Books
in black and white
Main menu
Share a book About us Home
Books
Biology Business Chemistry Computers Culture Economics Fiction Games Guide History Management Mathematical Medicine Mental Fitnes Physics Psychology Scince Sport Technics
Ads

The porphyrin handbook - Kadish K.M.

Kadish K.M. The porphyrin handbook - Academic press, 2000. - 368 p.
Download (direct link): kadishsmishgulilard2000.djvu
Previous << 1 .. 82 83 84 85 86 87 < 88 > 89 90 91 92 93 94 .. 240 >> Next

as initiator for the polymerization of 1,2-epoxypropane (11, R = Me)
allows formation of a tailored polyether with a polymerizable (styryl)
end group (27).31
In relation to the polymerization of epoxides, Amass et al. have
reported that lc, at a high temperature such as 60C, can also bring
about anionic polymerization of
140
Aida and Inoue
/- / W
^ m n
[11 (R = H)M1c]0
Figure 4. Polymerization of epoxyethane (11, R = H) initiated with
chloroaluminum tetraphenylporphyrin (1c) in CH2CI2 at room temperature.
Relationship between molecular weight (Mn; O), molecular-weight
distribution (/Ww/Mn; #), and feed mole ratio of monomer to initiator
([11]o/[1c]o) at 100% monomer conversion.
oxetane (12), a four-membered cyclic ether, to give a narrow MWD
polyether with an aluminum alcoholate reactive end.12 This observation is
interesting, since cyclic ethers other than epoxides have been understood
to be polymerizable only cationically because of their high basicities.32
Therefore, the successful example of controlled anionic polymerization of
12 indicates one of the very unique reactivities of lc.
As summarized in Table 5, aluminum porphyrins (1) can also be used as
initiators for ring-opening polymerization of other heterocyclic monomers
such as lactones (13-15), 13~17 lactide (16),18 cyclic carbonates (17)19
and cyclic siloxanes
23
(19),20 where the axial ligands of the complexes play a very important
role. For example, ring-opening polymerization of four-membered lactones
is initiated by a chloroaluminum porphyrin (lc) to give a chlorine-
terminated polyester with a narrow MWD, where the monomer is cleaved at
the O-C bond to give an aluminum carboxylate growing species (28, Scheme
).13 In contrast, lc is inert for the polymerization of larger-membered
lactones such as six- and seven-membered lactones (14, 15).'617 For the
polymerization of these monomers, alcoholate complexes (Id) are quite
effective, where the monomer is cleaved at the O-C(O) bond to give a
polyester bearing an aluminum alcoholate growing species (29, Scheme 3B).
Among metalloporphyrins containing nontransition metals, zinc N-
substituted porphyrins (5) (Table 3) are effective initiators for
controlled ring-opening polymerization of certain heterocyclic monomers
such as epoxides
(ll)3-1 and episulfides (18)34 (Table 5). For example, a zinc thiolate
complex of /V-methyltetraphenylporphyrin (5g) can initiate living
polymerization of 1,2-epoxypropane (11, R = Me) to give a narrow MWD
polyether with a zinc alcoholate growing terminal (30, Scheme 4A).33
Similarly, 5g is also capable of initiating the polymerization of a
three-membered cyclic thioether such as 1,2-epithiopropane (18, R = Me),
to give a polythioether with a zinc thiolate reactive end (31) (Scheme
4B).34 Of interest here is that the former
Scheme 2
I
i
Me
Al - X +



11 (R = Me)
I
(2A)
24 (R = Me)
11 (R = Me)
I
Me
25 (R = Me)
(2B)
11 (R = H) | Me
A|- /\ \ N
u
1 . n -
23 (2C)
26
42 / Metalloporhpyrins as Catalysts
141
Table 3. Selected 'H NMR Data for the Axi.il Ligands of Zinc N-
Methyltetraphenylporphyrins (5) at Room Temperature
Compound Chemical shifts in <> (ppm)
Reference
Zinc alk\I
I
I
a b
Me Zn CH?CH4 -1.75 (a).
I.IS'lib). - 3.82 (N-Me) |ChD(l]
34
Zinc aieoholaie
I
Me Zn CH(CH3)2 0.13(a), -i.li(b). -- 3.84 ('-) |OJ)r,
I
Zinc phenolatc
| (H3C)3C
Me 'zn -0CH3 0.32 (a), 3.08
(h). 4.44 (yV-Me) [C(1D<>] 79
1
Zinc carboxvUites
Zn-o c-ch3 -0.79(a). - 3.83 (/-) |C1>C1,|
34
I
Me Zn c OCH2CH3 2.19(a), -0.12(b), - 4.02 (;V-Me) |C(,D6]
X0
I
a b
Me' 'zn N(CH2CH3)2 1.31(a), 0.36(h). - 4.10
(/V-) |C6Dh] HO
I
Zinc liiiolates
'zn S CH2CH2CH3 0.S (a). -0.45 (bj, -
0.09(c). - 3.83 (W-Me> [Cr,D6]
i I
a b
Ph' Zn S CH2CH2CH3 O.ftS (a). - 0.38 (b), -
0.11(c).
| 2..4? (N I'll " 11). 5.0i
(/V-PIwh-H). 5.39 (/V-Ph-/> H) [C"D"| -34
polymeri/alion (Scheme 4A) requires irradiation with visible light at the
initiation step (Figure 5). but Ihe latter (Scheme 4) is not affected by
the irradiation. Such a difference in photosensitivity between these two
Previous << 1 .. 82 83 84 85 86 87 < 88 > 89 90 91 92 93 94 .. 240 >> Next