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Chemical Science
DOI: 10.1039/C3SC52054D
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27 See SI for alternative computational methods applied to the Pd(I)
radical vs dinuclear oxidative addition pathways (Figure S24, Table
S4, page S31).
5
6
28 A. Klapars, S. L. Buchwald, J. Am. Chem. Soc., 2002, 124, 14844; A.
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5
10
15
20
25
30
75
29 The barrier for Pd(I)ꢀIꢀBrꢀdimer 3 to add to 9ꢀiodoanthracene is ∆∆G‡
= 3.0 kcal/mol lower than for the addition to PhI.
7
First application as a precatalyst in crossꢀcoupling reactions: J. P.
Stambuli, R. Kuwano, J. F. Hartwig, Angew. Chem. Int. Ed., 2002, 80 30 G. Manolikakes, P. Knochel, Angew. Chem. Int. Ed., 2009, 48, 205.
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J. P. Stambuli, C. D. Incarvito, M. Bühl, J. F. Hartwig, J. Am. Chem.
Soc., 2004, 126, 1184.
31 For example, PtBu3•HBr is formed; 31PꢀNMR spectra given in SI in
Figure S1, S4, S7, S10. The mechanism of fragmentation is currently
under study. The sideꢀproducts do not trigger halide exchange
however. See SI, page S78 for tests.
85 32 In this experiment, the temperature was 25°C (ambient temperature).
For comparison, a 1:1 mixture of iodoanthracene and Pd(I)ꢀBrꢀdimer
1 gave 93% bromoanthracene under the analogous conditions [the
yield is relative to ArI starting material used, not 1].
31 For example, PtBu3•HBr is formed; 31PꢀNMR spectra given in SI in
Figure S1ꢀS5, page S5 onwards. The mechanism of fragmentation is
currently under study. The sideꢀproducts do not trigger halide
exchange however. See SI, page S22 for tests.
8
9
Catalysis by Di- and Polynuclear Metal Cluster Complexes, ed. R. D.
Adams and F. A. Cotton, WileyꢀVCH, New York, 1998.
10 For reactivities of related Pd(I) dimers with CO2, see: D. P.
Hruszkewycz, J. Wu, J. C. Green, N. Hazari, T. J. Schmeier,
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Hazari, C. D. Incarvito, J. Am. Chem. Soc., 2011, 133, 3280; for
reactivity with arenes, see: T. Murahashi, K. Takase, M. Oka, S.
Ogoshi, J. Am. Chem. Soc., 2011, 133, 14908; for other studies and
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11 T. J. Colacot, Platinum Metals Rev., 2009, 53, 183; U. Christmann,
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12 For a recent commentary, see: R. S. Paton, J. M. Brown, Angew.
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13 F. Proutiere, M. Aufiero, F. Schoenebeck, J. Am. Chem. Soc., 2012,
134, 606.
35 14 U. Christmann, D. A. Pantazis, J. BenetꢀBuchholz, J. E. McGrady, F.
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15 Conditions: Pd(I)ꢀBrꢀdimer 1 (0.04 M), ArI (10 equiv.). Reactions
40
carried out in the dark, in the glovebox. The yield was determined
with calibrated SFC or 1HꢀNMR.
16 The number of equiv ArBr formed are relative to Pd(I)ꢀBrꢀdimer 1.
The maximum amount of ArBr formed is 2.0 equiv (=100% yield), as
1.0 equiv. of 1 can give 2.0 equiv. of ArBr.
45 17 T. D. Sheppard, Org. Biomol. Chem., 2009, 7, 1043.
18 Halogenation via Pd (III/IV) complexes is a promising alternative: A.
J. Hickman, M. S. Sanford, Nature, 2012, 484, 177; K. M. Engle, T.ꢀ
S. Mei, X. Wang, J.ꢀQ. Yu, Angew. Chem. Int. Ed., 2011, 50, 1478;
A. J. Canty, Dalton Trans., 2009, 47, 10409.
50 19 D. A. Watson, M. Su, G. Teverovskiy, Y. Zhang, J. GarcíaꢀFortanet,
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20 A. H. Roy, J. F. Hartwig, J. Am. Chem. Soc., 2003, 125, 13944.
21 C. T. Hunt, A. L. Balch, Inorg. Chem., 1982, 21, 1641; for analogous
55
60
65
70
scrambling with Pd(III)ꢀdimers: M. C. Nielsen, E. Lyngvi, F.
Schoenebeck, J. Am. Chem. Soc., 2013, 135, 1978.
22 For a recent review of catalysis derived from transition metal radicals,
see: U. Jahn, Top. Curr. Chem., 2012, 320, 323.
23 Gaussian09, Revision A.01, M. J. Frisch et al. (see SI for full
reference).
24 Calculated at CPCM (THF) M06L/6ꢀ311++G(d,p)//B3LYP/6ꢀ
31G(d), with SDD for Pd, I.
25 For appropriateness of M06L, see: N. Sieffert, M. Bühl, Inorg.
Chem., 2009, 48, 4622; S. O. N. Lill, P. Ryberg, T. Rein, E.
Bennström, P.ꢀO. Norrby, Chem. Eur. J., 2012, 18, 1640; for B3LYP,
see: C. L. McMullin, J. Jover, J. N. Harvey, N. Fey, Dalton Trans.,
2010, 39, 10833; C. J. Cramer, D. G. Truhlar, Phys. Chem. Chem.
Phys., 2009, 11, 10757.
26 C. L. Lee, B. R. James, D. A. Nelson, R. T. Hallen, Organometallics,
1984, 3, 1360.
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