Synthesis of a new class of cationic Pd(II) complexes with 1,2,3-triazol-5-ylidene ligand and their catalytic application in the conversion of internal alkynes to 1,2-diketones

Article abstract of DOI:10.1016/j.jorganchem.2018.02.011

A new class of cationic Pd(II) complexes of the type [Pd(Tz)(Cl)(bipy)]⁺Cl^? and [Pd (Tz)(Cl)(phen)]⁺Cl^? (Tz = 1,4-diaryl-3-methyl-1,2,3-triazol-5-ylidene, bipy = 2,2′-bipyridine and phen = 1,10-phenanthroline) with various wing tip groups were synthesized from the corresponding 1,2,3-triazolium iodide via the corresponding chloro bridged dinuclear complexes [(Tz)(Cl)Pd(μ-Cl)₂Pd(Cl)(Tz)]. The synthesized cationic complexes were screened for their catalytic activity of hydration of alkynes and found to be excellent towards the selective conversion of internal alkynes to the corresponding 1,2-diketones in good yields. A plausible mechanism was proposed for this conversion.

Full text of DOI:10.1016/j.jorganchem.2018.02.011

Accepted Manuscript
Synthesis of a new class of cationic Pd(II) complexes with 1,2,3-triazol-5-ylidene
ligand and their catalytic application in the conversion of internal alkynes to 1,2-
diketones
Jeelani Basha Shaik, Venkatachalam Ramkumar, Sethuraman Sankararaman
PII:
S0022-328X(18)30100-1
10.1016/j.jorganchem.2018.02.011
JOM 20310
DOI:
Reference:
To appear in: Journal of Organometallic Chemistry
Received Date: 7 December 2017
Revised Date: 1 February 2018
Accepted Date: 7 February 2018
Please cite this article as: J.B. Shaik, V. Ramkumar, S. Sankararaman, Synthesis of a new class
of cationic Pd(II) complexes with 1,2,3-triazol-5-ylidene ligand and their catalytic application in the
conversion of internal alkynes to 1,2-diketones, Journal of Organometallic Chemistry (2018), doi:
10.1016/j.jorganchem.2018.02.011.
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to
our customers we are providing this early version of the manuscript. The manuscript will undergo
copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please
note that during the production process errors may be discovered which could affect the content, and all
legal disclaimers that apply to the journal pertain.

ACCEPTED MANUSCRIPT
1
Synthesis of a new class of cationic Pd(II) complexes with 1,2,3-triazol-5-ylidene ligand and
their catalytic application in the conversion of internal alkynes to 1,2-diketones
Jeelani Basha Shaik, Venkatachalam Ramkumar, Sethuraman Sankararaman*
Department of Chemistry, Indian Instituteof Technology Madras, Chennai 600036, India
Corresponding author: email: sanka@iitm.ac.in, phone: +91 44 2257 4210, fax: +91 44 2257
0545
Abstract
A
new class of cationicPd(II) complexes of the type [Pd(Tz)(Cl)(bipy)]+Cl− and
[Pd(Tz)(Cl)(phen)]+Cl− (Tz = 1,4-diaryl-3-methyl-1,2,3-triazol-5-ylidene , bipy = 2,2’-bipyridine
and phen = 1,10-phenanthroline) with various wing tip groups were synthesized from the
corresponding 1,2,3-triazolium iodide via the corresponding chloro bridged dinuclear complexes
[(Tz)(Cl)Pd(µ-Cl)2Pd(Cl)(Tz)]. The synthesized cationic complexes were screened for their
catalytic activity of hydration of alkynes and found to be excellent towards the selective
conversion of internal alkynes to the corresponding 1,2-diketones in good yields. A plausible
mechanism was proposed for this conversion.
Keywords
Alkyne, cationic Pd complex,1,2-diketone,hydration,NHC-Pd complex,1,2,3-triazol-5-ylidene,
1. Introduction
N-Heterocyclic carbenes (NHCs) have gained exclusive, rapid popularity and emerged as
versatile ligands for a wide variety of metal complexes.[1] The success achieved by NHCs is
because of their strong σ-electron donating capacity which will allow them to form strong NHC-
metal bonds. Due to their stability to air, moisture and strong σ-donor but poor π-acceptor
abilities NHCs have been receiving a great amount of attention and becoming a very important

ACCEPTED MANUSCRIPT
2
class of ligands in transition metal catalysis.[2] Over past few years 1,2,3-triazol-5-ylidenes have
attracted many research groups and emerged as promising ligands for transition metal chemistry,
these ligands are often referred as abnormal (aNHCs) or mesoioniccarbenes (MICs) due to the
fact that their structures can only be represented as zwitter ions and not in the neutral canonical
form.[3] Albrecht first reported the synthesis and structural characterization of 1,2,3-triazol-5-
ylidene-metal (Pd, Rh and Ir) complexes.[3a] The first example of chiral and chelate type
palladium-1,2,3-triazol-5-ylidene complexes and their catalytic activity in Suzuki-Miyaura
coupling was reported by our group.[3b]
π-Complexes of palladium (II) are widely used in organic transformations.[4] Coordination of Pd
(II) to π bond increases the reactivity of the π-bond towards nucelophilic attack.[5] In this regard
cationic palladium complexes are catalytically more reactive than their neutral counter parts.[6]
They have been primarily used in the catalytic activation of alkenes and alkynes towards addition
of nucelophiles.[7] Catalysis of copolymerization of olefins and carbon monoxide,[8] hetero
Diels-Alder reaction[9] and telomerization of butadiene[10] are few of the reactions catalyzed by
cationic palladium (II) complexes. Cationic palladium (II) complexes bearing N-heterocyclic
carbene (NHC) ligands have been reported in the literature,[10b,11] especially imidazol-2-
ylidene based complexes are common.[10b,11c-j,11l,11m] In addition to imidazole-2-ylidene
ligands these complexes contained
a
variety of other ligands that include
phosphanes,[11f,11j,11m] allyl, thiolate,[10b,11b] 2,2’-bipyridine,[11b] quinolone[11k] and
pyridine.[11d,11f-g] Cationic palladium (II) complexes containing chelating bis-imidazol-2-
ylidene ligands were also reported.[11c-d, 11h-i] Cationic palladium complexes of 1,2,3-triazol-
5-ylidene ligands are less explored in comparison to the cationic complexes of imidazole-2-
ylidene ligands. The first example of cationic Pd(II) and Pt(II) complexes of 1,2,3-triazol-5-

ACCEPTED MANUSCRIPT
3
ylidene ligands has been reported by Gandelman.[12] An unconventional approach involving
post-synthesis modification of Pd(II) and Pt(II) complexes containing PCP-pincer ligands was
used as the methodology for the synthesis of cationic Pd and Pt complexes. Conventional
synthesis of chiral cationic 1,2,3-triazol-5-ylidene-Pd complex from the corresponding
triazoliumtriflate has also been reported.[13] 1,2-Diketones are important building blocks in
organic synthesis, valuable motifs often found in many natural products and biologically active
compounds.[14] Several synthetic methods have been reported with different Pd-catalysts for the
catalytic oxidation of alkynes to 1,2-diketones.[15]In this study we report the synthesis of a new
class of cationic palladium (II) complexes of the type [Pd(Tz)(Cl)(bipy)]+Cl− and
[Pd(Tz)(Cl)(phen)]+Cl− (Tz = 1,4-diaryl-3-methyl-1,2,3-triazol-5-ylidene, bipy = 2,2’-bipyridine
and phen = 1,10-phenanthroline) and explore their catalytic activity towards the conversion of
internal alkynes to 1,2-diketones.To the best of our knowledge this is the first example for the
oxidation of alkynes to 1,2-diketones catalyzed by cationic Pd-complexes bearing 1,2,3-triazol-
5-ylidne ligands.
2. Results and discussion
2.1. Synthesis of cationic palladium complexes bearing 1,2,3-triazol-5-ylidene ligands.
1,4-Diphenyl-3-methyl-1,2,3-triazolium iodide (1a) was treated with freshly prepared silver
oxide in dichloromethane at room temperature. Formation of the corresponding silver
triazolylidenecarbene complex was inferred from the disappearance of the triazolium proton
1
signal at 9.61 ppm in the H NMR spectrum of the crude product obtained by working up a
aliquot of the reaction mixture.[3a-b,16] Typically after stirring for 16 h at room temperature,
complete disappearance of the starting material was observed. The silver carbene complex thus
generated was not isolated. It was directly treated with 1 equivalent of Pd(Cl)2(CH3CN)2 and

ACCEPTED MANUSCRIPT
4
stirred for additional 16 h at room temperature. After workup the crude product was obtained as
a pale yellow solid. It was identified as the chloro bridged dinuclear complex 2a.[17] Complex
2a was further treated with 2 equivalent of either 2,2’-bipyridine or 1,10-phenanthroline to
obtain the corresponding cationic complex 3a or 4a, respectively (Scheme 1)[17,18].In this
preparation it was not necessary to isolate 2a. It can be in situ treated with 2,2’-bipyridine or
1,10-phenanthroline to obtain 3a or 4a, respectively without any detrimental effect in the yield.
Triazolium iodides (1a-g) bearing different wing-tip groups were treated in asimilar manner to
obtain the corresponding cationic complexes 3a-g and 4a-gin excellent yields (Table 1).All the
complexes were fully characterized by spectroscopic methods. In addition, complex 3a was also
characterized by single crystal XRD data. Complex 3a crystallized in P-1 space group and
triclinic crystal system. The geometry around palladium was distorted square planar (Figure 1).
The unit cell contained two molecules of 3a and four molecules of chloroform, solvent of
crystallization. In the crystal structure of 3a one of the chloride ion was bonded to the palladium
atom and the other chloride ion remained free, clearly indicating the cationic nature of the
palladium center in 3a.

ACCEPTED MANUSCRIPT
5
N
Ar2
N
Me
N
Me
Cl
1. Ag2O (1.1 equiv)
CH2Cl2, rt, 16 h
Cl
N
N N
I
Pd
Pd
Ar1
Ar1
N
2. PdCl2(CH3CN)2
(1.1 equiv), rt, 16 h
Ar1
Ar2
Cl
Cl
Ar2
1a-g
N
N
Me
2a-g
CH2Cl2
rt, 8-16 h
CH2Cl2
rt, 8-16 h
Me
N
N
N N
(2.2 equiv)
N
Ar2
Ar1
N
N
Me
(2.2 equiv)
N N
Pd Cl Cl
N
N
N
Ar2
Ar1
N
Pd Cl Cl
N
3a-g
4a-g
Scheme 1.Synthesis of cationic palladium (II) complexes through chloro bridged dinuclear
complex.
Table 1.Synthesis of cationic palladium (II) complexes3a-g and 4a-g
1
Ar1
Ar2
Product
Duration (h)a Isolated yield
(%)
Phenyl
Phenyl
Phenyl
Mesityl
1-Naphthyl
Mesityl
Phenyl
8
98%
97%
93%
96%
97%
94%
92%
95%
97%
92%
96%
94%
94%
1a
1b
1c
1d
1e
1f
3a
3b
3c
3d
3e
3f
8
Phenyl
16
8
Mesityl
1-Naphthyl
1-Naphthyl
8
Mesityl
8
1-Napthyl 1-Naphthyl
16
8
1g
1a
1b
1c
1d
1e
1f
3g
4a
4b
4c
4d
4e
4f
Phenyl
Phenyl
Phenyl
Mesityl
1-Naphthyl
Mesityl
Phenyl
8
Phenyl
16
8
Mesityl
1-Naphthyl
1-Naphthyl
8
Mesityl
8

ACCEPTED MANUSCRIPT
6
1-Napthyl 1-Naphthyl
acorresponds to conversion of 2a-g to 3a-g and 4a-g.
16
92%
1g
4g
Figure 1. Stick representation of structure of [3a-2CHCl3] in the crystal. Hydrogen atoms are not
labeled for clarity. Selected bond angles: N1-Pd-N2 79.92(15)o, N1-Pd-C11 96.10(11)o, C11-Pd-
Ccarbene 88.15(11)o, N2-Pd-Ccarbene 95.87(14)o, Selected bond lengths: Pd-Ccarbene 197.6(4) pm, Pd-
Cl1 230.12(10) pm.
2.2. Catalytic conversion of internal alkynes to 1,2-diketones
Initially we aimed at the addition of water as a nucleophile to the internal alkynes catalyzed by
the cationic palladium complexes.1,2-Diphenylacetylene (5a) was chosen as the model substrate
for the optimization of reaction conditions. When the reaction was carried out in the presence of
2 mol% of 3a in 1,4-dioxane-water mixture (4:1 v/v) as solvent under N2 atmosphere from room
o
temperature to refluxing conditions (rt to 110 C) only starting material remained intact even
after prolonged period (Table 2, entry 1). Addition of 2 mol% of AgNO3 to the same reaction
o
mixture at 90 C for 36 h surprisingly yielded benzil (6a) as the only product in 32% yield and
the balance being the unreacted starting alkyne (Table 2, entry 2). The course of the reaction was

ACCEPTED MANUSCRIPT
7
followed by TLC which indicated formation of benzil (6a) as the only product. Careful
comparison of the TLC of the crude product with authentic samples of benzoin, hydrobenzoin
and deoxybenzoin (as possible byproducts) revealed that none of these compounds were formed
in the reaction. Upon addition of AgNO3a white precipitate was observed immediately due to the
formation of AgCl. The yield of 6a increased to 69% when the reaction was carried out in the
presence of 4 mol% of AgNO3. Finally in the presence of 4 mol% of the catalyst 3a and 8 mol%
of AgNO3 the yield of 6a increased to 94% (Table 2, entry 3 and 4). Control experiments clearly
showed that there was no reaction in the absence of 3a(Table 2, entry 5), only starting material
was recovered after prolonged period. Neither Ag(OTf) nor CuSO4(as oxidant to convert any
Pd(0) formed during course of the reaction to Pd(II)) was as effective as AgNO3 as additive
(Table 2, entry 6 and 7). Similarly other palladium sources, namely PdCl2 and Pd(OAc)2 were
not as effective as 3a as catalyst for this reaction (Table 2, entry 8 and 9). The presence of
cationic palladium complex 3a and AgNO3 in the mole ratio of 1:2, respectively was essential for
the success of the transformation shown in Scheme 2.
Scheme 2.Catalytic conversion of diphenylacetylene (5a) to benzil (6a).
Table 2. Optimization of reaction conditions for the catalytic conversion of diphenylacetylene
(5a) to benzil (6a).
Entrya
Pd(II) source
Additive
none
Temp/duration
rt to 100 oC/36 h
90 oC / 36 h
Yield of benzilb
(6a) (%)
1
2
3
complex 3a
(2 mol%)
complex 3a
(2 mol%)
complex 3a
(2 mol%)
no reaction
AgNO3 (2 mol%)
AgNO3 (4 mol%)
32%
69%
90 oC / 36 h

ACCEPTED MANUSCRIPT
8
4
complex 3a
(4mol%)
none
AgNO3 (8 mol%)
90 oC / 16 h
94%
5
6
AgNO3 (8 mol%)
Ag(OTf) (8 mol%)
90 oC / 36 h
90 oC / 36 h
no reaction
no reaction
complex 3a
(4 mol%)
complex 3a
(4 mol%)
PdCl2
(4 mol%)
Pd(OAc)2
(4 mol%)
7
8
9
CuSO4 (8 mol%)
AgNO3 (8 mol%)
AgNO3 (8 mol%)
90 oC / 36 h
90 oC / 48 h
90 oC / 48 h
no reaction
trace amount
trace amount
aall reactions were carried out on a 100 mg (0.56 mmol) scale in 1,4-dioxane:H2O (4 mL:1mL)
under N2atm, bisolated yield of 6a.
The catalytic activities of complexes 3a-c and 4a-c were tested under optimized reaction
conditions (Table 2, entry 4) for the conversion of 5a and 5b to 6a and 6b, respectively. 5b (with
electron withdrawing NO2 group) reacted slower than 5ain all cases. Complex 3a was found to
be more active than other catalysts as evident from time taken for the completion of the reaction
under identical conditions (Table 3, entry 1). Therefore complex 3a was used as the catalyst for
further studies.
Scheme 3. Screening of Pd(II) complexes for the conversion of internal alkynes (5a-b) to 1,2-
diketones (6a-b).
Table 3.Screening of Pd(II) complexes for the conversion of internal alkynes (5a-b) to 1,2-
diketones (6a-b).
Entrya
Pd(II) complex Substrate Duration (h)
Product/
Yield (%)b
6a/ 94
1
2
3
16
16
24
3a
3b
3c
5a
5a
5a
6a/94
6a/91

ACCEPTED MANUSCRIPT
9
4
5
24
24
24
21
24
36
36
36
36
6a/89
6a/ 90
6a/85
6b/80
6b/78
6b/74
6b/72
6b/72
6b/71
4a
4b
4c
3a
3b
3c
4a
4b
4c
5a
5a
5a
5b
5b
5b
5b
5b
5b
6
7
8
9
10
11
12
asubstrate (100 mg), Pd complex (4 mol%), AgNO3 (8 mol%), 1,4-dioxane:H2O (5 mL,
4:1 v/v). N2 atm. 90 oC, bisolated yield of the product.
To demonstrate the scope of substrates for the conversion of internal alkyne to 1,2-diketones a
variety of 1,2-diarylalkynes bearing electron donating, electron withdrawing groups and easily
oxidizable group were chosen. In all the cases the reaction proceeded smoothly to furnish the
corresponding 1,2-diketones (Table 4). The easily oxidizable aldehyde group in 5c remained
intact during the course of this reaction and 6c was formed in good yield (Table 4, entry 3).
Sterically hindered substrates 5f and 5lreacted slower and gave moderate yields of the
corresponding diketones6f and 6l, respectively (Table 4, entry 6, 10 and 12). 1-alkyl-2-
arylalkynes 5h and 5i also reacted to furnish the corresponding diketones6h and 6i, respectively
in excellent yields (Table 4, entry 8 and 9). Conversion of 5a to 6a was carried out in 500 mg
scale. After 19 h 551 mg (93%) of 6a was isolated along with 28 mg (94% conversion) of
unreacted 5a after column chromatographic separation. Similarly conversion of 5b to 6b was
carried out in 1 gram scale. After 28 h 871 mg (76%) of 6b was isolated along with 217 mg
(78% conversion) of 5b after column chromatographic sepearation.

ACCEPTED MANUSCRIPT
10
Scheme 4.Substrate scope on the catalytic conversion of internal alkynes to 1,2-diketones.
Table 4. Catalytic conversion of internal alkynes to 1,2-diketones. Substrate scope.
Entry
1
Substrate/Ar/Ra
Product
6a
Duration (h)
Yield (%)
5a / Ph /Ph
16 (19)b
21 (28)c
21
94 (93)b
80 (76)c
83
2
5b / Ph / 4-NO2C6H4-
5c / Ph / 4-CHOC6H4-
5d / Ph / 2-MeC6H4-
5e / Ph / 4-MeC6H4-
5f / Ph / mesityl
6b
6c
3
4
19
89
6d
6e
5
18
91
6
30
48
6f
7
5g / Ph / -1-naphthyl
5h / Ph / Me
28
81
6g
8
14
94
6h
6i
9
5i / Ph / n-Bu
14
92
10
11
12
5j / 2-MeC6H4- / 2-MeC6H4-
5k / 4-MeC6H4- / 4-MeC6H4-
5l / 1-naphthyl / 1-Naphthyl
48
63
6j
48
69
6k
60
52
6l
aall reactions were carried out on a 100 mg scale of substrate, bon a 500 mg scale reaction with
94% conversion, con a 1 gram scale reaction with 78% conversion.
Both trans-stilbene and 1,4-diphenylbuta-1,4-diyne did not react even after prolonged period of
time under conditions described in Scheme 4. We have clearly established by TLC analysis of
the crude product and its comparison with authentic samples of benzoin, hydrobenzoin and
deoxybenzoin that they were not formed in the conversion of 5a to 6a. Nevertheless their
formation and involvement as short lived intermediates cannot be ruled out. Control experiments
were carried out to test the above hypothesis. Benzoin, hydrobenzoin and deoxybenzoin were
separately reacted in the presence of 3a as the catalyst under optimized conditions as described

ACCEPTED MANUSCRIPT
11
in Scheme 4 (Scheme 5). While benzoin and hydrobenzoin reacted to furnish benzil as the sole
product, deoxybenzoin did not react even after prolonged period (Scheme 5). Thus the formation
of deoxybenzoin as a possible intermediate through Pd(II) catalyzed hydration of 5a can be
clearly ruled out in the conversion of 5a to 6a. The involvement of benzoin and hydrobenzoin in
the conversion of 5a to 6a as short lived intermediates cannot be ruled out. A plausible
mechanism of the catalytic process is depicted in Scheme 6. Initially silver nitrate removes the
chloride ions as insoluble AgClto generate the dicationic intermediate B which coordinates to the
alkyne forming the π-complex produce intermediate C. Addition of water to the triple bond
followed by deprotonation results in the formation of intermediate E which undergoes
deprotonation to yield Pd-carbene intermediate F. This electrophilic Pd-carbeneintermediate
undergoes addition of water to give intermediate G which on β-elimination releases the observed
product. The resulting palladium hydrido complex loses hydrogen to give back the catalytically
active species B completing the catalytic cycle. It is effectively the sequential addition of water
molecules to the alkyne that results in the formation of 1,2-diketone as the product. Such an
addition of water as a nucleophile to alkyne is catalyzed by electrophilic cationic palladium
complex.

ACCEPTED MANUSCRIPT
12
Scheme 5.Control experiments to test the involvement of benzoin, hydrobenzoin and
deoxybenzoin in the conversion of 5a to 6a.
Scheme 6. Plausible mechanism for the catalytic conversion of alkyne to 1,2-diketone
3. Conclusions

ACCEPTED MANUSCRIPT
13
A new class of cationic palladium-NHC complexes containing mixed 1,2,3-triazol-5-ylidene
(bearing a variety of wingtip groups) and 2,2’-bipyridine/1,10-phenanthroline ligands were
synthesized from the corresponding 1,2,3-triazolium iodide via the silver carbene complex and
chlorobridgeddinuclear palladium complex. Complex 3a was structurally characterized by single
crystal XRD data and all the others were characterized thoroughly by spectroscopic data. These
cationic complexes showed excellent catalytic activity for the conversion of internal alkynes to
1,2-diketones in excellent yield with AgNO3 as an additive in 1,4-dioxane-water mixture.
Several symmetrical and unsymmetrical aryl and alkyl substituted 1,2-diketones were
synthesized using these cationic complexes. A plausible mechanism involving hydration of triple
bond catalyzed by the electrophilic cationic Pd complex was proposed.
4. Experimental section
General instrumentation used in the study has been described elsewhere.[13a]
Synthesis of complex 2a
1,4-Diphenyl-3-methyl-1,2,3-triazolium iodide (1a) (2.18 g, 6 mmol) was treated with freshly
prepared silver oxide (1.67 g, 7.2 mmol, 1.1 equiv.) in CH2Cl2 (35 mL). The solution was stirred
at room temperature in the dark for 16 h under nitrogen atmosphere. The silver carbene complex
thus generated was not isolated, it was directly treated with Pd(CH3CN)2Cl2 (1.71 g, 6.6 mmol,
1.1 equiv.) and stirred for 8 h. The reaction mixture was passed through a bed of celite, and then
removal of CH2Cl2 gave complex 2aas a pale yellow solid (1.19 g) in 96% yield. mp: 189-191
°C; 1H NMR (500 MHz, CDCl3) δ 8.37-8.35 (m, 4H), 7.97-7.95 (m, 4H), 7.58 (s, 12H), 4.06 (s,
6H) ); 13C NMR (125 MHz, CDCl3) δ 143.9, 138.5, 130.7, 130.6, 129.6, 129.3, 125.3, 38.0; ESI-
MS: HRMS: m/zcalcd for C30H27N6Pd2Cl4 [M+H]+ 822.9121, found 822.9136.
Synthesis of complex3a
To a solution of complex 2a (825 mg, 1 mmol) in 20 mL dichloromethane 2,2’-bipyridine (343
mg, 2.2 mmol) was added and the reaction mixture was stirred for 8 h at room temperature to
give complex 3a as a pale yellow solid (556 mg, 0.97 mmol) in 98%. Crystals of 3asuitable for

ACCEPTED MANUSCRIPT
14
single-crystal diffraction were grown by slow evaporation of a solution of 3afrom chloroform.
Complexes 3b-gwere synthesized using similar procedure. Complexes 4a-g were also
synthesized using similar procedure using 1,10-phenanthroline instead of 2,2-bipyridine.
Complex 3a: mp: 174-176 °C; 1H NMR (400 MHz, CDCl3) δ 9.14 (d, J = 4.8 Hz, 1H), 8.75 (d, J
= 4.8 Hz, 1H), 8.35 (d, J = 6.8 Hz, 2H), 8.27 (d, J = 7.2 Hz, 2H), 8.14-8.02 (m, 3H), 7.88-7.79
13
(m, 2H), 7.55 (t, J = 6.0 Hz, 1H), 7.51-7.46 (m, 6H), 4.38 (s, 3H); C NMR (100 MHz, CDCl3)
δ 155.3, 155.1, 154.4, 149.2, 144.5, 141.8, 140.9, 140.3, 139.0, 131.2, 130.5, 130.4, 129.7, 129.5,
129.1, 126.5, 126.4, 125.7, 123.4, 122.9, 38.7; ESI-MS: HRMS: m/zcalcd for C25H21N5ClPd [M-
Cl]+ 528.0542, found 528.0560.
Complex 3b
Prepared from 1,2,3-triazolium iodide2b (405 mg, 1 mmol), Ag2O (256 mg, 1.1 equiv.),
Pd(CH3CN)2Cl2(286 mg, 1.1 equiv.), 2,2’-bipyridine (343 mg, 2.2 equiv.). Yield 592 mg, 97%,
1
mp: 195 °C; H NMR (500 MHz, CDCl3) δ 9.09 (dd, J = 6, 1 Hz, 1H), 8.95 (t, J = 3 Hz, 1H),
8.48 (d, J = 7.5 Hz, 2H), 8.11 (d, J = 8 Hz, 1H), 8.07-8.03 (m, 2H), 7.97-7.95 (m, 2H), 7.52-7.49
(m, 1H), 7.46 (t, J = 7.5 Hz, 2H), 7.37 (t, J = 7.5 Hz, 1H), 7.01 (s, 1H), 6.89 (s, 1H), 4.48 (s, 3H),
2.31 (s, 3H), 2.21 (s, 3H), 2.13 (s, 3H); 13C NMR (125 MHz, CDCl3) δ 155.2, 155.17, 155.12,
149.6, 144.1, 144.0, 140.48, 140.41, 140.1, 136.4, 135.2, 134.8, 131.4, 130.2, 129.8, 129.5,
129.3, 129.0, 126.4, 126.3, 122.6, 122.1, 38.9, 21.3, 19.1, 18.8; ESI-MS: HRMS: m/zcalcd for
C28H27N5ClPd [M-Cl]+ 574.0990, found 574.0993.
Complex 3c
Prepared from 1,2,3-triazolium iodide2c (413 mg, 1 mmol), Ag2O (256 mg, 1.1 equiv.),
Pd(CH3CN)2Cl2(286 mg, 1.1 equiv.), 2,2’-bipyridine (343 mg, 2.2 equiv.). Yield 576 mg,
93%,light brown solid,mp: 201-202 °C; 1H NMR (500 MHz, CDCl3) δ 9.02-8.98 (m, 2H), 8.49-
8.42 (m, 3H), 8.27 (d, J = 7 Hz, 1H), 7.94 (d, J = 8 Hz, 2H), 7.84-7.73 (m, 4H), 7.67-7.66 (m,
2H), 7.59-7.53 (m, 3H), 7.45 (t, J = 7 Hz, 3H), 4.49 (s, 3H); 13C NMR (125 MHz, CDCl3) δ
155.8, 154.9, 154.8, 149.3, 144.5, 144.4, 140.4, 139.8, 135.3, 133.9, 131.7, 131.3, 130.3, 129.9,
129.1, 128.7, 127.7, 127.4, 127.0, 126.4, 126.3, 124.7, 124.4, 122.4, 122.0, 39.2; ESI-MS:
HRMS: m/zcalcd for C29H23N5ClPd [M-Cl]+ 582.0677, found 582.0665.
Complex 3d
Prepared from 1,2,3-triazolium iodide2d (447 mg, 1 mmol), Ag2O (256 mg, 1.1 equiv.),
Pd(CH3CN)2Cl2(286 mg, 1.1 equiv.), 2,2’-bipyridine (343 mg, 2.2 equiv.). Yield 627 mg,

ACCEPTED MANUSCRIPT
15
96%,off white solid,mp: 197-199 °C; 1H NMR (500 MHz, CDCl3) δ 9.08 (d, J = 8 Hz, 1H), 8.99
(d, J = 5.5 Hz, 1H), 8.88 (d, J = 8 Hz, 1H), 8.42 (t, J = 6.5 Hz, 1H), 8.14 (t, J = 8 Hz, 1H), 8.01
(d, J = 5.5 Hz, 1H), 7.61 (t, J = 6.5 Hz, 1H), 7.44 (t, J = 7 Hz, 1H), 7.04 (s, 1H), 7.03 (s, 1H),
6.97 (s, 1H), 6.95 (s, 1H), 4.05 (s, 3H), 2.39 (s, 3H), 2.32 (s, 3H), 2.31 (s, 3H), 2.29 (s, 3H), 2.26
13
(s, 3H), 2.16 (s, 3H); C NMR (125 MHz, CDCl3) δ 156.8, 155.1, 151.5, 151.2, 149.0, 147.3,
144.0, 142.4, 141.5, 141.3, 141.1, 140.0, 136.9, 136.4, 135.1, 133.0, 130.2, 130.1, 129.6, 129.2,
126.9, 126.5, 126.1, 124.6, 121.1, 37.5, 21.9, 21.3, 21.1, 19.37, 19.32; ESI-MS: HRMS: m/zcalcd
for C31H33N5ClPd [M-Cl]+ 616.1459, found 616.1481.
Complex 3e
Prepared from 1,2,3-triazolium iodide2e (413 mg, 1 mmol), Ag2O (256 mg, 1.1 equiv.),
Pd(CH3CN)2Cl2(286 mg, 1.1 equiv.), 2,2’-bipyridine (343 mg, 2.2 equiv.). Yield 600 mg,
97%’pale yellow solid, mp: 185-187 °C; 1H NMR (500 MHz, CDCl3) δ 9.04 (d, J = 5.5 Hz, 1H),
8.98 (d, J = 5.5 Hz, 1H), 8.51 (d, J = 7.5 Hz, 2H), 8.46 (d, J = 8.5 Hz, 1H), 8.27 (d, J = 7 Hz,
1H), 7.96-7.92 (m, 2H), 7.81 (t, J = 6.5 Hz, 1H), 7.82-7.77 (m, 2H), 7.69 (t, J = 8 Hz, 1H), 7.65-
7.61 (m, 2H), 7.57 (t, J = 7.5 Hz, 1H), 7.53 (d, J = 7.5 Hz, 2H), 7.46-7.41 (m, 3H), 4.49 (s, 3H);
13C NMR (125 MHz, CDCl3) δ 155.6, 154.8, 154.7, 149.2, 144.4, 144.3, 140.5, 139.7, 135.3,
133.8, 131.6, 131.2, 130.3, 129.7, 129.0, 128.7, 127.7, 127.4, 126.9, 126.5, 126.3, 124.7, 124.3,
122.3, 122.0, 39.1; ESI-MS: HRMS: m/zcalcd for C29H23N5ClPd [M-Cl]+ 582.0677, found
582.0690.
Complex 3f
Prepared from 1,2,3-triazolium iodide2f (455 mg, 1 mmol), Ag2O (256 mg, 1.1 equiv.),
Pd(CH3CN)2Cl2(286 mg, 1.1 equiv.), 2,2’-bipyridine (343 mg, 2.2 equiv.). Yield 621 mg,
1
94%,pale yellow solid, mp: 204 °C; H NMR (500 MHz, CDCl3) δ 9.30 (d, J = 3.3 Hz, 1H),
8.95-8.93 (m, 2H), 8.19-8.18 (m, 2H), 8.02-7.95 (m, 1H), 7.90 (t, J = 8 Hz, 4H), 7.84 (d, J = 8
Hz, 1H), 7.61-7.57 (m, 2H), 7.52-7.49 (m, 1H), 7.35-7.32 (m, 1H), 7.04 (s, 1H), 6.92 (s, 1H),
4.27 (s, 3H), 2.32 (s, 3H), 2.31 (s, 3H), 2.27 (s, 3H); 13C NMR (125 MHz, CDCl3) δ 156.0,
154.9, 149.5, 140.4, 140.1, 140.0, 136.6, 134.9, 133.7, 132.5, 131.7, 131.1, 129.8, 129.47,
129.41, 128.2, 127.4, 126.8, 126.2, 125.8, 123.2, 122.3, 121.9, 38.7, 21.4, 19.4, 19.0; ESI-MS:
HRMS: m/zcalcd for C32H29N5ClPd [M-Cl]+ 624.1146, found 624.1119.
Complex 3g

ACCEPTED MANUSCRIPT
16
Prepared from 1,2,3-triazolium iodide2g (463 mg, 1 mmol), Ag2O (256 mg, 1.1 equiv.),
Pd(CH3CN)2Cl2(286 mg, 1.1 equiv.), 2,2’-bipyridine (343 mg, 2.2 equiv.). Yield 616 mg,
1
92%,yellow solid, mp: 208-210 °C; H NMR (500 MHz, DMSO-d6) δ 9.15-8.56 (m, 2H), 8.44-
8.02 (m, 12H), 7.83-7.53 (m, 8H), 4.14 (s, 3H); 13C NMR (125 MHz, DMSO-d6) δ 156.5, 155.8,
155.7, 154.37, 154.34, 153.0, 152.5, 149.8, 148.2, 148.1, 146.5, 143.0, 142.4, 141.48, 141.46,
141.41, 134.97, 134.91, 133.7, 133.6, 133.4, 133.2, 132.0, 131.76, 131.71, 131.6, 131.4, 131.3,
130.2, 129.0, 128.4, 128.37, 128.32, 128.1, 128.0, 127.9, 127.7, 127.6, 127.59, 127.52, 127.45,
127.41, 127.1, 126.9, 126.6, 126.4, 126.3, 125.7, 125.6, 125.3, 125.2, 124.3, 124.2, 124.0, 123.7,
123.6, 123.4, 123.3, 123.1, 123.0, 38.5, 38.2; ESI-MS: HRMS: m/zcalcd for C33H25N5ClPd [M-
Cl]+ 632.0833, found 632.0834.
Complex 4a
Prepared from 1,2,3-triazolium iodide 2a (447 mg, 1 mmol), Ag2O (256 mg, 1.1 equiv.),
Pd(CH3CN)2Cl2(286 mg, 1.1 equiv.), 1,10-phenanthroline (436 mg, 2.2 equiv.). Yield 563 mg,
1
95%,pale yellow solid,mp: 231 °C; H NMR (400 MHz, DMSO-d6) δ 9.16 (d, J = 4.4 Hz, 1H),
8.93 (d, J = 8.4 Hz, 1H), 8.89 (d, J = 8.4 Hz, 1H), 8.61 (d, J = 4.8 Hz, 1H), 8.25 (d, J = 7.2 Hz,
2H), 8.22 (d, J = 4.8 Hz, 2H), 8.13 (dd, J = 8, 4.8 Hz, 1H), 8.03 (d, J = 7.2 Hz, 2H), 7.89-7.86
(m, 1H), 7.61-7.46 (m, 6H), 4.33 (s, 3H); 13C NMR (100 MHz, DMSO-d6) δ 152.6, 149.3,
146.3, 145.1, 144.2, 141.2, 140.4, 140.3, 138.4, 130.7, 130.4, 130.3, 130.2, 129.8, 129.0, 127.8,
127.5, 126.4, 126.2, 124.7, 38.5; ESI-MS: HRMS: m/zcalcd for C27H21N5ClPd [M-Cl]+
556.0520, found 556.0505.
Complex 4b
Prepared from 1,2,3-triazolium iodide 2b (405 mg, 1 mmol), Ag2O (256 mg, 1.1 equiv.),
Pd(CH3CN)2Cl2(286 mg, 1.1 equiv.), 1,10-phenanthroline (436 mg, 2.2 equiv.). Yield 616 mg,
97%,off white solid, mp: 213-215 °C; 1H NMR (500 MHz, CDCl3) δ 9.57 (d, J = 5 Hz, 1H), 9.33
(dd, J = 5, 1 Hz, 1H), 8.57 (d, J = 7 Hz, 2H), 8.50 (dd, J = 8.5, 1 Hz, 1H), 8.42 (d, J = 8 Hz, 1H),
8.33 (dd, J = 8, 5.5 Hz, 1H), 7.91 (s, 2H), 7.82 (dd, J = 8, 5 Hz, 1H), 7.42 (t, J = 8 Hz, 2H), 7.30
(t, J = 8 Hz, 1H), 7.02 (s, 1H), 6.84 (s, 1H), 4.54 (s, 3H), 2.29 (s, 3H), 2.25 (s, 3H), 2.15 (s, 3H);
13C NMR (125 MHz, CDCl3) δ 156.3, 149.7, 146.5, 146.0, 144.3, 142.8, 140.4, 138.9, 138.6,
136.4, 135.3, 135.1, 131.6, 130.19, 130.12, 129.7, 129.4, 129.2, 128.9, 128.5, 127.6, 126.7,
126.5, 125.0, 39.0, 21.3, 19.2, 18.8; ESI-MS: HRMS: m/zcalcd for C30H27N5ClPd [M-Cl]+
598.0990, found 598.0984.

ACCEPTED MANUSCRIPT
17
Complex 4c
Prepared from 1,2,3-triazolium iodide 2c (413 mg, 1 mmol), Ag2O (256 mg, 1.1 equiv.),
Pd(CH3CN)2Cl2(286 mg, 1.1 equiv.), 1,10-phenanthroline (436 mg, 2.2 equiv.). Yield 592 mg,
1
92%,yellow solid, mp: 225 °C; H NMR (500 MHz, CDCl3) δ 9.63 (s, 1H), 9.28 (dd, J = 5, 1.5
Hz, 1H), 8.55 (d, J = 7 Hz, 3H), 8.40 (dd, J = 8.5, 1.5 Hz, 1H), 8.35 (d, J = 7.5 Hz, 1H), 8.29-
8.26 (m, 2H), 7.93 (d, J = 8 Hz, 1H), 7.79-7.75 (m, 4H), 7.69 (t, J = 8 Hz, 1H), 7.58 (t, J = 8 Hz,
13
1H), 7.51 (t, J = 7 Hz, 2H), 7.45 (t, J = 7.5 Hz, 1H), 7.41 (t, J = 7.5 Hz, 1H) 4.55 (s, 3H); C
NMR (125 MHz, CDCl3) δ 156.4, 149.5, 144.7, 143.4, 138.8, 138.4, 133.9, 131.7, 131.2, 130.2,
129.6, 129.0, 128.8, 128.4, 127.6, 127.5, 127.4, 127.0, 126.6, 124.9, 124.7, 124.4, 39.2; ESI-MS:
HRMS: m/zcalcd for C31H23N5ClPd [M-Cl]+ 606.0677, found 606.0682.
Complex 4d
Prepared from 1,2,3-triazolium iodide 2d (447 mg, 1 mmol), Ag2O (256 mg, 1.1 equiv.),
Pd(CH3CN)2Cl2(286 mg, 1.1 equiv.), 1,10-phenanthroline (436 mg, 2.2 equiv.). Yield 650 mg,
96%, off white solid, mp: 196 °C; 1H NMR (500 MHz, CDCl3) δ 9.28 (dd, J = 5, 1 Hz, 1H), 9.10
(d, J = 8 Hz, 1H), 8.70 (d, J = 8, 1 Hz, 1H), 8.43 (dd, J = 8.5, 5.5 Hz, 1H), 8.22 (d, J = 8.5 Hz,
1H), 8.02 (d, J = 8.5 Hz, 1H), 8.79 (dd, J = 8.5, 5 Hz, 1H), 7.02 (s, 1H), 6.97 (s, 1H), 6.94 (s,
1H), 6.89 (s, 1H), 4.10 (s, 3H), 2.45 (s, 3H), 2.36 (s, 3H), 2.27 (s, 3H), 2.25 (s, 6H), 2.23 (s, 3H);
13C NMR (125 MHz, CDCl3) δ 153.5, 149.5, 146.7, 145.9, 145.5, 144.0, 141.4, 141.2, 140.8,
139.9, 139.4, 138.0, 136.6, 135.2, 133.7, 131.0, 130.1, 129.9, 129.7, 129.6, 129.3, 128.3, 127.4,
127.1, 125.1, 121.5, 37.7, 21.7, 21.6, 21.3, 19.5, 19.2; ESI-MS: HRMS: m/zcalcd for
C33H33N5ClPd [M-Cl]+ 640.1459, found 640.1473.
Complex 4e
Prepared from 1,2,3-triazolium iodide 2e (413 mg, 1 mmol), Ag2O (256 mg, 1.1 equiv.),
Pd(CH3CN)2Cl2(286 mg, 1.1 equiv.), 1,10-phenanthroline (436 mg, 2.2 equiv.). Yield 605 mg,
1
94%,yellow solid, mp: 207-209 °C; H NMR (500 MHz, CDCl3) δ 9.03 (s, 1H), 8.98 (d, J = 5.5
Hz, 1H), 8.51 (d, J = 4.5 Hz, 2H), 8.45 (s, 1H), 8.28 (d, J = 7.5 Hz, 1H), 7.93 (d, J = 8.5 Hz,
2H), 7.82-7.41 (m, 12H) 4.49 (s, 3H); 13C NMR (125 MHz, CDCl3) δ 149.5, 144.7, 143.4, 138.8,
138.4, 133.9, 131.7, 131.2, 130.2, 129.6, 129.0, 128.8, 128.4, 127.6, 127.5, 127.4, 127.0, 126.6,
126.5, 124.9, 124.7, 124.5, 39.2; ESI-MS: HRMS: m/zcalcd for C31H23N5ClPd [M-Cl]+
606.0677, found 606.0697.
Complex 4f

ACCEPTED MANUSCRIPT
18
Prepared from 1,2,3-triazolium iodide 2f (455 mg, 1 mmol), Ag2O (256 mg, 1.1 equiv.),
Pd(CH3CN)2Cl2(286 mg, 1.1 equiv.), 1,10-phenanthroline (436 mg, 2.2 equiv.). Yield 644 mg,
94%,pale yellow solid, mp: 219-221 °C; 1H NMR (500 MHz, CDCl3) δ 9.87 (d, J = 4.5 Hz, 1H),
9.17 (dd, J = 5, 1.5 Hz, 1H), 9.13 (d, J = 6.5 Hz, 1H), 8.51-8.43 (m, 2H), 8.32 (dd, J = 8, 1.5 Hz,
1H), 8.26 (d, J = 8 Hz, 1H), 7.84 (t, J = 8 Hz, 2H), 7.78-7.76 (m, 2H), 7.66-7.57 (m, 3H), 7.49-
7.45 (m, 1H), 7.06 (s, 1H), 6.88 (s, 1H), 4.33 (s, 3H), 2.36 (s, 3H), 2.31 (s, 3H), 2.29 (s, 3H); 13C
NMR (125 MHz, CDCl3) δ 156.7, 149.6, 146.5, 145.9, 144.4, 142.2, 140.4, 138.69, 138.63,
136.6, 135.6, 135.1, 133.7, 132.6, 131.8, 130.9, 130.1, 129.67, 129.61, 129.4, 129.3, 128.4,
128.1, 127.5, 127.3, 126.9, 126.79, 126.72, 125.9, 124.8, 123.3, 38.8, 21.4, 19.4, 19.0; ESI-MS:
HRMS: m/zcalcd for C34H29N5ClPd [M-Cl]+ 648.1146, found 648.1147.
Complex 4g
Prepared from 1,2,3-triazolium iodide 2g (463 mg, 1 mmol), Ag2O (256 mg, 1.1 equiv.),
Pd(CH3CN)2Cl2(286 mg, 1.1 equiv.), 1,10-phenanthroline (436 mg, 2.2 equiv.). Yield 638 mg,
1
92%, light brown solid, mp: 221-223 °C; H NMR (500 MHz, DMSO-d6) δ 9.29-9.22 (m, 1H),
9.02-8.40 (m, 4H), 8.23-7.84 (m, 12H), 7.78-7.59 (m, 6H), 4.16 (s, 3H); 13C NMR (125 MHz,
DMSO-d6) δ 153.3, 152.7, 150.1, 148.9, 148.8, 146.6, 145.9, 145.8, 145.56, 145.54, 144.6,
143.1, 142.4, 140.5, 140.0, 139.9, 132.0, 131.7, 131.5, 131.4, 131.3, 131.2, 131.1, 130.26,
130.20, 130.1, 129.87, 129.84, 128.80, 128.3, 128.19, 128.15, 128.0, 127.8, 127.64, 127.61,
127.55, 127.50, 127.4, 127.34, 127.30, 127.2, 126.9, 126.8, 126.6, 126.4, 126.3, 126.1, 125.9,
125.88, 125.81, 125.6, 125.5, 125.25, 125.21, 123.38, 123.34, 123.0, 38.4, 38.3; ESI-MS:
HRMS: m/zcalcd for C35H25N5ClPd [M-Cl]+ 656.0833, found 656.0857.
Representative procedure for the conversion of internal alkynes to 1,2-diketones:
To a solution of 1,2-diphenylethyne (5a) (500 mg, 2.808 mmol) in 1,4-dioxane, water (20 mL:5
mL v/v), complex 3a (63 mg, 0.112 mmol, 4 mol%), AgNO3 (38 mg, 0.224 mmol, 8 mol%) were
o
added and the reaction mixture was stirred at 90 C, the progress of the reaction was monitored
by TLC. After 19 h the reaction mixture was cooled to room temperature, diluted with water and
extracted with CH2Cl2. The separated organic layer was dried over Na2SO4, concentrated under
vacuum. The residue was subjected to silica gel column chromatography by using hexane/EtOAc
(9:1, v/v) as eluent to give benzil (6a) (551 mg, 2.623 mmol) as a yellow solid in 93% yield.
Similarly to a solution of 5b (1000 mg, 4.48 mmol) in 1,4-dioxane, water (40 mL:10 mL v/v),

ACCEPTED MANUSCRIPT
19
complex 3a (102 mg, 0.179 mmol, 61 mg, 4 mol%), AgNO3 (61 mg, 0.358 mmol, 8 mol%) were
o
added and the reaction mixture was stirred at 90 C+ for 28 h to give 6b (871 mg, 3.415 mmol)
as a yellow solid in 76% yield. The characterization data for all the 1,2-diketones (6a-l) are given
in the supporting information.
Acknowledgements
JBS thanks CSIR, New Delhi for a fellowship and SS thanks CSIR and DST, New Delhi,
for research grants and the Department of Chemistry, IIT Madras for infrastructure.
Appendix A. Supplementary material
The following is the supplementary data related to this article:
Spectroscopic data for6a-l. CCDC number1484554contain the supplementary crystallographic
data for compound3a. These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www. ccdc.cam.ac.uk/data_request/cif.
References
[1] a) W. A. Herrmann, Angew. Chem. Int. Ed. 41 (2002) 1290-1309.
b) S. P. Nolan, Ed. N-Heterocyclic Carbene in Synthesis; Wiley-VCH: New York, 2006.
c) S. Dıez-González, N. Marion, S. P. Nolan, Chem. Rev. 109 (2009) 3612-3676.
́
d) H. D. Velazquez, F. Verpoort, Chem. Soc. Rev. 41 (2012) 7032-7060.
e) M. N. Hopkinson, C. Richter, M. Schedler, F. Glorius, Nature 510 (2014) 485-496.
f) S. Bellemin-Laponnaz, S. Dagorne, Chem. Rev. 114 (2014) 8747-8774.
[2] a) M. Albrecht, Chem. Commun. (2008) 3601-3610.
b) O. Schuster, L. Yang, H. G. Raubenheimer, M. Albrecht, Chem. Rev. 109 (2009) 3445-
3478.
c) G. Song, Y. Zhang, X. Li, Organometallics 27 (2008) 1936-1943.
[3] a) P. Mathew, A. Neels, M. Albrecht, J. Am. Chem. Soc. 130 (2008) 13534-13535.
b) T. Karthikeyan, S. Sankararaman, Tetrahedron Lett. 50 (2009) 5834-5837.
c) G. Guisado-Barrios, J. Bouffard, B. Donnadieu, G. Bertrand, Angew. Chem. Int. Ed. 49
(2010) 4759-4762.
d) J. D. Crowley, A. Lee, K. J. Kilpin, Aust. J. Chem. 64 (2011) 1118-1132.
e) K. F. Donnelly, A. Petronilho, M. Albrecht, Chem. Commun. 49 (2013) 1145-1159.

ACCEPTED MANUSCRIPT
20
[4] a) K. L. Granberg, J.-E. Bäckvall, J. Am. Chem. Soc. 114 (1992)6858-6863.
b) B. M. Trost, M. L. Crawley, Chem. Rev. 103 (2003) 2921-2943.
c) B. M. Trost, J. Org. Chem. 69 (2004) 5813-5837.
d) L. F. Tietze, H. Ila, H. P. Bell, Chem. Rev. 104 (2004) 3453-3516.
e) V. K. Jain, L. Jain, Coord. Chem. Rev. 249 (2005) 3075-3197.
f) S. M. A. Sohel, R.-S. Liu, Chem. Soc. Rev. 38 (2009) 2269-2281.
g) N. A. Butt, W. Zhang, Chem. Soc. Rev. 44 (2015) 7929-7967.
h) W. Du, Q. Gu, Y. Li, Z. Lin, D. Yang, Org. Lett. 19 (2017) 316-319.
[5] a) A. M. Castaño, A.Aranyos, K. J. Szabó,J.-E. Bäckvall, Angew. Chem. Int. Ed. Engl.
34 (1995) 2551-2553.
b) T. M. Pedersen, E. L. Hansen, J. Kane, T. Rein, P. Helquist, P.-O.Norrby, D. Tanner, J.
Am. Chem. Soc. 123 (2001) 9738-9742.
c) I. D. G. Watson, A. K. Yudin, J. Am. Chem. Soc. 127 (2005) 17516-17529.
d) R. I. McDonald, G. Liu, S. S. Stahl, Chem. Rev. 111 (2011) 2981-3019.
[6] a) Y. Kayaki, F. Kawataka, I. Shimizu, A. Yamamoto, Chem. Lett. (1994) 2171-2174.
b) A. Yamamoto, J. Organomet. Chem. 500 (1995) 337-348.
c) N. R. Conley, L. A. Labios, D. M. Pearson, C. C. L. McCrory, R. M. Waymouth,
Organometallics 26 (2007) 5447-5453.
d) T. Nishikata, A. R. Abela, S. Huang, B. H. Lipshutz, Beilstein J. Org. Chem. 12 (2016)
1040-1064.
[7] a) Y. Miyazaki, N.Ohta, K.Semba, Y.Nakao, J. Am. Chem. Soc. 136 (2014) 3732-3735.
b) D. S. Suslov, M. V. Bykov, M. V. Pakhomova, P. A. Abramov, I. A. Ushakov, V. S.
Tkach, Catal.Commun. 94 (2017) 69-72.
c) N. Chatani, T. Takeyasu, N. Horiuchi, T. Hanafusa, J. Org. Chem. 53 (1988) 3539-
3548.
d) Y. N Cheng, Z. Duan, L. Yu, Z. Li, Y. Zhu, Y. Wu, Org. Lett. 10 (2008) 901-904.
[8] M. Brookhart, F. C. Rix, J. M. DeSimone, J. Am. Chem. Soc. 114 (1992)5895-5897.
[9] S. Oi, K. Kashlwagi, E. Terada, K. Ohuehi, Y. Inoue, Tetrahedron Lett. 37 (1996)
6351-6354.

ACCEPTED MANUSCRIPT
21
[10] a) F. Bouachir, P. Grenouillet, D. Neibecker, J. Poirier, I. Tkatchenko, J. Organomet. Chem.
569 (1998) 203-215.
b) M. S. Viciu, F. K. Zinn, E. D. Stevens, S. P. Nolan, Organometallics 22 (2003) 3175-
3177.
[11] a) J. A. Cabeza, I. del Río, M. G. Sánchez-Vega, M. Suárez, Organometallics 25 (2006)
1831-1834.
b) J. C. Slootweg, P. Chen, Organometallics 25 (2006) 5863-5869.
c) F. Churruca, R. SanMartin, B. Inés, I. Tellitu, E. Domínguez, Adv. Synth. Catal.348
(2006) 1836-1840.
d) Y.-J. Song,I. G. Jung, H. Lee, Y. T. Lee, Y. K. Chung, H.-Y. Jang, Tetrahedron Lett.
48 (2007) 6142-6146.
e) A. T. Normand, A. Stasch, L.-L. Ooi, K. J. Cavell, Organometallics 27 (2008)6507-
6520.
f) H. M. Peng, G. Song, Y. Li, X. Li, Inorg. Chem. 47 (2008) 8031-8043.
g) G.-N. Ma, T. Zhang, M. Shi, Org. Lett. 11(2009)875-878.
i) F. Li, J. J. Hu, L. L.Koh,T. S. A. Hor, Dalton Trans. 39 (2010) 5231-5241.
j) I. Abdellah, C. Lepetit, Y. Canac, C. Duhayon, R. Chauvin, Chem. Eur. J. 16 (2010)
13095-13108.
k) B. Hildebrandt, G. Reiß, C. Ganter, J. Organomet. Chem. 695, (2010) 474-477.
l) S. L. M. Goh, M. P. Högerl, N. B Jokić, A. D. Tanase, B. Bechlars, W. Baratta, J. Mink, F.
E. Kühn,Eur. J. Inorg. Chem. (2014) 1225-1230.
m) R. Das, A.Hepp, C. G.Daniliuc, F. E. Hahn, Organometallics 33 (2014) 6975-6987.
n) O. Santoro, F. Lazreg, D. B. Cordes, A. M. Z. Slawin, C. S. J. Cazin, Dalton Trans. 45
(2016) 4970-4973.
[12] E. M. Schuster, M. Botoshansky, M. Gandelman, Dalton Trans. 40 (2011) 8764-8767.
[13] S. N. Sluijter, L. J. Jongkind, C. J. Elsevier, Eur. J. Inorg. Chem. (2015) 2948-2955.
[14] a) N. Hatae, J. Nakamura, T. Okujima, M. Ishikura, T. Abe, S. Hibino, T. Choshi, C. Okada,
H. Yamada, H. Uno, E. Toyota, Bioorg. Med. Chem. Lett. 23 (2013) 4637-4640.
b) E. I. Parkinson, M. J. Hatfield, L. Tsurkan, J. L. Hyatt, C. C. Edwards, L. D. Hicks, B.
Yan, P. M. Potter, Bioorg. Med. Chem. 19 (2011) 4635-4643.
c) J. L. Hyatt, R. M. Wadkins, L. Tsurkan, L. D. Hicks, M. J. Hatfield, C. C. Edwards, C. R.

ACCEPTED MANUSCRIPT
22
Ross II, S. A. Cantalupo, G. Crundwell, M. K. Danks, R. K. Guy, P. M. Potter, J. Med.
Chem. 50 (2007) 5727-5734.
d) R. M. Wadkins, J. L. Hyatt, X. Wei, K. J. P. Yoon, M. Wierdl, C. C. Edwards, C. L.
Morton, J. C. Obenauer, K. Damodaran, P. Beroza, M. K. Danks, P. M. Potter, J. Med.
Chem. 48 (2005) 2906-2915.
[15] a) K.-W. Chi, M. S. Yusubov, V. D. Filimonov, Synth.Commun. 24 (1994) 2119-2122.
b) H.-G. Kim, J.-K.Lee, J.-T.Lee, C.-S. Lee, Bull. Korean Chem. Soc. 21 (2000) 345-347.
c) M. S. Yusubov, V. D. Filimonov, K.-W. Chi, Russ. Chem. Bull. 50 (2001) 649-653.
d) W. Ren, Y. Xia, S.-J, Ji, Y. Zhang, X. Wan, J. Zhao, Org. Lett. 11 (2009) 1841-1844.
e) S. Mori, M. Takubo, T. Yanase, T. Maegawa, Y. Monguchi, H. Sajiki, Adv. Synth. Catal.
352 (2010) 1630-1634.
f) J. Muzart, J. Mol. Catal. A: Chem. 338 (2011) 7-17.
g) A. Gao, F. Yang, J. Li, Y. Wu, Tetrahedron 68 (2012) 4950-4954.
h) S. Byun, J. Chung, T. Lim, J. Kwon, B. M. Kim, RSC Adv. 4 (2014) 34084-34088.
i) H.-M. Jong, Y.-H.Liu, S.-M.Peng, S.-T. Liu, Eur. J. Inorg. Chem. (2016) 5449-5455.
[16] a) J. C. Y. Lin, R. T. W. Huang, C. S. Lee, A. Bhattacharyya,W. S. Hwang, I. J. B. Lin,
Chem. Rev. 109 (2009) 3561-3598.
b) E. C. Keske, O. L. Zenkina, R. Wang, C. M. Crudden,Organometallics, 31 (2012)
456-461.
c) J. Cai, X. Yang,K. Arumugam, C. W. Bielawski, J. L. Sessler, Organometallics,30
(2011) 5033-5037.
d) R. Visbal, A. Laguna,M. C. Gimeno, Chem. Commun. 49 (2013) 5642-5644.
e) I. J. B. Lin, C. S. Vasam, Coord. Chem. Rev. 251 (2007)642-670.
[17] a) J. Huang, J. -T. Hong, S. H. Hong, Eur. J. Org. Chem. (2012) 6630-6635.
b) A. Dasgupta, V. Ramkumar, S. Sankararaman, Eur. J. Org. Chem. (2016) 4817-4823.
c)Y. D. Bidal, O. Santoro, M. Melaimi, D. B. Cordes, A. M. Z. Slawin, G. Bertrand, C. J.
Cazin, Chem. Eur. J. 22 (2016) 9404-9409.
[18] B. Sureshbabu, V. Ramkumar, S. Sankararaman, J. Orgmet. Chem. 799-800 (2015) 232-
238.

ACCEPTED MANUSCRIPT
Synthesis of a new class of cationic Pd(II) complexes with 1,2,3-triazol-5-ylidene ligand and
their catalytic application in the conversion of internal alkynes to 1,2-diketones
Jeelani Basha Shaik, Venkatachalam Ramkumar, Sethuraman Sankararaman*
Department of Chemistry, Indian Instituteof Technology Madras, Chennai 600036, India
Corresponding author: email: sanka@iitm.ac.in, phone: +91 44 2257 4210, fax: +91 44 2257
0545
Highlights
•
•
•
•
•
Synthesis of cationic Pd(II) complexes with 1,2,3-triazolylidene ligands is reported
Cationic Pd(II) complexes bear bipyridine and 1,10-phenanthroline as co-ligands
One of the cationic complex is structurally characterized by single crystal XRD data
Cationic complexes are catalytically active for the conversion of alkynes to 1,2-diketones
Catalytic conversion of 1,2-diarylalkynes to benzil derivatives is highly selective