A versatile cuprous synthon: [Cu(IPr)(OH)] (IPr = 1,3 bis(diisopropylphenyl)imidazol-2-ylidene)

Article abstract of DOI:10.1021/om100733n

The novel 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (hydroxy) copper ([Cu(IPr)(OH)]) exhibits a versatile capacity to activate numerous X-H bonds including all major hybridizations of C-H (i.e., sp, sp², sp ³), N-H, P-H, O-H, S-H, and one example of M-H (M = Mo) bonds. This reactivity also includes the cleavage of the Si-N and Si-C bonds to form unprecedented Cu-centered complexes.

Full text of DOI:10.1021/om100733n

3966 Organometallics 2010, 29, 3966–3972
DOI: 10.1021/om100733n
A Versatile Cuprous Synthon: [Cu(IPr)(OH)] (IPr = 1,3
bis(diisopropylphenyl)imidazol-2-ylidene)
George C. Fortman, Alexandra M. Z. Slawin, and Steven P. Nolan*
EastCHEM School of Chemisty, University of St Andrews, St Andrews, KY16 9ST, U.K.
Received July 26, 2010
The novel 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (hydroxy) copper ([Cu(IPr)(OH)]) exhi-
bits a versatile capacity to activate numerous X-H bonds including all major hybridizations of C-H
(i.e., sp, sp2, sp3), N-H, P-H, O-H, S-H, and one example of M-H (M = Mo) bonds. This reactivity
also includes the cleavage of the Si-N and Si-C bonds to form unprecedented Cu-centered complexes.
Introduction
complexes.5 Gunnoe et al. employed [Cu(IPr)Me] to activ-
ate a limited number of X-H bonds (X = N, O, and C).6
[Cu(SIPr)(CF3)] has proven an efficient trifluoromethylating
agent, while [Cu(IPr)F], in reactions with Ar-Si(OR)3 (R =
CH3 and CH2CH3), has permitted the isolation of several
Cu(I)-Ar derivatives.5a With these diverse reactivities and
potential for more, we reasoned that the design and synthesis
of a versatile, stable Cu(I) synthon would be highly desirable.
Although, a number of copper-hydroxide complexes have
been reported, these have been bimetallic or Cu(II) deri-
vatives.7 To our knowledge, no example of 14-electron dico-
ordinate [Cu(L)OH] (L = two-electron donor) complex has
been reported to date.8 Our working hypothesis hoped for a
versatile reactivity of a Cu-OH moiety associated with the
stabilizing properties of an NHC ancillary ligand. Prospec-
tive applications included, at the early stage, the use of such a
species as a synthon and as a probe for mechanistic studies.
Herein, we disclose the optimized synthesis of such a versatile
copper(I) synthon and its use as a key entryway into a myriad
of novel organocopper complexes.
The ever-increasing number of applications involving
organocopper complexes in organic synthesis has led to the
discovery of a plethora of innovative transformations.1 In
the past decade, this has been particularly true of dicoordinate
14e- [Cu(NHC)X] complexes (NHC = N-heterocyclic car-
benes). The use of Cu-NHC with alkoxide ligands has greatly
enhanced the potential reaches of this chemistry. A most
interesting accomplishment was reported by Sadighi, who,
by using [Cu(NHC)(OtBu)], generated [Cu(NHC)(Bpin)]
(pin = pinacolato) in situ. This complex was identified as an
active catalyst for the reduction of CO2 to CO.2 Addition-
ally, [Cu(NHC)(alkoxide)] have previously been shown to
catalytically enable the formation of boryl aldehydes3 and
carboxylate boronic esters4 and aid in the synthesis of novel
*To whom correspondence should be addressed. E-mail: snolan@
st-andrews.ac.uk.
(1) (a) Alexakis, A.; Backvall, J. E.; Krause, N.; Pamies, O.; Dieguez,
M. Chem. Rev. 2008, 108, 2796. (b) Breit, B.; Schmidt, Y. Chem. Rev. 2008,
108, 2928. (c) Daugulis, O.; Do, H.-Q.; Shabashov, D. Acc. Chem. Res.
2009, 42, 1074. (d) Deutsch, C.; Krause, N.; Lipshutz, B. H. Chem. Rev.
€
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Results and Discussion
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2008, 108, 2916. (e) Díaz-Requejo, M. M.; Perez, P. J. Chem. Rev. 2008, 108,
3379. (f ) Evano, G.; Blanchard, N.; Toumi, M. Chem. Rev. 2008, 108, 3054.
(g) Gschwind, R. M. Chem. Rev. 2008, 108, 3029. (h) Harutyunyan, S. R.;
den Hartog, T.; Geurts, K.; Minnaard, A. J.; Feringa, B. L. Chem. Rev. 2008,
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Hwang, W. S.; Lin, I. J. B. Chem. Rev. 2009, 109, 3561. ( j) Matsuo, Y.;
Nakamura, E. Chem. Rev. 2008, 108, 3016. (k) Meldal, M.; Tornøe, C. W.
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The reaction of [Cu(IPr)Cl] (1) with 2 equiv of anhydrous
CsOH in THF led to the formation of [Cu(IPr)(OH] (2) in
very good yield (eq 1).9
€
(2) Laitar, D. S.; Muller, P.; Sadighi, J. P. J. Am. Chem. Soc. 2005,
127, 17196.
(3) Bonet, A.; Lillo, V.; Ramırez, J.; Dıaz-Requejo, M. M.; Fernandez,
1
Formation of 2 was somewhat difficult to detect by H
ꢀ
E. Org. Biomol. Chem. 2009, 7, 1533.
(4) Ohishi, T.; Nishiura, M.; Hou, Z. Angew. Chem., Int. Ed. 2008, 47,
5792.
NMR due to the strikingly similar NMR spectra. For
example, the carbene backbone protons of the hydroxide
are shifted upfield by only 0.02 ppm in CD2Cl2 with respect
to 1 (CH-imide 1 δ 7.17 ppm; 2 δ 7.19 ppm in CD2Cl2).
To unequivocally determine the atom connectivity in 2,
single crystals suitable for X-ray diffraction (XRD) were
grown by slow diffusion of pentane into a THF-saturated
(5) (a) Herron, J. R.; Ball, Z. T. J. Am. Chem. Soc. 2008, 130, 16486.
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(b) Díez-Gonzalez, S.; Stevens, E. D.; Scott, N. M.; Petersen, J. L.; Nolan,
S. P. Chem.;Eur. J. 2008, 14, 158. (c) Bhattacharyya, K. X.; Akana, J. A.;
Laitar, D. S.; Berlin, J. M.; Sadighi, J. P. Organometallics 2008, 27, 2682.
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Petersen, J. L. Inorg. Chem. 2005, 44, 8647.
r
pubs.acs.org/Organometallics
Published on Web 08/10/2010
2010 American Chemical Society

Article
Organometallics, Vol. 29, No. 17, 2010 3967
formal C-H bond activation reaction. Moreover, the reac-
tion of 2 with dimethylmalonate in toluene proceeded in-
stantaneously to form [Cu(IPr)(CH(COOMe)2)] (4). The pre-
sence of an acidic C-H is suspected to favor the Cu-C bond
forming reaction. [Cu(NHC)(alkyl)] complexes are relatively
rare; for example the route to [Cu(IPr)(CH3)] involved
treatment of [Cu(IPr)(OAc)] with dimethylaluminum eth-
oxide generated in situ.13 [Cu(IPr)(Et)] was prepared by a
similar method.6 Use of [Cu(IPr)(OH)] as a synthon enables
efficient and clean Cu-alkyl bond formation at room tem-
perature without the necessity of additional reagents. The
C-H bond is required to be acidic, and at this stage we esti-
mate the C-H pKa requirement to be on the order of 27-
30 pKa units. To support the hypothesis of reactions pro-
ceeding predominately via a protonolysis mechanism, NMR
experiments were carried out in which a radical trap was
present. Reactions of 2 with CH3NO3 in C6D6 in the presence
of 2 equiv of TEMPO (2,2,6,6-tetramethylpiperidin-1-oxyl)
proceeded cleanly to produce 3. The absence of side products
formed with TEMPO present is in line with a mechanism
involving proton and not radical transfer.
Activation of the CH2 moiety of cyclopentadiene (CpH)
resulted in the formation of the half-sandwich complex [Cu-
(IPr)(η5-Cp)] (5). π-Coordination of the Cp unit was con-
firmed by both 1H and 13C NMR spectroscopy. Wang et al.
reported the synthesis of a series of [Cu(NHC)(η5-Cp)]
complexes using LiCp and [Cu(NHC)Cl].14 The reaction
was reported to require several hours, whereas the reac-
tion of 1 with C5H6 was observed to reach completion within
minutes.
Figure 1. Molecular representation of [Cu(IPr)OH] (2). All
hydrogens are omitted with the exception of H10. Cu1-O1
o
˚
˚
1.804(2) A, Cu1-C1 1.867(3) A, O1-Cu1-C1 177.13(11) .
solution of 2. Figure 1 shows a molecular representation of
[Cu(IPr)(OH)].
Noteworthy, among metrical parameters, is the shorter
˚
Cu1-O1 bond (1.804(2) A) observed in 2 compared to most
7c-h
˚
Cu(II) complexes with Cu-O bond lengths of >1.9 A.
Presumably, the shorter bond length is not due to the dif-
ference in charge but to the fact that the central copper atom
in 2 is only two-coordinate. When compared to [Au(IPr)-
(OH)],10 2 possesses a much shorter M-O bond length
˚
˚
(Au-O = 2.078(6) A; Cu-O 1.804(2) A).
The reactivity of 2 toward H-X activation was examined
next and expected to be very similar to that of the gold
derivative [Au(IPr)(OH)].10,11 For the gold congener, syn-
thetic feasibility of complexes was rationalized by simple
Brønsted-Lowry acid/base theory.12 Investigations into
C-H activation were guided by the pKa hypothesis. Gratify-
ingly, activations of sp3, sp2, and sp C-H bonds were all
successfully achieved. The reaction of 2 with nitromethane
resulted in the production of [Cu(IPr)(CH2NO2)] (3). The
reaction occurred upon addition of nitromethane to a solu-
tion of 2 in toluene at room temperature. This represents a
Activation of an aromatic sp2 C-H bond was exemplified
with 1,2,4,5-tetrafluorobenzene. The reaction was observed
to reach completion within minutes. Ball et al. have synthe-
sized several Cu-aryl compounds but were required to
resort to transmetalation with organosilanes.5a The workups
in these reactions are further complicated by the presence of
silanol byproduct and led to difficult isolation of the target
compounds. Formation of Cu-aryl bonds without the use of
silanes is therefore desirable and demonstrated here to
generate the targeted product and water as sole byproduct.
As compared to gold, very few studies have focused on
(NHC)Cu-acetylide complexes.6,7h,15 Reaction of 2 with
1,3,5-triethynylbenzene in toluene proved to easily produce
the trisubstituted 1,3,5-(IPrCu-CtC)C6H3 (7). The reaction
was observed to reach completion in as little as 14 h, while the
synthesis of [Cu(IPr)(CtCPh)] from phenylacetylene and
[Cu(IPr)Me] reportedly requires 22 h.6 Two discrete princi-
ples were confirmed by the synthesis of complex 7. First,
addition of the (IPr)Cu moiety to acetylene derivatives in a
sterically demanding environment was achieved. This could
in principle be extended to the modification of polymers (or
other large repetitive structures) with (NHC)Cu moieties.
Second, the compound was observed to be luminescent when
placed under UV radiation. While the photoluminescent
properties of gold acetylide complexes have been extensively
studied,11,16 few data have been reported for NHC copper
complexes.17
(7) (a) Liu, B.; Liu, B.; Zhou, Y.; Chen, W. Organometallics 2010, 29,
1457. (b) Yamaguchi, K.; Oishi, T.; Katayama, T.; Mizuno, N. Chem.;Eur.
J. 2009, 15, 10464. (c) Shahid, M.; Mazhar, M.; Brien, P. O.; Malik, M. A.;
Raftery, J. Polyhedron 2009, 28, 807. (d) Balboa, S.; Carballo, R.;
~
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ꢀ
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Castineiras, A.; Gonzalez-Perez, J. M.; Niclos-Gutierrez, J. Polyhedron 2008,
27, 2921. (e) Padhi, S. K.; Manivannan, V. Inorg. Chem. 2006, 45, 7994.
(f ) Price, J. R.; Fainerman-Melnikova, M.; Fenton, R. R.; Gloe, K.; Lindoy, L. F.;
Rambusch, T.; Skelton, B. W.; Turner, P.; White, A. H.; Wichmann, K. Dalton
Trans. 2004, 3715. (g) Tubbs, K. J.; Fuller, A. L.; Bennett, B.; Arif, A. M.;
Berreau, L. M. Inorg. Chem. 2003, 42, 4790. (h) Fujisawa, K.; Kobayashi, T.;
Fujita, K.; Kitajima, N.; Moro-oka, Y.; Miyashita, Y.; Yamada, Y.; Okamoto, K.-
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(8) Complex 2 was recently shown to be active in C-H bond
functionalization reactions : Boogeart, I. F. F.; Fortman, G. C.; Furst,
M.R. L.; Cazin C. S. J; Nolan, S. P., manuscript submitted.
(9) Unlike its gold congener10 synthetic attempts using NaOH and
KOH proved unsuccessful, yet once isolated, solid-state samples of 2 left
in the air for more than 1 month showed no visible decomposition as
monitored by NMR spectroscopy.
(10) Gaillard, S.; Slawin, A. M. Z.; Nolan, S. P. Chem. Commun.
2010, 46, 2742.
(11) Fortman, G. C.; Poater, A.; Levell, J. W.; Gaillard, S.; Slawin,
A. M. Z.; Samuel, I. D. W.; Cavallo, L.; Nolan, S. P. Dalton Trans. 2010,
39, DOI: 10.1039/c0dt00276c.
(12) Potentiometric titration data in DMSO revealed a pKa = 30.4(2)
for [Au(IPr)(OH)] ( Boogaerts, I. I. F.; Slawin, A. M. Z.; Nolan, S. P.
J. Am. Chem. Soc. 2010, 132, 8858–8859). A lower pKa of 2 is suspected as
a result of the the higher electronegativity of Cu(I) compared to Au(I). This
greater electronegativity would decrease the electron density about the
oxygen atom and thus lower its nucleophilicity.
(13) (a) Mankad, N. P.; Gray, T. G.; Laitar, D. S.; Sadighi, J. P.
Organometallics 2004, 23, 1191. (b) Kaur, H.; Kauer, F.; Stevens, E. D.;
Nolan, S. P. Organometallics 2004, 23, 1157.
(14) Ren, H.; Zhao, X.; Xu, S.; Song, H.; Wang, B. J. Organomet.
Chem. 2006, 691, 4109.
ꢀ
(15) Dıez-Gonzalez, S.; Nolan, S. P. Angew. Chem., Int. Ed. 2008, 47,
8881.

3968 Organometallics, Vol. 29, No. 17, 2010
Fortman et al.
Cu-Si complexes have been reported.21 None are however
14-electron dicoordinate linear complexes.
N-H bonds were also readily activated. Two such com-
plexes were prepared as proof-of-concept examples. First,
the reaction of 2 with a thiocarbonylamide (eq 2) selectively
led to activation of the amide N-H bond. The product was
isolated as a white solid in 79% yield. This demonstrates the
regioselectivity of 2 for activation of the most acidic proton
of the substrate.22
Figure 2. Molecular representation of [Cu(IPr)(CN)] (8). Hy-
˚
drogens are omitted for clarity. Cu1-C31 1.862(5) A, Cu1-C1
o
˚
˚
1.900(4) A, C31-N31 1.139(6) A, C1-Cu1-C31 177.5(3) ,
Cu1-C31-N31 177.9(7)o.
The [Cu(IPr)(CN)] (8) species was not accessed by C-H
activation, but rather via the reaction of 2 with trimethylsilyl
cyanide. Unfortunately, the reaction with TMS-CN led to
simultaneous formation of a salt formed in ∼15% yield.18
This salt was later identified by single-crystal XRD (Figure S1)
1
and H NMR spectroscopy to be [IPrH][Cu(CN)2]. X-ray
The second example of N-H activation was inspired from
a gold analogue. [Cu(IPr)(NTf2)] (11) was successfully pre-
pared in 86% yield from 2 and HNTf2 (Tf = SO2CF3). The
gold analogue, also known as a Gagosz-type complex,23 has
been utilized in the functionalization of bicycloheptanes,24
[4þ1] cyclization of propargyl tosylates with N-tosylaldimines,25
and rearrangement of 3-cyclopropyl propargylic acetates.26 In-
deed, initial catalytic screenings in our laboratory have shown
the ability of 11 to transform phenylpropargyl acetates into the
corresponding allenes as shown in eq 3.27
structures of several Cu-CN compounds have been pre-
viously published; however most are polymeric in nature.19
To our knowledge [Cu(IPr)(CN)] is the first isolated example
of a 14-electron, dicoordinate Cu(I) complex. Single crystals
suitable for XRD analysis were obtained from vapor diffu-
sion of pentane into a saturated solution of 8 in THF. A
graphical representation of 8 is shown in Figure 2. Bond
lengths and angles for 8 are similar to those of other more
electron rich Cu(I)-CN complexes.19c,f
Attempted formation of Cu-Si bonds through Si-H
activation failed, as formation of Si-OH is more favorable
than H-OH formation by more than 20 kcal/mol.20 For-
mation of a Cu-Si bond was however successfully accom-
plished through reaction of 2 with Me2N-SiMe3 to produce
[Cu(IPr)(SiMe3)] (9). Relatively few examples of neutral
Single crystals of 11 were grown from vapor diffusion of
pentane into a saturated solution of 11 in benzene. A
graphical representation of 11 is presented in Figure 3.
Similar metrical comparisons between the Cu and Au com-
plexes are found and are in line with those found for the [M-
(IPr)OH] (M = Cu and Au) complexes. Both the M-C and
(16) (a) Feilchenfeld, H.; Weaver, M. J. J. Phys. Chem. 1989, 93, 4276.
(b) Fluegge, S.; Anoop, A.; Goddard, R.; Thiel, W.; F€urstner, A. Chem.;
Eur. J. 2009, 15, 8558. (c) Hunks, W. J.; MacDonald, M.-A.; Jennings, M. C.;
Puddephatt, R. J. Organometallics 2000, 19, 5063. (d) Schmidbaur, H. Gold
Bull. 1990, 23, 11.
(17) Fujimura, O.; Fukunaga, K.; Honma, T.; Machida, T. JP
2007297347, Japan, 2007.
(18) See Supporting Information for details. X-ray diffraction data
for this complex can be found in the SI.
M-N bonds are shorter in the copper case (M-C Au:
23
˚
˚
1.969(2), Cu 1.859(5) A; M-N Au: 2.091(2), Cu 1.911(4) A).
Activation of the P-H bond of diphenylphosphine was
seemingly instantaneous, producing the yellow [Cu(IPr)-
(PPh2)] (11). Fortunately, the phosphine appears to be some-
what resistant to electrophilic attack by water, which is the
(19) (a) Pike, R. D.; deKrafft, K. E.; Ley, A. N.; Tronic, T. A. Chem.
Commun. 2007, 3732. (b) Saravanabharathi, D.; Nethaji, M.; Venugopalan,
P.; Samuelson, A. G. Polyhedron 2002, 21, 2433. (c) Coles, M. P.; Hitchcock,
P. B. Polyhedron 2001, 20, 3027. (d) Chesnut, D. J.; Plewak, D.; Zubieta, J.
J. Chem. Soc., Dalton Trans. 2001, 2567. (e) Chesnut, D. J.; Kusnetzow, A.;
Birge, R.; Zubieta, J. J. Chem. Soc., Dalton Trans. 2001, 2581.
(f ) Ellermann, J.; Knoch, F. A.; Meier, K. J.; Moll, M. J. Organomet. Chem.
1992, 428, C44. (g) Anderson, O. P.; Packard, A. B. Inorg. Chem. 1980, 19,
2941.
(22) Bordwell, F. G. Acc. Chem. Res. 1988, 21, 456–463.
(23) Ricard, L.; Gagosz, F. Organometallics 2007, 26, 4704.
(24) Li, G.; Huang, X.; Zhang, L. J. Am. Chem. Soc. 2008, 130, 6944.
(25) Suarez-Pantiga, S.; Rubio, E.; Alvarez-Rua, C.; Gonzalez, J. M.
Org. Lett. 2009, 11, 13.
(26) Garayalde, D.; Gomez-Bengoa, E.; Huang, X.; Goeke, A.;
Nevado, C. J. Am. Chem. Soc. 2010, 132, 4720.
(27) 1-Acetate-1-hexyn-1-ylbenzenemethanol was observed to be
converted to 3-acetate-1-phenyl-1,2-heptadien-3-ol in 91% yield as
determined by 1H NMR spectroscopy.
(20) Comprehensive Handbook of Chemical Bond Energies; Luo, Y.-R.,
Ed.; CRC Press: Boca Raton, FL, 2007; 462 and 255.
(21) (a) Avent, A. G.; Gehrhus, B.; Hitchcock, P. B.; Lappert, M. F.;
Maciejewski, H. J. Organomet. Chem. 2003, 686, 321. (b) Klett, J.;
Klinkhammer, K. W.; Niemeyer, M. Chem.;Eur. J. 1999, 5, 2531.
(c) Schubert, U.; Mayer, B. C. Russ. Chem. Ber. 1994, 127, 2189. (d)
Cowley, A. H.; Elkins, T. M.; Jones, R. A.; Nunn, C. M. Angew. Chem., Int.
Ed. Engl. 1988, 27, 1349.

Article
Organometallics, Vol. 29, No. 17, 2010 3969
Figure 3. Molecular representation of [Cu(IPr)(NTf2)] (Tf =
trifluoromethanesulfonate) (11). Hydrogens are omitted for
clarity. Cu-C1 1.859(5) A, Cu1-N16 1.911(4) A, C10-Cu1-
N16 180.00°.
Figure 4. Molecularrepresentationof[(IPr)Cu-Mo(CO)3Cp] (16).
˚
Hydrogens are omitted for clarity. Cu1-C1 1.916(5) A, Cu1-Mo1
˚
˚
o
˚
2.5600(8) A, C1-Cu1-Mo1 167.28(15) .
a metal hydride to form bimetallic complexes was also
examined.33 The combination of the intrinsic basicity of 2
with the abundance of metal hydrides provides a perfect
route to form just such a novel complex. The reaction of
[Cu(IPr)(OH)] with [HMo(CO)3(η5-C5H5)] led to the forma-
tion of a Cu-Mo bond. A graphical representation as
determined by XRD of 16 is shown in Figure 4. Of particular
note is the large deviation from linearity of the Mo1-Cu-C1
bond angle (167.28(15)o) presumably caused by steric repulsion
between the pendant iPr groups and the carbonyls. Analysis of
the νCO stretching frequencies in CH2Cl2 revealed three major
stretches (1925.8, 1821.9, and 1798.6 cm-1), which are char-
acteristic of a [(L)M-M0(CO)3Cp] (L = two-electron donor;
M = Au, Cu; M0 = Cr, Mo, W) tightly bound ion pair.34
byproduct in this reaction. The proton-coupled 31P NMR
spectrum of 11 in C6D6 displayed a single resonance at δ
-26.0 ppm [for comparison: HPPh2 (δ -41.4 ppm) and PPh3
(δ -5.5 ppm)]. Caulton et al. have reported the synthesis of
the sole other example of this type, [Cu(PPh3)(PPh2)], which
exhibits a 31P NMR resonance at δ -32.2 ppm.28 The
downfield shift of the NHC derivative compared with the
triphenylphosphane complex can be explained by the greater
σ-donating ability of the NHC.29
Alcohols were also activated using 2. Stirring [Cu(IPr)-
(OH)] in MeOH overnight resulted in formation of the Cu-
methoxide complex [Cu(IPr)(OMe)] (13) in high yield, 91%.
Additionally reaction of 2 with tert-butanol resulted in high
yields of [Cu(IPr)(OtBu)] (14), 93%. Stoichiometric reac-
tions in C6D6 resulted in similarly high yields, as confirmed
Conclusion
1
by H NMR spectroscopy. Although the synthesis of these
complexes2,5b,14 and their use in catalysis2-4,5c,6 have previ-
ously been reported, the simple fact that they can be synthe-
sized directly from [Cu(IPr)(OH)] suggests that 2 is a more
reactive and consequently more versatile synthon.
In summary, the synthesis of 2 has been achieved and its
chemical versatility as a key synthon has been demonstrated
(see Figure 5) in reactions involving numerous X-H bond
activation including C-H bonds (i.e., sp, sp2, sp3) as well as
N-H, P-H, O-H, and S-H bonds. The cleavage of Si-N
and Si-C bonds has also been shown as a viable synthetic
route leading to unprecedented copper complexes. Addition-
ally, we have demonstrated that the use of 2 with a metal
hydride can serve as a simplistic strategy for the synthesis of
heterobimetallic complexes. Further work in our laboratory
is aimed at exploring the use of 2 as a synthon and as a
(pre)catalyst.
Access to the formation of Cu-S bonds through S-H was
also accomplished. Protonation of 2 with para-thiocresol
resulted in formation of [Cu(IPr)(S-p-tol)] (15) in 88% yield.
Thiocopper species have been know for several centuries.30
Preparation of these complexes was accomplished with the
use of alkyl copper complexes, and they have been proposed
as catalytic intermediates in the hydrothiolation of vinyla-
renes31 and olefins.32
In addition to reactions with H-A bonds commonly
found in organic chemistry, examination of reactions with
Experimental Section
General Considerations. Unless stated otherwise all reactions
were carried out inside an MBraun glovebox under inert condi-
tions. Solvents were distilled and dried as required. Nitrome-
thane and 1,2,4,5-tetraflourobenzene were purchased from Alfa-
Aesar. Dimethyl malonate, dicyclopentadiene, trimethylsilane
(28) Lemmen, T. H.; Goeden, G. V.; Huffman, J. C.; Geerts, R. L.;
Caulton, K. G. Inorg. Chem. 1990, 29, 3680.
(29) (a) For a monograph on NHC in synthesis see: N-Heterocyclic
Carbenes in Synthesis; Nolan, S. P., Ed.; Wiley-VCH: Weinheim, 2006.
ꢀ
(b) For a review on NHC in late transition metal catalysis see: Díez-Gonzalez,
S.; Marion, N.; Nolan, S. P. Chem. Rev. 2009, 109, 3612.
(30) (a) Bridges, A. J.; Ross, R. J. Tetrahedron Lett. 1983, 24, 4797.
(b) Kubota, M.; Yamamoto, A. Bull. Chem. Soc. Jpn. 1978, 51, 3622.
(31) Munro-Leighton, C.; Delp, S. A.; Alsop, N. M.; Blue, E. D.;
Gunnoe, T. B. Chem. Commun. 2008, 111.
(33) Hetero-bimetallic complexes have led to some interesting chem-
istry; see for example: Ruiz, J.; Perandones, B. F. J. Am. Chem. Soc.
2007, 129, 9298.
(32) Delp, S. A.; Munro-Leighton, C.; Goj, L. A.; Ramirez, M. A.;
(34) Haines, R. J.; Nyholm, R. S.; Stiddard, M. H. B. J. Chem. Soc., A
Gunnoe, T. B.; Petersen, J. L.; Boyle, P. D. Inorg. Chem. 2007, 46, 2365.
1968, 46.

3970 Organometallics, Vol. 29, No. 17, 2010
Fortman et al.
Figure 5. Summary of complexes synthesized using [Cu(IPr)(OH] (2).
cyanide, dimethyltrimethysilane amine, triflimide, diphenyl-
phosphane, tert-butanol, methanol, and para- and thiocresol
were purchased from Sigma-Aldrich and used as received. 1,3,5-
Triethynylbenzene was purchased from ABCR. [Cu(IPr)Cl],35
[HMo(CO)3Cp],36 and N-phenyl-2-thioxo-1-imidazolidinecar-
boxamide36 were prepared according to literature procedures.
1H and 13C NMR were recorded on either a Burker 400 MHz or
a Bruker 300 MHz NMR spectrometer. Spectra were referenced
to CD2Cl2 at δ 5.32 (13C, δ 54.0), C6D6 at δ 7.16 (13C δ 128.4),
CDCl3 at δ 7.26 (δ 13C 77.2), or THF-d8 at δ 3.58 (δ 13C 67.6)
ppm. Elemental analyses were performed at the University of St
Andrews.
δ ppm): 7.56 (t, 2H, 2JH = 7.8 Hz, Ar-CH), 7.35 (d, 4H, 2JH
7.8 Hz Ar-CH), 7.17 (s, 2H, imid-CH), 2.60 (sept, 4H, 2JH = 6.9
Hz, iPr-CH), 1.32 (d, 12H, 2JH = 7.0 Hz, iPr-CH3), 1.24 (d, 12H,
=
2JH = 7.0 Hz, Pr-CH3), OH proton not observed. 13C NMR
i
(CD2Cl2, 75.5 MHz, δ ppm): 182.3 (s, carbene C), 146.3 (s, Ar-
C), 135.5 (s, Ar-C), 130.7 (s, imid-C), 124.6 (s, Ar-C), 123.6 (s,
Ar-C), 29.2 (s, iPr-C), 25.0 (s, iPr-C), 24.1 (s, iPr-C). Anal. Calcd
for C27H37CuN2O (MW 469.14): C, 69.12; H, 7.95; N, 5.97.
Found: C, 68.84; H, 7.95; N, 5.99.
Synthesis of [Cu(IPr)(R)] Utilizing R-H Bond Activation.
Typically 100 mg (0.213 mmol) of [Cu(IPr)OH] (2) was placed
with 2 mL of toluene. One molar equivalent of H-R was added
to the white suspension. Generally, dissolution of the complex
occurred within minutes, at which point the reaction was stirred
for an additional 1 h. The solvent was subsequently stripped
in vacuo to approximately 0.75 mL, at which point the product
was precipitated from solution with the addition of pentane. The
products were filtered from the solution, washed with pentane
(3 ꢀ 3 mL), and dried under reduced pressure.
Synthesis of [Cu(OH)(IPr)] (2). In the glovebox a 20 mL
scintillation vial was charged with 100 mg (0.205 mmol) of
[Cu(IPr)Cl] and 2 equiv of anhydrous CsOH. The solids were
then dissolved in 4.0 mL of dry, degassed THF. The solution was
stirred at rt for 8 h. The resulting clear light yellow solution was
filtered through a plug of Celite, and the solution was concen-
trated in vacuo until a white precipitate formed (ca. 1 mL
remaining). Slow addition of pentane (ca. 8 mL) was then used
to precipitate the remaining product. The white microcrystalline
product was collected on a glass frit, then dried in vacuo to yield
82 mg of 2 (85% yield). Single crystals for XRD were grown
from a saturated solution of THF and pentane at -40 °C.
CD2Cl2 used to take NMR was first passed through basic
[Cu(IPr)(CH2(NO2))] (3): white microcrystals, 89% yield,
unstable in DCM. 1H NMR (C6D6, 300 MHz, δ ppm): 7.18 (t,
2H, 2JH = 7.8 Hz, Ar-CH), 7.07 (d, 4H, 2JH = 7.6 Hz Ar-CH),
6.32 (s, 2H, imid-CH), 5.35 (s, 1H, Cu-CH2(NO2)), 3.28 (s, 6H,
2
i
OCH3), 2.63 (sept, 4H, JH = 6.9 Hz, Pr-CH), 1.44 (d, 12H,
2JH = 6.8 Hz, iPr-CH3), 1.08 (d, 12H, 2JH = 6.9 Hz, iPr-CH3).
13C NMR (C6D6, 75 MHz, δ ppm): 185.0 (s, carbene C), 174.0 (s,
CdO), 146.8 (s, Ar-C), 136.2 (s, Ar-C), 130.4 (s, imid-C), 124.4
(s, Ar-C), 122.7 (s, Ar-C), 63.2 (s, Cu-CH), 50.2 (s, OCH3), 29.2
1
alumina to remove HCl traces. H NMR (CD2Cl2, 300 MHz,
(35) Citadelle, C. A.; LeNouy, E.; Bisaro, F.; Slawin, A. M. Z.; Cazin,
C. S. J. Dalton Trans. 2010, 4489.
(36) Burchell, R. P. L.; Sirsch, P.; Decken, A.; McGrady, G. S. Dalton
i
i
i
(s, Pr-C), 24.35 (s, Pr-C), 24.31 (s, Pr-C). Anal. Calcd for
C28H38CuN3O2 (MW 512.17): C, 65.66; H, 7.48; N, 8.20.
Found: C, 65.77; H, 7.32; N, 8.12.
Trans. 2009, 5851.

Article
Organometallics, Vol. 29, No. 17, 2010 3971
[Cu(IPr)(CH(COOMe)2)] (4): 70% yield. 1H NMR (CD2Cl2,
[Cu(IPr)(thiocarbonylamide)] (10): white powder, 79% yield.
1H NMR (CD2Cl2, 400 MHz, δ ppm): 12.42 (s, 1H, NH), 7.54 (t,
2H, 2JH = 7.8 Hz, Ar-CH), 7.45 (d, 2H,, 2JH = 8.2 Hz, CH-Ph),
7.36 (d, 4H, 2JH = 7.9 Hz, Ar-CH), 7.21 (s and t overlapping, 2H
and 2H, imid-CH and CH-Ph), 6.95 (t, 1H, 2JH = 7.5 Hz, CH-
Ph), 3.83 (t, 2H, 2JH = 8.8 Hz, CH2), 3.00 (t, 2H, 2JH = 8.3 Hz,
2
300 MHz, δ ppm): 7.49 (t, 2H, JH = 7.8 Hz, Ar-CH), 7.32
(d, 4H, 2JH = 7.7 Hz Ar-CH), 7.11 (s, 2H, imid-CH), 3.80 (s, 1H,
Cu-CH), 3.28 (s, 6H, OCH3), 2.71 (sept, 4H, 2JH = 6.9 Hz, iPr-
CH), 1.31 (d, 12H, 2JH = 6.7 Hz, iPr-CH3), 1.23 (d, 12H, 2JH
=
7.0 Hz, iPr-CH3). 13C NMR (CD2Cl2, 75 MHz, δ ppm): 184.1
(s, carbene C), 146.3 (s, Ar-C), 135.7 (s, Ar-C), 130.9 (s, imid-C),
124.6 (s, Ar-C), 122.7 (s, Ar-C), 96.8 (s, Cu-CH2(NO2)), 29.4 (s,
iPr-C), 25.2 (s, iPr-C), 24.2 (s, iPr-C). Anal. Calcd for C32H43Cu-
N2O4 (MW 583.25): C, 65.90; H, 7.43; N, 4.80. Found: C, 65.97;
H, 7.44; N, 4.86.
i
CH2), 2.63 (sept, 4H, 2JH = 6.8 Hz, Pr-CH), 1.34 (d, 12H,
2JH = 6.9 Hz, iPr-CH3), 1.25 (d, 12H, 2JH = 7.0 Hz, iPr-CH3).
13C NMR (CD2Cl2, 100 MHz, δ ppm): 181.7 (s, carbene C),
179.0 (s, CdS), 152.2 (s, CdO) 146.4 (s, Ar-C), 139.9 (s, Ph-C),
135.3 (s, Ar-C), 130.8 (s, imid-C), 129.1 (s, Ph-C), 124.6 (s, Ar-C),
123.6 (s, Ar-C), 122.8 (s, Ph-C), 119.6 (s, Ph-C), 48.6 (s, C-
[Cu(IPr)Cp] (5): light yellow powder, 89% yield. Compound
1
i
i
identity was confirmed with literature H NMR.37 13C NMR
imidazole), 48.0 (s, C-imidizole), 29.3 (s, Pr-C), 25.0 (s, Pr-C),
24.3 (s, iPr-C). Anal. Calcd for C38H48CuN5OS (MW 686.43): C,
66.49; H, 7.05; N, 10.20. Found: C, 66.11; H, 6.85; N, 10.03.
[Cu(IPr)(NTf2)] (11) (Tf = SO2CF3): white powder, XRD
crystals grown from slow vapor diffusion of pentane into a
saturated solution of benzene, 86% yield. 1H NMR (CDCl3, 300
MHz, δ ppm): 7.51 (t, 2H, 2JH = 7.8 Hz, Ar-CH), 7.31 (d, 4H,
2JH = 8.0 Hz Ar-CH), 7.32 (s, 2H, imid-CH), 2.53 (sept, 4H,
2JH = 6.8 Hz, iPr-CH), 1.26 (d, 12H, 2JH = 6.9 Hz, iPr-CH3),
was not included in original publication. 13C NMR (CD2Cl2,
100 MHz, δ ppm): 188.3 (s, carbene C), 146.5 (s, Ar-C), 136.7
(s, Ar-C), 130.1 (s, imid-C), 124.2 (s, Ar-C), 123.0 (s, Ar-C), 95.1
(s, Cp), 29.1 (s, iPr-C), 24.6 (s, iPr-C), 24.1 (s, iPr-C).
[Cu(IPr)(C6F4H)] (6): white powder, 85% yield. 1H NMR
(CD2Cl2, 300 MHz, δ ppm): 7.53 (t, 2H, 2JH = 7.8 Hz, Ar-CH),
7.35 (d, 4H, 2JH = 7.8 Hz Ar-CH), 7.23 (s, 2H, imid-CH), 6.50
(m, 1H, C6F4H), 3.28 (s, 6H, OCH3), 2.67 (sept, 4H, 2JH = 6.8
Hz, iPr-CH), 1.34 (d, 12H, 2JH = 6.8 Hz, iPr-CH3), 1.27 (d, 12H,
2JH = 6.9 Hz, iPr-CH3). 13C NMR (CD2Cl2, 75 MHz, δ ppm):
183.0 (s, carbene C), 174.0 (s, CdO), 151.7, 148.7, 146.6, 143.4
(m, CF), 146.5 (s, Ar-C), 135.2 (s, Ar-C), 130.8 (s, imid-C), 124.5
2
i
1.22 (d, 12H, JH = 6.9 Hz, Pr-CH3). 13C NMR (CDCl3, 75
MHz, δ ppm): 178.7 (s, carbene C), 145.7 (s, Ar-C), 134.2 (s, Ar-
C), 130.9 (s, imid-C), 124.4 (s, Ar-C), 123.9 (s, Ar-C), 119.1 (q,
1JF = 322 Hz, CF3), 29.0 (s, iPr-C), 24.5 (s, iPr-C), 24.2 (s, iPr-
C). 19F NMR (CDCl3, 282.4 MHz, δ ppm): -77.15 (s, CF3).
Anal. Calcd for C29H36CuF6N3O4S2 (MW 732.28): C, 47.57; H,
4.96; N, 5.74. Found: C, 47.62; H, 5.05; N, 5.83.
3
(s, Ar-C), 123.7 (s, Ar-C), 102.4 (t, JF = 23 Hz Cu-C), 29.4
i
i
i
(s, Pr-C), 25.0 (s, Pr-C), 24.2 (s, Pr-C). Anal. Calcd for
C33H37CuF4N2 (MW 601.20): C, 65.90; H, 7.43; N, 4.80. Found:
C, 65.74; H, 7.87; N, 4.98.
[Cu(IPr)(PPh2)] (12): synthesis performed in benzene, yellow
powder, 67% yield, decomposition observed in CD2Cl2. 1H
NMR (C6D6, 300 MHz, δ ppm): 7.36 (m, 4H, PPh), 7.27 (t,
2H, 2JH = 7.5 Hz, Ar-CH), 7.07 (d, 4H, 2JH = 7.6 Hz Ar-CH),
7.00-6.94 (m, 6H, PPh), 6.24 (s, 2H, imid-CH), 2.50 (sept, 4H,
2JH = 6.5 Hz, iPr-CH), 1.20 (d, 12H, 2JH = 6.9 Hz, iPr-CH3),
1.04 (d, 12H, 2JH = 7.0 Hz, iPr-CH3). 13C NMR (THF-d8, 75
MHz, δ ppm): 183.5 (s, carbene C), 148.4 (d, 1JP = 27 Hz, C-P),
146.7 (s, Ar-C), 136.2 (s, Ar-C), 134.1 (d, 2JP = 17 Hz, C-Ph),
131.1 (s, imid-C), 127.8 (d, 2JP = 5.2 Hz, C-Ph), 125.0 (s, Ar-C),
[1,3,5-((IPr)-Cu-CC)3C6H3] (7): reaction left stirring for 14 h,
87% yield. 1H NMR (CD2Cl2, 300 MHz, δ): 7.53 (t, 6H, 2JH
=
7.8 Hz, Ar-CH), 7.34 (d, 12H, 2JH = 7.3 Hz Ar-CH), 7.13 (s, 6H,
imid-CH), 6.60 (s, 3H, benzene-CH), 2.59 (sept, 12H, 2JH = 7.0
Hz, iPr-CH), 1.32 (d, 36H, 2JH = 6.8 Hz, iPr-CH3), 1.22 (d, 36H,
2JH = 6.9 Hz, iPr-CH3). 13C NMR (CH2Cl2, 75 MHz, δ ppm):
183.2 (s, carbene C), 146.3 (s, Ar-C), 135.2 (s, Ar-C), 132.3
(s, benzene-C), 130.8 (s, imid-C), 126.9 (s, benzene-C), 124.6
(s, Ar-C), 123.5 (s, Ar-C), 121.0 (s, alkyne) 105.0 (s, alkyne), 29.3
i
i
i
i
i
124.4 (s, Ar-C), 123.3 (s, C-Ph), 29.8 (s, Pr-C), 25.2 (s, Pr-C,
(s, Pr-C), 24.8 (s, Pr-C), 24.3 (s, Pr-C). Anal. Calcd for
C93H111Cu3N6 (MW 1503.55): C, 74.29; H, 7.44; N, 5.59.
Found: C, 74.56; H, 7.64; N, 5.88.
overlapping solvent), 24.2 (s, Pr-C). 31P NMR (C6D6, 121.5
i
MHz, δ ppm): -27.8 (s, CF3). Anal. Calcd for C39H46CuN2P
(MW 637.32): C, 73.50; H, 7.28; N, 4.40. Found: C, 73.68; H,
7.56; N, 4.59.
[Cu(IPr)(CN)] (8). The product obtained was recrystallized
from a minimal amount of THF to remove the side product
[HIPr][Cu(CN)2]. XRD of 8 and Cu salt were grown from a
saturated solution of pentane and THF at -40 °C. Colorless
crystals, 47% yield. 1H NMR (CD2Cl2, 300 MHz, δ ppm): 7.55
[Cu(IPr)(OMe)] (13): reaction left to stir for 14 h, white
powder, 91% yield. Identity was confirmed by 1H NMR of
previously reported preparation.38
[Cu(IPr)(OtBu)] (14): reaction left to stir for 14 h, white
powder, 93% yield. Identity was confirmed by 1H NMR of
previously reported preparation.39
2
(t, 2H, 2JH = 7.7 Hz, Ar-CH), 7.35 (d, 4H, JH = 7.8 Hz Ar-
CH), 7.20 (s, 2H, imid-CH), 2.53 (sept, 4H, 2JH = 7.0 Hz, iPr-
CH), 1.28 (d, 12H, 2JH = 6.9 Hz, iPr-CH3), 1.23 (d, 12H, 2JH
=
[Cu(IPr)(S-p-tol)] (15): white microcrystalline powder, 88%
6.8 Hz, iPr-CH3). 13C NMR (CD2Cl2, 75 MHz, δ ppm): 180.7 (s,
carbene C), 146.2 (s, Ar-C), 142.4 (s, CN), 134.6 (s, Ar-C), 131.2
(s, imid-C), 124.7 (s, Ar-C), 124.1 (s, Ar-C), 29.3 (s, iPr-C), 25.2
yield. 1H NMR (CDCl3, 400 MHz, δ ppm): 7.52 (t, 2H, 2JH
=
7.8 Hz, Ar-CH), 7.30 (d, 4H, 2JH = 7.8 Hz Ar-CH), 7.14 (s, 2H,
imid-CH), 6.5 (m, 4H, cresol-CH) 2.61 (sept, 4H, 2JH = 7.0 Hz,
iPr-CH), 2.14 (s, 3H, CH3) 1.28 (d, 12H, 2JH = 6.9 Hz, iPr-CH3),
1.23 (d, 12H, 2JH = 6.9 Hz, iPr-CH3). 13C NMR (CDCl3, 100
MHz, δ ppm): 181.6 (s, carbene C), 145.7 (s, Ar-C), 139.5 (s,
C-S), 134.5 (s, Ar-C), 132.5 (s, CH-cresol), 130.4 (s, imid-C),
128.2 (s, CH-cresol), 124.7 (s, CH-cresol), 124.2 (s, Ar-C), 122.8
(s, Ar-C), 28.7 (s, iPr-C), 24.7 (s, iPr-C), 23.8 (s, iPr-C), 20.7 (s,
CH3-cresol). Anal. Calcd for C34H43CuN2S (MW 575.24): C,
70.98; H, 7.53; N, 4.87. Found: C, 71.13; H, 7.86; N, 4.95.
[(IPr)Cu-Mo(CO)3Cp] (16): yellow powder, 83% yield. 1H
NMR (CD2Cl2, 300 MHz, δ ppm): 7.52 (t, 2H, 2JH = 7.8 Hz,
Ar-CH), 7.36 (d, 4H, 2JH = 7.9 Hz Ar-CH), 7.18 (s, 2H, imid-
i
i
(s, Pr-C), 24.1 (s, Pr-C). Anal. Calcd for C28H36CuN3 (MW
478.15): C, 70.33; H, 7.59; N, 8.79. Found: C, 70.53; H, 7.40; N,
8.96.
[Cu(IPr)(SiMe3)] (9): product isolated from a saturated solu-
tion of THF and pentane at -40 °C, colorless crystals, 43%
yield. 1H NMR (CD2Cl2, 400 MHz, δ ppm): 7.51 (t, 2H, 2JH
=
7.8 Hz, Ar-CH), 7.32 (d, 4H, 2JH = 7.8 Hz Ar-CH), 7.14 (s, 2H,
imid-CH), 2.58 (sept, 4H, 2JH = 6.9 Hz, iPr-CH), 1.30 (d, 12H,
2JH = 6.8 Hz, iPr-CH3), 1.22 (d, 12H, 2JH = 6.8 Hz, iPr-CH3),
-0.45 (s, 9H, SiMe3). 13C NMR (CD2Cl2, 100 MHz, δ ppm):
182.5 (s, carbene C), 146.3 (s, Ar-C), 135.5 (s, Ar-C), 130.7 (s,
imid-C), 124.6 (s, Ar-C), 123.6 (s, Ar-C), 29.2 (s, iPr-C), 25.0 (s,
iPr-C), 24.2 (s, iPr-C), 4.2 (s, SiMe3). Anal. Calcd for
C30H45CuN2Si (MW 525.32): C, 68.59; H, 8.63; N, 5.33. Found:
C, 68.31; H, 8.39; N, 5.02.
2
i
CH), 4.82 (s, 5H, Cp), 2.70 (sept, 4H, JH = 7.2 Hz, Pr-CH),
(38) Ren, H.; Zhao, X.; Xu, S.; Song, H.; Wang, B. J. Organomet.
Chem. 2006, 691, 4109.
ꢀ
(39) Bonet, A.; Lillo, V.; Ramırez, J.; Dıaz-Requejo, M. M.; Fernandez,
(37) Pilling, G. M.; Johnson, R. E. Tetrahedron Lett. 1990, 31, 6763.
E. Org. Biomol. Chem. 2009, 7, 1533.

3972 Organometallics, Vol. 29, No. 17, 2010
Fortman et al.
1.31 (d, 12H, 2JH = 6.8 Hz, iPr-CH3), 1.21 (d, 12H, 2JH = 7.0
Catalytic Conversion of Phenylpropargyl Acetate to Allene
with [Cu(IPr)(NTf2)]. In the glovebox a J-Young tube was
charged with 0.2 mmol (46.1 mg) of phenylpropargyl acetate
and 0.01 mmol (7.3 mg) of [Cu(IPr)(NTf2)]. CD2Cl2 (0.7 mL)
was added to the tube, which was subsequently sealed and
removed from the glovebox. A blank experiment containing the
exact amount of the phenylpropargyl acetates and CD2Cl2 but
without the catalyst was also prepared. An initial 1H NMR was
taken of both NMR solutions. The tubes were kept at a constant
temperature of 50 °C, and spectra were run over the course of 4
days. No conversion of the blank was observed. Production of the
allene was monitored by the characteristic allenic proton at δ 6.58
ppm.40 A 91% conversion was reached in 4 days at 50 °C, as
determined by 1H NMR using CH2Cl2 as an internal standard.
i
Hz, Pr-CH3). 13C NMR (CD2Cl2, 75 MHz, δ ppm): 230.0 (s,
CO) 181.5 (s, carbene C), 146.5 (s, Ar-C), 135.5 (s, Ar-C), 130.8
(s, imid-C), 124.5 (s, Ar-C), 123.7 (s, Ar-C), 87.7 (s, Cp), 29.3 (s,
i
i
iPr-C), 24.8 (s, Pr-C), 24.1 (s, Pr-C). FTIR (CH2Cl2, cm-1):
1925.8, 1821.9, 1798.6. Anal. Calcd for C36H47CuMoN2O3
(MW 715.26): C, 60.45; H, 6.62; N, 3.92. Found: C, 60.54; H,
6.82; N, 4.01.
Reaction of [Cu(IPr)(OH)] with Nitromethane in the Presence
of TEMPO (TEMPO = 2,2,5,5-tetramethylpiperidin-1-oxyl).
In the glovebox a J-Young tube was charged with 10.0 mg (2.13 ꢀ
10-2 mmol) of [Cu(IPr)(OH)] and 2 equiv (6.6 mg) of TEMPO.
The solids were dissolved in 0.7 mL of C6D6, after which 1 equiv
(1.1 μL) of nitromethane was injected to the solution with
stirring. The contents were examined by 1H NMR and con-
firmed to be [Cu(IPr)(CH2NO3)] with the aid of a separately pre-
pared sample.
Reaction of [Cu(IPr)(OH)] with Quantitative Amounts of
ROH (R = tBu, Me). In a glovebox a 2.5 mL vial was charged
with 10.0 mg (2.13 ꢀ 10-2 mmol) of [Cu(IPr)(OH)], which was
dissolved in 0.7 mL of C6D6. The solution was then injected with
1 equiv of ROH (R = tBu, Me) and stirred for 14 h. The contents
were examined by 1H NMR and confirmed to be [Cu(IPr)(OR)]
(R = tBu, Me) with the aid of a separately prepared sample.
Acknowledgment. The authors would like to thank
Drs. Ine I. F. Boogaerts and Sylvain Gaillard for fruitful
discussions. The authors would also like to thank Chris-
topher Britton for his artisanship. S.P.N. acknowledges
the EPSRC and the ERC (Advanced Researcher Grant-
FUNCAT) for support. S.P.N. is a Royal Society-
Wolfson Research Merit Award holder.
Supporting Information Available: Supporting Information
for this manuscript including XRD and spectroscopic data can
be found free of charge via the Internet at http://pubs.acs.org.
ꢀ
ꢀ
(40) Marion, N.; Dıez-Gonzalez, S.; Fremont, P. d.; Noble, A. R.;
Nolan, S. P. Angew. Chem., Int. Ed. 2006, 45, 3647.