exposure to dioxygen, acetonitrile solutions of (Et
Et N) [2] form deep purple and burgundy solutions,
respectively. To test the ability of (Et N) [1] and (Et N) [2] to
4
N)
2
[1] and
wR
3
2
= 0.1505, 9495 independent reflections [y = 30.711] and
20 parameters, GOF on F = 1.063.
2
(
4
2
4
2
4
2
1 (a) T. Punniyamurthy, S. Velusamy and J. Iqbal, Chem. Rev., 2005,
105, 2329–2363; (b) C. N. Cornell and M. S. Sigman, Activation of
Small Molecules, Wiley-VCH, Weinheim, Germany, 2006,
pp. 159–186.
2 (a) A. E. Martell, J. Mol. Catal., 1988, 44, 1–14; (b) E. C.
Niederhoffer, J. H. Timmons and A. E. Martell, Chem. Rev.,
act as oxidation catalysts, both complexes were exposed to
dioxygen in the presence of an excess of triphenylphosphine. An
acetonitrile solution containing (Et N) [1] (0.02 mmol) and
4
2
PPh
monitored using gas chromatography. After fifteen minutes,
4% of the PPh had been converted to triphenylphosphine
oxide (OPPh ). After two hours, the reaction mixture yielded
9% (1.38 mmol) of the oxidized product. In a separate
experiment, an acetonitrile solution containing (Et N) [2]
(1.9 mmol) was exposed to dioxygen
1 atm). After fifteen minutes, 78% of the PPh was converted
3
(2.0 mmol) was exposed to dioxygen (1 atm) and
1
984, 84, 137–203; (c) P. R. Warburton and D. H. Busch, Perspect.
Bioinorg. Chem., 1993, 2, 1–79.
4
3
3
4
L. I. Simandi, Advances in Catalytic Activation of Dioxygen by
Metal Complexes, Kluwer Academic Publishers, 2003, [In: Catal.
Met. Complexes, 2003, 26].
3
6
(a) C. L. Bailey and R. S. Drago, Coord. Chem. Rev., 1987, 79,
4
2
3
1
21–332; (b) T. Mukaiyama and T. Yamada, Bull. Chem. Soc. Jpn.,
995, 68, 17–35.
(
0.019 mmol) and PPh
3
(
5 (a) G. Pozzi, F. Montanari and S. Quici, Chem. Commun., 1997,
69–70; (b) T. Mukaiyama, K. Yorozu, T. Takai and T. Yamada,
Chem. Lett., 1993, 439–442; (c) T. Takai, E. Hata, K. Yorozu and
T. Mukaiyama, Chem. Lett., 1992, 2077–2080; (d) P. M. O’Neill,
S. Hindley, M. D. Pugh, J. Davies, P. G. Bray, B. K. Park,
D. S. Kapu, S. A. Ward and P. A. Stocks, Tetrahedron Lett.,
3
to OPPh , and after two hours, 95% of the PPh had been
3
3
converted to OPPh (1.81 mmol). Performing these reactions
3
with large substrate to catalyst loading ratios (500 : 1) gives
maximum turnover numbers (TON = mol product/mol cat) of
2
and J. Iqbal, Tetrahedron, 1993, 49, 6101–6122.
(a) R. Giannandrea, P. Mastrorilli, C. F. Nobile and G. P.
Suranna, J. Mol. Catal., 1994, 94, 27–36; (b) M. M. Dell’Anna,
P. Mastrorilli and C. F. Nobile, J. Mol. Catal. A: Chem., 1996, 108,
003, 44, 8135–8138; (e) S. Bhatia, T. Punniyamurthy, B. Bhatia
1
85 and 345 for (Et
4
8
N)
2
[1] and (Et
(g) were conducted to confirm that
) of these
reactions is derived from dioxygen. At this point, we cannot rule
out the possibility that both (Et N) [1] and (Et N) [2] react with
4 2
N) [2], respectively.
1
Labeling studies with
O
2
6
the oxygen atom incorporated into the products (OPPh
3
5
7–62; (c) M. M. Dell’Anna, P. Mastrorilli, C. F. Nobile,
M. R. Taurino, V. Calo and A. Nacci, J. Mol. Catal. A: Chem.,
000, 151, 61–69.
4
2
4
2
dioxygen to form similar reactive intermediates. While triphenyl-
phosphine is a relatively easy substrate to oxidize, few transition
metal catalysts are capable of carrying out this transformation
2
7 (a) Y.-M. Lin and M. J. Miller, J. Org. Chem., 2001, 66,
8282–8285; (b) L. Martiny and K. A. Jorgensen, J. Chem. Soc.,
Perkin Trans. 1, 1995, 699–704.
S. L. Jain and B. Sain, Angew. Chem., Int. Ed., 2003, 42,
1265–1267.
ꢁ1 18
with good efficiency (TOF > 60 h ).
8
i
In summary, the HN(o-PhNHC(O) Pr) ligand has been
2
2ꢁ
used to stabilize both mononuclear ([1] ) and dinuclear
9 A. Huber, L. Mu
Inorg. Chem., 2005, 1459–1467.
0 S. Nemeth, Z. Szeverenyi and L. I. Simandi, Inorg. Chim. Acta,
980, 44, L107–L109.
¨
ller, H. Elias, R. Klement and M. Valko, Eur. J.
2ꢁ
(
[2] ) cobalt(II) complexes. Under ambient conditions in the
1
1
1
1
`
`
presence of excess dioxygen, both species catalytically oxidize
triphenylphosphine to triphenylphosphine oxide with much
better catalytic efficiencies than those previously observed for
cobalt(II) complexes. Studies addressing the mechanism of
these reactions are ongoing to further our understanding of
the role of supporting ligands in dioxygen activation by
transition metal complexes.
1
1 (a) T. J. Collins, Acc. Chem. Res., 1994, 27, 279–285;
(b) D. W. Margerum, Pure Appl. Chem., 1983, 55, 23–34.
2 D. S. Black and N. E. Rothnie, Aust. J. Chem., 1983, 36,
1141–1147.
3 L. Yang, D. R. Powell and R. P. Houser, Dalton Trans., 2007,
955–964.
14 (a) G. Mund, A. J. Gabert, R. J. Batchelor, J. F. Britten and
D. B. Leznoff, Chem. Commun., 2002, 2990–2991; (b) B. D. Murray
and P. P. Power, Inorg. Chem., 1984, 23, 4584–4588; (c) H. Hope,
M. M. Olmstead, B. D. Murray and P. P. Power, J. Am. Chem.
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5 P. Chaudhuri, C. N. Verani, E. Bill, E. Bothe, T. Weyhermueller
and K. Wieghardt, J. Am. Chem. Soc., 2001, 123, 2213–2223.
6 A. I. Nguyen, K. J. Blackmore, S. M. Carter, R. A. Zarkesh and
A. F. Heyduk, J. Am. Chem. Soc., 2009, 131, 3307–3316.
We thank the Donors of the ACS-Petroleum Research
Fund (49049-DNI3) and the Emory University Research
Council (URC) for financial support. We thank J. Song and
Dr. K. S. Hagen for helpful discussions.
1
1
Notes and references
z Crystal data. (Et
4
N)
2
[1]: C56
H
86
N
8
O
4
Co, M = 994.26, 0.17 ꢂ
17 P. Zanello, Inorganic Electrochemistry: Theory, Practice, and
Application., Royal Society of Chemistry, Cambridge, UK, 2003,
pp. 445–495.
18 For examples see: (a) B. G. Jacobi, D. S. Laitar, L. Pu,
M. F. Wargocki, A. G. DiPasquale, K. C. Fortner, S. M. Schuck
and S. N. Brown, Inorg. Chem., 2002, 41, 4815–4823;
(b) M. O’Reilly, J. M. Falkowski, V. Ramachandran, M. Pati,
K. A. Abboud, N. S. Dalal, T. G. Gray and A. S. Veige, Inorg.
Chem., 2009, 48, 10901–10903; (c) E. Y. Tshuva, D. Lee, W. Bu
and S. J. Lippard, J. Am. Chem. Soc., 2002, 124, 2416–2417.
3
˚
, a = 17.364(4) A,
0
.11 ꢂ 0.07 mm , orthorombic, space group Pca2
1
˚
b = 16.539(4) A, c = 19.385(5), V = 5567(2), Rint = 0.1821, Z = 4,
ꢁ
3
ꢁ1
r
cald = 1.186 g cm , m = 0.359 mm , F(000) = 2148, T = 172(2) K,
2
R(F > 2s) = 0.0662, wR
2
= 0.1229, 16 016 independent reflections
2
[
C
y = 30.631] and 622 parameters, GOF of F = 1.006. For (Et
H84Co N O
56 2 8 4
4
N)
, M = 1051.18, 0.44 ꢂ 0.40 ꢂ 0.37 mm , tetragonal,
˚ ˚
1
22, a = 18.7790(8) A, b = 18.7790(8) A, c = 35.798(3),
3
2
[2]:
3
space group I4
V = 12624.1(1), Rint = 0.0500, Z = 8, rcald = 1.106 g cm , m =
0
ꢁ
ꢁ1
2
.571 mm , F(000) = 4496, T = 172(2) K, R(F > 2s) = 0.0506,
This journal is c The Royal Society of Chemistry 2011
Chem. Commun., 2011, 47, 1827–1829 1829