P. Pongrácz et al. / Journal of Organometallic Chemistry 723 (2013) 149e153
153
Table 2
regioselectivities towards the branched aldehyde compared to the
Rh analogues, reported previously [29e31].
Hydroformylation of styrene in the presence of ‘in situ’ platinum catalysts.a
Entry
Ligand (or
preformed
complex)
SnCl2/Pt
PTSAb/Pt
Time
(h)
Conv.
(%)
Rc
Rbr
c
d
(%)
(%)
Acknowledgement
1
2
3
1
1
1
1
1
1
2
1a
2
e
e
2
2
48
48
48
48
48
48
48
72
48
48
96
48
72
48
12
8
5
8
5
5
7
16
9
5
79
90
72
82
77
81
68
80
91
84
71
95
63
84
56
92
72
62
86
77
72
53
91
75
50
51
44
34
The authors thank the Hungarian Research Fund (CK78553) and
Developing Competitiveness of Universities in the Transdanubian
Region (SROP-4.2.1.B-10/2/KONV-2010-0002), SROP-4.2.2./B-16 10/
1-2010-0029 and COST Action (CM0802, PhoSciNet) for financial
support.
2
2
4e
5e
6e
7
e
e
2
2
e
e
2
2
2
2
e
8
9
1a
1a
References
10
11
12
13
14
2
2
2
e
2a/2bf
2a/2bf
3a
5
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pp. 1e354.
e
2
e
2
28
33
18
2
e
3a
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a
Reaction conditions (unless otherwise stated): 0.01 mmol of PtCl2(PhCN)2 and
0.01 mmol of ligand (entries 1e7) or 0.01 mmol of PtCl2(L) preformed catalyst
(entries 8e14); Pt/styrene ¼ 1/100; p(CO) ¼ p(H2) ¼ 40 bar; 100 ꢀC; solvent: 10 mL
of toluene.
b
PTSA ¼ p-toluenesulfonic acid.
c
Chemoselectivity towards aldehydes (5, 6). [(moles of 5 þ moles of 6)/(moles of
5 þ moles of 6 þ moles of 7) ꢁ 100 ].
d
Regioselectivity towards branched aldehyde (5). [moles of 5/(moles of 5 þ moles
of 6) ꢁ 100 ].
e
Two eq. of 1 was used.
An inseparable mixture of 2a/2b (25/75).
f
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were
tested recently in the hydroformylation of styrene. In general, lower
chemo- and regioselectivities ranging from 56 to 71% and from 63 to
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respectively [37]. However, they pretended much higher activities
than those ones in the present study.
One of the possible explanations for the unexpectedly large
difference in regioselectivities is the coordination of the hydroxyl
group of ligand 1 to platinum in the key-intermediates. A less likely
possibility is the coordination of the para-toluenesulfonate ion to
platinum. It could be stated that the activation of the alkene
(styrene) by the hydridoeplatinum complex and its insertion into
PteH bond, leading to platinum-alkyl intermediate, is strongly
affected by the geometry of the Pt complex.
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}
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In summary, the chemoselectivity of hydroformylation was
rather high (up to 91%), accompanied by low rates of reaction. The
regioselectivity of the hydroformylation reaction is significantly
influenced both by the phosphorus ligands and para-toluene-
sulfonic acid additive employed in this study. While the two alde-
hyde regioisomers are formed in nearly equimolar ratios in the
presence of the ligands containing phosphinite moiety(ies), a high
preference of branched regioisomer was observed with the ami-
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