Influence of bulky yet flexible N-heterocyclic carbene ligands in gold catalysis

Article abstract of DOI:10.3762/bjoc.11.196

Three new Au(I) complexes of the formula [Au(NHC)(NTf₂)] (NHC = N-heterocyclic carbene) bearing bulky and flexible ligands have been synthesised. The ligands studied are IPent, IHept and INon which belong to the 'ITent' ('Tent' for 'tentacular') family of NHC derivatives. The effect of these ligands in gold-promoted transformations has been investigated.

Full text of DOI:10.3762/bjoc.11.196

Influence of bulky yet flexible N-heterocyclic carbene ligands
in gold catalysis
Alba Collado1, Scott R. Patrick1, Danila Gasperini1, Sebastien Meiries1
and Steven P. Nolan*2
Full Research Paper
Open Access
Address:
Beilstein J. Org. Chem. 2015, 11, 1809–1814.
1EaStCHEM School of Chemistry, University of St Andrews, St
Andrews, KY16 9ST, UK and 2Chemistry Department, College of
Science, King Saud University, Riyadh 11451, Saudi Arabia
doi:10.3762/bjoc.11.196
Received: 28 July 2015
Accepted: 04 September 2015
Published: 02 October 2015
Email:
Steven P. Nolan* - stevenpnolan@gmail.com
This article is part of the Thematic Series "N-Heterocyclic carbenes".
Associate Editor: J. P. Wolfe
* Corresponding author
Keywords:
catalysis; flexible and bulky ligands; gold; ligand design;
N-heterocyclic carbenes
© 2015 Collado et al; licensee Beilstein-Institut.
License and terms: see end of document.
Abstract
Three new Au(I) complexes of the formula [Au(NHC)(NTf2)] (NHC = N-heterocyclic carbene) bearing bulky and flexible ligands
have been synthesised. The ligands studied are IPent, IHept and INon which belong to the ‘ITent’ (‘Tent’ for ‘tentacular’) family of
NHC derivatives. The effect of these ligands in gold-promoted transformations has been investigated.
Introduction
Homogeneous gold catalysis has witnessed an exponential utilised by Organ, IHept, and INon (Figure 1). IPr [22], which is
growth in the last 15 years [1-12]. Gold complexes have been one of the most commonly used NHC derivatives, can be
shown to be efficient catalysts in a wide variety of transforma- considered as the simplest congener of the ITent family
tions [1-12]. N-heterocyclic carbenes (NHC) have attracted par- (Figure 1). These ligands belong to the class of NHC with ‘flex-
ticular attention as ancillary ligands due to their donating prop- ible sterics’, i.e., ligands capable of adjusting their steric
erties and steric hindrance [13-20]. These can be easily tuned by hindrance towards incoming substrates and, at the same time,
modifying the architecture of the imidazole ring, typically, by stabilising low-valent species. This concept, first proposed by
changing the N-substituents or the backbone [13-20]. One of Glorius [23-26], has been applied by a number of research
our research interests is the study of the electronic and steric groups to metal-catalysed transformations, leading to improve-
properties of new N-heterocyclic carbenes and their influence in ments in catalytic activity over other known systems [27-41].
catalysis upon coordination to a metal centre. We have recently The ITent ligands have been successfully used in challenging
reported the synthesis of the ‘ITent’ family (‘Tent’ stands for Pd cross-coupling reactions and other Pd-promoted transforma-
‘tentacular’) of NHC carbenes [21] which comprises IPent, first tions [21-41].
1809

Beilstein J. Org. Chem. 2015, 11, 1809–1814.
Figure 1: ‘ITent’ family of ligands, including IPr. First row: percentage buried volume (% Vbur) calculated in [Au(ITent)Cl] complexes using the
SambVca software [42-45]. Second and third row: Tolman Electronic Parameter (TEP) calculated from IR measurements in solution of the
[Ni(ITent)CO3] complexes [21,42].
The electronic and steric properties of the ITent family have In order to study the impact of the ITent ligands in gold cataly-
been determined [21,42,45] and compared to the parent ligand sis, we sought to synthesise the corresponding Gagosz-type
IPr. The observed trend for both electronic and steric properties derivatives [46,47]. These complexes, bearing a labile NTf2
is as follows: IPr << IPent < IHept ≈ INon showing that an group, do not require additives to promote catalytic transforma-
increase in the length of the chain translates into an increase of tions. Gagosz-type species have been typically prepared by
the donating properties and the steric hindrance. The limit of reacting the corresponding [Au(L)Cl] derivative (L = PR3,
this increment was found to lie between IHept and INon, where NHC) with AgNTf2 [46,47]. Alternative protocols that avoid
the additional carbon atoms did not have a significant impact on the use of silver salts involve the treatment of gold-hydroxide
the properties of the ligands.
[48] or gold-acetonyl [49] complexes with trifluoromethane-
sulfonimide. Following this silver-free procedure,
Herein we report the catalytic activity of gold complexes [Au(ITent)(OH)] complexes 4–6 were reacted with HNTf2 to
containing the ITent ligands.
obtain the corresponding [Au(ITent)(NTf2)] species 7–9 which
were isolated as white solids in good to excellent yields
(Scheme 2).
Results and Discussion
Synthesis of complexes
We have recently reported the synthesis of [Au(ITent)Cl] and Complexes 7–9 were characterised by 1H, 13C{1H}, and
[Au(ITent)(OH)] derivatives following the synthetic protocol 19F{1H} NMR spectroscopies and elemental analysis. The
shown in Scheme 1 [45].
13C{1H} NMR spectra of all the complexes showed a singlet in
Scheme 1: Synthesis of gold complexes bearing the ITent ligands.
1810

Beilstein J. Org. Chem. 2015, 11, 1809–1814.
Scheme 2: Silver-free synthesis of [Au(ITent)(NTf2)] complexes.
the low field region of the spectra corresponding to the carbenic gold complexes have been shown to be active in this transfor-
carbon atom of the molecule. These signals appear at mation [51-58]. Much effort has been devoted to
167.5–167.8 ppm, in agreement with other [Au(NHC)(NTf2)] the development of more sustainable gold-promoted protocols
complexes bearing unsaturated NHC ligands [46,50]. Each and several advances have been made in this field, e.g., very
19F{1H} NMR spectrum contains a singlet at ca. −76 ppm, in low catalyst loadings (10–1000 ppm) [51-53,56] have been
agreement with the presence of an inner-sphere NTf2 ligand achieved and the transformation has been successfully
[50].
performed in aqueous media [54,57]. Due to its relevance and
importance, the hydration of phenylacetylene was selected as a
model transformation to explore the different activity of
Catalytic transformations
Once fully characterised, the catalytic activity of the new complexes 7–9.
complexes was investigated. To this end, three model reactions
were selected: alkyne hydration, nitrile hydration, and the syn- The reactions were performed under the reported optimised
thesis of homoallylic ketones. To place these results into conditions for this transformation: using a 2:1 mixture of 1,4-
context, [Au(IPr)(NTf2)] (10) [46] was also tested under the dioxane/water at 80 °C [56]. All complexes showed excellent
same conditions.
catalytic activity at 0.5 mol % catalyst loading, after 3 hours,
and full conversion to the ketone was observed in all cases
(Table 1, entries 1–4). In order to determine the influence of the
Alkyne hydration
Alkyne hydration is an attractive transformation to generate ligands in the catalytic activity, the catalyst loading was
ketones from alkynes with high atom economy. A number of reduced.
Table 1: Influence of the ITent ligands in gold-catalysed alkyne hydration.a
entry
complex
[Au] (mol %)
time (h)
conversion (%)b
1
2
3
4
5
6
7
8
[Au(IPr)(NTf2)] (10)
[Au(IPent)(NTf2)] (7)
[Au(IHept)(NTf2)] (8)
[Au(INon)(NTf2)] (9)
[Au(IPr)(NTf2)] (10)
[Au(IPent)(NTf2)] (7)
[Au(IHept)(NTf2)] (8)
[Au(INon)(NTf2)] (9)
0.5
0.5
3
3
3
3
3
3
3
3
>99
>99
>99
>99
87
0.5
0.5
0.25
0.25
0.25
0.25
68
77
70
aReaction conditions: [Au(NHC)(NTf2)] (0.5 mol %), phenylacetylene (0.5 mmol), 1,4-dioxane/water (2:1, 1 mL), or [Au(NHC)(NTf2)] (0.25 mol %),
phenylacetylene (1.0 mmol), 1,4-dioxane/water (2:1, 2 mL). bGC conversion, average of at least two runs.
1811

Beilstein J. Org. Chem. 2015, 11, 1809–1814.
When the catalyst loading was reduced to 0.25 mol % and the Synthesis of homoallylic ketones
reactions were analysed after 3 h, the differences between the After the observed trend in hydration transformations, we
ligands became evident. Good conversions were obtained in all focused our attention on non-water inclusive reactions and
cases (Table 1, entries 5–8). However, the best conversion was decided to explore the catalytic activity of complexes 7–9 in the
observed when complex 10 bearing the IPr ligand was used synthesis of homoallylic ketones via hydroalkoxylation/Claisen
(Table 1, entry 5). Complexes 7–9 afforded lower conversions, rearrangement [61,62]. [Au(NHC)(NTf2)] complexes have
with [Au(IHept)(NTf2)] (8) being the most efficient amongst proven to be efficient catalysts for this transformation,
them (Table 1, entries 6–9).
promoting the reaction under neat conditions and low catalyst
loadings [61].
Nitrile hydration
Once it was shown that the use of the ITent ligands in the gold- The reactions were conducted under the reported optimised
catalysed hydration of phenylacetylene did not improve upon conditions [61] and were analysed after 20 min. An inverse
the performance of the parent IPr ligand, we explored the trend was observed in this case: the increase in the length of the
behaviour of the [Au(ITent)(NTf2)] complexes in the hydration alkyl chain resulted in lower conversions (Table 3). Complex 10
of nitriles. Mono- and digold complexes have been shown to be (Table 3, entry 1) was also found to be more efficient than
efficient catalysts in this transformation [52,59,60] which complexes 7–9 for this transformation (Table 3, entries 2–4).
proceeds with 100% atom economy. In addition, previous Complex 7, containing the IPent ligand, was the most active
findings showed that the digold complex, [{Au(NHC)}2(μ- catalyst among the ITent series (Table 3, entry 2).
OH)][BF4], bearing IPent was more efficient than the IPr
analogue in this reaction [52]. This result encouraged us to test Conclusion
the influence of the ITent ligands in the hydration of nitriles In conclusion, three new gold complexes bearing the ITent
promoted by monogold species.
ligands (IPent, IHept, and INon) have been synthesised and
fully characterised. The impact of varying the length of the
The reactions were conducted in a 1:1 mixture THF/water and alkyl chain of the ligands in gold-promoted transformations has
heated at 140 °C under microwave irradiation [60]. Low cata- been explored. All gold complexes were shown to be active in
lyst loadings were employed in order to observe the differences water inclusive reactions (alkyne and nitrile hydration) and in
between the four catalysts studied. At 1 mol %, the complexes the synthesis of homoallylic ketones from allylic alcohols and
showed poor to good catalytic activity depending on the ligand alkynes. [Au(IHept)(NTf2)] was the most efficient complex
(Table 2). As we observed for the hydration of alkynes, the of the series in the hydration of alkynes while the
ITent series were found to be less active than complex 10, [Au(IPent)(NTf2)] analogue was found to be superior in the
which afforded the desired product in 56% conversion (Table 2, hydration of nitriles and in the synthesis of homoallylic ketones.
entry 1). However, in this case, the gold complex bearing IPent However, when the performance of the catalysts was compared
(7) was more efficient than the IHept (8) and INon (9) deriva- to that of the parent [Au(IPr)(NTf2)] complex, this appeared to
tives (Table 2, entries 2–4).
be more active than the remaining complexes, showing that an
Table 2: Influence of the ITent ligands in gold-catalysed nitrile hydration.a
entry
complex
[Au] (mol %)
time (h)
conversion (%)b
1
2
3
4
[Au(IPr)(NTf2)] (10)
[Au(IPent)(NTf2)] (7)
[Au(IHept)(NTf2)] (8)
[Au(INon)(NTf2)] (9)
1.0
1.0
1.0
1.0
2
2
2
2
56
38
13
16
aReaction conditions: [Au(NHC)(NTf2)] (1.0 mol %), 4-methoxybenzonitrile (0.5 mmol), THF (0.5 mL), water (0.5 mL). b1H NMR conversion, average
of at least two runs.
1812

Beilstein J. Org. Chem. 2015, 11, 1809–1814.
Table 3: Influence of the ITent ligands in the gold-catalysed synthesis of homoallylic ketones.a
entry
complex
[Au] (mol %)
conversion (%)b
1
2
3
4
[Au(IPr)(NTf2)] (10)
[Au(IPent)(NTf2)] (7)
[Au(IHept)(NTf2)] (8)
[Au(INon)(NTf2)] (9)
0.2
0.2
0.2
0.2
98
81
73
56
aReaction conditions: [Au(NHC)(NTf2)] (0.2 mol %), diphenylacetylene (1.0 mmol), allylic alcohol (3 equiv). bGC conversion, average of 3 runs.
8. Hashmi, A. S. K.; Schwarz, L.; Choi, J.-H.; Frost, T. M.
increase of the alkyl chain length of the ligands has a detri-
Angew. Chem., Int. Ed. 2000, 39, 2285.
mental effect in the gold-mediated transformations selected in
doi:10.1002/1521-3773(20000703)39:13<2285::AID-ANIE2285>3.0.CO
this study. Further studies on the catalytic activity of the ITent
;2-F
ligands with different metals are currently ongoing.
9. Hashmi, A. S. K.; Frost, T. M.; Bats, J. W. J. Am. Chem. Soc. 2000,
122, 11553. doi:10.1021/ja005570d
10.Riedel, D.; Wurm, T.; Graf, K.; Rudolph, M.; Rominger, F.;
Supporting Information
Hashmi, A. S. K. Adv. Synth. Catal. 2015, 357, 1515.
doi:10.1002/adsc.201401131
Supporting Information File 1
11.Hashmi, A. S. K.; Lothschütz, C.; Graf, K.; Häffner, T.; Schuster, A.;
Experimental information and full characterisation of the
complexes including a copy of the NMR spectra.
[http://www.beilstein-journals.org/bjoc/content/
supplementary/1860-5397-11-196-S1.pdf]
Rominger, F. Adv. Synth. Catal. 2011, 353, 1407.
doi:10.1002/adsc.201100183
12.Hashmi, A. S. K.; Lothschütz, C.; Böhling, C.; Hengst, T.; Hubbert, C.;
Rominger, F. Adv. Synth. Catal. 2010, 352, 3001.
doi:10.1002/adsc.201000472
13.Nolan, S. P., Ed. N-Heterocyclic Carbenes: Effective Tools for
Organometallic Synthesis; Wiley-VCH Verlag GmbH & Co. KGaA:
Weinheim, 2014.
Acknowledgements
The ERC (Advanced Investigator Award-FUNCAT) and
Syngenta are gratefully acknowledged for support. Umicore AG
is acknowledged for their generous gift of materials.
14.Hopkinson, M. N.; Richter, C.; Schedler, M.; Glorius, F. Nature 2014,
510, 485. doi:10.1038/nature13384
15.Nelson, D. J.; Nolan, S. P. Chem. Soc. Rev. 2013, 42, 6723.
doi:10.1039/c3cs60146c
16.Diez-Gonzalez, S., Ed. N-Heterocyclic Carbenes: From Laboratory
Curiosities to Efficient Synthetic Tools; The Royal Society of Chemistry:
Cambridge, 2011.
References
1. Gagosz, F. Organogold Catalysis: Homogeneous Gold-Catalyzed
Transformations for a Golden Jubilee. In Advances in Organometallic
Chemistry and Catalysis; Pombeiro, A. J. L., Ed.; John Wiley & Sons,
Inc: Hoboken, 2013. doi:10.1002/9781118742952.ch16
2. Krause, N. Organogold Chemistry. In Organometallics in Synthesis;
Lipshutz, B. H., Ed.; John Wiley & Sons, Inc., 2013.
doi:10.1002/9781118651421.ch4
17.Clavier, H.; Nolan, S. P. Chem. Commun. 2010, 46, 841.
doi:10.1039/b922984a
18.Dröge, T.; Glorius, F. Angew. Chem., Int. Ed. 2010, 49, 6940.
doi:10.1002/anie.201001865
19.Díez-González, S.; Marion, N.; Nolan, S. P. Chem. Rev. 2009, 109,
3612. doi:10.1021/cr900074m
3. Nolan, S. P. Acc. Chem. Res. 2011, 44, 91. doi:10.1021/ar1000764
4. Rudolph, M.; Hashmi, A. S. K. Chem. Commun. 2011, 47, 6536.
doi:10.1039/c1cc10780a
20.Glorius, F., Ed. N-Heterocyclic Carbenes in Transition Metal Catalysis;
Springer: Berlin, Heidelberg, 2007.
21.Meiries, S.; Le Duc, G.; Chartoire, A.; Collado, A.; Speck, K.;
Arachchige, K. S. A.; Slawin, A. M. Z.; Nolan, S. P. Chem. – Eur. J.
2013, 19, 17358. doi:10.1002/chem.201302471
22.Jafarpour, L.; Stevens, E. D.; Nolan, S. P. J. Organomet. Chem. 2000,
606, 49. doi:10.1016/S0022-328X(00)00260-6
5. Li, Z.; Brouwer, C.; He, C. Chem. Rev. 2008, 108, 3239.
doi:10.1021/cr068434l
6. Hashmi, A. S. K. Chem. Rev. 2007, 107, 3180. doi:10.1021/cr000436x
7. Hashmi, A. S. K.; Hutchings, G. J. Angew. Chem., Int. Ed. 2006, 45,
7896. doi:10.1002/anie.200602454
23.Würtz, S.; Lohre, C.; Fröhlich, R.; Bergander, K.; Glorius, F.
J. Am. Chem. Soc. 2009, 131, 8344. doi:10.1021/ja901018g
24.Würtz, S.; Glorius, F. Acc. Chem. Res. 2008, 41, 1523.
doi:10.1021/ar8000876
1813

Beilstein J. Org. Chem. 2015, 11, 1809–1814.
25.Altenhoff, G.; Goddard, R.; Lehmann, C. W.; Glorius, F.
J. Am. Chem. Soc. 2004, 126, 15195. doi:10.1021/ja045349r
26.Altenhoff, G.; Goddard, R.; Lehmann, C. W.; Glorius, F.
Angew. Chem., Int. Ed. 2003, 42, 3690. doi:10.1002/anie.200351325
27.Soleilhavoup, M.; Bertrand, G. Acc. Chem. Res. 2015, 48, 256.
doi:10.1021/ar5003494
50.Gómez-Suárez, A.; Ramón, R. S.; Songis, O.; Slawin, A. M. Z.;
Cazin, C. S. J.; Nolan, S. P. Organometallics 2011, 30, 5463.
doi:10.1021/om200705y
51.Wang, Y.; Wang, Z.; Li, Y.; Wu, G.; Cao, Z.; Zhang, L. Nat. Commun.
2014, 5, 3470. doi:10.1038/ncomms4470
52.Gómez-Suárez, A.; Oonishi, Y.; Meiries, S.; Nolan, S. P.
Organometallics 2013, 32, 1106. doi:10.1021/om301249r
53.Nun, P.; Ramón, R. S.; Gaillard, S.; Nolan, S. P. J. Organomet. Chem.
2011, 696, 7. doi:10.1016/j.jorganchem.2010.08.052
54.Czégéni, C. E.; Papp, G.; Kathó, Á.; Joó, F. J. Mol. Catal. A: Chem.
2011, 340, 1. doi:10.1016/j.molcata.2011.03.009
55.Leyva, A.; Corma, A. J. Org. Chem. 2009, 74, 2067.
doi:10.1021/jo802558e
28.Chartoire, A.; Lesieur, M.; Falivene, L.; Slawin, A. M. Z.; Cavallo, L.;
Cazin, C. S. J.; Nolan, S. P. Chem. – Eur. J. 2012, 18, 4517.
doi:10.1002/chem.201104009
29.Chartoire, A.; Frogneux, X.; Nolan, S. P. Adv. Synth. Catal. 2012, 354,
1897. doi:10.1002/adsc.201200207
30.Berthon-Gelloz, G.; Siegler, M. A.; Spek, A. L.; Tinant, B.;
Reek, J. N. H.; Markó, I. E. Dalton Trans. 2010, 39, 1444.
doi:10.1039/B921894G
56.Marion, N.; Ramón, R. S.; Nolan, S. P. J. Am. Chem. Soc. 2008, 131,
448. doi:10.1021/ja809403e
31.Lavallo, V.; Canac, Y.; Präsang, C.; Donnadieu, B.; Bertrand, G.
Angew. Chem., Int. Ed. 2005, 44, 5705. doi:10.1002/anie.200501841
32.Groombridge, B. J.; Goldup, S. M.; Larrosa, I. Chem. Commun. 2015,
51, 3832. doi:10.1039/C4CC08920K
57.Sanz, S.; Jones, L. A.; Mohr, F.; Laguna, M. Organometallics 2007, 26,
952. doi:10.1021/om060821y
58.Mizushima, E.; Sato, K.; Hayashi, T.; Tanaka, M.
Angew. Chem., Int. Ed. 2002, 41, 4563.
33.Sharif, S.; Rucker, R. P.; Chandrasoma, N.; Mitchell, D.;
Rodriguez, M. J.; Froese, R. D. J.; Organ, M. G.
Angew. Chem., Int. Ed. 2015, 54, 9507–9511.
doi:10.1002/1521-3773(20021202)41:23<4563::AID-ANIE4563>3.0.CO
;2-U
doi:10.1002/anie.201502822
59.Ramón, R. S.; Gaillard, S.; Poater, A.; Cavallo, L.; Slawin, A. M. Z.;
Nolan, S. P. Chem. – Eur. J. 2011, 17, 1238.
34.Marelli, E.; Corpet, M.; Davies, S. R.; Nolan, S. P. Chem. – Eur. J.
2014, 20, 17272. doi:10.1002/chem.201404900
doi:10.1002/chem.201002607
35.Pompeo, M.; Farmer, J. L.; Froese, R. D. J.; Organ, M. G.
Angew. Chem., Int. Ed. 2014, 53, 3223. doi:10.1002/anie.201310457
36.Suzuki, Y.; Fukui, N.; Murakami, K.; Yorimitsu, H.; Osuka, A.
Asian J. Org. Chem. 2013, 2, 1066. doi:10.1002/ajoc.201300162
37.Hoi, K. H.; Coggan, J. A.; Organ, M. G. Chem. – Eur. J. 2013, 19, 843.
doi:10.1002/chem.201203379
60.Ramón, R. S.; Marion, N.; Nolan, S. P. Chem. – Eur. J. 2009, 15, 8695.
doi:10.1002/chem.200901231
61.Gómez-Suárez, A.; Gasperini, D.; Vummaleti, S. V. C.; Poater, A.;
Cavallo, L.; Nolan, S. P. ACS Catal. 2014, 4, 2701.
doi:10.1021/cs500806m
62.Ketcham, J. M.; Biannic, B.; Aponick, A. Chem. Commun. 2013, 49,
4157. doi:10.1039/C2CC37166A
38.Le Duc, G.; Meiries, S.; Nolan, S. P. Organometallics 2013, 32, 7547.
doi:10.1021/om4010143
39.Valente, C.; Çalimsiz, S.; Hoi, K. H.; Mallik, D.; Sayah, M.;
Organ, M. G. Angew. Chem., Int. Ed. 2012, 51, 3314.
doi:10.1002/anie.201106131
License and Terms
And references therein.
40.Organ, M. G.; Çalimsiz, S.; Sayah, M.; Hoi, K. H.; Lough, A. J.
Angew. Chem., Int. Ed. 2009, 48, 2383. doi:10.1002/anie.200805661
41.Çalimsiz, S.; Sayah, M.; Mallik, D.; Organ, M. G.
Angew. Chem., Int. Ed. 2010, 49, 2014. doi:10.1002/anie.200906811
42.Collado, A.; Balogh, J.; Meiries, S.; Slawin, A. M. Z.; Falivene, L.;
Cavallo, L.; Nolan, S. P. Organometallics 2013, 32, 3249.
doi:10.1021/om400168b
This is an Open Access article under the terms of the
Creative Commons Attribution License
(http://creativecommons.org/licenses/by/2.0), which
permits unrestricted use, distribution, and reproduction in
any medium, provided the original work is properly cited.
43.Poater, A.; Cosenza, B.; Correa, A.; Giudice, S.; Ragone, F.;
Scarano, V.; Cavallo, L. Eur. J. Inorg. Chem. 2009, 1759.
doi:10.1002/ejic.200801160
The license is subject to the Beilstein Journal of Organic
Chemistry terms and conditions:
(http://www.beilstein-journals.org/bjoc)
44.This software is available free of charge at
http://www.molnac.unisa.it/OMtools.php.
The definitive version of this article is the electronic one
which can be found at:
45.Patrick, S. R.; Collado, A.; Meiries, S.; Slawin, A. M. Z.; Nolan, S. P.
J. Organomet. Chem. 2015, 775, 152.
doi:10.1016/j.jorganchem.2014.04.022
doi:10.3762/bjoc.11.196
46.Ricard, L.; Gagosz, F. Organometallics 2007, 26, 4704.
doi:10.1021/om7006002
47.Mézailles, N.; Ricard, L.; Gagosz, F. Org. Lett. 2005, 7, 4133.
doi:10.1021/ol0515917
48.Gaillard, S.; Slawin, A. M. Z.; Nolan, S. P. Chem. Commun. 2010, 46,
2742. doi:10.1039/c0cc00018c
49.Gasperini, D.; Collado, A.; Goméz-Suárez, A.; Cordes, D. B.;
Slawin, A. M. Z.; Nolan, S. P. Chem. – Eur. J. 2015, 21, 5403.
doi:10.1002/chem.201406543
1814