complexes have been used for this purpose, although such applications are not cov-
ered in this article. The aim here is (1) to characterize polymer-metal complexes
and their behavior in such simple but important elementary reactions as complex
formation, ligand substitution, and electron transfer, and (2) to describe their cata-
lytic activity.
Polymer-Metal Complexes and Their Catalytic Activity 7
II. Formation and Structure of Pendant-Type Polymer-Metal Complexes
Examples of the pendant-type polymer-metal complexes represented by Schemes
4 and 5 are shown in Table 2. They are obtained by the reactioni n Scheme 8:
a polymer ligand is made to coordinate to a vacant site of a previously prepared,
stable, low-molecular-weight metal complex. The structure and hence the functions
of the metal complex are hardly changed by attachment to the polymer ligand. The
metal complexes attached to the polymer ligands I to 8 are the classic cobaltic
E
E = Elimination-ligand (weak ligand)
chelates 9-13, paramagnetic chromic chelate ,41 metalloporphyrin ,51 which reacts
with molecular oxygen, metal-chlorophyllin ,61 which si a derivative of chlorophyll,
and so on. In Scheme 8, the degree of coordination (x) means the molar ratio [metal
complex]/[repeating unit of polymer tigand]. If all the ligands in the polymer are
coordinated to M, the value ofx becomes unity.
A. Pendant-type Polymer-Co( I I I) and -Cr( I II) Complexes
We prepared a series of pendant-type polymer-metal complexes having a uniform
structure by the substitution reaction between a polymer ligand and a Co(Ill) or
Cr(III) chelate, the chelate being inert in ligand-substitutiorne actions '1 .)2 A poly-
mer-Co(Ill) complex, .g.e 21C]1C)PVP(z)ne(oC[-sic (en=ethylenediamine, PVP=
poly(4-vinylpyridine)) 17, was prepared as follows1):
CH--CHz
X = ;1C Br, or N3
N N : ethylenediamine
x 71
An aqueous solution of 21C2)ne(oC[-sic 1C] was added to an ethanolic solution of
PVP and the mixture heated. After a few hours the mixture was filtered and dia-
8 .E adihcusT dna .H edihsiN
Table .2 complexes polymer-metal Pendant-type
HC 2~"" ILC--I """x_-feHC-H
""/ L~ H
Polymer dnagil L] lateM complex M__~__/ ,~2._
H2
-HC-2HC- H cx--N~-b- 1C;7
V / ,'
Co +2
PVP 1 Hql~F--~/--N~C2H 2. CI- 2
H 2 H HC,c,N2 2
2H
-CH2-CH- H c'IN~s 1C;7--~
I 2H /~2 / +2rC /
IVNP 2 9 H~/'-~-~I'--"L~-'q/~'C~H 2 2 -1C
21-1 / I
2H HC,c,N2H 2
H _-~N'-'C: F ~:-;f t 2H
-CH2-~H- / _Co( ,
2HN--r-C~-N.~C2H 2 -1C 14
N IVMP 3 ~ I 1 H k
3HCLNN~I H U,C,N/C,"C2 2
2H 2H
H~_~HC- -
IVP 4
N~,,NH
C3H t /CH3
/C-O-<-t'--;O=C
-CH2-CH- HC "> ,'_..Co."-/ .2SH 15
/C=O~__.r~0_C. /
SAP 5 C3H HCk 3
NO 2
HN 2 11 2HC=HC .C 3H
HC_2HCN_ 2_ H a C ~ sH2C
H IEPL 6 C3H ~O--H-O ~HC
~"N~ -~,'~tC/ H ~ C H ~
I .~oC~...', , ~ 3HC
/C~lq .... ,L~N~--~-
1-2HC-2HCN-2HC-2HC'N- H C3H ()-H'~'O" 3HC ~H~ ~H 2 COONa
2HC 1C ~
I IEPB 2H COONa
2HC 7 12
I aNOOC
2HN
16
3H C /CH3
~c-o=---I-->o-c
-NH-CH-CO-
-~OIC
I n c/c=N~ .... ~C=N'~-F
(~H2)4 LLP 8 3 H~2HC 2 3HC
!
~HN 2HO
13
Polymer-Metal Complexes and Their Catalytic Activity 9
lyzed in cold water, then, after the water had evaporated, the PVP-Co(III) com-
plex was obtained as a transparent, dark-reddish filmy substance. The polymer com-
plex, 21C]1C)PVP(2)ne(oC[ 17, had one bivalent cation per complex repeating unit
and was water-soluble, regardless of the solubility of the polymer ligand.
Co(Ill) and Cr(III) chelates are inert in ligand-substitution reactions, sow e
considered that complex formation between a polymer ligand and the Co(III) or
Cr(III) chelate would be irreversible under the applied experimental conditions .)2
This assumption was supported by the fact that the degree of coordination (x) did
not decrease either during the reaction time or during the purification of the poly-
mer complexesa nd that no degradation product from the polymer-Co(Ill) com-
plexes could be found. Figure 1 shows the formation curves of the polymer-Co(Ill)
@
O O-.-- "O'-
.~ 0.5
.-,O,---
0 0 2 4 6 /f 4~2
Time (h)
Fig. 1. Complex formation curves for polymer-Co(III) and -Cr(III) complexes 1-5)
o: [Co(acac)2(PVP)(NO2)I, o: [Co(en)2(BPEI)CIlC12, ®: [Cr(en)2(PVP)CIICI2,
e: [Co(en)2(PVP)CI]C12, (cid:127): [Co(en)2(QPVP)C1]CI2(-R = -CH3) , m: [Co(en)2(QPVP)C12
(-R = -CH2C6Hs), m: [Co(en)2(PAS)CI]C12, PVP -- poly(4-vinylpyridine), BPEI = branched
poly(ethyleneimine), QPVP = partially quaternized PVP, PAS = poly(p-aminostyrene),
acac = acetylacetone, en = ethylenediamine, 80 ~C
and polymer-Cr(III) complexes, i.e. the variation ofx with time l-s). The initial
rates of complexation for [Co(acac)2(PVP)(NO2)] (acac=acetylacetone) 11, for
21C]1C)PVP(z)ne(rC[ 14, and for 21C]1C)IEPB(2)ne(oC[ (BPEI = branched
poly(ethyleneimine) = 7), 9 are larger than those for the other complexes under the
same conditions. These differences are attributed to the relatively high ligand sub-
stitution activity of the acac chelate and the Cr(III) chelate and to the higher basic-
ity of BPEI as compared to PVP and PAS(pots(p-aminostyrene) = 5). Complexation
of PVP of a lower degree of polymerization proceeds more easily ,)1 and the com-
plexation rate for partially alkylated poly(4-vinylpyridine) (QPVP) 18 is
-R = -H >3 -CH3 > -CH2C6Hs, as shown in Fig. .1 These findings are interpreted
as due to the steric hindrance of the polymer ligands .)3