Synthesis of cationic gold(III) complexes using iodine(III)

Article abstract of DOI:10.1080/00958972.2019.1620936

We report the synthesis and characterization of cationic Au(III) complexes supported by nitrogen-based ligands. The syntheses are achieved by reacting Au(I) complexes [Au(N-Me-imidazole)₂]⁺ and [Au(pyridine)(NHC)]⁺ with iodine(III) reagents PhI(OTf)(OAc) and [PhI(pyridine)₂]²⁺ yielding a series of cationic gold(III) complexes. In contrast, reactions of phosphine ligated gold(I) complexes with iodine(III) reagents results in the oxidation of the phosphine ligand.

Full text of DOI:10.1080/00958972.2019.1620936

Journal of Coordination Chemistry
ISSN: 0095-8972 (Print) 1029-0389 (Online) Journal homepage: https://www.tandfonline.com/loi/gcoo20
Synthesis of cationic gold(III) complexes using
iodine(III)
Mohammad Albayer & Jason L. Dutton
To cite this article: Mohammad Albayer & Jason L. Dutton (2019): Synthesis of
cationic gold(III) complexes using iodine(III), Journal of Coordination Chemistry, DOI:
10.1080/00958972.2019.1620936
To link to this article: https://doi.org/10.1080/00958972.2019.1620936
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JOURNAL OF COORDINATION CHEMISTRY
https://doi.org/10.1080/00958972.2019.1620936
Synthesis of cationic gold(III) complexes using iodine(III)
Mohammad Albayer and Jason L. Dutton
Department of Chemistry and Physics, La Trobe Institute for Molecular Science, La Trobe University,
Melbourne, Victoria, Australia
ABSTRACT
ARTICLE HISTORY
We report the synthesis and characterization of cationic Au(III)
Received 14 January 2019
Accepted 1 May 2019
complexes supported by nitrogen-based ligands. The syntheses
þ
are achieved by reacting Au(I) complexes [Au(N-Me-imidazole) ]
2
þ
KEYWORDS
Iodine; trivalent; gold(III);
tricationic; homoleptic
and [Au(pyridine)(NHC)] with iodine(III) reagents PhI(OTf)(OAc)
2þ
and [PhI(pyridine)
2
]
yielding a series of cationic gold(III) com-
plexes. In contrast, reactions of phosphine ligated gold(I) com-
plexes with iodine(III) reagents results in the oxidation of the
phosphine ligand.
1. Introduction
Gold I/III redox catalysis has attracted much attention in organic synthesis [1], how-
ever, oxidative addition reactions are not readily accessible at Au(I) due to the high
oxidation potential of Au(I) [2, 3]. For catalysis to occur via Au(I)/Au(III) redox, forcing
conditions are required, which can be achieved using external oxidants such as triva-
lent iodine reagents [4–10]. In one report, Blanc and de Fr eꢀ mont displayed the use of
PhICl in generating (NHC)-Au(III) complexes. However, attempts in generating trica-
2
tionic Au(III) complexes bound by only neutral ligands by exchanging the chlorides
with pyridines using silver salts were unsuccessful (Scheme 1) [11].
Our group has demonstrated the use of I(III) based reagents in accessing tricationic
Au(III) complexes. These reagents have proved to be an effective oxidant for the syn-
thesis of homoleptic and pseudo-homoleptic tricationic Au(III) complexes (Scheme 2)
[12]. In the reaction of 1 with 2R, compounds of the class 3R were generated in high
yields. In contrast, the reaction of NHC–Au(I)–Cl 4 with 2NMe gave a complex mixture
2
of products arising from ligand exchange and anion scrambling (Scheme 3).
We also found that phosphine-containing Ir(I) (Vaska’s complex) and Rh(I)
(Wilkinson’s catalyst) reacted with I(III) reagents generally resulted in scrambling. These
CONTACT Jason L. Dutton
j.dutton@latrobe.edu.au
Department of Chemistry and Physics, La Trobe Institute
for Molecular Science, La Trobe University, Melbourne, VIC 3086, Australia
Supplemental data for this article is available online at here.
ß 2019 Informa UK Limited, trading as Taylor & Francis Group

2
M. ALBAYER AND J. L. DUTTON
Scheme 1. Attempts to generate tricationic Au(III) complexes.
Scheme 2. Synthesis of tricationic Au(III) complexes.
Scheme 3. Reaction of 4 with 2NMe2.
starting materials bear a chloride ligand as did 4. Reactions involving homoleptic com-
plexes (i.e. [dppe] Rh(I)) without halides went much more cleanly [13].
2
Direct reaction of PPh with 2NMe resulted in oxidation of the phosphine, gener-
3
2
ating dication 5 (Scheme 4), previously reported by Burford from halide abstraction/
coordination reactions at chlorophosphonium cations [14, 15].
Based on these results, we hypothesized that scrambling is induced by the pres-
ence of a halide substituent and have investigated the reactions of selected phosphine
or NHC containing Au(I) complexes as well as N-bound Au(I) complexes 6–9 with 2R
(Figure 1). The results show that oxidized phosphine and/or scrambling were observed
in all phosphine-containing Au(I) complex reactions. In the reaction of N-bound Au(I)
complexes with 2R, cationic Au(III) compounds were generated in high yields and no

JOURNAL OF COORDINATION CHEMISTRY
3
Scheme 4. Reaction of 2NMe with PPh .
2
3
Figure 1. Au(I) complexes used in this study.
scrambling was observed. For Au(I) –NHC complexes without halides we are able to
generate previously inaccessible mono-NHC-trispyridine trications.
2
. Results and discussion
.1. Reactions of phosphine gold complexes
Reaction of 6 with 2NMe2 in CD CN resulted in a color change to orange within
2
3
1
10 min. The H NMR spectrum of the reaction mixture indicated that there was a com-
31
plex mixture of products present. The P NMR spectrum of the reaction mixture gave
four resonances (65.6, 57.6, 33.0, and 29.9 ppm). The peaks at 65.6 and 57.6 ppm are
consistent with the reported 5 and Ph PCl , respectively [14, 16]. The peaks at 33.0
3
2
and 29.9 are consistent with the gold compounds 6 and 7, respectively [17, 18].
Positive mode ESI-MS detection of a CH CN solution of the reaction mixture gave frag-
3
þ
þ
ments that could be identified at [m/z] ¼ 510.4 consistent with 10 and [m/z]
¼
4
40.8 consistent with 1 (Scheme 5). The outcome of this reaction showed similar
scrambling pattern to that observed in reaction of 7 with 2NMe with the addition of
2
5
and Ph PCl apparently arising from reductive elimination reactions.
3 2

4
M. ALBAYER AND J. L. DUTTON
3
1
Scheme 5. Reaction of 6 with 2NMe outcome as identified by mass spectrometry and P NMR.
2
Scheme 6. Reaction of 6 with 2OAc-OTf outcome as identified by mass spectrometry, X-ray diffrac-
3
1
tion, and P NMR.
The reaction of 6 with 2OAc-OTf in a 1:1 ratio in CDCl resulted in a color change
3
1
to yellow instantly (Scheme 6). The H NMR spectrum of the mixture indicated the
presence of iodobenzene and one other species. The P NMR of the solution had one
singlet at 52.1 ppm. Searching the literature for potential oxidized phosphine products
31
revealed that [Ph P-OTf][OTf] has been reported to give an identical chemical shift
3
31
[
14]. The Ph PO was not detected in the P NMR of the crude reaction, but it can be
3
rationalized by the reported behavior of [Ph P-OTf][OTf] where an equilibrium
3
between [Ph P-OTf][OTf] and Ph PO þ triflic anhydride was observed [19, 20]. The posi-
3
3
þ
tive ESI-MS detection of the mixture contained a signal at [m/z] ¼ 556.1 correspond-
þ
ing to [(Ph PO) H] . X-Ray diffraction studies done on single crystals obtained from
3
2
vapor diffusion of Et O into concentrated CH Cl solution revealed the crystal to be
2
2
2
–
1
1, which consists of two Ph PO that are bridged with a proton and [AuCl ] . This
3 4
unproductive byproduct was previously reported as [FeBr ] , [ICl ] , [AuBr ] , and
AuCl ] salts [21–25].
–
–
–
4
4
4
–
[
4
Treatment of 7 with 2NMe resulted in a color change to orange within 10 min.
2
3
1
The P NMR spectrum of the mixture contained signals at 57.6 and 26.6 ppm, which
are consistent with 5 and Ph PO, respectively (Scheme 7) [11, 14]. The starting material
3
31
(
7) was also detected in the P NMR at 29.7 ppm and in the cationic ESI mass spec-
þ
trum of the reaction mixture ([m/z] 580.0). The fragment in the ESI mass spectrum at
þ
[m/z] ¼ 440.8 is consistent with 1.
The reaction of 7 with 2OAc-OTf resulted in color change to yellow instantly fol-
31
lowed by formation of a black solid. The P NMR of the reaction mixture gave signals

JOURNAL OF COORDINATION CHEMISTRY
5
3
1
Scheme 7. Reaction of 7 with 2NMe outcome as identified by mass spectrometry and P NMR.
2
at 52.1 ppm representing [Ph P-OTf][OTf], which is in equilibrium with Ph PO and triflic
3
3
anhydride. Positive mode ESI-MS detection of a CH CN solution of the reaction mixture
3
þ
gave fragments that could be identified at [m/z] ¼ 556.2 consistent with
þ
þ
þ
[
(PPh O) H] and [m/z] ¼ 499.4 consistent with [Au(PPh )(CH CN)] .
3
2
3
3
It is evident that the reactions of phosphine-containing gold(I) complexes with the
selected I(III) resulted in the oxidation of PPh and no phosphine-Au(III) complexes
3
were isolated. Reaction of 7 with PhICl2 (2Cl) was not attempted as this reaction
(
using pyridine-Au(I)–PPh instead of (4-DMAP)-Au(I) –PPh as starting material) was
3
3
previously reported and gave similar scrambling patterns to what has been observed
in our reactions [11].
2
.2. Reactions of N-imidazole Au(I) complexes
The Au(I) starting complex 8 was achieved via adapting the synthetic protocol of Lin
26] and using N-methylimidazole as the ligand in place of 4-DMAP (Scheme 8). The
[
–
same cation has previously been reported as a [AuCl ] salt [27]. Compound 8 has a
2
linear structure with normal Au–N bond lengths and they are aligned parallel with a
Au–Au contact of about 3.26 Å (Figure 2).
Reaction of 8 with 2Cl in CH Cl resulted in the formation of a yellow solid. The
2
2
1
solid was filtered and washed with CH Cl . H NMR analysis of the solid in CD CN
2
2
3
gave a set of resonances consistent with a single N-methylimidazole containing prod-
uct (Scheme 9). Mass spectrometry in CH CN showed signals arising from 12, which
3
was further confirmed by X-ray diffraction studies on single crystals obtained from
vapor diffusion of Et O into concentrated CH CN solution of the isolated solid
2
3
(Figure 3).
Reaction of 8 with 2IM in CH CN (Scheme 10) resulted in a color change to yellow
3
within 5 min. The solvent was removed under reduced pressure to give a pale yellow
solid. The solid was then recrystallized from CH CN/Et O.
3
2
1
H NMR spectroscopy was consistent with a single compound containing N-methyli-
þ
midazole. The signal at [m/z] ¼ 823.1 in the positive ESI-MS spectrum of the mixture
þ
corresponds to [Au(N-methylimidazole)4 2OTf] . Single crystals were grown from a
CH CN solution of the compound via slow vapor diffusion of Et O and subsequent X-
3
2
ray diffraction studies confirmed homoleptic complex 13 (Figure 4), which is isolated
in 79% yield. This compound is the second example of a homoleptic N-imidazole con-
taining Au(III) trication. The first reported example incorporated an extended Au-ligand

6
M. ALBAYER AND J. L. DUTTON
Scheme 8. Synthesis of 8.
Figure 2. Solid-state structure of 8. Thermal ellipsoids are drawn at the 50% probability level.
Anions and solvate were omitted for clarity (OTf, CH CN). Selected bond distance (Å): Au1-
3
N1 2.000(7).
Scheme 9. Synthesis of 12.
framework for the synthesis of Au nanoparticles without structural or spectroscopic
characterization [28].
Using I(III) oxidant 2R resulted in the corresponding pseudo-homoleptic compounds
1
4H, 14CN, and 14NMe , respectively, in good yields (Scheme 11). In previous work
2
we reported the synthesis and the use of 14CN in generating difluorogold(III) com-
plexes but the crystal structure was not reported [29]. The solid state structures of
1
4H and 14CN are depicted in Figures 5 and 6. Unfortunately, no crystals of diffrac-
tion quality could be obtained for 14NMe2.
The reaction of 2OAc-OTf with 8 in CHCl resulted in a decomposition of the Au
3
complex which was indicated by the formation of black solid.
The starting complex 9 was synthesized using the synthetic protocol of de Fr ꢀe mont
[11] and using 1,3-dimethylbenzimidazol-2-ylidene as the ligand (Scheme 12). The solid
state structure of 9 is shown in Figure 7.
Reaction of 9 with PhICl was not attempted as similar reactions were previously
2
reported on Au(I) compounds with different NHC ligands [11]. Treatment of 9 with 2H
in CH CN at room temperature for 30 min followed by workup resulted in the isolation
3
1
of a yellow solid. The H NMR spectrum of the isolated solid was consistent with a sin-
gle compound containing one 1,3-dimethylbenzimidazol-2-ylidene and three pyridine

JOURNAL OF COORDINATION CHEMISTRY
7
Figure 3. Solid-state structure of 12. Thermal ellipsoids are drawn at the 50% probability level.
Anions and solvate were omitted for clarity (OTf, CH CN). Selected bond distances (Å) are Au1-N1
3
2.007(6) and Au1-Cl1 2.277(17).
Scheme 10. Synthesis of 13.
ligands (Scheme 13). The positive ESI-MS detection of the mixture indicated the pres-
þ
þ
ence of 15 at [m/z] ¼ 877.8 as monocationic [Au(NHC)(pyridine) 2OTf] .
3
X-Ray diffraction studies done on single crystals obtained from vapor diffusion of
Et O into concentrated CH CN solution of the isolated solid confirmed the compound
2
3
to be 15 (Figure 8).
Reaction of 9 with 2OAc-OTf in CDCl resulted in formation of a black solid due to
3
decomposition of Au complex.
The syntheses of Au(III) cationic complexes (13–15) were achieved in good yields
(68-85%) and purity. Prior attempts to generate tricationic Au(III) compounds using sil-
ver salts to replace two chlorides from Au(III) compounds with pyridine ligands
resulted in complex decomposition demonstrating the ability of I(III) reagents to
cleanly oxidize N-bound Au(I) complexes [11].
3. Conclusion
We had previously shown that Au(I) starting materials of the type NHC–Au–Cl when
2
þ
reacted with I(III) oxidants [PhI(pyr)] results in complex mixtures arising from chlor-
ide scrambling. Here it was shown that eliminating chloride and replacing it with a
neutral pyridine ligand suppresses the scrambling reactions. With Ph P–Au–Cl starting
3
complexes, scrambling and phosphine oxidation processes result. Substituting the

8
M. ALBAYER AND J. L. DUTTON
Figure 4. Solid-state structure of 13. Thermal ellipsoids are drawn at the 50% probability level.
Anions and solvate were omitted for clarity (OTf, CH CN). Selected bond distances (Å) are Au1-N1
3
1.996(3) and Au1-N2 1.999(3).
Scheme 11. Synthesis of Au(III) trications 14R.
halide with a pyridine ligand still resulted in oxidation of the phosphine in reactions
with I(III), indicating phosphine ligands are not ideal for exploring this class of reaction.
Imidazole ligated Au(I) starting complexes were shown to undergo clean oxidations
2
þ
with both [PhI(py)2] and PhICl oxidants.
2
4. Experimental procedures
Solvents were obtained from Caledon Laboratories and dried using an Innovative
Technologies Solvent Purification System with dual columns packed with alumina. The
dried solvents were stored under an N atmosphere over 3 Å molecular sieves in the
2

JOURNAL OF COORDINATION CHEMISTRY
9
Figure 5. Solid-state structure of 14H. Thermal ellipsoids are drawn at the 50% probability level.
Anions and solvate were omitted for clarity (OTf, CH CN). Selected bond distances (Å) are Au1-N1
3
2.016(5) and Au1-N2 2.009(4).
glovebox. Solvents used for NMR spectroscopy were purchased from Cambridge
Isotopes or Sigma-Aldrich and were dried with CaH , stirred for 2 days, distilled and
2
then stored in the glove box over 3 Å molecular sieves. Compounds 6 [30], 7 [18], 8
[26], 9 [11], 2Cl [31], and 2R [32] were synthesized via literature procedures. 2OAc-OTf
was prepared in situ by treating one equivalent of diacetoxyiodobenzene with two
equivalents of TMS-triflate in CHCl . Gold powder was purchased from Precious Metals
3
Online. All other reagents were purchased from Alfa Aesar or Sigma Aldrich and used
as received.
4.1. Reaction of 6 with 2NMe2
A solution of 2NMe (82 mg, 0.11 mmol) in 3 mL CD CN was added dropwise to 6
2
3
(
50 mg, 0.10 mmol) in 3 mL CD CN. The mixture was stirred for 3 h resulting in a color
3
31
change to orange. Aliquot was removed for NMR and mass spectrometry analysis.
NMR (162 MHz, CDCl ) d (ppm): 65.6 (s), 57.6 (s), 33.0 (s), 29.9 (s). ESI-MS [M] : m/z
2
P
nþ
3
þ
þ
þ
73.8 [Au(CH CN)Cl] , 440.8 [Au(4-dmap) ] , 510.4 [Au(4-dmap) Cl ] . See Supporting
3 2 2
2
1
Information for H NMR.
4
.2. Reaction of 6 with 2OAc-OTf
A mixture of diacetoxyiodobenzene (21 mg, 0.065 mmol) and TMS-OTf (24 lL,
.13 mmol) in 2 mL CDCl was added dropwise to a solution of 6 (30 mg, 0.061 mmol)
0
3
in 2 mL CDCl . The mixture was stirred for 30 min resulting in a yellow mixture and a
3

1
0
M. ALBAYER AND J. L. DUTTON
Figure 6. Solid-state structure of 14CN. Thermal ellipsoids are drawn at the 50% probability level.
Anions and solvate were omitted for clarity (OTf, CH CN). Selected bond distances (Å) are Au1-N1
3
2.006(4), Au1-N2 2.035(4), Au1-N3 2.024(4), and Au1-N4 1.991(4).
black solid. The solid was filtered and the filtrate was collected. Solvent was removed
3
1
under reduced pressure to give a yellow solid, which was washed with Et O. P NMR
2
nþ
þ
(
[
162 MHz, CD CN) d (ppm): 52.1 (s). ESI-MS [M] : m/z 273.8 [Au(CH CN)Cl] , 556.1
3 3
þ
1
(Ph PO) H] . H NMR (400 MHz, CD CN): d (ppm) ¼ 7.91–7.87 (m), 7.78–7.70 (m).
3
2
3
4.3. Reaction of 7 with 2NMe2
A solution of 2NMe (52 mg, 0.070 mmol) in 2 mL CH CN was added to a solution of 7
2
3
(
50 mg, 0.068 mmol) in 2 mL CH CN dropwise. The mixture was stirred for 3 h resulting
3
in an orange solution. Solvent was removed under reduced pressure and the resulting
3
1
orange solid was washed with Et O. P NMR (162 MHz, CD CN) d (ppm): 57.6 (s), 29.7
2
3
nþ
2þ
–
þ
(
[
s), 26.6 (s). ESI-MS [M] : m/z 395.0 [Ph P] [Tf] , 440.8 [Au(4-dmap) ] , 499.4
3
2
þ
þ
þ
Au(PPh )(CH CN)] , 580.0 [Au(PPh )(4-dmap)] , 736.2 [Au(PPh )(Ph PO)] . See
3
3
3
3
3
1
Supporting Information for H NMR.
4
.4. Reaction of 7 with 2OAc-OTf
A mixture of diacetoxyiodobenzene (21 mg, 0.065 mmol) and TMS-OTf (24 lL,
.13 mmol) in 2 mL CHCl was added dropwise to 7 (45 mg, 0.062 mmol) in 2 mL CHCl
0
3
3
and stirred for 30 min. The resulting black solid was filtered, and aliquot of the filtrate
31
was removed for NMR and mass spectrometry analysis. P NMR (162 MHz, CHCl ) d
3

JOURNAL OF COORDINATION CHEMISTRY
11
Scheme 12. Synthesis of 9.
Figure 7. Solid-state structure of 9. Thermal ellipsoids are drawn at the 50% probability level.
Anions and solvate were omitted for clarity (OTf, CH CN). Selected bond distances (Å) are Au1-N1
3
2.052(5) and Au1-C1 1.975(7).
þ
þ
(
[
ppm): 52.1 (s), 27.8 (s). ESI-MS [M] : m/z 556.2 [(PPh O) H] , 499.4
3
2
þ
Au(PPh )(CH CN)] .
3
3
4.5. Synthesis of 8
N-Methylimidazole (175 mL, 2.20 mmol) was added to a dichloromethane solution
20 mL) containing tht-AuCl (350 mg, 1.09 mmol) and KOTf (210 mg, 1.12 mmol). The
(
mixture was stirred for 24 h in the dark. The solvent was removed under vacuum to
give a light yellow solid. The solid was washed with Et O and recrystallized from
2
1
CH Cl /Et O to give a white solid (457 mg, 82%). H NMR (400 MHz, CDCl ): d (ppm) ¼
2
2
2
3
13
8
1
.26 (s, 2H), 7.13 (s, 2H), 7.05 (s, 2H), 3.84 (s, 6H). C NMR (100 MHz, CDCl ): d (ppm) ¼
3
þ
þ
41.00, 129.44, 121.71, 35.23. ESI-MS [M] : m/z 361 [Au(N-methylimidazole) ] .
2
4.6. Synthesis of 12
A solution of 2Cl (27 mg, 0.098 mmol) in 2 mL CH Cl was added dropwise to a solu-
2
2
tion of 8 (50 mg, 0.098 mmol) in 2 mL CH Cl . The mixture was then stirred for 30 min
2
2
resulting in a yellow solid. The solid was filtered, washed with CH Cl (3 ꢀ 3 mL), and
2
2
1
dried in vacuo (49 mg, 85% yield). H NMR (400 MHz, CD CN): d (ppm) ¼ 8.30 (s, 2H),
3
13
7
.39 (s, 2H), 7.35 (s, 2H), 3.86 (s, 6H). C NMR (100 MHz, CD CN): d (ppm) ¼ 139.69,
3

1
2
M. ALBAYER AND J. L. DUTTON
Scheme 13. Synthesis of 15.
Figure 8. Solid-state structure of 15. Thermal ellipsoids are drawn at the 50% probability level.
Anions and solvate were omitted for clarity (OTf, CH CN). Selected bond distances (Å) are Au1-N1
3
2.085(3), Au1-N2 2.025(3), Au1-N3 2.021(3), and Au1-C1 2.032(3).
þ
þ
1
27.74, 123.89, 36.54. ESI-MS [M] : m/z 361.0 [Au(N-methylimidazole) ] , 395.0 [Au(N-
2
þ
þ
methylimidazole) Cl] 431.0 [Au(N-methylimidazole) Cl ] .
2
2
2
4.7. Synthesis of 13
A solution of 2IM (66 mg, 0.098 mmol) in 2 mL CH CN was added dropwise to a solu-
3
tion of 8 (50 mg, 0.098 mmol) in 2 mL CH CN. The mixture was stirred for 30 min
3
resulting in a yellow solution. Solvent was reduced to half in vacuo followed by add-
ition of 5 mL of Et O to afford a yellow solid. The solid was then washed with Et O
2
2
1
(
3 ꢀ 3 mL) and dried in vacuo (76 mg, 70% yield). H NMR (400 MHz, CD CN): d (ppm)
3

JOURNAL OF COORDINATION CHEMISTRY
13
1
3
¼
8.20 (s, 4H), 7.32 (s, 4H), 7.20 (s, 4H), 3.80 (s, 12H). C NMR (100 MHz, CD CN): d
3
þ
(
ppm) ¼ 139.50, 126.53, 124.76, 36.66. ESI-MS [M] : m/z 361.1 [Au(N-methyl-
þ
3þ
–
imidazole) ] , 823.1 [Au(N-methylimidazole) ] [OTf] .
2
4
2
4.8. Synthesis of 14NMe2
A solution of 2NMe (74 mg, 0.098 mmol) in 2 mL CH CN was added dropwise to a
2
3
solution of 8 (50 mg, 0.098 mmol) in 2 mL CH CN and stirred for 30 minutes. A color
3
change from white to orange was observed. Solvent was reduced to half in vacuo fol-
lowed by addition of 5 mL of Et O to afford a yellow solid. The solid was then washed
2
1
with Et O (3 ꢀ 3 mL) and dried in vacuo (78 mg, 76% yield). H NMR (400 MHz, CD CN):
2
3
d (ppm) ¼ 8.24 (s, 2H), 7.95 (d, 4H, J ¼ 8 Hz), 7.33 (s, 2H), 7.22 (s, 2H), 6.71 (d, 4H,
13
J ¼ 8 Hz), 3.79 (s, 6H) 3.11 (s, 12H). C NMR (100 MHz, CD CN): d (ppm) ¼ 157.02,
3
þ
1
47.10, 139.46, 126.26, 124.98, 110.25, 40.24, 36.70. ESI-MS [M] : m/z 361.1 [Au(N-
þ
þ
þ
2
methylimidazole) ] , 401.1 [Au(N-methylimidazole)(4-dmap)] , 441.1 [Au(4-dmap) ] ,
2
þ
–
9
02.9 [Au(N-methylimidazole) (4-dmap) ] [OTf] .
2 2 2
4.9. Synthesis of 14H
A solution of 2H (65 mg, 0.098 mmol) in 2 mL CH CN was added dropwise to a solu-
3
tion of 8 (50 mg, 0.098 mmol) in 2 mL CH CN and stirred for 30 mins. A color change
3
from white to yellow was observed. Solvent was reduced to half in vacuo followed by
addition of 5 mL of Et O to afford a yellow solid. The solid was then washed with Et O
2
2
1
(
3 ꢀ 3 mL) and dried in vacuo (68 mg, 72% yield). H NMR (400 MHz, CD CN): d (ppm)
3
¼
8.77 (d, 4H, J ¼ 8 Hz), 8.36-8.31 (m, 4H), 7.83 (t, 4H, J ¼ 8 Hz), 7.3 (s, 4H), 3.75 (s, 6H).
1
3
C NMR (100 MHz, CD CN): d (ppm) ¼ 150.75, 146.29, 139.56, 130.62, 125.92, 125.40,
3
þ
þ
3
6.76. ESI-MS [M] : m/z 358.1 [Au(N-methylimidazole)(pyridine)] , 361.1 [Au(N-methyl-
þ
3þ
–
imidazole) ] , 816.5 [Au(N-methylimidazole) (pyridine) ] [OTf] .
2
2
2
2
4.10. Synthesis of 14CN
A solution of 2CN (278 mg, 0.392 mmol) in CH CN (5 mL) was added dropwise to a
3
solution of 8 (200 mg, 0.392 mmol) in CH CN (5 mL). The mixture was then stirred for
3
10 min giving a yellow solution. The solvent was removed under reduced pressure to
give a yellow solid. The solid was recrystallized from CH CN/Et O (317 mg, 79% yield).
3
2
1
H NMR (400 MHz, CD CN): d (ppm) ¼ 8.95 (d, J ¼ 7.0 Hz, 4H), 8.31 (s, 2H), 8.18 (d,
3
1
3
J ¼ 7.0 Hz 4H), 7.33 (s, 2H), 7.30 (s, 2H), 3.77 (s, 6H). C NMR (100 MHz, CD3CN): d
þ
(
3
ppm) ¼ 152.19, 139.76, 133.15, 129.15, 125.98, 125.52, 114.76, 36.87. ESI-MS [M] : m/z
þ
61 [Au(N-methylimidazole) ] .
2
4.11. Synthesis of 9
Au(1,3-dimethylbenzimidazole)Cl (300 mg, 0.79 mmol) was dissolved in 20 mL CH Cl2
2
followed by addition of 640 mL of pyridine (7.9 mmol). AgOTf (203 mg, 0.79) was added
to the mixture and stirred overnight in the dark. The mixture was filtered through

1
4
M. ALBAYER AND J. L. DUTTON
celite and the solvent was reduced to half in vacuo. Addition of Et O (20 mL) to the
2
1
mixture afforded a white solid which was washed with Et O (3 ꢀ 5 mL). 81% yield. H
2
NMR (400 MHz, CD CN): d (ppm) ¼ 8.71 (d, J ¼ 4.0 Hz, 2H), 8.18 (br, 1H), 7.78 (br, 2H),
3
1
3
7
(
3
[
.69 (dd, J ¼ 6.2, 3.1 Hz, 2H), 7.54 (dd, J ¼ 6.2, 3.1 Hz, 2H), 4.12 (s, 6H). C NMR
100 MHz, CD3CN): d (ppm) ¼ 173.11, 152.54, 142.64, 134.86, 127.80, 125.74, 112.84,
þ
þ
6.10. ESI-MS [M] : m/z 384.0 [Au(1,3-dimethylbenzimidazolole)(CH CN)] , 422.0
3
þ
Au(1,3-dimethylbenzimidazole)(pyridine)] .
4.12. Synthesis of 15
A solution of 2H (59 mg, 0.088 mmol) in CH CN (2 mL) was added dropwise to a solu-
3
tion of 9 (50 mg, 0.088 mmol) in CH CN (2 mL). The mixture was then stirred for
3
3
0 min giving a yellow solution. The solvent was removed under reduced pressure to
1
give a yellow solid, which was recrystallized from CH CN/Et O (62 mg, 68% yield). H
3
2
NMR (400 MHz, CD CN): d (ppm) ¼ 8.81 (d, J ¼ 7.96 Hz, 4H), 8.44–8.40 (m, 4H), 8.33 (t,
3
J ¼ 7.72 Hz, 1H), 7.88 (t, J ¼ 7.72, 4H), 7.78 (dd, J ¼ 6.44, 3.16 Hz, 2H), 7.76–7.72 (m, 2H),
1
3
7
1
[
.63 (dd, J ¼ 6.32, 3.24 Hz, 2H), 4.18 (s, 6H). C NMR (100 MHz, CD3CN): d (ppm) ¼
52.31, 150.87, 147.10, 145.79, 135.26, 131.59, 129.55, 128.16, 114.20, 36.11. ESI-MS
M] : m/z 719.1 [Au(1,3-dimethylbenzimidazole)(pyridine)] [OTf] , 798.4 [Au(1,3-
dimethylbenzimidazole)(pyridine) ] [OTf] , 877.8 [Au(1,3-dimethylbenzimidazole)
þ
3þ
–
2
3
þ
–
2
2
3
þ
–
(
pyridine)3] [OTf] .
2
Disclosure statement
No potential conflict of interest was reported by the authors.
Funding
We thank La Trobe University and the Australian Research Council (JLD; FT16010007) for their
generous funding of this work.
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