Synthesis, characterisation, and oxygen atom transfer reactions involving the first gold(i)-alkylperoxo complexes

Article abstract of DOI:10.1039/c3cc47030j

The synthesis of a new class of organogold species containing a peroxo moiety is reported. Complexes [Au(IPr)(OO^tBu)] and [Au(SIPr)(OO ^tBu)] have been synthesised via a straightforward methodology using the parent gold(i) hydroxide complexes as synthons. These complexes have been successfully used in oxygen-transfer reactions to triphenylphosphine.

Full text of DOI:10.1039/c3cc47030j

ChemComm
View Article Online
View Journal | View Issue
COMMUNICATION
Synthesis, characterisation, and oxygen atom transfer
reactions involving the first gold(I)-alkylperoxo
complexes†
Cite this: Chem. Commun., 2013,
4
9, 10745
Received 13th September 2013,
Accepted 27th September 2013
Alba Collado, Adri a´ n G o´ mez-Su a´ rez, Yoshihiro Oonishi, Alexandra M. Z. Slawin
and Steven P. Nolan*
DOI: 10.1039/c3cc47030j
www.rsc.org/chemcomm
The synthesis of a new class of organogold species containing
t
a peroxo moiety is reported. Complexes [Au(IPr)(OO Bu)] and
t
[
Au(SIPr)(OO Bu)] have been synthesised via a straightforward
methodology using the parent gold(I) hydroxide complexes as
synthons. These complexes have been successfully used in oxygen-
transfer reactions to triphenylphosphine.
Since the renaissance of gold chemistry more than a decade
1
ago, organometallic chemists have attempted to isolate key
organogold species in order to gain a better understanding of
2
their reactivity. Amongst the plethora of gold complexes
currently available, catalysts bearing N-heterocyclic carbenes
(
NHCs) as ancillary ligands have distinguished themselves due
3
to their unique electronic and steric properties. In addition,
gold-complexes bearing NHC ligands are usually more stable
than their phosphine analogues, thus providing a better scaf-
4
fold for the synthesis of possible reaction intermediates. For Scheme 1 [Au(IPr)OH] (1) as a powerful synthon.
example, the use of NHC ligands has permitted the synthesis of
the first example of a mononuclear Au(I)-hydroxide [Au(IPr)OH]‡
5
6
(
1) and its saturated derivative [Au(SIPr)OH]‡ (2). The former peroxo (O–O) unit. Peroxo-metal complexes have been postu-
has been shown to be a very useful synthon allowing the lated as intermediates in important biochemical and industrial
1
0
preparation of a wide variety of organogold species under very processes. They are involved in enzymatic cycles, and are key
5
,7
mild conditions (Scheme 1).
intermediates in dioxygen activation and selective oxidation
1
1
Recently, there has been increased interest in the isolation of reactions. In this context, much effort has been devoted to the
oxo-, hydroxo-, and alkoxo-gold(I) complexes, as oxygen nucleophiles isolation and characterisation of different metal complexes
are common reagents in gold-catalysed processes. We have recently containing a peroxo moiety in order to better understand the
contributed to this field with the isolation of the aforementioned mechanism of such processes.
hydroxides 1 and 2, a series of [{Au(NHC)}
8
1
1a–c,12
A handful of these have
5,6
9
2
7
(m-OH)][BF
4
] species,
been isolated, typically prepared by insertion of O into a metal–
2
13
14
11c,12a
12h,15
and finally various gold-phenolate complexes.
hydride bond. Amongst others, Rh-, Fe-,
Cu-,
1
6
13a,17
13b
As part of our research programme involving the prepara- Mn-, Pt-,
or Pd-peroxo
complexes have been success-
tion of novel organogold species, we have most recently focused fully isolated. The formation of gold-peroxo species has been
our attention on the synthesis of gold complexes containing a proposed to occur on the surface of gold nanoparticles during
1
8
O activation and on gold electrodes as intermediates in water
2
19
EaStCHEM School of Chemistry, University of St. Andrews, St. Andrews, KY16 9ST,
UK. E-mail: snolan@st-andrews.ac.uk; Fax: +44 (0)1334463808;
Tel: +44 (0)1334463763
splitting processes. Homogeneous mononuclear gold(III) com-
plexes have been used for oxidative esterification reactions using
tert-butylhydroperoxide as oxidants and homogeneous gold(I)
catalysts have been reported to tolerate organic hydroperoxides.
During the preparation of this manuscript, Bochmann reported
the first example of Au(III)-peroxo complexes. To the best of
20
†
Electronic supplementary information (ESI) available: Synthesis and full char-
acterization details of 3 and 4, and reactivity towards PPh . CCDC 950318 and
50319. For ESI and crystallographic data in CIF or other electronic format see
21
3
9
2
2
DOI: 10.1039/c3cc47030j
This journal is c The Royal Society of Chemistry 2013
Chem. Commun., 2013, 49, 10745--10747 10745

View Article Online
Communication
ChemComm
t
t
Scheme 2 Synthesis of [Au(IPr)(OO Bu)] and [Au(SIPr)(OO Bu)].
our knowledge, gold(I)-peroxo compounds remain unknown.
Therefore, the formation of these species was explored, using
complexes 1 and 2 as starting materials.
t
Fig. 2 ORTEP representation of 4 [Au(SIPr)(OO Bu)] showing 50% thermal
ellipsoid probability. Most H atoms were omitted for clarity.
Treatment of [Au(IPr)OH] (1) or [Au(SIPr)OH] (2) with 1 equivalent
t
of BuOOH in toluene at room temperature leads to the formation
of the new alkylperoxo species 3 and 4 as white microcrystalline
solids (Scheme 2).§ It should be noted that these reactions were
conducted under air in technical grade solvents. However, they
Table 1 Selected distances (Å) for complexes 3–4
Complex
Ccarbene–Au
Au–O
O–O
t
were protected from light to avoid decomposition of the final [Au(IPr)(OO Bu)](3a, 3b)
1.964(16)
.989(16)
2.000(12)
2.014(11)
2.019(12)
2.001(12)
1.512(17)
1.496(16)
1.51(2)
1
product. Complexes 3 and 4 have been fully characterised by
t
1
13
1
[Au(SIPr)(OO Bu)](4)
H and C{ H} NMR spectroscopy, infrared spectroscopy, elemental
analysis and single crystal X-ray diffraction analysis.
1
The H NMR spectra of 3 and 4 display singlets at 0.87 and
24
between 177.71 and 178.41. Table 1 presents the most relevant
0
.83 ppm, respectively, which correspond to the tert-butyl moieties.
distances for these complexes. The Au–Ccarbene distances are
13
1
The most noticeable feature of the C{ H} NMR spectra of these
complexes is the presence of a low field signal corresponding to
the carbenic carbon atom. This signal appears at 170.9 ppm for
1.964(16) (3a), 1.989(16) (3b) and 2.000(18) Å (4). The Au–O
distances are: 2.014(11) (3a), 2.019(12) (3b), and 2.001(12) (4) Å.
The O–O distances between 1.496(16) and 1.512(17) Å lie in
the upper limit of the typical range observed for peroxo
3
and 192.4 ppm for 4, and compares well with the related data
5
,6
for 1 and 2. As observed for the precursors 1 and 2, the signal
corresponding to the carbenic atom appears at lower field for
the complex containing the saturated ligand, SIPr.
13,16b,17,25
t
complexes.
The Au–O–O and O–O– Bu angles for the
three structures are in the range 102.9–109.71, in agreement
3
with a sp hybridisation of the oxygen atoms.
The IR spectra of 3 and 4 in toluene solution showed bands
The ability of complexes 3 and 4 to transfer oxygen was tested
À1
at 803 and 804 cm , respectively, consistent with the presence
by reacting them with PPh
6 6
or 4 and PPh were mixed in C D
3
(Scheme 3). Equimolar amounts of 3
of the O–O unit.
3
under an argon atmosphere
In order to unambiguously confirm the atom connectivity
in 3 and 4, single crystals were obtained by slow diffusion of
1
31
1
and the mixture was analysed by H and P{ H} NMR spectro-
1
scopy. After 10 min, the H NMR spectra of the mixtures showed
23
pentane into their saturated toluene solutions. Two conformers
of complex 3 (3a and 3b) were found in the crystal lattice (Fig. 1)
while only one variant of 4 was obtained (Fig. 2). The three
structures show the expected linear geometry around the metal
centre, typical for Au(I) complexes with Ccarbene–Au–O angles
the formation of the corresponding tert-butoxy-gold complexes,
5
or 6, and triphenylphosphine oxide as a result of the transfer of
one oxygen atom from the peroxo species to triphenylphosphine.
Complexes 5 and 6 have been previously described and the
8c,26
signals observed are in agreement with the reported data.
The formation of triphenylphosphine oxide was further con-
3
1
1
firmed by the presence of a singlet at 25.0 ppm in the P{ H}
NMR spectrum.
In conclusion, we have synthesised the alkylperoxo species
t
t
[
Au(IPr)(OO Bu)] (3) and [Au(SIPr)(OO Bu)] (4) via a straightforward
t
Fig. 1 ORTEP representation of 3a [Au(IPr)(OO Bu)] showing 50% thermal
ellipsoid probability. Most H atoms were omitted for clarity.
3
Scheme 3 Oxygen atom transfer reaction from 3 and 4 to PPh .
1
0746 Chem. Commun., 2013, 49, 10745--10747
This journal is c The Royal Society of Chemistry 2013

View Article Online
ChemComm
Communication
route from the corresponding gold(I) hydroxide species [Au(IPr)OH]
9 (a) S. Gaillard, J. Bosson, R. S. Ram ´o n, P. Nun, A. M. Z. Slawin and
S. P. Nolan, Chem.–Eur. J., 2010, 16, 13729–13740; (b) R. S. Ram ´o n,
S. Gaillard, A. Poater, L. Cavallo, A. M. Z. Slawin and S. P. Nolan,
Chem.–Eur. J., 2011, 17, 1238–1246; (c) A. G o´ mez-Su ´a rez, Y. Oonishi,
S. Meiries and S. P. Nolan, Organometallics, 2013, 32, 1106–1111.
0 (a) L. Boisvert and K. I. Goldberg, Acc. Chem. Res., 2012, 45, 899–910;
(1) and [Au(SIPr)OH] (2). These complexes are the first examples
of isolated Au(I)-peroxo complexes and have been fully char-
acterised by NMR spectroscopy and X-ray diffraction analysis.
Complexes 3 and 4 have been shown to be able to transfer
oxygen to triphenylphosphine. Further studies focusing on the
mechanism of this transformation and other reactivity of these
new species are currently underway.
The ERC (Advanced Investigator Award-FUNCAT), EPSRC
and Syngenta are gratefully acknowledged for support of this
work. Umicore AG is acknowledged for their generous gift of
auric acid. S. P. N. is a Royal Society Wolfson Research Merit
Award holder. Y. O. thanks the Uehara Memorial Foundation
for a Fellowship. We thank Dr David J. Nelson for helpful
discussions.
1
(
2
b) M. Costas, M. P. Mehn, M. P. Jensen and L. Que, Chem. Rev.,
004, 104, 939–986; (c) E. I. Solomon, T. C. Brunold, M. I. Davis,
J. N. Kemsley, S.-K. Lee, N. Lehnert, F. Neese, A. J. Skulan, Y.-S. Yang
and J. Zhou, Chem. Rev., 1999, 100, 235–350.
1
1 (a) Y. Wang, D. Janardanan, D. Usharani, K. Han, L. Que and S. Shaik,
ACS Catal., 2013, 3, 1334–1341; (b) G. Katona, P. Carpentier,
V. Nivi `e re, P. Amara, V. Adam, J. Ohana, N. Tsanov and D. Bourgeois,
Science, 2007, 316, 449–453; (c) E. G. Kovaleva and J. D. Lipscomb,
Science, 2007, 316, 453–457; (d) A. Decker and E. I. Solomon, Curr.
Opin. Chem. Biol., 2005, 9, 152–163; (e) K. Kim and S. J. Lippard,
J. Am. Chem. Soc., 1996, 118, 4914–4915; ( f ) H. Mimoun, J. Mol.
Catal., 1980, 7, 1–29.
1
2 (a) F. Avenier, C. Herrero, W. Leibl, A. Desbois, R. Guillot, J.-P. Mahy
and A. Aukauloo, Angew. Chem., Int. Ed., 2013, 52, 3634–3637;
(
b) T. Wada, H. Maki, T. Imamoto, H. Yuki and Y. Miyazato, Chem.
Commun., 2013, 49, 4394–4396; (c) D. Moonshiram, I. Alperovich,
J. J. Concepcion, T. J. Meyer and Y. Pushkar, Proc. Natl. Acad. Sci.
U. S. A., 2013, 110, 3765–3770; (d) S. Maji, I. L ´o pez, F. Bozoglian,
J. Benet-Buchholz and A. Llobet, Inorg. Chem., 2013, 52, 3591–3593;
(e) S. Fukuzumi and K. D. Karlin, Coord. Chem. Rev., 2013, 257,
187–195; ( f ) J. R. Frisch, R. McDonnell, E. V. Rybak-Akimova and
L. Que, Inorg. Chem., 2013, 52, 2627–2636; (g) T. Ohta, J.-G. Liu and
Y. Naruta, Coord. Chem. Rev., 2013, 257, 407–413; (h) C. J. Cramer
and W. B. Tolman, Acc. Chem. Res., 2007, 40, 601–608.
Notes and references
‡
(
§
IPr = 1,3-bis(2,6-diisopropyl-phenyl)imidazol-2-ylidene, SIPr = 1,3-bis-
2,6-diisopropylphenyl)-4,5-dihydroimidazol-2-ylidene.
General experimental procedure: protected from light (in the dark
and wrapped in aluminium foil), a vial was charged, under air, with 1 or
t
2
and toluene. An equimolar amount of BuOOH (5.5 M solution in
decane) was added to the suspension and the mixture was stirred at
room temperature for 30 min. After this time, the solvent was concen-
trated under vacuum and pentane was added to precipitate a white 13 (a) K. A. Grice and K. I. Goldberg, Organometallics, 2009, 28,
solid that was washed with further portions of pentane. See ESI† for
details.
953–955; (b) M. C. Denney, N. A. Smythe, K. L. Cetto, R. A. Kemp
and K. I. Goldberg, J. Am. Chem. Soc., 2006, 128, 2508–2509.
4 G. Meier and T. Braun, Angew. Chem., Int. Ed., 2012, 51, 12564–12569.
1
1
(a) M. Rudolph and A. S. K. Hashmi, Chem. Soc. Rev., 2012, 41, 15 (a) T. Hoppe, S. Schaub, J. Becker, C. W u¨ rtele and S. Schindler, Angew.
2
1
448–2462; (b) N. Krause and C. Winter, Chem. Rev., 2011, 111,
994–2009; (c) A. Corma, A. Leyva-P ´e rez and M. J. Sabater, Chem.
Chem., Int. Ed., 2013, 52, 870–873; (b) S. Kim, C. Saracini, M. A. Siegler,
N. Drichko and K. D. Karlin, Inorg. Chem., 2012, 51, 12603–12605.
Rev., 2011, 111, 1657–1712; (d) G. J. Hutchings, M. Brust and 16 (a) M. K. Coggins, X. Sun, Y. Kwak, E. I. Solomon, E. Rybak-Akimova
H. Schmidbaur, Chem. Soc. Rev., 2008, 37, 1759–1765; (e) A. S. K.
Hashmi, Chem. Rev., 2007, 107, 3180–3211; ( f ) A. S. K. Hashmi and
G. J. Hutchings, Angew. Chem., Int. Ed., 2006, 45, 7896–7936.
A. S. K. Hashmi, Angew. Chem., Int. Ed., 2010, 49, 5232–5241.
and J. A. Kovacs, J. Am. Chem. Soc., 2013, 135, 5631–5640; (b) M. K.
Coggins, V. Martin-Diaconescu, S. DeBeer and J. A. Kovacs, J. Am.
Chem. Soc., 2013, 135, 4260–4272.
2
3
17 D. D. Wick and K. I. Goldberg, J. Am. Chem. Soc., 1999, 121, 11900–11901.
(a) S. P. Nolan, Acc. Chem. Res., 2011, 44, 91–100; (b) N. Marion and 18 (a) A. P. Woodham, G. Meijer and A. Fielicke, J. Am. Chem. Soc.,
S. P. Nolan, Chem. Soc. Rev., 2008, 37, 1776–1782; (c) L. Cavallo,
A. Correa, C. Costabile and H. Jacobsen, J. Organomet. Chem., 2005,
2013, 135, 1727–1730; (b) A. P. Woodham, G. Meijer and A. Fielicke,
Angew. Chem., Int. Ed., 2012, 51, 4444–4447.
19 O. Diaz-Morales, F. Calle-Vallejo, C. de Munck and M. T. M. Koper,
Chem. Sci., 2013, 4, 2334–2343.
20 A. S. K. Hashmi, C. Lothsch u¨ tz, M. Ackermann, R. Doepp,
S. Anantharaman, B. Marchetti, H. Bertagnolli and F. Rominger,
Chem.–Eur. J., 2010, 16, 8012–8019.
6
90, 5407–5413.
(a) H. Clavier and S. P. Nolan, Chem. Commun., 2010, 46, 841–861;
b) W. A. Herrmann, Angew. Chem., Int. Ed., 2002, 41, 1290–1309.
S. Gaillard, A. M. Z. Slawin and S. P. Nolan, Chem. Commun., 2010,
6, 2742–2744.
4
5
6
7
8
(
4
A. G ´o mez-Su ´a rez, R. S. Ramon, A. M. Z. Slawin and S. P. Nolan, 21 A. S. K. Hashmi, M. C. Blanco Jaimes, A. M. Schuster and F. Rominger,
Dalton Trans., 2012, 41, 5461–5463. J. Org. Chem., 2012, 77, 6394–6408.
J. D. Egbert, A. M. Z. Slawin and S. P. Nolan, Organometallics, 2013, 22 D.-A. Ros-ca, J. A. Wright, D. L. Hughes and M. Bochmann,
2, 2271–2274. Nat. Commun., 2013, 4, 2167.
(a) N. Ibrahim, M. H. Vilhelmsen, M. Pernpointner, F. Rominger and 23 CCDC 950318 (3), 950319 (4).
A. S. K. Hashmi, Organometallics, 2013, 32, 2576–2583; (b) A. Zhdanko, 24 P. de Fr ´e mont, N. M. Scott, E. D. Stevens and S. P. Nolan, Organo-
3
M. Str o¨ bele and M. E. Maier, Chem.–Eur. J., 2012, 18, 14732–14744;
metallics, 2005, 24, 2411–2418.
(
c) D. S. Laitar, P. M u¨ ller, T. G. Gray and J. P. Sadighi, Organometallics, 25 D. Mukherjee, A. Ellern and A. D. Sadow, J. Am. Chem. Soc., 2012,
2
005, 24, 4503–4505; (d) A. N. Nesmeyanov, E. G. Perevalova, Y. T.
134, 13018–13026.
Struchkov, M. Y. Antipin, K. I. Grandberg and V. P. Dyadhenko, 26 E. Y. Tsui, P. M u¨ ller and J. P. Sadighi, Angew. Chem., Int. Ed., 2008,
J. Organomet. Chem., 1980, 201, 343–349. 47, 8937–8940.
This journal is c The Royal Society of Chemistry 2013
Chem. Commun., 2013, 49, 10745--10747 10747