Four-Coordinate Copper Halonitrosyl {CuNO}10 Complexes

Article abstract of DOI:10.1002/anie.201904732

While copper nitrosyl complexes are implicated in numerous biological systems, isolable examples remain limited. In this report, we show that [Cl₃CuNO]^?, with a {CuNO}¹⁰ electron configuration, can be generated by nitrite reduction at a copper(I) dichloride anion or by nitric oxide addition to a copper(II) trichloride precursor. The bromide analogue, [Br₃CuNO]^? was synthesized analogously, and both copper halonitrosyl complexes were characterized by X-ray diffraction and a variety of spectroscopic methods. Experimental data and multireference (CASSCF/NEVPT2) calculations provide strong evidence for a Cu^II–NO^. ground state. Both [Cl₃CuNO]^? and [Br₃CuNO]^? release and recapture NO^. reversibly, and exhibit nitrosative reactivities toward a wide range of biological nucleophiles, such as amines, alcohols, and thiols.

Full text of DOI:10.1002/anie.201904732

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Title: Four-Coordinate Copper Halonitrosyl {CuNO}¹⁰ Complexes
Authors: Jamey K Bower, Alexander Yu Sokolov, and Shiyu Zhang
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Four-Coordinate Copper Halonitrosyl {CuNO}10 Complexes
Jamey K. Bower, Alexander Yu Sokolov, and Shiyu Zhang*
Abstract: While copper nitrosyl complexes are implicated in
numerous biological systems, isolable examples remain limited. In
this report, we show that [Cl3CuNO]−, with a {CuNO}10 electron
configuration, can be generated by nitrite reduction at a copper(I)
dichloride anion or by nitric oxide addition to a copper(II) trichloride
precursor. The bromide analog, [Br3CuNO]− was synthesized
analogously, and both copper halonitrosyl complexes were
characterized by X-ray diffraction and a variety of spectroscopic
methods. Experimental data and multireference (CASSCF/NEVPT2)
calculations provide strong evidence for a CuII-NO• ground state. Both
[Cl3CuNO]− and [Br3CuNO]− release and recapture NO• reversibly,
and exhibit nitrosative reactivities toward a wide range of biological
nucleophiles such as amines, alcohols, and thiols.
structurally characterized.[20–22] Given the relevance of copper
nitrosyl complexes to biology, further development of copper
nitrosyl chemistry is certainly merited.
−
The biological reduction of nitrite (NO2 ) to nitric oxide (NO•)
is intimately connected to copper ions. For example, copper-
containing dissimilatory nitrite reductases (CuNiRs) catalyze the
reduction of nitrite with a type 2 copper site (T2) ligated by three
Scheme 1. (A) CuNiR-catalyzed nitrite reduction and (B) the proposed reaction
mechanism.
−
histidines and a substrate (H2O, NO2 , or NO•, Scheme 1A).[1–5]
In this report, we demonstrate that the copper(I) dichloride
anion, despite its simplicity, can promote the reduction of nitrite
Similarly, aberrant “free” copper ions could promote the reduction
of nitrite to NO•, which consequently induces nitrosative stress by
producing reactive nitrogen species (RNS, e.g., NO2• and
OONO−), exacerbating the progression of neurodegenerative
−
(NO2 ) to NO• via a {CuNO}10 intermediate, TBA[Cl3CuNO]. We
isolated and thoroughly characterized this copper halonitrosyl
complex and its bromide analog, TBA[Br3CuNO], including by
single crystal X-ray diffraction. Spectroscopy alongside
multiconfigurational calculations suggest that copper halonitrosyl
complexes adopt a CuII-NO• open-shell singlet (↑↓, 2S+1 = 1)
electronic structure, which has a profound impact on their
reactivity. The copper halonitrosyl complexes display nitrosative
reactivity toward O-, N- and S-based nucleophiles. The last
reaction affords the S-nitrosothiol, representing the first example
of S-nitrosylation via a discrete {CuNO}10 species.
diseases, such as Parkinson’s and Alzheimer’s disease.[6–8]
A
widely accepted mechanism of copper-mediated nitrite reduction
implicates the intermediacy of a {CuNO}10 species (Enemark-
Feltham notation[9]) which readily releases NO• (Scheme 1B).[10,11]
However, attempts to capture and structurally characterize the
{CuNO}10 intermediate in CuNiR resulted in the isolation of a one-
electron reduced {CuNO}11 species in an unusual side-on nitrosyl
binding mode,[1–3] most likely not relevant to the catalytic
cycle.[12,13] Due to the lack of synthetic and biological examples of
{CuNO}10 species, the validity of a {CuNO}10 intermediate in the
mechanism of CuNiR has been brought into question.[14]
Despite the significant interest in the bioinorganic chemistry
of copper nitrosyl complexes in the past decades,[15] the study of
NO• coordination to copper centers has been relatively
underdeveloped. Kohlschütter originally reported the binding of
NO• to copper(II) halides (CuIIX2, X = Cl, Br) to form putative
{CuNO}10 complexes more than 100 years ago.[16,17] Lacking
structural characterization, a later report by Fraser and Dasent
proposed the identity of Kohlschütter’s {CuNO}10 complexes as
four-coordinate X2(solvent)CuNO species.[18] To date, the only
structurally characterized {CuNO}10 is a six-coordinate copper
complex with five nitromethane ligands and a bent nitrosyl moiety
(Cu-N-O 121.0(3)°).[19] Additionally, several synthetic {CuNO}11
complexes with linear Cu-N-O units have been isolated and
Scheme 2. (A) Formation of copper halonitrosyl {CuNO}10 by nitrite reduction
and subsequent release of NO• to form the copper(II) trichloride dimer. (B)
Temperature-dependent, reversible NO• binding to copper(II) trichloride.
We first consider if the copper(I) chloride motif is active
−
toward NO• evolution from NO2 . Addition of one equivalent of
tetrabutylammonium nitrite (TBANO2) to PPN[Cl2CuI][23] (PPN =
bis(triphenylphosphine)iminium) in dichloromethane results in a
light-yellow solution (Figure 1A, green trace). Treatment of this
solution with one equivalent of HCl at −80 °C results in the
formation of a purple species with a strong UV-Vis absorbance at
350 nm (εmax = 3300 M−1 cm−1) and a broad shoulder from 430 nm
to 720 nm (εmax = 660 M−1 cm−1) (Scheme 2A, Figure 1A), which
we assigned as the {CuNO}10 formed by nitrite reduction. Upon
[*]
J. K. Bower, Prof. Dr. A. Yu. Sokolov, Prof. Dr. S. Zhang
Department of Chemistry and Biochemistry
The Ohio State University
100 W. 18th Ave, Columbus, OH (USA)
E-mail: zhang.8941@osu.edu
Supporting information for this article is given via a link at the end of
the document.
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10.1002/anie.201904732
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raising the temperature, the features assigned to the putative
copper nitrosyl decayed and were replaced by peaks at 326 nm
and 476 nm corresponding to the copper(II) trichloride dimer
[Cl6CuII2]2− (Scheme 2A, Figure S1B).[24] This observation is
consistent with the loss of NO• from the purple intermediate,
supporting that the observed purple species could be a copper
nitrosyl complex.
[Cl3CuNO]−. The binding of NO• at [Cl6CuII2]2− is general in a range
of protic and aprotic solvents, including dichloromethane,
tetrahydrofuran, and methanol (Figure S3-S5). Van’t Hoff analysis
of the reversible binding of NO• at [Cl6CuII2]2− in methanol from
−80 °C to 20 °C gives the thermodynamic parameters ∆Hr = −4.71
kcal mol−1 and ∆Sr = −27.9 cal (K･mol)−1 (Figure S5), supporting
the highly reversible nature of NO• binding at copper(II) chloride.
1.6
1.4
1.2
1
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
0.8
0.6
0.4
0.2
0
275
375
475
575
675
275
375
475
575
675
Wavelength (nm)
Wavelength (nm)
Figure 1. UV-Vis spectra (−80 °C) for the convergent synthesis of [Cl3CuNO]−
by (A) nitrite reduction at copper(I) dichloride, PPN[Cl2CuI], and (B) NO• addition
to the copper(II) trichloride dimer, TBA[Cl6CuII2].
To confirm this hypothesis, we attempted to directly access
the purple intermediate from the copper(II) trichloride anion and
NO•. The homoleptic copper(II) trichloride salt was synthesized
from tetrabutylammonium (TBA) chloride and anhydrous
copper(II) chloride in ethanol, and isolated as dimeric
TBA2[Cl6CuII2]. Injection of excess NO• to a dichloromethane
solution of TBA2[Cl6CuII2] at −80 °C results in the formation of the
same purple intermediate prepared from the reaction of [Cl2CuI]−,
−
NO2 , and HCl (Scheme 2B, Figure 1B). The small discrepancy in
the UV-Vis signal around 280 nm was attributed to the difference
in counter ions (TBA vs PPN). This purple species is clearly
related to the copper halonitrosyl complexes reported by
Kohlschütter,[16,17] Fraser, and Dasent,[18,25] whose structural
identity have remained unknown for many years. Further
evidence of NO• binding at copper was obtained by solution-state
infrared spectroscopy, which reveals a single stretch at 1834 cm−1
that is sensitive to 15N labeling (∆vNO14N−15N = 28 cm−1, Hooke’s
Law = 33 cm−1, Figure S16). The NO stretching frequency is
similar to the related solvento {CuNO}10 species reported by
Wilkinson ([(CH2CH2OH)3Cu(NO)]2+, 1854 cm−1)[26], but quite
different from that of Hayton’s [CuNO(MeNO2)5]2+ (1933 cm−1).[19]
We attribute the high NO stretching frequency of
[CuNO(MeNO2)5]2+ to the weak donating nature of the copper
center. EPR analysis (CH2Cl2, 100 K) of a reaction mixture of
TBA2[Cl6CuII2] with NO• shows the purple {CuNO}10 species is
EPR silent (Figure S18), consistent with previous reports for
{CuNO}10 complexes.[19,27]
Figure 2. Solid-state structure of [Cl3CuNO]− (top) and [Br3CuNO]− (bottom) with
selected structural parameters. Thermal ellipsoids are shown at 50% probability
level. The TBA cation and the minor components of disorder are omitted for
clarity.
X-ray diffraction analysis of thermally sensitive crystals of
TBA[Cl3CuNO] reveals a rare {CuNO}10 copper nitrosyl complex
with a distorted square-planar Cu center (4 = 0.15)[28] bound to a
bent nitrosyl ligand (Cu-N-O bond angle = 119.9(6)°, N-O =
1.127(6) Å, Figure 2A) that is disordered over two positions
(Figure S20). The trans chloride has a Cu-Cl bond distance
slightly longer than the other two Cu-Cl bonds, indicative of the
trans influence of the nitrosyl ligand. A survey of structurally
characterized metal nitrosyls reveals the extreme rarity of
{CuNO}10 complexes. Four-coordinate metal nitrosyls complexes
(M = Cu, Ni, Co, Ir) typically exhibit tetrahedral geometry and a
linear nitrosyl in order to promote π backbonding to the doubly
degenerate NO π* orbitals.[9] In contrast, TBA[Cl3CuNO] — the
first structurally characterized four-coordinate {CuNO}10 complex
— displays a square planar geometry, but have the same bent
NO binding mode as Hayton’s six-coordinate {CuNO}10 complex
(Cu-N-O angle = 121.0(3)°; NO bond distance = 1.109(5) Å).
The binding of NO• at [Cl6CuII2]2− is highly reversible. Upon
raising the temperature to 35 °C, the UV-Vis features associated
with the copper nitrosyl complex decay with the isosbestic
formation of the initial [Cl6CuII ]2− complex in near-quantitative
2
yield (Scheme 2B, Figure S3A). Lowering the temperature of the
same solution back to −80 °C in the presence of excess NO•
results in the quantitative regeneration of the copper nitrosyl
species at previous equilibrium levels (Scheme 2B, Figure S3B).
The reversible release and capture of NO• can be repeated
To expand the scope of {CuNO}10 halonitrosyl complexes,
we also synthesized the bromide analog, TBA[Br3CuNO], through
the treatment of TBA2[Br6CuII2] with excess NO•. Van’t Hoff
analysis performed by variable temperature UV-Vis spectroscopy
(−80 °C to 20 °C) afforded thermodynamic parameters ∆Hr =
multiple times without decomposition of either [Cl6CuII ]2− or
2
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−6.74 kcal mol−1 and ∆Sr = −38.0 cal (K･mol)−1 (Figure S6),
indicating that the binding of NO• to [Br6CuII2]2− is slightly less
agreement with experiment (Table 1). However, using the
CCSD(T) geometry, the singlet-triplet energy gap computed by
CCSD and CCSD(T) is 4.1 and 19.3 kcal mol−1, respectively. The
discrepancy between CCSD and CCSD(T) results suggests that
multiple electron configurations may be necessary to describe the
{CuNO}10 system. Multiconfigurational ground states have been
explored for {FeNO}7, {CoNO}9, {NiNO}10, and {CuNO}11
compounds using the complete active space self-consistent field
(CASSCF) method,[32,34] but such an investigation of {CuNO}10
electronic structure has not been explicitly documented.
favored compared to [Cl6CuII ]2−. The X-ray structure of
2
TBA[Br3CuNO] exhibits a distorted square-planar geometry (4 =
0.17) with a Cu-N-O bond angle (120.4(5)°) and N-O bond
distance (1.125(8) Å). (Figure 2B). The IR stretching frequency of
1820 cm−1 (∆vNO14N−15N = 33 cm−1, Hooke’s Law = 33 cm−1, Figure
S17) is 14 cm−1 red-shifted from the chloride analog. Together,
structural and spectroscopic data suggest similar electronic
structures for TBA[Cl3CuNO] and TBA[Br3CuNO].
With the full characterization of TBA[Cl3CuNO] and
TBA[Br3CuNO], we begin to evaluate the electronic structure of
the {CuNO}10 halonitrosyl motif. Due to the redox noninnocence
of the nitrosyl ligand, there are several possible electronic
structures (CuI-NO+, CuII-NO•, or CuIII-NO−). Given the square
planar geometry and low energy d-d transitions in the electronic
spectrum (Figure S24, see TD-DFT calculations), formulation as
CuI-NO+ is unlikely. While the strongly bent Cu-N-O bond angle
suggests CuIII-NO−, it has been shown that metal nitrosyl bond
angle is not a reliable indicator of electronic structure.[29]
Meanwhile, the silent EPR, the NO stretching frequency (1834
cm−1, free NO• 1875 cm−1),[30] and N-O bond distance (1.127(6)
Å, free NO• 1.15 Å)[31] collectively suggest an open-shell singlet
CuII-NO• electronic structure with antiferromagnetic coupling
between the d9 copper and NO• ligand (↑↓, 2S+1 = 1).
Figure 3. Plots of HONO and LUNO of [Cl3CuNO]− computed using the
CASSCF(12,12) method. Occupations of natural orbitals are shown as
superscripts, contributions of Cu and NO orbitals are given in percent.
CASSCF computations of [Cl3CuNO]− using 12 electrons
and 12 orbitals in the active space at the NEVPT2 (N-electron
valence second-order perturbation theory)[35] optimized geometry
(Table 1) reveal a significant degree of multireference character
in the valence orbitals (Figure 3). Occupation of the Cu–NO
bonding highest occupied natural orbital (HONO) is lowered from
2 to 1.55, while the antibonding natural orbital (LUNO) is
significantly populated (0.45), indicating that the Cu–NO bond is
rather weak (bond order = ~0.5) and that the two valence orbitals
are close in energy. Analysis of the CASSCF ground state active
space composition for [Cl3CuNO]− shows that the leading
electronic configuration (75.5%) places both electrons in the
copper-based HONO, thus describing a CuI-NO+ species.
Meanwhile, the second most contributing configuration (21.5%) is
the excited singlet state, in which two electrons are placed in the
NO-based LUNO, corresponding to CuIII-NO−. Considering these
two descriptions as resonance forms, the overall electronic
structure is best described as antiferromagnetically coupled CuII-
NO• with a bent Cu-N-O angle due to the σ-bonding interaction
between the dx2−y2 orbital of Cu and out-of-plane π* orbital of NO•.
Similar σ-bonding is observed in end-on copper(II)-superoxide
Table 1. Selected computed and crystallographic structural parameters
(Å, °) of [Cl3CuNO]−. Cl(t) and Cl(c) refer to chloride ligands trans and cis to
NO. Asterisk denotes the average of experimental values.
Parameter
Cu–N
CCSD
1.933
1.141
2.228
2.219
115.6
CCSD(T)
1.996
NEVPT2
1.963
1.146
2.207
2.204
122.5
X-Ray
2.000
1.127
2.213
2.188*
119.9
N–O
1.149
Cu–Cl(t)
Cu–Cl(c)
Cu–N–O
2.232
2.236
120.6
To further elucidate the nature of the Cu–NO bonding
interaction, we performed electronic structure computations of the
[Cl3CuNO]− and [Br3CuNO]− anions using broken-symmetry
density functional theory (BS-B3LYP/def2-TZVPPD).[32,33] While
the broken symmetry solution of [Cl3CuNO]− and [Br3CuNO]−
describes antiferromagnetically coupled CuII-NO• electronic
structures (see SI), the optimized geometries deviate significantly
from the X-ray structure, suggesting that more advanced
theoretical methods are required. Given the similarity between the
two copper halonitrosyl complexes, we continued our
investigation with [Cl3CuNO]− for computational expediency.
We then performed geometry optimization of [Cl3CuNO]−
with coupled cluster methods (CCSD and CCSD(T)), which take
electron correlation effects into account. While the CCSD method
improves the description of bond angles, the Cu–N bond distance
is underestimated by nearly 0.07 Å (Table 1). The geometry of the
Cu–NO fragment is significantly improved using the CCSD(T)
method, producing a [Cl3CuNO]− optimized structure in excellent
complexes, which feature
a strongly bent Cu-O-O angle
(~120°).[36,37] The results for [Cl3CuNO]− are consistent with a
small singlet-triplet gap computed using NEVPT2 (7.8 kcal mol−1).
Interestingly, a CASSCF (9, 13) calculation of the related iron
halonitrosyl compound [Cl3FeNO]− reveals striking similarities. In
this case, the Fe-NO π bonding and antibonding orbitals exhibit
populations of 1.73 and 0.27 electrons, respectively, and the
leading S = 3/2 electronic configuration contributes 65% to the
ground state.[34] Together, computational and experimental
results support a multiconfigurational, open-shell singlet CuII-NO•
electronic structure, giving insight into how facile capture and
release of NO• from copper(II) ions is achieved electronically.
Having established the electronic structure of copper
halonitrosyl complexes, we set out to explore their nitrosative
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reactivity with biologically relevant nucleophiles, such as amines,
alcohols, and thiols (Scheme 3). Consistent with the NO-based
LUNO, we found that [Cl3CuNO]− performs reductive nitrosylation
of N-, O-, and S-based nucleophiles, producing N-, O-, S-nitroso
compounds in 93%, 95%, and 77% yield, respectively (Scheme
3). The S-nitrosylation reactivity of [Cl3CuNO]− represents the first
example of such occurring via a discrete copper nitrosyl complex.
The reactivity of [Cl3CuNO]− compounds mirrors that of the
copper(II) nitrite complex [Cl2NNF6]CuII(κ2-O2N), adding further
Keywords: copper • electronic structure • nitrite reduction •
nitrosyl • reductive nitrosylation •
[1]
[2]
[3]
E. I. Tocheva, F. I. Rosell, A. G. Mauk, M. E. P. Murphy, Science
2004, 304, 867–870.
E. I. Tocheva, F. I. Rosell, A. G. Mauk, M. E. P. Murphy, Biochemistry
2007, 46, 12366–12374.
S. V. Antonyuk, R. W. Strange, G. Sawers, R. R. Eady, S. S. Hasnain,
Proc. Natl. Acad. Sci. 2005, 102, 12041–12046.
[4]
[5]
B. A. Averill, Chem. Rev. 1996, 96, 2951–2964.
P. M. Vitousek, J. D. Aber, R. W. Howarth, G. E. Likens, P. A. Matson,
D. W. Schindler, W. H. Schlesinger, D. G. Tilman, Ecol. Appl. 1997,
7, 737–750.
implications
for
nitrite-derived
nitrosative
reactivity.[38]
Additionally, the isoelectronic and isostructural [Br3CuNO]−
analog performs similar N-, O-, and S-nitrosylation in 93%, 91%,
18% yields, respectively. The low yield of [Br3CuNO]− promoted
S-nitrosylation is perhaps due to its weak NO• binding affinity.
[6]
[7]
[8]
N. Asiimwe, S. G. Yeo, M. S. Kim, J. Jung, N. Y. Jeong, Oxid. Med.
Cell. Longev. 2016, 2016, 7205747.
L. L. Moroz, S. W. Norby, L. Cruz, J. V Sweedler, R. Gillette, R. B.
Clarkson, Biochem. Biophys. Res. Commun. 1998, 253, 571–576.
C. Nathan, N. Calingasan, J. Nezezon, A. Ding, M. S. Lucia, K. La
Perle, M. Fuortes, M. Lin, S. Ehrt, N. S. Kwon, et al., J. Exp. Med.
2005, 202, 1163–1169.
[9]
J. H. Enemark, R. D. Feltham, Coord. Chem. Rev. 1974, 13, 339–
406.
[10]
S. Suzuki, T. Yoshimura, T. Kohzuma, S. Shidara, M. Masuko, T.
Sakurai, H. Iwasaki, Biochem. Biophys. Res. Commun. 1989, 164,
1366–1372.
[11]
[12]
[13]
A. C. Merkle, N. Lehnert, Dalt. Trans. 2012, 41, 3355–3368.
A. C. Merkle, N. Lehnert, Inorg. Chem. 2009, 48, 11504–11506.
S. Ghosh, A. Dey, O. M. Usov, Y. Sun, V. M. Grigoryants, C. P.
Scholes, E. I. Solomon, J. Am. Chem. Soc. 2007, 129, 10310–10311.
C. M. Moore, N. K. Szymczak, Chem. Sci. 2015, 6, 3373–3377.
J. A. McCleverty, Chem. Rev. 2004, 104, 403–418.
V. Kohlschütter, M. Kutscheroff, Berichte der Dtsch. Chem.
Gesellschaft 1904, 37, 3044–3052.
[14]
[15]
[16]
[17]
V. Kohlschütter, P. Sazanoff, Berichte der Dtsch. Chem. Gesellschaft
1911, 44, 1423–1432.
[18]
[19]
R. T. M. Fraser, W. E. Dasent, J. Am. Chem. Soc. 1960, 82, 348–351.
A. M. Wright, G. Wu, T. W. Hayton, J. Am. Chem. Soc. 2010, 132,
14336–14337.
[20]
[21]
S. M. Carrier, C. E. Ruggiero, W. B. Tolman, G. B. Jameson, J. Am.
Chem. Soc. 1992, 114, 4407–4408.
K. Fujisawa, A. Tateda, Y. Miyashita, K. Okamoto, F. Paulat, V. K. K.
Praneeth, A. Merkle, N. Lehnert, J. Am. Chem. Soc. 2008, 130,
1205–1213.
Scheme 3. N-, O-, and S-nitrosylation reactivities of [Cl3CuNO]− and [Br3CuNO]−.
[22]
[23]
[24]
J. L. Schneider, S. M. Carrier, C. E. Ruggiero, V. G. Young, W. B.
Tolman, J. Am. Chem. Soc. 1998, 120, 11408–11418.
G. A. Bowmaker, M. I. Bruce, B. W. Skelton, N. Somers, A. H. White,
Zeitschrift für Anorg. und Allg. Chemie 2007, 633, 1024–1030.
K. J. Doyle, H. Tran, M. Baldoni-Olivencia, M. Karabulut, P. E.
Hoggard, Inorg. Chem. 2008, 47, 7029–7034.
R. T. M. Fraser, J. Inorg. Nucl. Chem. 1961, 17, 265–272.
W. P. Griffith, J. Lewis, G. Wilkinson, J. Chem. Soc. 1958, 3993–3998.
N. Tsumori, Q. Xu, Bull. Chem. Soc. Jpn. 2002, 75, 1861–1862.
L. Yang, D. R. Powell, R. P. Houser, Dalt. Trans. 2007, 955–64.
G. B. Richter-Addo, P. Legzdins, Metal Nitrosyls, Oxford University
Press, New York, 1992.
In summary, we have described a simple copper motif that
mediates the evolution of NO• from nitrite. The direct product of
nitrite reduction by [Cl2CuI]− is a {CuNO}10 species with the
formula [Cl3CuNO]−, adding evidence for a {CuNO}10 intermediate
in the mechanism of CuNiR enzymes. We independently
synthesized and fully characterized TBA[Cl3CuNO], along with the
bromide analog, TBA[Br3CuNO], which represent the second and
[25]
[26]
[27]
[28]
[29]
third
structurally
characterized
{CuNO}10
complexes.
Spectroscopic and high-level theoretical calculations support a
multiconfigurational CuII-NO• electronic structure for copper
halonitrosyl complexes. This unique electronic structure
illuminates how {CuNO}10 species perform both facile release of
NO• and reductive nitrosylation reactivity.
[30]
[31]
[32]
H. Hoshina, M. Slipchenko, K. Prozument, D. Verma, M. W. Schmidt,
J. Ivanic, A. F. Vilesov, J. Phys. Chem. A 2016, 120, 527–534.
L. E. Sutton, Tables of Interatomic Distances and Configuration in
Molecule and Ions, The Chemical Society, London, 1958.
N. C. Tomson, M. R. Crimmin, T. Petrenko, L. E. Rosebrugh, S.
Sproules, W. C. Boyd, R. G. Bergman, S. DeBeer, F. D. Toste, K.
Wieghardt, J. Am. Chem. Soc. 2011, 133, 18785–18801.
S. Kundu, P. N. Phu, P. Ghosh, S. A. Kozimor, J. A. Bertke, S. C. E.
Stieber, T. H. Warren, J. Am. Chem. Soc. 2019, 141, 1415–1419.
A. In-Iam, M. Wolf, C. Wilfer, D. Schaniel, T. Woike, P. Klüfers, Chem.
– A Eur. J. 2019, 25, 1304–1325.
C. Angeli, R. Cimiraglia, S. Evangelisti, T. Leininger, J.-P. Malrieu, J.
Chem. Phys. 2001, 114, 10252–10264.
C. Würtele, E. Gaoutchenova, K. Harms, M. C. Holthausen, J.
Sundermeyer, S. Schindler, Angew. Chemie - Int. Ed. 2006, 45,
3867–3869.
[33]
[34]
[35]
[36]
Acknowledgments
We acknowledge the Ohio Supercomputer Center for high-
performance computing resources. We thank the lab of Prof.
Christine Thomas for assistance with the solution IR
measurement. We are also grateful to Dr. Judith Gallucci and Dr.
Curtis Moore for X-ray crystallography assistance.
[37]
[38]
J. S. Woertink, L. Tian, D. Maiti, H. R. Lucas, R. A. Himes, K. D. Karlin,
F. Neese, C. Würtele, M. C. Holthausen, E. Bill, et al., Inorg. Chem.
2010, 49, 9450–9459.
S. Kundu, W. Y. Kim, J. A. Bertke, T. H. Warren, J. Am. Chem. Soc.
2017, 139, 1045–1048.
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10.1002/anie.201904732
Angewandte Chemie International Edition
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J. K. Bower, A. Yu. Sokolov, S. Zhang*
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Four-Coordinate Copper Halonitrosyl
{CuNO}10 Complexes
Text for Table of Contents
A mystery NO more: For more than 100 years, copper halides have been known to absorb nitric oxide, but the structures of the
products were never elucidated. We show that the copper halonitrosyl compound TBA[Cl3CuNO] can be generated by nitrite reduction
at a copper(I) dichloride anion or by nitric oxide addition to a copper(II) trichloride precursor. We also synthesized the bromide analog,
TBA[Br3CuNO], in similar fashion. These rare {CuNO}10 species, with full structural and spectroscopic characterization, reversibly bind
nitric oxide and nitrosylate biologically relevant nucleophiles.
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