Bidentate Phosphine-Assisted Synthesis of an All-Alkynyl-Protected Ag74 Nanocluster

Article abstract of DOI:10.1021/jacs.7b05243

Determining the total structure of metal nanoparticles is vital to understand their properties. In this work, the first all-alkynyl-protected Ag nanocluster, Ag₇₄(C≡CPh)₄₄, was synthesized and structurally characterized by single cry

Full text of DOI:10.1021/jacs.7b05243

Subscriber access provided by Grand Valley State | University
Communication
Bidentate Phosphine–Assisted Synthesis of
an All–Alkynyl–Protected Ag74 Nanocluster
Mei Qu, Huan Li, Lin-Hua Xie, Shuai-Ting Yan, Jian Rong Li, Jun-
Hao Wang, Cai-Yun Wei, Yu-Wei Wu, and Xian-Ming Zhang
J. Am. Chem. Soc., Just Accepted Manuscript • DOI: 10.1021/jacs.7b05243 • Publication Date (Web): 24 Aug 2017
Downloaded from http://pubs.acs.org on August 24, 2017
Just Accepted
“Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted
online prior to technical editing, formatting for publication and author proofing. The American Chemical
Society provides “Just Accepted” as a free service to the research community to expedite the
dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts
appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been
fully peer reviewed, but should not be considered the official version of record. They are accessible to all
readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered
to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published
in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just
Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor
changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers
and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors
or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
Journal of the American Chemical Society is published by the American Chemical
Society. 1155 Sixteenth Street N.W., Washington, DC 20036
Published by American Chemical Society. Copyright © American Chemical Society.
However, no copyright claim is made to original U.S. Government works, or works
produced by employees of any Commonwealth realm Crown government in the course
of their duties.

Page 1 of 4
Journal of the American Chemical Society
1
2
3
4
5
6
7
8
9
Bidentate Phosphine–Assisted Synthesis of An All–Alkynyl–
Protected Ag74 Nanocluster
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Mei Qu,† Huan Li,*,† Lin-Hua Xie, ‡ Shuai-Ting Yan,† Jian-Rong Li,‡ Jun-Hao Wang,† Cai-Yun
Wei,† Yu-Wei Wu,† Xian-Ming Zhang*,†
† Institute of Crystalline Materials, Shanxi University, Taiyuan 030006, Shanxi, China
‡Beijing Key Laboratory for Green Catalysis and Separation and Department of Chemistry and Chemical Engineering,
College of Environmental and Energy Engineering, Beijing University of Technology, Beijing 100124, China.
Supporting Information Placeholder
complex, multinuclear clusters to supramolecular assemblies
ABSTRACT: Determining the total structure of metal nano-
particles is vital to understand their properties. In this work,
in the last decades.24-26 This leaves how to access alkynyl-
protected Ag(0) nanocluster an outstanding puzzle to be
solved.
the first all alkynyl protected Ag nanocluster, Ag74(C≡CPh)44,
was synthesized and structurally characterized by single crys-
tal diffraction. Ag atoms are arranged in a Ag4@Ag22@Ag48
three shell structure and all 44 phenylethynyl ligands coor-
dinated with Ag in a µ3 mode. In spite of being absent in
nanocluster, 31P NMR study reveals that bidentate phosphine
firstly reacts with Ag(I) to form a dinuclear complex, from
which Ag atoms are then released to phenylethynyl ligands.
This phosphine mediated strategy may find general applica-
tion in synthesis of alkynyl protected Ag nanoclusters.
Herein, we propose a phosphine mediated approach for
synthesis of the first all alkynyl-protected Ag74(C≡CPh)44
nanocluster (Ag74 for short). Its structural features including
Ag-ligand interfacial bonding will be revealed in detail. Espe-
cially, the role of phosphine ligand during synthesis will be
fully unraveled by 31P NMR.
To fundamentally understand the nature and properties of
metal nanoparticles, determining their total structures in-
cluding metal-ligand interface is of paramount significance.1-3
However, to realize such a goal is a daunting task even for
the state-of-the-art transmission electron microscope (TEM)
technology, which cannot directly image the stabilizers (usu-
ally organic) or the interfacial bonding. Fortunately, the past
several years have witnessed significant progress in isolation
of atomically precise metal nanoclusters as single crystals for
X-ray crystallography.4 One prominent example is the total
structural determination of Au102(SR)44 (SR=SPh-p-COOH),
in which a fascinating “RS-Au-SR” staple surface bonding
motif was revealed.5 A family of atomically precise Au
nanoclusters has since been discovered,6-8 while the number
of Ag nanoclusters is relatively small.9-14
Figure 1. The overall structure of Ag74(C≡CPh)44.
Beyond the conventional thiolate and phosphine ligands,
alkynyl-protected nanoclusters have begun to draw attention
only very recently. Their structural features were exemplified
The preparation of Ag74 involves reduction of Ag(I) in the
presence of phenylacetylene (denoted as PA) and a bidentate
phosphine. Typically, AgNO3 was dissolved in ethanol before
PA and dppp (1,3-Bis(diphenylphosphino)propane) were
introduced. A fresh NaBH4 solution was then added. The
reaction was aged for 12 h during which the color gradually
changed from pale-yellow to brown-red (supporting infor-
mation). A black block crystal was obtained by diffusing hex-
ane and ether into CH2Cl2 containing Ag74 (Figure S1).
18
in a series of Au8,15 Au19,16 Au23,17 Au24 and intermetallic
22
Au7Ag8,19 Au24Ag20,20 Au34Ag28,21 Au80Ag30 nanoclusters.
They exhibited interesting Au-alkynyl staple motifs, resem-
bling that of thiolate protected Au nanoclusters. However,
what is the bonding motif of alkynyl ligands on Ag nanopar-
ticle remains elusive. This is actually highly unexpected,
since alkynyl ligands are of strong affinity toward Ag and are
versatile in coordination abilities (in both σ and π modes).23-
26
Single crystal analysis revealed that Ag74 is a 1.2 nm Ag
These features have already inspired the emergence of a
nanoparticle peripherally protected by a monolayer com-
large variety of Ag(I)-alkynyl structures ranging from simple
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 2 of 4
posed of 44 PAs (Figure 1). It crystallized in R-3 space group
subsurface simultaneously (Figure 2e and S3). Therefore,
1
2
3
4
5
6
7
8
(Figure S2). The metal core includes 74 Ag atoms that are
arranged into a three-shell Russian doll architecture, i.e.,
Ag4@Ag22@Ag48 (Figure 2a). Its anatomy is illustrated in Fig-
ure 2. The first inner shell is a Ag4 tetrahedron (Figure 2b)
which are surrounded by the second Ag22 shell. A combina-
tion of the inner two shells can be viewed as a fusion of four
centered Ag13 icosahedrons by sharing the Ag4 tetrahedron.
Each Ag atom of Ag4 is located at the center of one icosahe-
dron (Figure 2c). The outermost shell consists of 48 Ag at-
oms which are enclosed into 12 pentagons and 56 triangles
(Figure 2d). Every three pentagons (in orange) form a triad
through an edge-sharing triangle (in green, Type A triangle).
There are four triads that are tetrahedrally arranged on the
Ag48 shell. The space between them is filled with the rest 52
triangles, which, for simplicity, are divided into another two
categories. One is a super triangle composed of four triangles
(Figure 2d, blue, Type B), and the other one is a saddle-
shaped subunit made up of six triangles (yellow, Type C).
There are four super triangles and six saddles respectively.
The average Ag–Ag bond length between inner shell 1 and
shell 2 is 2.802 Å, close to that in bulk. Under the influence of
peripheral ligands, the Ag–Ag bonds between shell 2 and 3
were significantly elongated to 2.980 Å.
there are totally twelve Ag atoms from Ag22 shell coordinat-
ing with PA through σ bonds. In addition, every Type A tri-
angle is capped by a PA. For each Type B super triangle, a PA
only coordinates with the centered triangle. For each Type C
saddle, there are four PA ligands capping the four corner
triangles (Figure S3). Altogether, there are 44 PA ligands
forming a protective monolayer. On the other hand, the
binding motif of PA on Ag74 seems dull. All 44 PA ligands
employ a µ3-bridging mode (Figure 2f), with the only differ-
ence being the bond type (σ or π). This sharply contrasts
with the vivid coordination patterns in Ag(I) alkynyl com-
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
plexes.26 Also, the V-shaped PhC C–Au–C C(Ph)–Au–C CPh
≡
≡
≡
≡
≡
or L-shaped PhC C–Au–C CPh staple motifs in alkynyl stabi-
lized Au nanoclusters was not observed in Ag74 either.16,18
The results indicated that alkynyl does not necessarily take
on the same coordination mode for all coinage metal
nanoclusters. We did not observe the counterion by Xꢀray crysꢀ
tallography, possibly because the anions are not locked into place
in the lattice. However, the electrospray ionization mass specꢀ
trometry (ESIꢀMS) showed a single peak corresponding to a moꢀ
lecular ion [Ag74(C≡CPh)44]2+ (Figure S4). FTꢀIR of Ag74 single
crystal displayed a stretching absorption of NO3ꢀ (Figure S5). The
ꢀ
presence of NO3 was further confirmed by ion chromatography
(Figure S6). Thus, the electric neutrality was likely balanced by
ꢀ
NO3 . Furthermore, Ag74 shows two absorption peaks at 245 and
514 nm respectively. And stimulated by a 296 nm light, Ag74
exhibited two sharp emission bands at 572 and 620 nm (Figure
S7). These results are similar with that in references.27
≡
Figure 2. The structure anatomy of Ag74(C CPh)44. (a) Ag74
metal core, (b) Ag4 shell. (c) Ag4@Ag22 shells, the brown pol-
yhedron indicated one of the four centered icosahedrons. (d)
Ag48 shell. Color lables: orange, pentagon; green, Type A tri-
angle; blue, Type B; yellow, Type C (e) The distribution of PA
ligands on Ag74 surface. The grey polyhedron is Ag22 shell. (f)
An illustration of bonding motif of PA with surface Ag atoms.
Figure 3. Trace of phosphine ligands with 31P NMR in
CDCl3. (a) dppp. (b) Ag+dppp+PA. (c) Ag+dppp. Reaction for
2 hours (d) and 12 hours (e) after adding NaBH4.
The distribution of peripheral ligands is closely dependent
on the arrangement of surface Ag atoms. A dozen PA ligands
penetrate through twelve pentagons and bond to surface and
ACS Paragon Plus Environment

Page 3 of 4
Journal of the American Chemical Society
Our repeated attempts to stabilize Ag nanoclusters solely
ASSOCIATED CONTENT
1
2
3
4
5
6
7
8
by PA proved to be futile, flocculent precipitate was always
seen upon reduction. In the presence of phosphine, however,
a gradual color change from pale-yellow to brown-red was
observed during hours. The necessity of phosphine ligand in
the synthesis and its absence on Ag74 surface proposed a
question of particular interest: what is the role of it? 31P NMR
was used to trace its evolution. As shown in Figure 3a, dppp
dissolved in CDCl3 showed one peak at -17.61 ppm, represent-
ing the “free” bidentate phosphine.28 The mixture formed
after introduction of PA and dppp into AgNO3 solution gave
a distinct 31P singlet at 8.44 ppm (Figure 3b). The change of
the chemical environment is most likely due to the coordina-
tion of phosphine with Ag. To probe whether PA participates
in the coordination, the same mixture but without PA was
subjected to NMR test and a same signal was detected (Fig-
ure 3c). The possibility that the signal represents a Ag-dppp
complex in both cases stimulated us to isolate it. And two
same single crystals from Ag+dppp and Ag+dppp+PA solu-
tions were successfully obtained, which turned out to be a
Supporting Information
The Supporting Information is available free of charge on the
ACS
Publications
website.
Experimental details, photos, TEM images and crystallo-
graphic data (PDF)
Detailed crystallographic structure and data (CIF)
9
AUTHOR INFORMATION
Corresponding Author
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
59584340@sxu.edu.cn (H. Li)
xmzhang@sxu.edu.cn (X.-M. Zhang)
Notes
The authors declare no competing financial interests.
ACKNOWLEDGMENT
known
dinuclear
Ag(I)
complex,
Bis-µ-[1,3-
We appreciate Professor Nanfeng Zheng (Xiamen University)
for his generous suggestions. We also thank the National
Natural Science Foundation of China (21503123), Sanjin
Scholar and Starting fund of Shanxi University for the finan-
cial support.
bis(diphenylphosphino)propane]-dinitratodisilver(I) (Figure
3c and S8).29 Redissolving the crystals for 31P NMR test con-
firmed the signal at 8.44 ppm originated from this complex.
Furthermore, in the first two hours upon addition of NaBH4,
an evident peak at 32.25 ppm revealed itself (Figure 3d). After
12 hours, it became the only phosphorus species in solution
(Figure 3e). Considering the signal is at low field, one might
suggest it is bonded with electron-withdrawing group, such
as oxygen. In order to verify this, we synthesized oxide of
dppp following a reported procedure.30 A comparison of its
31P NMR (δ=32.21 ppm) with that in Figure 3e implies dppp
ends up as dioxide. Thus, dppp functions more like a reser-
voir of Ag. Before adding NaBH4, it binds Ag in the form of
dinuclear complex. During reduction, Ag atoms were gradu-
ally given away, while dppp was converted to oxide. Also of
note, we obtained the same crystals of Ag74 by using either
dppe (1,2-Bis-(diphenylphosphino)ethane) or dppb (1,4-Bis-
(diphenylphosphino)butane) as auxiliary ligands, indicating
this method might be general for bidentate phosphines.
REFERENCES
(1) Daniel, M.-C.; Astruc, D. Chem. Rev. 2004, 104, 293.
(2) Schmid, G. Chem. Soc. Rev. 2008, 37, 1909.
(3) Parker, J. F.; Fields-Zinna, C. A.; Murray, R. W. Acc. Chem. Res.
2010, 43, 1289.
(4) Jin, R.; Zeng, C.; Zhou, M.; Chen, Y. Chem. Rev. 2016, 116, 10346.
(5) Jadzinsky, P. D.; Calero, G.; Ackerson, C. J.; Bushnell, D. A.;
Kornberg, R. D. Science 2007, 318, 430.
(6) Qian, H.; Zhu, M.; Wu, Z.; Jin, R. Acc. Chem. Res. 2012, 45, 1470.
(7) Liu, P.; Qin, R.; Fu, G.; Zheng, N. J. Am. Chem. Soc. 2017, 139,
2122.
(8) Hakkinen, H. Nat. Chem. 2012, 4, 443.
(9) Desireddy, A.; Conn, B. E.; Guo, J.; Yoon, B.; Barnett, R. N.;
Monahan, B. M.; Kirschbaum, K.; Griffith, W. P.; Whetten, R. L.;
Landman, U.; Bigioni, T. P. Nature 2013, 501, 399.
(10) Yang, H.; Wang, Y.; Huang, H.; Gell, L.; Lehtovaara, L.; Malola,
S.; Häkkinen, H.; Zheng, N. Nat. Commun. 2013, 4, 2422.
(11) AbdulHalim, L. G.; Bootharaju, M. S.; Tang, Q.; Del Gobbo, S.;
AbdulHalim, R. G.; Eddaoudi, M.; Jiang, D. E.; Bakr, O. M. J. Am.
Chem. Soc. 2015, 137, 11970.
(12) Yang, H.; Wang, Y.; Chen, X.; Zhao, X.; Gu, L.; Huang, H.; Yan,
J.; Xu, C.; Li, G.; Wu, J.; Edwards, A. J.; Dittrich, B.; Tang, Z.; Wang,
D.; Lehtovaara, L.; Hakkinen, H.; Zheng, N. Nat. Commun. 2016, 7,
12809.
(13) Conn, B. E.; Atnagulov, A.; Yoon, B.; Barnett, R. N.; Landman,
U.; Bigioni, T. P. Sci. Adv. 2016, 2, e1601609.
(14) Alhilaly, M. J.; Bootharaju, M. S.; Joshi, C. P.; Besong, T. M.;
Emwas, A.-H.; Juarez-Mosqueda, R.; Kaappa, S.; Malola, S.; Adil, K.;
Shkurenko, A.; Häkkinen, H.; Eddaoudi, M.; Bakr, O. M., J. Am.
Chem. Soc. 2016, 138, 14727.
(15) Kobayashi, N.; Kamei, Y.; Shichibu, Y.; Konishi, K. J. Am.
Chem. Soc. 2013, 135, 16078.
(16) Wan, X.-K.; Tang, Q.; Yuan, S.-F.; Jiang, D.-E.; Wang, Q.-M. J.
Am. Chem. Soc. 2015, 137, 652.
(17) Wan, X.-K.; Yuan, S.-F., Tang, Q.; Jiang, D.-E.; Wang, Q.-M.
Angew. Chem. Int. Ed. 2015, 54, 5977.
(18) Wan, X.-K.; Xu, W. W.; Yuan, S.-F.; Gao, Y.; Zeng, X.-C.;
Wang, Q.-M. Angew. Chem. Int. Ed. 2015, 54, 9683.
(19) Wang, Y.; Su, H.; Ren, L.; Malola, S.; Lin, S.; Teo, B. K.; Häk-
kinen, H.; Zheng, N. Angew. Chem. Int. Ed. 2016, 55, 15152.
Ag74 is fairly stable. The as-prepared colloidal solution was
stored at ambient conditions for at least ten days without
deterioration (Figure S9). Also, immobilization of Ag74 na-
noparticles on activated carbon was realized by simply add-
ing its solution into a dispersion of the support (Figure S10).
As Figure S11 shows, monodispersed Ag nanoparticles with
size of 1 nm were smoothly immobilized on the support. It is
believed that hydrophobic PA surface ligands enhanced the
interaction of the clusters with the support. These features
should facilitate the applications of Ag74 in catalysis in fu-
ture.31
In conclusion, our finding here suggests that the ligands
introduced in the synthesis of metal nanoclusters may play
very different roles. Although bidentate phosphine did not
directly involved in the protection of Ag74, it slowed down
the reduction rate of Ag(I) by coordinating with and then
releasing it. The strategy gave rise to an unprecedented all
alkynyl protected Ag nanocluster. It is hoped this approach
will pave the way for the synthesis of more alkynyl protected
Ag nanoclusters.
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 4 of 4
(20) Wang, Y.; Su, H.; Xu, C.; Li, G.; Gell, L.; Lin, S.; Tang, Z.; Häk-
(27) Russier-Antoine, I.; Bertorelle, F.; Hamouda, R.; Rayane, D.;
kinen, H.; Zheng, N. J. Am. Chem. Soc. 2015, 137, 4324.
(21) Wang, Y.; Wan, X.-K.; Ren, L.; Su, H.; Li, G.; Malola, S.; Lin, S.;
Tang, Z.; Häkkinen, H.; Teo, B. K.; Wang, Q.-M.; Zheng, N. J. Am.
Chem. Soc. 2016, 138, 3278.
(22) Zeng, J.-L.; Guan, Z.-J.; Du, Y.; Nan, Z.-A.; Lin, Y.-M.; Wang,
Q.-M. J. Am. Chem. Soc. 2016, 138, 7848.
(23) Schmidbaur, H.; Schier, A. Angew. Chem. Int. Ed. 2015, 54,
746.
(24) Halbes-Letinois, U.; Weibel, J.-M.; Pale, P. Chem. Soc. Rev.
2007, 36, 759.
Dugourd, P.; Sanader, Z.; Bonacic-Koutecky, V.; Brevet, P. F.; An-
toine, R. Nanoscale 2016, 8, 2892.
1
2
3
4
5
6
7
8
(28) Lassahn, P.-G.; Lozan, V.; Wu, B.; Weller, A. S.; Janiak, C.
Dalton Trans. 2003, 4437.
(29) Tiekink, E. R. T. Acta Cryst. 1990, C46, 1933.
(30) Petersson, M. J.; Loughlin, W. A.; Jenkins, I. D. Chem. Com-
mun. 2008, 4493.
(31) Dong, X.-Y.; Gao, Z.-W.; Yang, K.-F.; Zhang, W.-Q.; Xu, L.-W.
Catal. Sci. Technol. 2015, 5, 2554.
9
(25) Yam, V. W.-W.; Lo, K. K.-W.; Wong, K. M.-C. J. Organomet.
Chem. 1999, 578, 3.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
(26) Mak, T. C. W.; Zhao, L. Chem. Asian J. 2007, 2, 456.
For Table of Content only
ACS Paragon Plus Environment