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Polymerization via Suzuki coupling in aqueous solution was first reported by
Novak et al. [Eq. (11)] [236]. A water-soluble catalyst precursor, [Pd(TPPMS)
3
]
(TPPMS=3-Ph
2
PC
6
H
4
SO
3
Na) was employed. The resulting polymer is water solu-
ble, and has a weight average molecular weight on the order of 5
10
4
g mol
-1
.
11
In later reports, Novak et al. pointed out that, as for traditional Suzuki coupling
in non-aqueous organic solvents, the aqueous Suzuki coupling reaction is accom-
panied by side reactions that strongly affect the structure of the resulting polymer.
Scheme 7.13
Effect of aryl-aryl exchange in polymerization by Suzuki coupling, and modes of
incorporation of phosphorus in the polymer.
First, a strong inhibition of the oxidative addition of aryl halide to Pd
0
by the co-
ordination of the phosphine has been reported to be the source of slow kinetics [237].
Accordingly, when using phosphine-free catalyst precursors such as Pd(OAc)
2
,[(
3
-
C
3
H
5
)PdCl]
2
or [Pd
2
(dba)
3
]·C
6
H
6
(dba=dibenzylidene acetone) for Suzuki coupling
(to prepare low-molecular-weight compounds) activities are an order of magnitude
higher by comparison to polymerization with [Pd(aryl)I(PPh
3
)
2
] [237]. However,
their use in polymerization has not been reported to date, perhaps due to a low sta-
bility of the active species, which is prone to decomposition to Pd black. Another side
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