New 1,2,3-triazole based bis- And trisphosphine ligands: Synthesis, transition metal chemistry and catalytic studies

Article abstract of DOI:10.1039/c9dt04302k

The syntheses and transition metal chemistry of triazole-based bis- and tris-phosphines, 5-(diphenylphosphanyl)-1-(2-(diphenylphosphanyl)phenyl)-4-phenyl-1H-1,2,3-triazole (2), 5-(diphenylphosphanyl)-4-(2-(diphenylphosphanyl)phenyl)-1-phenyl-1H-1,2,3-tria

Full text of DOI:10.1039/c9dt04302k

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New 1,2,3-triazole based bis- and trisphosphine ligands: synthesis, transition
metal chemistry and catalytic studies
a
a
a
b
§
§
Latchupatula Radhakrishna, Harish S. Kunchur, Pavan K. Namdeo, Ray J. Butcher and
Maravanji S. Balakrishna*a
The syntheses and transition metal chemistry of triazole-based bis- and tris-phosphines 5-
(diphenylphosphanyl)-1-(2-(diphenylphosphanyl)phenyl)-4-phenyl-1H-1,2,3-triazole (2), 5-
(diphenylphosphanyl)-4-(2-(diphenylphosphanyl)phenyl)-1-phenyl-1H-1,2,3-triazole (5), 1,4-
bis(2-(diphenylphosphanyl)phenyl)-1H-1,2,3-triazole (6) and 5-(diphenylphosphanyl)-1,4-bis(2-
(diphenylphosphanyl)phenyl)-1H-1,2,3-triazole (7) are described. Bisphosphines 5 and 6 show
versatile coordination behavior due to the presence of at least four donor atoms. The reactions of
5 and 6 with group VI metal carbonyl derivatives were found to be highly sensitive to the reaction
conditions. Bisphosphine 5 on treatment with [M(CO)4(piperidine)2] (M = Mo and W) yielded
both P,P and P,N coordinated complexes [M(CO)4(5)] [M = Mo-2-P,N (8); W-2-P,N (9); Mo-
2-P,P (10); W-2-P,P (11)], whereas 6 afforded only P,N coordinated complexes [{o-
Ph2P(C6H4){1,2,3-N3C(o-Ph2P(C6H4))CH}-2-P,N}Mo(CO)4] (12) and [{o-Ph2P(C6H4){1,2,3-
N3C(o-Ph2P(C6H4))CH}-2-P,N}W(CO)4] (13). The reactions of 5 with [M(COD)Cl2] (M = Pd,
Pt) yielded 2-P,P chelate complexes 14 and 15, whereas treatment of 6 with [Pd(COD)Cl2] at
ambient temperature resulted in the formation a rare fused six-membered PCP pincer complex [{o-
Ph2P(C6H4){1,2,3-N3C(o-Ph2P(C6H4))-3-P,C,P}PdCl] (16). Similar reactions of 6 with
[NiCl2(DME)] and [Pt(COD)Cl2] in the presence of LiHMDS yielded [{o-Ph2P(C6H4){1,2,3-
N3C(o-Ph2P(C6H4))C}-3-P,C,P}NiCl] (17) and [{o-Ph2P(C6H4){1,2,3-N3C(o-Ph2P(C6H4))C}-
3-P,C,P}PtCl] (18), respectively. Reaction between 6 and [M(COD)Cl]2 (M = Rh and Ir)
produced
cationic
complexes
[{o-Ph2P(C6H4){1,2,3-N3C(o-Ph2P(C6H4))CH}-κ2-
P,N}Rh(C8H12)]Cl (19) and [{o-Ph2P(C6H4){1,2,3-N3C(o-Ph2P(C6H4))CH}-κ2-P,N}Ir(C8H12)]Cl
(20), whereas the reaction with [Rh(acac)(CO)2] resulted in a pincer complex [{o-
Ph2P(C6H4){1,2,3-N3C(o-Ph2P(C6H4))C}-3-P,C,P}Rh(CO)] (21). The structures of most of the
compounds have been determined by single crystal X-ray analyses. The fused six-membered PCP
palladium pincer complex 16 is found to be an excellent catalyst for the Mizoroki-Heck coupling
reactions.
aPhosphorus Laboratory, Department of Chemistry, Indian Institute of Technology Bombay, Powai,
Mumbai 400076, India.
bDepartment of Chemistry, Howard University, Washington, D. C. 20059, USA
*Author to whom correspondence should be addressed. E-mail: krishna@chem.iitb.ac.in,
msb_krishna@iitb.ac.in (M. S. Balakrishna); Fax: +91-22-5172-3480/2576-7152.
§Contributed equally to this work
1

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† Electronic supplementary information (ESI): Tables of selected structural data and selected spectroscopic
data. CCDC 1943087 and 1917497. For ESI and crystallographic data in CIF or other electronic format
see DOI:
Introduction
Copper-catalyzed “click chemistry”1 has enabled the facile synthesis of 1, 4-disubstituted 1,2,3-
triazole molecules having applications in polymers, material science,2 and also in the synthesis of
biologically active macromolecules.3 The presence of nitrogen atoms makes it a polydentate ligand
as well as an useful precursor to generate a host of new ligand systems,4 which on complexation
with suitable platinum metals can promote catalytic reactions such as carbon-carbon coupling,
amination, allylic alkylation, asymmetric and transfer hydrogenation areactions.5 Although C5, N2,
and N3 atoms are available for coordination in 1, 2, 3-triazole ligands,6 N3 is preferred one due to
its electron richness. Metallation at C5 can be achieved through C-H activation or by transforming
it into a singlet carbene through quternization of N3 atom.7
The incorporation of phosphorous moieties into 1,2,3-triazoles can generate monodentate,
bidentate and tridentate ligands which are very valuable in coordination chemistry, catalysis5a-d, 8
and also in photo-response materials.9 A 1,4-diphenyl-1,2,3-triazole framework can be envisioned
to support either one, two or three phosphine moieties leading to a large number of potential
derivatives (Chart 1). While examples of these phosphines of type A, B and D have been reported10
we focused our attention on preparing members of the unknown Chart 1 classes. The possibility
of bisphosphine F was particularly intriguing as these were hypothesized as PCP pincer complex
precursors.
A typical triazole can add phosphine moieties to form at least seven derivatives having one, two
or three phosphines as shown in Chart 1. Since only A, B and D are known, we focused our
2

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attention to synthetically access the remaining isomers C, E, PCP pincer capable bisphosphine F
and also trisphosphine G.
N3
N3
N3
N2
N1
N2
N1
N2
N1
PR2
PR2
R2P
C
B
A
N3
N3
N2
N1
N2
N1
PR2
N3
N2
N1
PR2
PR2
PR2
N3
R2P
R2P
D
F
E
N2
N1
PR2
R2P
R = aryl or alkyl
PR2
G
Chart 1 Synthetically possible triazole-based mono, bis and tris-phosphines.
Phosphorus-based pincer ligands are of fundamental interest in coordination chemistry and
homogenous catalysis.11 Several pincer complexes of symmetrical PCP type ligands featuring two
fused five- or six-membered metallacycles. are known in the literature;12 a few such systems are
given in Chart 2. Similar pincer complexes made up of nonsymmetrical ligands featuring two
fused six-membered metallacycles are scant. Most of these are imidazolium (I-III)13 and
pyrimidine (IV and V)14 based neutral sp2-carbon (carbene) centered PCP systems. Pincer ligands
with central anionic heterocyclic-C(sp2) donor group in the ligand-backbone are scarce.
Gandelman and co-workers have reported fused five-membered anionic triazole-C(sp2) centered
phosphine-functionalized pincer complexes (VI).7e However, the anionic triazole sp2 carbon-based
fused six-membered PCP-pincer complexes of the type VII have remained a challenge due to the
3

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thermally sensitive nature of lithiation and phosphination reactions in the ligand preparation, 15,16
which have been resolved recently by our group.10
N
N
N
N
N
N
N
N
M
L
PPh2
Ph2P
P
P
iPr
M
L
iPr
iPr
Ph2P
PPh2
M
L
M
L
P
P
iPr
Ph2
Ph2
I
II
III
Fryzuk13d
IV
Hill14a
Rieger13a
Lee13b and Hahn13c
R2P
PR2
N
N
N
N
N
N
N
N
N
M
L
M
L
N
PPh2
Ph2P
M
M
P
P
R2P
Ph
Ph
Ph
Ph
PR2
L
iPr
L
R
= Ph,
Cy,
V
VI
VII
(This work)
Gade14b
Gandelman7e
Chart 2 Central five-membered heterocyclic-C(sp2) donor based PCP-pincer complexes
In this context, we sought to make triazole functionalized bisphosphines to explore their
coordination behavior and catalytic applications. This paper describes detailed synthetic
investigations, coordination chemistry and preliminary catalytic studies on triazolyl
bisphosphines.
Results and discussion
Synthesis of 5-(diphenylphosphanyl)-4-(2-(diphenylphosphanyl)phenyl)-1-phenyl-1H-1,2,3-
triazole (5), 1,4-bis(2-(diphenylphosphanyl)phenyl)-1H-1,2,3-triazole (6) and 5-
(diphenylphosphanyl)-1,4-bis(2-(diphenylphosphanyl)phenyl)-1H-1,2,3-triazole (7).
4

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There are mainly two synthetic strategies to synthesize triazoles with phosphine functionalities: 1)
Cu catalyzed reaction of phosphine-alkynes with organic azides, but this process involves
protection and deprotection of phosphine moieties,7e,f which increases the number of steps
involved in the synthesis. 2) Direct lithiation of selective carbon atom followed by post-
modification with suitable chloro-phosphines.10a Although this method limits the number of steps
involved, selective lithiation of the 1,4-phenyl sustituent when a C-H bond is present in the 5-
position of the triazole ring, render this pathway practically challenging. As a result, the selective
mono functionalization of triazole carbon-attached aryl group (C in Chart 1) and phosphination of
both the aryl groups on 1,2,3- triazole (F in Chart 1) were unsuccessful or not reported,8a mainly
due to the fast Li/H exchange with neighboring C5-atom which was confirmed recently by our
n
group.10a Treatment of triazoles 3 or 4 with two equivalents of BuLi at -78 °C followed by the
addition of two equivalents of PPh2Cl at room temperature afforded bisphosphine 2 (identified by
31P{1H} NMR spectroscopy δ -30.4 (d) and -17.5 (d), JPP = 22.3 Hz) instead of expected 5 and/or
6 (structural isomers of 2). The synthesis and transition metal chemistry of 2 has been reported
recently by our group. This is probably due to the intramolecular Li-H exchange10a between ortho-
carbon and triazole proton in 3 and 4. Interestingly, the reaction of 3 or 4 with two equivalents of
nBuLi at -78 ºC followed by the addition of two equivalents of PPh2Cl at -50 °C afforded
bisphosphine 5 (Scheme 1). The 31P{1H} NMR spectrum of 5 showed two doublets at -29.8 and -
12.6 ppm with a JPP coupling of 22.4 Hz. The reaction of 4 with two equivalents of nBuLi at -78
ºC and subsequent addition of two equivalents of PPh2Cl at -78 °C (reaction conditions iii) resulted
31
in bisphosphine, 6 (Scheme 1). The P{1H} NMR spectrum of 6 showed two doublets at -15.6
and -11.8 ppm with a JPP coupling of 4.7 Hz. The 1H NMR spectrum of 6 showed a singlet at 7.9
ppm for triazole proton, and mass spectrum showed [M+H]+ ion peak at m/z 590.1908. The
5

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reaction of 4 with three equivalents of nBuLi at -78 ºC followed by the addition of three equivalents
of PPh2Cl at room temperature yielded tris-phosphine, o-Ph2P(C6H4){1,2,3-N3C(o-
Ph2P(C6H4))C(PPh2)} (7) along with a trace amount of compound 2 (see Fig. 1) which was
separated by column chromatography. In the 31P{1H} NMR spectrum of 7, a deceptively simple
triplet at -14.3 ppm (JPP = 6.7 Hz) and two doublet of doublets -17.7 ppm (JPP = 28.7 Hz and 8JPP
= 6.0 Hz) and -29.8 ppm (JPP = 28.7 Hz and 5JPP = 7.5 Hz) are assigned (Fig. 1) to Pa, Pb and Pc,
respectively.
N
N
N
N
PPh2 N
N
N
i
i
N
N
PPh2
Br
Br
3
2
1
ii
Ph2P
i
Ph2P
N
N
N
N
N
N
N
N
iii
ii
N
Br
PPh2
Br
PPh2
4
6
5
iv
PPh2
Ph2P
N
N
N
7
PPh2
Scheme 1 Synthesis of di and tri-phosphines 2, 5, 6 and 7. Reaction conditions: i) a) nBuLi (2.1
eq.), -78 °C to rt, 6 h, Et2O. b) PPh2Cl (2.1 eq.), rt, 12 h, Et2O. ii) a) nBuLi (2.1 eq.), -78 °C to -50
°C, 8 h, Et2O. b) PPh2Cl (2.1 eq.), -50 °C, 12 h, Et2O. iii) a) nBuLi (2.1 eq.), -78 °C, 8 h, Et2O. b)
PPh2Cl (2.1 eq.), -78 °C, 12 h, Et2O. iv) a) nBuLi (3.1 eq.), -78 °C to rt, 6 h, Et2O. b) PPh2Cl (3.1
eq.), rt, 12 h, Et2O.
The 31P{1H} NMR spectral data of triazole-based mono-, bis- and tris-phosphines (2-7) are
summarized in Table 1. The chemical shifts of all compounds follow similar trends; the triazole
bound phosphorus atom being more shielded compared to the phosphorus on phenyl groups. This
6

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is probably due to the electron-rich nature of triazole moiety, which increases the electron density
at the phosphorus atom. Bisphosphines 5 and 6 show through-space coupling similar to 2,10b while
trisphosphine 7 showed both through-space coupling (28.7 Hz) as well as long-range through-bond
8
couplings (5JPP = 7.5 Hz, JPP = 6 Hz) (see Fig. 1 and Table 1). These are rare examples of
phosphines showing very large through-space as well as long-range through-bond couplings.
PaPh2
Ph2Pc
N
N
N
PbPh2
Fig. 1 31P{1H} NMR spectrum of 7
Table 1 31P{1H} spectral data for triazole-based mono, bis and tris-phosphines
Compound
31P{1H} NMRa, b
[o-Ph2P(C6H4){1,2,3-N3C(Ph)C(H)}]10a
[C6H5{1,2,3-N3C(Ph)C(PPh2)}]10a
-15.5 s
-30.2 s
[o-Ph2P(C6H4){1,2,3-N3C(Ph)C(PPh2)}] (2)10b
[C6H5{1,2,3-N3C(o-Ph2P(C6H4))C(PPh2)}] (5)
[o-Ph2P(C6H4){1,2,3-N3C(o-Ph2P(C6H4))CH}] (6)
-17.5 d -30.4 d (JPP = 22.3)
-12.6 d, -29.8 d (JPP = 22.4)
-11.8 d, -15.6 d (JPP = 4.7)
[o-Ph2P(C6H4){1,2,3-N3C(o-Ph2P(C6H4))C(PPh2)}] (7)c -14.3 t (5JPP + 8JPP = 6.7)Pa
-17.7 dd (JPP = 28.7, 8JPP = 6)Pb
-29.8 dd (JPP = 28.7, 5JPP = 7.5)Pc
a Record in CDCl3; in ppm; bJ in Hz. CShows a deceptively simple triple instead of a dd due to the
very similar magnitude of two JPP values.
7

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Single crystals of 5 and 6 suitable for X-ray diffraction analysis were obtained from a mixture of
petroleum ether and ethyl acetate solutions of 5 and 6, respectively. A perspective view of the
molecular structures 5 and 6 are shown in Fig. 2. The phosphorus centers of 5 and 6 exhibit
distorted trigonal pyramidal geometry. In 5, phosphorus atoms are orthogonal to each other with
P2‒C8 [1.826(2) Å] bond distance slightly shorter than P1‒C6 (1.843(2) Å). In 6, both P−C bond
distances are nearly the same (P1C6, 1.848(2) and P2C14, 1.840(2) Å). The P⋯P separation in
5 and 6 are 4.039 and 7.208 Å, respectively. The P⋯P distance influences the magnitude of the
JPP values, which is evident from the 31P NMR spectral data where compound 5 showed larger JPP
coupling (22.4 Hz) compared to 6 (4.7 Hz). The molecular structure of 5 shows both inter- and
intramolecular π‒π interactions between the phenyl groups, with interplanar distances being 3.544
Å and 3.333 Å (see Fig. S1 in supporting information), which lie within the range of π-π
interactions (3.58-4.29 Å) reported in the literature.17
5
6
Fig. 2 a) Molecular structures of 5 and 6 with 50% ellipsoid probability. All hydrogen atoms were
omitted for clarity. Selected bond distances (Å) and bond angles (°): 5: P1C6 1.843(2), P1C15
1.839(3), P2C8 1.826(2), P2C27 1.826(3), N1N2 1.356(3), N2N3 1.303(3), PP 4.039,
C6P1C15 101.93(11), C6P1C21 101.49(11), C15P1C21 100.96(12), C8P2C27
8

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98.66(12), C8P2C33 102.04(11), C27P2C33 100.02(13), N1N2N3 107.3(2). 6: P1C6
1.847(2), P1C15 1.829(2), P2C14 1.842(2), P2C33 1.827(2), N1N2 1.357(2), N2N3
1.308(3), PP 7.208, C6P1C15 103.99(10), C6P1C21 101.82(10), C15P1C21 102.35(10),
C14P2C27 101.54(10), C14P2C33 102.51(10), C27P2C33 103.92(10), N1N2N3
107.57(18).
Group 6 metal complexes of 5 and 6
Reactions of 5 with [M(CO)4(piperidine)2] (M = Mo and W) in dichloromethane at room
temperature afforded PN coordinated complexes, [{Ph{1,2,3-N3C(o-Ph2P(C6H4))C(PPh2)}-
κ2-P,N}M(CO)4] (M = Mo, 8 and M = W, 9) as shown in Scheme 2.
Ph2P
[M(L)2(CO)4]
8
9
CO
M = Mo
M = W
PPh2
N1
N3
Ph
CH2Cl2, rt, 4 h
N2
Ph
M
N2
N1
OC
CO
N3
CO
Toluene
PPh2
PPh2
L = piperidine
reflux, 12 h
N3
N2
N1
[M(L)2(CO)4]
5
Toluene
reflux, 12 h
Ph
PPh2
Ph2P
10
11
M = Mo
M = W
M
CO
OC
OC
CO
Scheme 2 Synthesis of complexes 8-11Treatment of 5 with [M(CO)4(piperidine)2] (M = Mo and
W) or complexes 8 and 9 on refluxing in toluene for 12 h yielded PP coordinated complexes
[{Ph{1,2,3-N3C(o-Ph2P(C6H4))C(PPh2)}-κ2-P,P}M(CO)4] (M = Mo (10) and M = W (11))
(Scheme 2). The isomerization of PN to PP complexes was monitored by 31P{1H} NMR
spectroscopy. In the case of molybdenum, only 70% of PN complex 8 was isomerized to
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PP complex 10 even after refluxing over a prolonged period of time, whereas the isomerization
of 9 to 11 was completed within 12 h under refluxing conditions. DFT calculations predict that the
difference in free energy between 8 and 10 (-1.09 kcal/mol) is less than that between 9 and 11 (-
2.1 kcal/mol). This relatively small difference between 8 and 10 supports our difficulties in
affecting quantitative isomerization of 8 to 10 even under refluxing conditions.
Ph2P
Ph2P
N3
N2
N1
N1
[M(CO)4(piperdine)2]
N2
N3
rt
h,
, 4
Cl2
CH2
CO
Ph2P
OC
12
13
M = Mo
M = W
6
M
PPh2
CO
CO
Scheme 3 Synthesis of complexes 12-13
31
The P{1H} NMR spectral data of 8-11 are summarized in Table 2. The assignment of
chemical shifts can be made unambiguously by comparing with corresponding monophosphines
and in the case of complexes with free ligand values. Complexation essentially leads to
deshielding. The molybdenum complex 8 showed two singlets at 36.9 and -26.9 ppm, whereas the
1
31
tungsten complex 9 showed JWP coupling of 242.4 Hz. The P{1H} NMR spectra of 10 (36.2,
2
2
24.6 ppm; JPP = 20.2 Hz) and 11 (20.3, 7.3 ppm; JPP = 16.1 Hz) showed two doublets. The
tungsten complex 11 showed 1JWP couplings of 237.3 and 251.1 Hz. The coordination shifts and
2JPP couplings are indicative of PP coordination in both cases.
The reactions of 6 with [M(CO)4(piperidine)2] (M = Mo, W) in 1:1 ratio in dichloromethane at
room temperature afforded κ2-P,N chelate complexes [{o-Ph2P(C6H4){1,2,3-N3C(o-Ph2P(C6H4))
CH}-κ2-P,N}M(CO)4] (M = Mo, 12; M = W, 13) (Scheme 3). Due to the better σ-donor capability
of triazolyl-N3 compared to triazolyl-N2, M-N3 (M = Mo, W) bond was preferred in complexes 12
10

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and 13. The 31P{1H} NMR spectra of complexes 12 (36.4 and -14.1 ppm) and 13 (24.7 and -13.9
ppm) showed two singlets while tungsten complex 13 showed a 1JWP coupling of 242 Hz. The 2JPP
coupling was absent in both the complexes as the orientation of phosphorus atoms in opposite
directions prevented any possibility of through-space coupling. In contrast to the coordination
behaviour of ligands 2 and 5, ligand 6 showed exclusively κ2-P,N coordination even under
refluxing conditions.
Table 2 31P{1H} NMR spectral data for 8-21
Complexes
31P{1H} NMRa
[{C6H5{1,2,3-N3C(o-Ph2P(C6H4))C(PPh2}}-κ2-P,N}Mo(CO)4] (8)
[{C6H5{1,2,3-N3C(o-Ph2P(C6H4))C(PPh2}}-κ2-P,N}W(CO)4] (9)
[{C6H5{1,2,3-N3C(o-Ph2P(C6H4))C(PPh2)}-κ2-P,P}Mo(CO)4] (10)
36.9 s, -26.9 s
26.2 s (242.4b) -26.1 s
36.2 d (20.2c)
24.6 d (20.2c)
[{C6H5{1,2,3-N3C(o-Ph2P(C6H4))C(PPh2)}-κ2-P,P}W(CO)4] (11)
20.3 d (16.1c, 237.3b),
7.3 d (16.1c, 251.1b)
36.4 s, -14.1 s
[{o-Ph2P(C6H4){1,2,3-N3C(o-Ph2P(C6H4))CH}-κ2-P,N}Mo(CO)4] (12)
[{o-Ph2P(C6H4){1,2,3-N3C(o-Ph2P(C6H4))CH}-κ2-P,N}W(CO)4] (13)
[{{C6H5{1,2,3-N3C(o-Ph2P(C6H4))C(PPh2}}-κ2-P,P}PdCl2] (14)
[{{C6H5{1,2,3-N3C(o-Ph2P(C6H4))C(PPh2}}-κ2-P,P}PtCl2] (15)
24.7 s (242b), -13.9 s
29.5 s, 12.5 s
11.0 d (17.6c, 3591d),
-5.2 d (17.6c, 3779d)
16.6 d (461.3c)
[{o-Ph2P(C6H4){1,2,3-N3C(o-Ph2P(C6H4))C}-κ3-P,C,P}PdCl] (16)
[{o-Ph2P(C6H4){1,2,3-N3C(o-Ph2P(C6H4))C}-κ3-P,C,P}NiCl] (17)
[{o-Ph2P(C6H4){1,2,3-N3C(o-Ph2P(C6H4))C}-κ3-P,C,P}PtCl] (18)
10.1 d (461.3c)
17.9 d (338.7c)
11.5 d (339.6c)
13.9 d (430.3c, 2591d)
5.6 d (430.3c, 2550d)
[{o-Ph2P(C6H4){1,2,3-N3C(o-Ph2P(C6H4))CH}-κ2-P,N}Rh(C8H12)]Cl (19) 29.2 d (148.7e) -16.6 s
[{o-Ph2P(C6H4){1,2,3-N3C(o-Ph2P(C6H4))CH}-κ2-P,N}Ir(C8H12)]Cl (20) 14.9 s, -16.3 s
11

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[{o-Ph2P(C6H4){1,2,3-N3C(o-Ph2P(C6H4))C}-κ3-P,C,P}Rh(CO)] (21)
26.4 dd (295.8b, 134e)
23.0 dd (295.8b, 131e)
e 1
a Record in CDCl3; in ppm, J in Hz; b 1JWP, c 2JPP, d 1JPtP ,
J
RhP
.
The IR spectra of compounds 8, 9 and 11-13 showed νCO in the region 1849-1918 cm-1 along with
a sharp band around 2000 cm-1. The νCO values of 2-P,P complex 11 (1885, 1918 and 2018 cm-1)
are slightly larger than those of 2-P,N complex 9 (1851, 1877, 1908 and 2010 cm-1) which indicate
more back bonding in the later due to the electron-rich N-coordination and these trends are
comparable with those of cis-[M(CO)4(2)] (M = Mo and W).10b
The PN to PP isomerization order of ligands 2, 5 and 6 is shown in Chart 3. The
PN to PP isomerization process is controlled by the coordinating nitrogen position in
1,2,3-triazole backbone as well as PP separation in the ligand. Due to the poor σ- donor ability
of triazole-N2 atom compared to N3, the isomerization was found to be faster for PN2
complexes (Mo0 and W0 complexes of 2) than P N3 complexes (8 and 9). In order to understand
the relative stability of PN coordinated molybdenum complexes of ligands 5 and 2, the G
values were obtained from DFT calculations which indicated that 8 is relatively more stable
compared to the molybdenum complex of 2 by a margin of -2.6 kcal/mol. However, in the case of
bisphosphine 6, no isomerization (-P,N to PP) was observed due to the large separation
between the phosphorus atoms.
Ph2P
N
PPh2
N
N
N
N
PPh2
N
N
N
N
PPh2
PPh2
PPh2
2
5
6
Chart 3 -P, to -P,P isomerization order of ligands 2, 5, and 6.
12

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Group 10 metal complexes of 5 and 6
The reactions of 5 with M(COD)Cl2 (M = Pd, Pt) yielded seven-membered chelate complexes
[MCl2(5)-κ2P,P] (M = Pd (14), M = Pt (15)) (Scheme 4). The 31P{1H} NMR spectrum of complex
14 showed two singlets at 29.5 and 12.5 ppm, whereas platinum complex 15 showed two doublets
2
1
centered at 11.0 and -5.2 ppm, with a JPP coupling of 17.6 Hz, and JPtP couplings of 3591 and
3779 Hz.
Ph
Ph
N
N
N
N
Ph2
N
N
P
PPh2
[M(COD)Cl2]
Cl
Cl
14
15
M = Pd
M = Pt
M
CH2Cl2, rt, 4 h
PPh2
P
Ph2
5
N
N
N
[Pd(COD)Cl2]
CH2Cl2, 4 h, rt
Pd
Cl
P
P
Ph2P
Ph2
Ph2
N
N
16
N
N
N
[NiCl2(DME)]/
[Pt(COD)Cl2]
N
PPh2
M
6
LiHMDS
P
P
17
18
M = Ni
M = Pt
Ph2
Ph2
Toluene, reflux, 12 h
Cl
Scheme 4 Synthesis of complexes 14-18
Gandelman and co-workers reported the metal-promoted C-H bond activation of triazole to form
fused five-membered PCP-pincer complexes7e-h and similar reactivity was anticipated with ligand
6. The ligand 6 upon reaction with [Pd(COD)Cl2] in dichloromethane at room temperature yielded
exclusively C-H activated fused six-membered palladium metallocycle 16 as shown in Scheme 4.
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The reactions of 6 with [NiCl2(DME)] and [Pt(COD)Cl2] in the presence of LiHMDS under
refluxing conditions resulted in similar pincer complexes 17 and 18, respectively (Scheme 4). To
the best of our knowledge, these are the first examples of 1,2,3 triazole-based fused six-membered
PCP pincer complexes. The 31P{1H} NMR spectra of 16 and 17 showed two doublets at 16.6 ppm,
10.1 ppm (2JPP = 461 Hz), and 17.9 ppm, 11.5 ppm (2JPP = 339 Hz), respectively. The larger P-P
coupling constants are indicative of two nonequivalent phosphorus atoms in a mutually trans-
disposition. Similarly, platinum complex 18 also showed two doublets at 13.9 and 5.6 ppm with a
1
1
2JPP of 430.3 Hz and JPtP couplings of 2591 and 2550 Hz. In H NMR spectra of 16-18, the
disappearance of the signal due to the triazole proton around 7.9 ppm confirms the M–C bond
formation through the elimination of HCl. The structures of 16 and 17 have been confirmed by
single-crystal X-ray analysis.
Synthesis of RhI and IrI complexes
Bisphosphine 6 on treatment of 0.5 equivalent of [M(COD)Cl]2 (M = Rh and Ir) in
dichloromethane afforded cationic complexes 19 and 20, whereas the 1:1 reaction of 6 with
[Rh(acac)(CO)2] produced pincer complex [{o-Ph2P(C6H4){1,2,3-N3C(o-Ph2P(C6H4))C}-κ3-
31
P,C,P}Rh(CO)] (21) in good yield as shown in Scheme 5. The P{1H} NMR spectrum of 19
showed a doublet at 29.2 (1JRhP = 148.7 Hz) and a singlet at -16.6 ppm while 20 displayed two
1
singlets at 14.9 and -16.3 ppm indicating κ2-P,N coordination. H NMR spectra of 19 and 20
showed single resonances at 9.93 and 9.92 ppm, respectively, for the triazole protons. Mass spectra
of 19 and 20 showed molecular ion peaks, respectively, at 800.1825 and 890.2401, corresponding
to [M‒Cl]+ ions. The 31P{1H} NMR spectrum of 21 consists of two doublets of doublets at 23.04
1
and 26.4 ppm (JPP = 295.8 Hz) with JRhP couplings of 131 and 134 Hz. The 13C{1H} NMR
14

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spectrum of 21 showed two broad singlets at 143.12 and 195 ppm for ipso carbon and terminal
carbonyl, respectively. The IR spectrum of 21 showed CO at 1987 cm-1.
Ph2P
Cl
N
0.5 [M(COD)Cl]2
N
N
N
Ph2P
Ph2P
CH2Cl2, rt, 4 h
M
19
20
M = Rh
M = Ir
N
N
N
N
6
N
[Rh(acac)(CO)2]
CH2Cl2, rt, 4 h
PPh2
Rh
P
P
Ph2
Ph2
CO
21
Scheme 5 Synthesis of complexes 19-21
Molecular structures of complexes 8, 9, 12-17 and 21
Perspective views of the molecular structures of complexes 8, 9, 12-17 and 21 with atom
numbering schemes are shown in Fig. 3-5. Selected bond distances and bond angles are listed in
Tables 3-5. Crystallographic data and the details of the structure determination are given in Tables
S1 and S2 (see in Supporting information).
Complexes 8, 9, 12 and 13 adopt pseudo-octahedral geometry around molybdenum and tungsten
metal atoms. The Mo−P bond distance in 8 [2.5152(14) Å] is slightly longer than the same in 12
[2.5062(11) Å] but comparable to -P,N based Mo0 complexes.18 The opposite trend was observed
in tungsten complexes; the W-P bond distances in 9 (2.4952(6) Å) and 13 (2.4943(5) Å) are slightly
shorter than the same found in [W(CO)4(2)] (2.5156(11) Å).10b The M-N bond distances in 8
[2.279(4) Å] and 9 [2.251(2) Å] are slightly longer than those of 12 [2.244(3) Å] and 13
[2.2346(16) Å] due to the presence of phosphine group at the triazole carbon atoms (C8) in 8 and
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9. The N2=N3 bond lengths in 8 and 9 were stretched by 0.021 and 0.014 Å as a result of
complexation. The M–CO bonds trans to phosphorus atom [1.986(2) to 2.007(3) Å] are longer
than those trans to the triazolyl N atom [1.948(5) to 1.970(2) Å] but shorter to other M-CO bonds
[2.009(5) to 2.049(6) Å]. The P-M-N bond angles are 76.10(10)°, 77.90(5)°, 80.20(9)° and
78.14(4)° for 8, 9, 12 and 13, respectively.
8
9
12
13
Fig. 3 Molecular structures of 8, 9, 12, and 13. All hydrogen atoms and solvent molecules were
omitted for clarity.
Fig. 4 Molecular structures of 14 (Pd) and 15 (Pt) with 50% ellipsoid probability. All hydrogen
atoms and solvent molecules were omitted for clarity.
16

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The crystals of 14 and 15 suitable for X-ray diffraction studies were obtained by diffusing
petroleum ether into the dichloromethane solution of corresponding complexes. The metal centers
in complexes 14 and 15 adopt slightly distorted square-planar geometries with ligand 5 forming a
seven-membered chelate ring via κ2-P,P coordination (Fig. 4). The P1‒M‒P2 bond angles in 14
and 15 are 93.261(11)° and 93.55(8)°, respectively. The M-P1 bond distances [M = Pd (14),
2.2703(3) Å and M = Pt (15), 2.261 (2) Å] are slightly longer than M‒P2 [(M = Pd (14) 2.2480(3)
Å and M = Pt (15), 2.232(2) Å] bond distances. The bond lengths and bond angles of 14 and 15
are comparable to the same in analogous complexes.10b, 19
Fig. 5 Molecular structures of 16 (Pd), 17 (Ni) and 21 (Rh) with 50% ellipsoid probability. All
hydrogen atoms and solvent molecules were omitted for clarity.
In the crystal structures of 16 and 17, the palladium and nickel centers adopt distorted square-
planar geometry with fused six-membered metallocycles. The P-M-P angles in 16 and 17 are
176.16(6) and 172.004(13)°, respectively. The cis bond angles involving the metal center are
88.24(17)°- 91.95(6)° for 16 and 86.51(4)°-92.814(13)° for 17 and these bond angles significantly
deviate from previously reported triazole-based fused five-membered palladium pincer complex
[1,4-((PPh2)CH2)2{1,2,3-N3CCH}PdCl] (79.23° and 103.45° for P-Pd-C and P-Pd-Cl,
respectively),7e which indicates that the strain around the metal center is reduced due to the
formation of six-membered metallacycles. In both 16 and 17, phenyl groups on triazole rings are
out of the coordinate plane, with the twist angles being 38.74° and 29.83° for 16 and 44.31° and
17

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39.15° for 17. The central triazole ring is also twisted making an angle with the coordination plane.
The angle between the triazole ring and the plane defined by Pd1-Cl1-C7-P1-P2 plane (the twist
angle) is 23.78° for 16. Interestingly, the triazole ring in 17 is highly twisted and the twist angle in
17 (33.42°) is significantly larger than that of 16. The Pd-C bond length (2.001(6) Å) is
considerably longer than the same observed in [1,4-((PPh2)CH2)2{1,2,3-N3CCH}PdCl] (1.934 Å)
and [1,4-((PiPr2)CH2)2{1,2,3-N3CCH}PdCl] (1.929(6) Å).7h The Pd-P bond distances are
comparable with the same observed in five-member triazole-based pincer complexes such as
[(iPr2P)(CH2){1,2,3-(CH3)(N3C2}(CH2)(iPr2P)-3-P,C,P}PdI]I
and
[(iPr2P)(CH2){1,2,3-
(N3C2}(CH2)(iPr2P)-3-P,C,P}PdCl].7f-h The Ni–P bond distances (2.1937(3) Å and 2.1896(3) Å)
in 17 are similar to the same found in [{2,6-{(iPr2POCH2)2C6H3}NiBr] (2.1951(6) Å), [(2, 6-
(iPr2PCH2)2C6H3)NiBr] (2.1645(6) Å)20 and [( 2, 6-(iPr2PO)2C6H3)NiBr] (ca. 2.142-2.153 Å).21
The Ni–C bond distance in 17 (1.8885(12) Å) is slightly shorter than the same observed in fused
six-member POCOP pincer complex[{2,6-{(iPr2POCH2)2C6H3}NiBr] (1.934(3) Å).21a
In 21 the geometry around the rhodium atom is distorted square-planar with bond angles,
P−Rh−P = 172.11(2)° and CO−Rh−Cl = 175.97(11)°. Similar to palladium (16) and nickel
complexes (17), the triazole attached phenyl groups are out of the coordinate plane and twisted
from each other (38.87° and 37.97° for triazole C-attached phenyl group and triazole N-attached
phenyl group, respectively). The Rh1-P1, Rh1-P2, and Rh-C7 bond distances are 2.2738(6),
2.2798(6) and 2.062(2) Å, respectively.
Table 3 Selected bond distances (Å) and bond angles for 8, 9, 12 and 13
Bond lengths (Å)
M-P1
8
9
12
13
2.5152(14)
2.279(4)
2.000(6)
2.4952(6)
2.251(2)
2.007(3)
2.5062(11)
2.244(3)
2.004(5)
2.4943(5)
2.2346(16)
1.986(2)
M-N3
M-C39
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M-C40
M-C41
M-C42
P1-C6
1.959(5)
2.049(6)
2.024(6)
1.854(5)
1.826(5)
-
1.961(3)
2.032(3)
1.948(5)
1.970(2)
2.016(2)
2.043(2)
1.827(2)
-
2.009(5)
2.022(5)
1.835(4)
-
2.025(3)
1.835(2)
P2-C8
1.836(2)
P2-C14
N2-N3
-
1.833(5)
1.320(4)
1.857(2)
1.317(2)
1.324(5)
1.317(3)
Bond angles (°)
77.90(5)
P1-M-N3
P1-M-C39
N3-M-C40
C41-M-C42
N1-N2-N3
76.10(10)
168.78(16)
173.9(2)
80.20(9)
171.38(12)
176.78(16)
171.68(17)
106.4(3)
78.11(4)
169.59(6)
174.21(7)
173.59(8)
169.76(7)
173.81(9)
171.88(11)
106.68(19)
170.1(2)
107.0(4)
106.39(15)
Table 4 Selected bond distances (Å) and angels (°) for compounds 14 and 15.
Bond lengths
(Å)
14
15
Bond algles
(°)
14
15
(M = Pd)
2.3311(3)
2.3417(3)
2.2703(3)
2.2480(3)
1.8382(13)
1.8216(12)
(M = Pt)
2.335(2)
2.350(2)
2.261(2)
2.232(2)
1.824(9)
1.843(9)
(M = Pd)
(M = Pt)
93.55(8)
87.87(8)
105.3(8)
170.59(9)
87.65(8)
92.29(8)
M-Cl1
M-Cl2
M-P1
M-P2
C6-P1
C8-P2
P-M-P
93.261(11)
90.077(12)
107.43(12)
169.880(12)
86.968(11)
91.515(11)
Cl-M-Cl
N1-N2-N3
P1-M-Cl1
P1-M-Cl2
P2-M-Cl1
P2-M-Cl2
168.786(13)
170.01(10)
Table 5 Selected bond distances (Å) and bond angles for compounds 16, 17 and 21
16 (M = Pd)
X = Cl
17 (M = Ni)
X = Cl
21 (M = Rh)
X = CO
Bond lengths (Å)
M-P1
M-P2
2.2957(16)
2.3091(16)
2.1937(3)
2.1896(3)
2.2738(6)
2.2798(6)
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M-C7
M-X
2.001(6)
2.3461(15)
1.815(6)
1.813(6)
1.8882(12)
2.1734(3)
1.8185(12)
1.8163(13)
2.062(2)
1.874(3)
1.819(2)
1.825(2)
P1-C1
P2-C14
Bond angles (°)
P1-M-P2
176.16(6)
179.39(18)
88.24(17)
88.58(17)
91.95(6)
91.25(6)
32.28
172.004(13)
175.60(4)
88.71(4)
86.51(4)
92.814(13)
92.422(13)
38.47
172.11(2)
175.97(11)
86.57(7)
85.77(7)
94.40(8)
93.37(8)
38.61
C7-M-X
P1-M-C7
P2-M-C7
P1-M-X
P2-M-X
C1-P1-M-C7
C14-P2-M-C7
36.57
45.51
39.75
Catalytic application in Heck reaction
Several palladium pincer complexes have been employed in Mizoroki-Heck reaction,22 with fused
six-membered pincers showing better conversions compared to five-membered pincer
complexes.23 Therefore as a preliminary study to assess the catalytic ability of the pincer
complexes, Mizoroki-Heck reactions were conducted. Initially, to assess the catalytic activity, in
situ generated palladium complexes of ligands 2, 5 and 6 were added to a mixture of 1 mmol of
bromobenzene, 1.2 mmol of styrene in dioxane (3 mL) and 1.5 equivalent of diisopropylamine
(Table 6, entry 2-4) which showed good conversion. The ligand 6 and Et3N provided excellent
conversion (Table 6, entry 6) at 110 °C. The isolated complexes [{(2)-κ2-P,P}PdCl2], 14, 16, and
17 are also employed for Heck coupling (Table 6, entries 8-11) and among all, palladium complex
16 produced the best result in as low as 0.25 mol% (Table 6, entry 13). However, the TON are
lower compared to the same observed with similar complexes [1,4-((PPh2)CH2)2{1,2,3-
N3CCH}PdCl]7e and fused six-membered Pd-pincer complex [{2,6-{(iPr2POCH2)2C6H3}PdCl].22,
20

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Using the optimized condition and using 0.25 mol% of complex 16, various combinations of aryl
bromides and alkenes were subjected to the Heck coupling reaction and the results are summarized
in Chart 4.
Table 6 Optimization of reaction conditions
Cat. (1 mol%)
Br
1.5 equvi. base
Dioxane (3 mL)
110 °C, 12 h
Ligand
Entry
Catalyst
Base
Conversion (%)a
(1 mol%)
1
2
Pd(COD)Cl2
Pd(COD)Cl2
Pd(COD)Cl2
Pd(COD)Cl2
Pd(COD)Cl2
Pd(COD)Cl2
Pd(OAC)2
[{(2)-κ2-P,P}PdCl2]
14
-
DIPA
DIPA
DIPA
DIPA
DEA
Et3N
Et3N
Et3N
Et3N
Et3N
Et3N
Et3N
Et3N
Et3N
35
94
2
5
6
6
6
6
3
94
4
96
5
70
6
97
7
97
8
95
9
-
-
-
96
10
11
12
13
14
16
98
16b
98
17c
-
16d
-
-
96(92)f
16e
82
d
aConversion determined by GC-MS. b0.5 mol% catalyst used. cno conversion. 0.25 mol% catalyst
used. e0.1 mol% catalyst used. fisolated yield.
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c
, 88%
a
, 92%
b
, 91%
Cl
e
, 81%
d
, 78%
f
, 91%
MeO
S
N
S
g
, 65%
h
, 86%
i
, 85%
Br
Conditions: arylbromide 0.5 mmol, alkenes 0.6 mmol, dioxane 3 mL, Et3N 0.75 mmol, 110 °C,
Catalyst (0.25 mol %). All are isolated yields.
Chart 4 Substrate scope for Heck coupling reaction
Conclusions
This paper describes an efficient and novel methodology for the synthesis of 1,2,3-triazole-based
di- and tri-phosphines. The temperature-controlled lithiation of bromo-triazoles and their
subsequent reactions with chlorodiphenylphosphine produced 1,2,3-triazole-based di- and tri-
phosphines (2, 5, 6 and 7). Using this method, a library of bisphosphines can be generated. The
synthetic methodology provides an opportunity to generate useful organic products by using
different electrophiles. The bisphosphines 5 and 6 showed interesting coordination behavior. These
ligands showed -P,N to -P,P isomerization with Mo0 and W0 metal precursors. The
coordinating nitrogen position in 1,2,3-triazole backbone and the PP separation control the
isomerization process.. Palladium(II) and rhodium(I) pincer complex were prepared at room
temperature in excellent yields. Also NiII and PtII pincer complexes were isolated. The palladium
complex 16 is found to be an efficient catalyst for Heck coupling reactions. It is foreseen that the
synthetic flexibility found in the current ligand system is expected to be an enormous aid in the
growing field of click-phosphines, particularly regarding their potential in catalytic and
22

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photophysical activities. Further, coordination chemistry of tris-phosphine 7, reactivity studies of
pincer complexes (16-18 and 21) and several other catalytic reactions with these systems are under
active investigation in our laboratory.
Experimental section
General procedures. All reactions were carried out under an inert atmosphere of dry nitrogen by
using standard Schlenk and vacuum line techniques. All the air and moisture sensitive compounds
were handled and stored in the MBRAUN Glove box. Solvents were dried by usual methods and
distilled before use. The compounds [M(piperidine)2(CO)4] (M = Mo and W),24 [NiCl2(DME)],
[M(COD)Cl2] (M = Pd or Pt),25 [M(COD)Cl]2 (M = Rh and Ir),26 [Rh(acac)(CO)2],27 1-(2-
bromophenyl)-4-phenyl-1H-1,2,3-triazole (1),10a 4-(2-bromophenyl)-1-phenyl-1H-1,2,3-triazole
(3)8a and 1,4-bis(2-bromophenyl)-1H-1,2,3-triazole (4)8a were prepared according to the published
procedures. Other reagents were obtained from commercial sources and used after purification.
The Heck reaction optimizations and % of conversion were determined by GC-MS analysis using
n-decane as the internal standard.
Instrumentation methods. The solution NMR spectra were recorded on a Bruker FT
13
31
spectrometers (Avance-400 or 500) MHz at ambient probe temperatures. C{1H} and P{1H}
NMR spectra were acquired using a broadband decoupling method. The spectra were recorded in
CDCl3 solutions with CDCl3 as an internal lock; chemical shifts of 1H and 13C{1H} NMR spectra
are reported in ppm downfield from TMS, used as an internal standard. The chemical shifts of
31P{1H} NMR spectra are referred to as 85% H3PO4 as an external standard. Infrared spectra were
recorded on a PerkinElmer 400 FTIR instrument in KBr disk. The microanalyses were performed
using an elementar Vario MICRO CUBE elemental analyzer. Mass spectra were recorded using
Waters Q-Tof micro (YA-105). Melting points of all compounds were determined on a Veego
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melting point apparatus and are uncorrected. GC-MS analyses were carried out in the Agilent
7890A GC system with an FID detector using a J & amp; WDB-1 column (10 m, 0.1 mm ID)
Computational methods Computations were performed using the Gaussian09. Calculations were
performed using the M0628 with Pople's 6-31G** basis set lanl2dz levels of theory29 for complexes
8-11. Crystal structure data were used for coordinates while performing the DFT calculations.30
Synthesis of [o-Ph2P(C6H4){1,2,3-N3C(Ph)C(PPh2)}] (2)
Method A: nBuLi (6.9 mL, 11 mmol, 1.6 M solution in hexane) was added dropwise to a solution
of 1-(2-bromophenyl)-4-phenyl-1H-1,2,3-triazole (1) (1.5 g, 5 mmol) in diethyl ether (50 mL) at -
78 ºC. The reaction mixture was warmed to room temperature and stirring was continued for 6 h.
The resulting reddish coloured solution was cooled to -78 ºC and the diethyl ether (10 mL) solution
of PPh2Cl (2.32 g, 10.5 mmol) was added dropwise through a cannula. The resulting mixture was
slowly warmed to room temperature and stirred for further 12 h. The crude product was filtered
through celite and washed with water and purified by column chromatography on silica gel using
petroleum ether: EtOAc (10:1) as the mobile phase to afford 2 as analytically pure colourless solid.
Yield: 68% (2.00 g) Mp: 167-170 °C. 1H NMR (500 MHz, CDCl3) δ 7.39 (td, J = 7.6, 1.3 Hz, 1H),
13
7.35 – 7.28 (m, 7H), 7.28 – 7.11 (m, 18H), 7.10 – 7.06 (m, 1H), 7.02 – 6.96 (m, 2H). C{1H}
NMR (101 MHz, CDCl3) δ 152.66, 141.69, 141.44, 137.59, 137.40, 136.38, 136.28, 135.35,
133.96, 133.76, 133.04, 132.85, 132.68, 132.59, 130.99, 130.48, 129.66, 129.23, 129.00, 128.92,
128.64, 128.58, 128.42, 127.70, 127.55, 77.52, 77.20, 76.88. 31P{1H} NMR (202 MHz, CDCl3): δ
-17.5 (d, JPP = 22.3 Hz), -30.4 (d, JPP = 22.3 Hz). HRMS (ES) m/z calcd for C38H30N3P2 ([M+H]+)
590.1909; found 590.1907.
Method B: This method is similar A for the preparation of compound 2 but using different triazole
derivatives, 4-(2-bromophenyl)-1-phenyl-1H-1,2,3-triazole (3) (1.5 g, 5 mmol) (yield: 60%)
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and/or 1,4-bis(2-bromophenyl)-1H-1,2,3-triazole (4) (1.9 g, 5 mmol) (yield: 56%) as starting
materials.
Synthesis of [C6H5{1,2,3-N3C(o-Ph2P(C6H4))C(PPh2)}] (5)
Method A: A solution of 4-(2-bromophenyl)-1-phenyl-1H-1,2,3-triazole (3) (1.5 g, 5 mmol) in
diethyl ether (40 mL) was cooled to -78 °C, followed by the addition of nBuLi (6.9 mL, 11 mmol,
1.6 M solution in hexane) via syringe while thawing. The reaction mixture was warmed to -50 °C
and stirred for 8 h. The resulting colourless solution was cooled to -78 °C and a solution of PPh2Cl
(2.32 g, 10.5 mmol) in diethyl ether (10 mL) was added dropwise through a cannula. The resulting
mixture was slowly warmed to -50 °C and stirred for a further period of 12 h. The crude product
was filtered through celite and washed with water and purified by column chromatography on
silica gel using petroleum ether: EtOAc (10:1) as the mobile phase to afford 5 as analytically pure
colourless solid. Yield: 66 % (1.95 g) Mp: 169-173 °C. Anal. Calcd. for C38H29N3P2: C, 77.41; H,
4.96; N, 7.13. Found C, 77.19; H, 4.84; N, 6.85%. 1H NMR (500 MHz, CDCl3) δ 7.33 (d, J = 13.7
Hz, 11H), 7.25 (t, J = 7.0 Hz, 8H), 7.15 (ddd, J = 15.9, 11.2, 6.7 Hz, 9H), 6.99 (dd, J = 6.5, 4.1
13
Hz, 1H). C{1H} NMR (101 MHz, CDCl3) δ 138.10, 137.69, 137.57, 137.48, 136.67, 134.13,
133.93, 133.79, 133.59, 133.07, 133.00, 131.55, 129.34, 129.16, 128.81, 128.54, 128.51, 128.46,
31
128.41, 128.40, 128.34, 126.59, 126.56. P{1H} NMR (202 MHz, CDCl3) δ -12.6 (d, J = 22.4
Hz), -29.8 (d, J = 22.4 Hz). HRMS (ES) m/z calcd for C38H30N3P2 ([M+H]+) 590.1909; found
590.1905.
Method B: Compound 5 was also prepared using the same method A but using a different triazole
derivative, 1,4-bis(2-bromophenyl)-1H-1,2,3-triazole (4) (1.9 g, 5 mmol) as the starting material.
Yield: 58% (1.71 g).
Synthesis of [o-Ph2P(C6H4){1,2,3-N3C(o-Ph2P(C6H4))CH}] (6)
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nBuLi (1.6 M in hexane, 6.9 mL, 11 mmol) was added dropwise to a stirred solution of 1,4-bis(2-
bromophenyl)-1H-1,2,3-triazole (4) (1.9 g, 5 mmol) in diethyl ether (40 mL) at -78 °C and the
reaction mixture was further stirred for 8 h at -78 °C. A solution of PPh2Cl (2.32 g, 10.5 mmol) in
diethyl ether (10 mL) was cannulated to the reaction mixture at −78 °C and stirred for 12 h and the
solution was slowly warmed to room temperature and stirring was continued for a further period
of 6 h. The crude product was filtered through celite and washed with water and purified by column
chromatography on silica gel using petroleum ether: EtOAc (10:1) as the mobile phase to afford 6
as analytically pure colourless solid. Yield: 62 % (1.82 g). Anal. Calcd. for C38H29N3P2: C, 77.41;
H, 4.96; N, 7.13. Found C, 77.31; H, 4.49; N, 6.77%. 1H NMR (400 MHz, CDCl3) δ 7.96 (s, 1H),
δ 7.96 (m, 1H), 7.51 – 7.40 (m, 3H), 7.40 – 7.35 (m, 1H), 7.34 – 7.27 (m, 12H), 7.24 (ddd, J = 7.7,
13
3.5, 1.2 Hz, 9H), 7.08 (ddd, J = 7.7, 3.4, 1.2 Hz, 1H), 7.01 – 6.95 (m, 1H). C{1H} NMR (101
MHz, CDCl3) δ 145.81, 140.88, 137.02, 136.91, 136.10, 135.76, 135.65, 135.31, 135.14, 134.97,
134.78, 134.26, 134.18, 134.05, 133.98, 130.17, 130.12, 129.85, 129.69, 129.23, 129.17, 128.88,
128.78, 128.76, 128.71, 128.69, 128.33, 126.54, 125.64, 125.53. 31P{1H} NMR (162 MHz, CDCl3)
δ -11.8 (d, J = 4.7 Hz), -15.6 (d, J = 4.7 Hz). HRMS (ES) m/z calcd for C38H30N3P2 ([M+H]+)
590.1909; found 590.1908.
Synthesis of [o-Ph2P(C6H4){1,2,3-N3C(o-Ph2P(C6H4))C(PPh2)}] (7)
To a Schlenk flask charged with 1,4-bis(2-bromophenyl)-1H-1,2,3-triazole (4) (1.9 g, 5 mmol) and
diethyl ether (40 mL) at -78 °C, nBuLi (9.7 mL, 15.5 mmol, 1.6 M solution in hexane) was added
dropwise and the reaction mixture was stirred at -78 ºC for 1 hour, warmed to room temperature
and stirring was continued for 6 h. The resulting solution was cooled to -78 ºC and the diethyl ether
(10 mL) solution of PPh2Cl (3.36 g, 15.2 mmol) was added dropwise through a cannula. The
resulting mixture was slowly warmed to room temperature and stirred for further 12 h and filtered
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through celite to remove LiCl. The solvent was removed under vacuum and purified by column
chromatography on silica gel using petroleum ether: EtOAc (10:1) as the mobile phase to afford 7
1
as analytically pure colourless solid. Yield: 70% (2.7 g). Mp: 156-160 °C. H NMR (400 MHz,
CDCl3) δ 7.43 – 7.18 (m, 27H), 7.18 – 7.01 (m, 8H), 6.97 (dd, J = 6.8, 3.3 Hz, 1H), 6.90 – 6.77
13
(m, 2H). C{1H} NMR (101 MHz, CDCl3) δ 152.33, 141.71, 141.45, 137.69, 137.50, 137.14,
135.24, 134.03, 133.84, 131.74, 131.69, 130.79, 130.24, 129.50, 129.09, 128.73, 128.55, 128.49,
128.41, 128.33, 128.26, 128.07. 31P{1H} NMR (162 MHz, CDCl3) δ -29.81 (dd, J = 28.9, 7.5 Hz),
-17.72 (dd, J = 28.7, 6.0 Hz), -14.35 (t, J = 6.7 Hz). HRMS (ES) m/z calcd for C50H39N3P3
([M+H])+ 774.2351; found 774.2373.
Synthesis of [{C6H5{1,2,3-N3C(o-Ph2P(C6H4))C(PPh2}}-κ2-P,N}Mo(CO)4] (8)
A solution of 5 (0.03 g, 0.051 mmol) and [Mo(CO)4(piperidine)2] (0.019 g, 0.051 mmol) in
dichloromethane (8 mL) was stirred for 4 h at room temperature. The solvent was evaporated under
vacuum, and the residue was washed with diethyl ether and petroleum ether. The resulting
compound dried under vacuo to give analytically pure product of 8 as a light yellow solid. Yield:
90% (0.037 g). Mp: 212-216 °C. IR (KBr disk): CO = 2015, 1913, 1889 and 1852 cm-1. Anal.
Calcd. for C42H29MoN3O4P2: C, 63.25; H, 3.66; N, 5.27. Found C, 63.29; H, 3.64; N, 5.00%. 1H
NMR (500 MHz, CDCl3) δ 7.64 – 7.54 (m, 4H), 7.53 – 7.45 (m, 6H), 7.29 (t, J = 7.5 Hz, 2H), 7.24
(s, 2H), 7.19 (t, J = 7.5 Hz, 3H), 7.14 (s, 4H), 6.99 (t, J = 7.9 Hz, 2H), 6.93 – 6.83 (m, 4H), 6.65
(d, J = 7.7 Hz, 2H). 13C{1H} NMR (101 MHz, CDCl3) δ 212.53, 208.41, 150.45, 137.11, 136.66,
136.46, 135.53, 135.18, 134.48, 133.93, 132.70, 132.51, 131.90, 131.55, 130.74, 130.41, 130.17,
129.91, 129.75, 129.57, 129.41, 129.22, 128.89, 128.82, 128.72, 128.43, 126.90, 126.47. 31P{1H}
NMR (202 MHz, CDCl3) δ 36.99, -26.89. HRMS (ES) m/z calcd for C42H30N3O4P2Mo ([M+H])+
800.0770; found 800.0773.
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Synthesis of [{C6H5{1,2,3-N3C(o-Ph2P(C6H4))C(PPh2}}-κ2-P,N}W(CO)4] (9)
This was synthesized by following the synthetic procedure of 8, using compound 5 (0.03 g, 0.051
mmol) and [W(CO)4(piperidine)2] (0.024 g, 0.051 mmol). Yield: 88% (0.04 g). Mp: 223-227 °C.
IR (KBr disk): νCO = 2010, 1908, 1877 and 1851 cm-1. Anal. Calcd. for C42H29N3O4P2W: C, 56.97;
1
H, 3.30; N, 4.75. Found C, 56.53; H, 3.2; N, 4.47%. H NMR (500 MHz, CDCl3) δ 7.62 – 7.54
(m, 4H), 7.54 – 7.45 (m, 6H), 7.31 (t, J = 7.4 Hz, 2H), 7.24 (s, 2H), 7.18 (dd, J = 13.1, 5.4 Hz,
7H), 7.00 (t, J = 7.9 Hz, 2H), 6.94 – 6.83 (m, 4H), 6.67 (d, J = 7.7 Hz, 2H). 13C{1H} NMR (126
MHz, CDCl3) δ 211.62, 210.12, 209.84, 203.28, 203.17, 155.00, 136.38, 136.31, 136.08, 134.56,
134.46, 134.23, 134.05, 133.97, 133.79, 133.58, 132.69, 132.53, 131.94, 131.62, 131.60, 131.53,
131.19, 130.80, 130.66, 130.03, 129.67, 129.50, 128.99, 128.94, 128.92, 128.82, 128.42, 128.37,
126.42. 31P{1H} NMR (202 MHz, CDCl3): δ 26.2 (1JWP = 242.4), -26.1. HRMS (ES) m/z calcd for
C42H30N3O4P2W ([M+H])+ 886.1222; found 886.1220.
Synthesis of [{C6H5{1,2,3-N3C(o-Ph2P(C6H4))C(PPh2)}-κ2-P,P}Mo(CO)4] (10)
A solution of 5 (0.03 g, 0.051 mmol) and [Mo(CO)4(piperidine)2] (0.019 g, 0.051 mmol) in toluene
(15 mL) was refluxed for 12 h, and then the reaction mixture was cooled to room temperature. The
solvent was completely removed under reduced pressure and the residue obtained was washed
with diethyl ether and petroleum ether (3 x 5 mL) and dried under vacuum to resulted in the
31
formation of an inseparable 2/1 mixture of 10 and 8. Due to signal overlap, only P{1H} NMR
31
2
and mass spectral data are provided. P{1H} NMR (162 MHz, CDCl3) 9: δ 36.2 (d, JPP = 20.2
Hz), 24.6 (d, 2JPP = 20.2 Hz), 7: δ 36.99 (s), -26.90 (s. HRMS (ES) m/z calcd for C42H30N3O4P2Mo
([M+H])+ 800.0770; found 800.0771.
Synthesis of [{C6H5{1,2,3-N3C(o-Ph2P(C6H4))C(PPh2)}-κ2-P,P}W(CO)4] (11)
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A solution of 5 (0.03 g, 0.051 mmol) and [W(CO)4(piperidine)2] (0.024 g, 0.051 mmol) in toluene
(15 mL) was refluxed for 12 h and then the reaction mixture was cooled to room temperature. The
solvent was completely removed under reduced pressure and the residue obtained was washed
with diethyl ether and petroleum ether (3 x 5 mL) and dried under vacuo to give analytically pure
product of 11 as a colorless solid. Yield: 90% (0.04 g) Mp: 227-231 °C. IR (KBr disk): CO = 2018,
1918 and 1885 cm-1 Anal. Calcd. for C42H29O4N3P2W: C, 56.97; H, 3.3; N, 4.75. Found C, 56.43;
H, 3.36; N, 4.54%. 1H NMR (500 MHz, CDCl3) δ 7.65 (s, 2H), 7.51 – 7.26 (m, 14H), 7.21 – 7.06
13
(m, 5H), 7.06 – 6.94 (m, 4H), 6.88 (s, 2H), 6.74 (d, J = 7.8 Hz, 2H). C{1H} NMR (126 MHz,
CDCl3) δ 206.07, 206.01, 205.88, 205.83, 205.47, 205.42, 205.25, 205.20, 201.37, 150.62, 150.51,
138.04, 136.64, 136.24, 135.96, 134.88, 134.75, 134.66, 134.47, 134.37, 134.32, 133.89, 133.80,
132.76, 131.99, 131.83, 130.85, 130.80, 130.71, 130.32, 129.88, 129.50, 129.28, 129.21, 128.75,
128.56, 128.49, 128.40, 128.27, 126.49, 125.47. 31P{1H} NMR (162 MHz, CDCl3) δ 20.33 (d, J =
1
1
16.1 Hz, JWP = 237.3 Hz,), 7.30 (d, J = 16.1 Hz, JWP = 251.1 Hz,). HRMS (ES) m/z calcd for
C42H30N3O4P2W ([M+H])+ 886.1222; found 886.1230.
Synthesis of [{o-Ph2P(C6H4){1,2,3-N3C(o-Ph2P(C6H4))CH}-κ2-P,N}Mo(CO)4] (12)
Compound 12 was synthesized by following the synthetic procedure of 8, using compound 6 (0.03
g, 0.051 mmol) and [Mo(CO)4(piperidine)2] (0.019 g, 0.051 mmol). Yield: 90% (0.036 g). Mp:
202-206 °C. IR (KBr disk): CO = 2015, 1889 and 1849 cm-1. C42H29MoN3O4P2: C, 63.25; H, 3.66;
N, 5.27. Found C, 63.56; H, 3.74; N, 5.00%. 1H NMR (400 MHz, CDCl3) δ 7.76 (d, J = 1.9 Hz,
1H), 7.51 – 7.28 (m, 21H), 7.24 (dd, J = 8.1, 1.5 Hz, 4H), 7.17 (d, J = 8.0 Hz, 1H), 7.07 (ddd, J =
13
7.7, 3.6, 1.4 Hz, 1H), 6.87 – 6.80 (m, 1H). C{1H} NMR (101 MHz, CDCl3) δ 211.50, 209.35,
209.02, 203.05, 202.98, 147.93, 139.21, 139.01, 135.08, 134.84, 134.54, 134.34, 134.27, 134.16,
134.06, 133.98, 133.85, 133.10, 133.03, 132.84, 132.78, 132.69, 132.64, 131.87, 131.50, 131.41,
29