Six-membered [C,N] cyclopalladated sym N,N0,N00-tri(4-tolyl) guanidines: Synthesis, reactivity studies and structural aspects

Article abstract of DOI:10.1016/j.jorganchem.2013.05.030

Six-membered [C,N] cyclopalladated sym N,N0,N00-tri(4-tolyl)guanidines, [(ArNH)2C]NAr] (sym = symmetrical; Ar = 4-MeC6H4; LH2 4-tolyl) of the types [(C,N)Pd(m-OC(O)R)]2 (1 and 2), [(C,N)Pd(m-Br)]2 (3), cis-[(C,N)PdLBr] (4e7), and [(C,N)Pd(acac)] (8) were prepared in high yield by established methods with a view aimed at understanding the influence of the 4-tolyl substituent of the guanidine moiety upon the solution behaviour of 1e8. The composition of 1e8 was confirmed by elemental analysis, IR, and NMR spectroscopy, and mass spectrometry. The molecular structures of 1e6 were determined by singlecrystal X-ray diffraction. Palladacycles 1e3 exist as a dimer in transoid conformation in the solid state while 4e6 exist as a monomer with cis configuration around the palladium atom as the Lewis base is placed cis to the PdeC bond due to antisymbiosis. The NMR spectra of 1e8 revealed the presence of a single isomer in solution and this spectral feature is ascribed to the rapid inversion of the six-membered [C,N]Pd ring due to the presence of sterically less hindered and more symmetrical 4-tolyl substituent in the ]NAr unit of the guanidine moiety.

Full text of DOI:10.1016/j.jorganchem.2013.05.030

Journal of Organometallic Chemistry 741-742 (2013) 141e147
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Six-membered [C,N] cyclopalladated sym N,N0,N00-tri(4-tolyl)
guanidines: Synthesis, reactivity studies and structural aspects
,
b
Palani Elumalai a, Natesan Thirupathi a , Munirathinam Nethaji
*
a Department of Chemistry, University of Delhi, Delhi 110 007, India
b Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560 012, India
a r t i c l e i n f o
a b s t r a c t
Six-membered [C,N] cyclopalladated sym N,N0,N00-tri(4-tolyl)guanidines, [(ArNH)2C]NAr] (sym ¼ sym-
Article history:
metrical; Ar ¼ 4-MeC6H4; LH42-tolyl) of the types [(C,N)Pd(
m-OC(O)R)]2 (1 and 2), [(C,N)Pd(m-Br)]2 (3), cis-
Received 31 March 2013
Received in revised form
16 May 2013
[(C,N)PdLBr] (4e7), and [(C,N)Pd(acac)] (8) were prepared in high yield by established methods with a
view aimed at understanding the influence of the 4-tolyl substituent of the guanidine moiety upon the
solution behaviour of 1e8. The composition of 1e8 was confirmed by elemental analysis, IR, and NMR
spectroscopy, and mass spectrometry. The molecular structures of 1e6 were determined by single-
crystal X-ray diffraction. Palladacycles 1e3 exist as a dimer in transoid conformation in the solid state
while 4e6 exist as a monomer with cis configuration around the palladium atom as the Lewis base is
placed cis to the PdeC bond due to antisymbiosis. The NMR spectra of 1e8 revealed the presence of a
single isomer in solution and this spectral feature is ascribed to the rapid inversion of the six-membered
“[C,N]Pd” ring due to the presence of sterically less hindered and more symmetrical 4-tolyl substituent in
the ]NAr unit of the guanidine moiety.
Accepted 23 May 2013
Keywords:
Palladacycle
Guanidine
Bridge-splitting reaction
nep Conjugation
Ó 2013 Elsevier B.V. All rights reserved.
1. Introduction
2. Results and discussion
Six-membered [C,N] cyclopalladated imines are one of the
interesting classes of palladacyclic compounds due to their
(i) intriguing structural and reactivity pattern such as bridge-
splitting reaction (bsr), (ii) regioselective aspects of CeH activation,
and (iii) role as precatalysts for CeC coupling reactions, and pho-
tophysical properties [1e10]. We have recently reported syntheses,
reactivity studies, structural aspects, and solution behaviour of five-
and six-membered [C,N] cyclopalladated sym N,N0,N00-triarylguani-
dines, [(ArNH)2C]NAr] (sym ¼ symmetrical; Ar ¼ 2ꢀRC6H4;
R ¼ OMe (LH22-anisyl) [11] and Me (LH22-tolyl) [12]). The number and
nature of solution species of six-membered [C,N] cyclopalladated
LH22-anisyl and LH22-tolyl varied depending upon the steric bulk and
donor capability of ortho substituent of the aryl ring in the ]NAr
unit of the guanidine moiety. Herein, we extend our investigation
on the synthesis, reactivity studies, structural aspects, and solution
behaviour of six-membered [C,N] cyclopalladated sym N,N0,N00-
2.1. Carboxylato bridged dimeric palladacycles (1 and 2)
The reaction of Pd(OC(O)R)2 (R ¼ CF3 and Bu) with LH42-tolyl in
t
1:1 mol ratio in toluene at 70 ꢁC for 6 h afforded 1 and 2 as greenish
yellow, and pale yellow crystals in 84% and 92% yields, respectively
as shown in Scheme 1.
The molecular structures of 1 and 2 are depicted in Fig. 1.
Selected bond distances and bond angles are listed in Tables 1 and
2, respectively. Palladacycles 1 and 2 exist as a dimer wherein two
palladium atoms are bridged by a pair of synesyn bidentate car-
boxylato moiety. Palladacycle 1 revealed a pseudo C2 symmetry
while 2 displayed a crystallographic C2 symmetry that passes
vertically across the centre of the Pd/Pd vector to afford a transoid
inein conformation. In this conformation, the imine nitrogen
bound to the palladium atom of one six-membered “[C,N]Pd” ring is
located trans to the identical atom of the other six-membered “[C,N]
Pd” ring and the ring NH proton of one six-membered “[C,N]Pd”
ring points toward the identical atom of the second six-membered
“[C,N]Pd” ring.
tri(4-tolyl)guanidines, [(ArNH)2C]NAr] (Ar ¼ 4-MeC6H4; LH42-tolyl
)
and the results emerged from our endeavour are presented in this
manuscript.
The palladium atom in 1 and 2 is surrounded by the oxygen
atom of two separate carboxylato moieties, an imine nitrogen atom,
and the aryl carbon atom. Further, the palladium atom revealed a
distorted square planar geometry as inferred from the dihedral
* Corresponding author. Tel.: þ91 2766 6646.
E-mail addresses: thirupathi_n@yahoo.com, tnat@chemistry.du.ac.in (N. Thirupathi).
0022-328X/$ e see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jorganchem.2013.05.030

142
P. Elumalai et al. / Journal of Organometallic Chemistry 741-742 (2013) 141e147
Scheme 1.
angle between two mean planes defined by NePdeC and OePdeO
units (5.63(22) and 2.92(6)ꢁ (1); 4.84(6)ꢁ (2)). The six-membered
“[C,N]Pd” ring exhibited a pseudo boat conformation. The bond
parameters around the palladium atom in 1 and 2 are comparable
with those reported for the related six-membered [C,N] cyclo-
palladated imines [8,11e13].
exception (see the Supplementary material for the molecular
structure of 3). The [Pd(
-Br)2Pd]2þ unit in 3 revealed a planar
m
rhomboid conformation (Pd(1)ꢀBr(1)ꢀPd(1): 95.42(1)ꢁ; Br(1)ꢀ
Pd(1)ꢀBr(1): 84.57(1)ꢁ) in contrast to the folded conformation of
the same unit observed in II [12]. The aforementioned difference is
ascribed to the presence of sterically less hindered 4-tolyl substit-
uent in the ]NAr unit of the guanidine moiety of 3. The degree of
The degree of nep conjugation involving the lone pair of the
ring and exocyclic amino nitrogen atoms with C]N
guanidine unit can be estimated from the values of DCN and DCN
p
* orbital of the
ne
p
conjugation involving the lonepair of the endocyclic and the
* orbital in 3 are
0
,
exocyclic amino nitrogen atoms with C]N p
ꢀ
respectively. The DCN value is the difference between the C]N
double bond and the adjacent endocyclic CeN single bond dis-
comparable as reflected from the values of DCN ¼ 0.051(6) A and
0
ꢀ
DCN ¼ 0.053(6) A. Both the amino nitrogen atoms in 3 are planar.
0
tances, whereas the DCN value is the difference between the C]N
double bond and the adjacent exocyclic CeN single bond distances
2.3. Monomeric palladacycles (4e8)
ꢀ
[11]. The values of DCN (0.047(8), and 0.036(8) Å (1); 0.061(6) A (2))
0
are comparable or smaller than the values of DCN (0.050(8), and
Palladacycle 1 was subjected to the bsr with 2,6-lutidine and
PTA in CH2Cl2 at ambient temperature to afford 4, and 5 in 96% and
94% yields, respectively. Similarly, 3 was subjected to the bsr with
2,6-lutidine, and PTA in CH2Cl2 at ambient temperature to afford 6,
and 7 in 97% and 86% yields, respectively (see Scheme 3). Pallada-
cycle 3 was treated with Na(acac) (acac ¼ acetylacetonate) in
CH2Cl2 at ambient temperature to afford a bis-chelated pallada-
cycle, 8 in 97% yield as illustrated in Scheme 4.
ꢀ
ꢀ
0.071(8) A (1); 0.069(6) A (2)) and these values in turn are com-
parable or smaller than the values of DCN and DCN0 observed for free
guanidine, LH42-tolyl
ne
atom with C]N
(
DCN ¼ 0.106(4) A; DCN ¼ 0.077(4) A) [14]. Thus,
conjugation involving the lone pair of the ring amino nitrogen
* orbital of the guanidine unit in 1 and 2 is
0
ꢀ
ꢀ
p
p
comparable or greater than that observed with the exocyclic amino
nitrogen atom. Both the amino nitrogen atoms in 1 and 2 are planar.
The 1H and 13C NMR spectra of 1 and 2 revealed the presence of
a single isomer in solution. In principle, acetato bridged six-
membered [C,N] cyclopalladated 2-benzylpyridine [15] and LH42-
The molecular structures of 4 and 5 are depicted in Fig. 2.
Selected bond distances and bond angles are listed in Table 3. The
molecular structure of 6 is practically identical to that found in [Pd
tolyl
{k
2(C,N)eC6H3Me-3(NHC(NHAr)(]NAr))-2}Br(2,6-Me2C6H3N)]
such as 1 and 2 can exist as a mixture of transoid inein,
transoid ineout, and transoid outeout conformers in solution.
(Ar ¼ 2-MeC6H4 (III); see the Supplementary material for the
molecular structure of 6). Two molecules crystallized in an asym-
metric unit in the case of 4 and the structural features are described
here only for molecule 1. The palladium atom is surrounded by the
imine nitrogen, the aryl carbon, nitrogen or phosphorus atom of the
Lewis base, and oxygen atom of the TFA (4 and 5) or bromide (6).
The palladium atom revealed a slightly distorted square planar
geometry. The angle between NPdC and OPdE planes (E ¼ N or P) in
4e6 are 2.79(28), 8.08(9), 11.37(17)ꢁ, respectively. The Lewis base is
coordinated to the palladium atom in cis relation with respect to
the PdeC bond due to antisymbiosis [16]. The molecular structures
of six-membered [C,N] cyclopalladated imines of the type [(C,N)
PdX(phosphine)] are known to contain the phosphine in cis
orientation with respect to the PdeC bond [5,7,11,12] due to anti-
symbiosis. The six-membered “[C,N]Pd” ring in 4e6 adopts a
pseudo boat conformation.
Further, [Pd{k m-OAc)]2
2(C,N)eC6H3Me-3(NHC(NHAr)(]NAr))-2}(
(Ar ¼ 2-MeC6H4; I), which was present in transoid inein conformer
in the solid state was shown to equilibrate with a small quantity of
k2-O,O0-OAc monomeric [C,N] cyclopalladated LH22-tolyl in solution
due to the presence of sterically hindered 2-tolyl substituent in the
]NAr unit of the guanidine moiety [12]. It appears that the rate of
six-membered “[C,N]Pd” ring inversion among three conformers
mentioned above is faster than the NMR time scale due to the
presence of sterically less hindered 4-tolyl substituent in the ]NAr
unit of the guanidine moiety of 1 and 2. Hence, the NMR spectra of
1 and 2 apparently indicated the presence of only one isomer in
solution.
2.2. Bromo bridged dimeric palladacycle (3)
ꢀ
Palladacycle 1 was subjected to a metathetical reaction with LiBr
in aq. ethanol at 80 ꢁC to afford 3 as yellow crystals in 94% yield as
illustrated in Scheme 2. The molecular structure of 3 is practically
The PdeC distance in 4e6 (1.982(5) Å (4), 1.978(3) A (5), and
ꢀ
1.983(3) A (6)), the PdeN distances in 4 and 6 (PdeNguanidine: 2.016(4)
ꢀ
ꢀ
Å (4), 2.038(2) A (6); PdeNlutidine ¼ 2.060(4) Å (4), 2.049(2) A (6)) are
identical to that found in [Pd{
k
2(C,N)eC6H3Me-3(NHC(NHAr)(]
comparable with the corresponding distances observed around the
ꢀ
ꢀ
NAr))-2}(m-Br)]2 (Ar ¼ 2-MeC6H4; II [12]) with the following
palladium atom in III (PdeC ¼ 1.985(2) A; PdeNguanidine ¼ 2.034(1) A;

P. Elumalai et al. / Journal of Organometallic Chemistry 741-742 (2013) 141e147
143
Table 1
ꢁ
ꢀ
Selected bond distances (A) and bond angles ( ) for 1.
Pd(1)eC(21)
Pd(1)eO(3)
Pd(1)eN(1)
Pd(1)eO(1)
Pd(2)eC(43)
Pd(2)eN(4)
Pd(2)eO(2)
Pd(2)eO(4)
N(1)eC(12)
N(2)eC(12)
N(3)eC(12)
N(3)eC(20)
N(4)eC(34)
N(5)eC(34)
N(6)eC(34)
N(6)eC(42)
1.955(5)
2.090(3)
2.003(4)
2.167(3)
1.947(5)
2.017(4)
2.110(4)
2.170(4)
1.311(6)
1.358(6)
1.361(6)
1.404(6)
1.308(6)
1.379(7)
1.344(6)
1.408(6)
Pd(1)/Pd(2)
3.0054(5)
C(21)ePd(1)eN(1)
N(1)ePd(1)eO(3)
C(21)ePd(1)eO(3)
C(21)ePd(1)eO(1)
N(1)ePd(1)eO(1)
C(21)ePd(1)eN(1)
C(43)ePd(2)eN(4)
C(43)ePd(2)eO(2)
N(4)ePd(2)eO(2)
C(43)ePd(2)eO(4)
N(4)ePd(2)eO(4)
C(12)eN(2)eC(13)
C(12)eN(3)eC(20)
C(34)eN(5)eC(35)
C(34)eN(6)eC(42)
89.3(2)
178.2(1)
91.9(2)
172.8(2)
95.2(1)
89.3(2)
90.2(2)
92.7(2)
176.3(2)
175.4(2)
94.0(2)
123.5(4)
126.1(4)
123.0(4)
127.2(4)
six-membered “[C,N]Pd” ring inversion. When the rate of six-
membered “[C,N]Pd” ring inversion is comparable with the NMR
timescale, two conformers can be detected and this situation per-
sists particularly when the palladium atom is present in sterically
more hindered environment [12,17]. When the palladium is present
in sterically less hindered environment as has been observed in the
six-membered [C,N] cyclopalladated 2-neopentylpyridine of the
type [(C,N)PdCl(3,5-Me2C6H3N)] [18], the six-membered “[C,N]Pd”
ring inversion occurs faster than the NMR time scale. Though pal-
ladacycles 4 and 6 possess sterically hindered 2,6-lutidine, the six-
membered [C,N] ring inversion appears to occur faster than the
NMR timescale due to the presence of sterically less hindered 4-
tolyl substituent in the ]NAr unit of the guanidine moiety.
In conclusion, four classes of six-membered [C,N] cyclo-
palladated LH42-tolyl were isolated in good yield and characterised by
elemental analysis, IR and NMR spectroscopy and the molecular
structures of six of them were determined by single-crystal X-ray
diffraction. The subtle differences observed in the structures of six-
membered [C,N] cyclopalladated LH42-tolyl with those of LH22-tolyl
were highlighted. The new palladacycles revealed the presence of
a single isomer in solution and this is attributed to the rapid
inversion of the six-membered “[C,N]Pd” ring due to the presence
of a less bulky and more symmetrical 4-tolyl substituent in the ]
NAr unit of the guanidine moiety.
3. Experimental section
3.1. General considerations
LH42-tolyl was prepared according to the literature procedure [14].
Other chemicals were procured from commercial sources and used
as received. The instrumental details pertinent to IR, NMR spec-
troscopy, mass spectrometry, and elemental analysis are as re-
ported in our previous publication [19]. For few samples, 31P{1H}
Fig. 1. Molecular structures of 1 (top) and 2 (bottom) at the 50% probability level. Only
hydrogen atoms of the amino moieties are shown for clarity.
ꢀ
PdeNlutidine ¼ 2.048(1) A) [12]. The PdeNguanidine distance of 2.100(2)
ꢀ
A in 5 is longer than the corresponding distance observed in 4, and 6
due to greater trans influence of PTA in the former palladacycle than
Table 2
ꢁ
ꢀ
ꢀ
Selected bond distances (A) and bond angles ( ) for 2.
2,6-lutidine in the latter two. The value of DCN ¼ 0.039(5) A in 6 is
slightly smaller than the corresponding value known for III
Pd(1)eO(1)
Pd(1)eO(2)
Pd(1)eN(1)
Pd(1)eC(10)
N(1)eC(1)
N(2)eC(1)
N(3)eC(1)
N(2)eC(9)
Pd(1)/Pd(1)
2.137(2)
2.045(2)
2.014(2)
1.959(3)
1.296(4)
1.357(4)
1.365(4)
1.403(4)
2.9214(9)
O(1)ePd(1)eN(1)
O(1)ePd(1)eC(10)
O(2)ePd(1)eN(1)
O(2)ePd(1)eC(10)
Pd(1)eC(10)eC(9)
N(2)eC(9)eC(10)
C(1)eN(2)eC(9)
N(1)eC(1)eN(2)
N(2)eC(1)eN(3)
N(1)eC(1)eN(3)
93.1(1)
175.0(1)
176.6(1)
91.1(1)
122.4(2)
122.7(3)
127.1(3)
121.9(3)
114.8(3)
121.9(3)
ꢀ
(
DCN ¼ 0.052(2)0A) [12] indicating a better ne
p conjugation in the
ꢀ
former. The DCN value of 0.043(4) A in 6 is comparable with the
0
ꢀ
corresponding value known for II (DCN ¼ 0.050(2) A). Both the amino
nitrogen atoms in 4e6 are planar.
The 1H and 13C NMR spectra of 4 and 6 revealed the presence of
only one isomer in solution. Six-membered [C,N] cyclopalladated 2-
benzylbenzothiazole and LH22-tolyl of the type [(C,N)PdX(2,6-
Me2C6H3N)] were shown to exist as a mixture of two boat con-
formers [12,17] and these conformers interconvert via the
O(1)ePd(1)eO(2)
85.5(1)

144
P. Elumalai et al. / Journal of Organometallic Chemistry 741-742 (2013) 141e147
Scheme 4.
Scheme 2.
3.2.2. Palladacycle 2
Palladacycle 2 was prepared from LH42-tolyl (107 mg, 0.325 mmol)
and Pd(OC(O)tBu)2 (100 mg, 0.324 mmol) in toluene (20 mL) and
purified by a procedure analogous to that described previously for
and 19F NMR spectra were recorded on a Bruker AMX 400 MHz
NMR spectrometer operating at field strengths of 85.8, and
282.4 MHz, respectively. The d( d(
31P) and 19F) values are reported
relative to 85% H3PO4 (external standard) and CFCl3, respectively
and are proton decoupled.
3.2. Synthesis and characterization
3.2.1. Palladacycle 1
A 50 mL Schlenk flask was charged with LH42-tolyl (248 mg,
0.753 mmol) and Pd(OC(O)CF3)2 (250 mg, 0.752 mmol) in toluene
(20 mL). The contents in the flask were stirred and heated simul-
taneously at 70 ꢁC for 6 h under the atmosphere of nitrogen. Sub-
sequently, the reaction mixture was cooled and filtered through a
Whatman filter paper. The filtrate was diluted with chloroform
(10 mL) and set aside at ambient temperature for several hours to
afford 1 as greenish yellow crystals in 84% yield (376 mg,
0.633 mmol). FTꢀIR (KBr, cmꢀ1): v(NH) 3414 (w); na(OCO) 1685 (vs);
n
(C]N) 1633 (s); ns(OCO) 1512 (m);
n
(CF3) 1206 (vs); 1147 (m). 1H
NMR (CDCl3, 300 MHz):
d
2.22, 2.37, 2.42 (each s, 3 ꢂ 3 H, CH3), 5.66
(s,1 H, NH), 6.29 (d, JHH ¼ 7.5 Hz,1 H, ArH), 6.38 (br, 2 H, ArH), 6.72 (d,
JHH ¼ 7.8 Hz, 2 H, ArH), 6.90 (d, JHH ¼ 8.1 Hz, 2 H, ArH), 6.95 (s, 1 H,
ArH or NH), 7.11 (d, JHH ¼ 7.8 Hz, 2 H, ArH), 7.29 (s, 2 H, ArH or NH).13
C
NMR (75.5 MHz, CDCl3):
d 20.78, 20.90, 20.94 (CH3), 112.80 (ArC/
ArCH), 115.16 (q, 1JCF ¼ 287.9 Hz, CF3), 118.28, 124.62, 125.54, 126.16,
129.83, 130.69, 131.22, 132.84, 133.56, 135.55, 136.02, 136.92, 141.30,
144.40 (ArC/ArCH, and C]N),163.54 (q, 2JCF ¼ 37.5 Hz, OC(O)).19FNMR
(CDCl3, 282.4 MHz): d e 75.0. Anal. Calcd for C48H44N6O4F6Pd2$C7H8
(Mw: 1095.75 þ 92.14): C, 55.61; H, 4.41; N, 7.07%. Found: C, 55.64;
H, 4.41; N, 7.04. Greenish yellow crystals of 1$3S(O)Me2 suitable for
X-ray diffraction were grown from Me2S(O) at ambient temperature
over a period of several days.
Fig. 2. Molecular structures of 4 (top) and 5 (bottom) at the 50% probability level. Only
Scheme 3.
hydrogen atoms of the amino moieties are shown for clarity.

P. Elumalai et al. / Journal of Organometallic Chemistry 741-742 (2013) 141e147
145
Table 3
6.10 (s, 1 H, ArH or NH), 6.28 (d, JHH ¼ 7.8 Hz, 1 H, ArH), 6.54 (s, 1 H,
ArH or NH), 6.73 (d, JHH ¼ 7.5 Hz,1 H, ArH), 6.99 (d, JHH ¼ 8.1 Hz, 2 H,
ArH), 7.09 (d, JHH ¼ 7.8 Hz, 2 H, ArH), 7.18 (br, 4 H, ArH), 7.23 (d,
JHH ¼ 8.4 Hz, 2 H, ArH), 7.57 (t, JHH ¼ 7.6 Hz, 1 H, NC5H3(CH3)2e2,6).
ꢁ
ꢀ
Selected bond distances (A) and bond angles ( ) for 4 and 5.
4
5
Pd(1)eC(17)
Pd(1)eN(1)
Pd(1)eN(4)/Pd(1)eP(1)
Pd(1)eO(1)
N(1)eC(8)
N(2)eC(8)
1.982(5)
2.016(4)
2.060(4)
2.139(3)
1.311(6)
1.371(6)
1.348(6)
1.413(6)
1.978(3)
2.100(2)
13C NMR (100.5 MHz, CDCl3):
d 20.9, 21.0 (CH3), 27.7 (NC5H3(CH3)2-
2,6), 114.1 (ArC/ArCH), 116.4 (q, 1JCF ¼ 293.2 Hz, CF3), 120.4, 122.5,
125.4, 125.6, 126.5, 130.1, 130.8, 131.5, 133.7, 134.4, 135.8, 136.2,
137.3, 138.0, 141.9, 146.4, 160.1 (ArC/ArCH, and C]N), 160.5 (q,
2.2397(8)
2.181(2)
1.317(4)
1.361(4)
1.367(4)
1.417(4)
3JCF ¼ 34.5 Hz, OC(O)). 19F NMR (CDCl3, 282.4 MHz):
d e 75.1. Anal.
N(3)eC(8)
N(3)eC(16)
Calcd for C31H31N4O2F3Pd (Mw: 655.03): C, 56.84; H, 4.77; N, 8.55%.
Found: C, 56.75; H, 4.83; N, 8.39. Crystals suitable for X-ray
diffraction were grown from CH2Cl2/MeOH mixture over a period of
several days at ambient condition.
C(17)ePd(1)eN(1)
90.4(2)
93.53(9)
91.04(9)
171.23(6)
90.22(6)
126.2(2)
122.0(2)
125.7(3)
113.9(2)
120.4(3)
117.4(4)
84.9(1)
91.04(9)
171.23(6)
177.3(1)
93.53(9)
90.22(6)
126.2(2)
122.0(2)
125.7(3)
120.4(3)
113.9(2)
C(17)ePd(1)eN(4)/C(17)ePd(1)eP(1)
N(1)ePd(1)eN(4)/N(1)ePd(1)eP(1)
C(17)ePd(1)eO(1)
N(1)ePd(1)eO(1)
N(4)ePd(1)eO(1)/P(1)ePd(1)eO(1)
C(8)eN(2)eC(9)
C(8)eN(3)eC(16)
N(1)eC(8)eN(2)
N(1)eC(8)eN(3)
N(2)eC(8)eN(3)
3.2.5. Palladacycle 5
Palladacycle 5 was prepared from 1 (100 mg, 0.091 mmol) and
PTA (30.0 mg, 0.191 mmol) in CH2Cl2 (7 mL) and purified by a
procedure analogous to that described previously for 4. Yield of
5$0.5CH2Cl2: 94% (121 mg, 0.858 mmol). FTeIR (KBr, cmꢀ1):
n
(NH)
(C]N) 1623 (s);
(CF3) 1200 (s); 1144 (m). 1H NMR (CDCl3,
3362 (br m); 3322 (br m); na(OCO) 1673 (vs);
ns(OCO) 1459 (m);
300 MHz):
n
n
1. Yield: 92% (160 mg, 0.149 mmol). FTꢀIR (KBr, cmꢀ1):
n
(NH) 3387
d
2.43, 2.47, 2.51 (each s, 3 ꢂ 3 H, CH3), 4.28 (s, 3 ꢂ 2 H,
(m); na(OCO) 1628 (s);
n
(C]N) 1604 (vs); ns(OCO) 1458 (m). 1H NMR
d 0.78 (s, 9 H, C(CH3)3), 2.18, 2.37, 2.38 (each s,
CH2, PTA), 4.57 (s, 3 ꢂ 2 H, CH2, PTA), 6.45 (d, JHH ¼ 8.4 Hz, 1 H, ArH),
6.49 (s, 2 H, ArH and NH), 6.93 (d, JHH ¼ 7.2 Hz, 1 H, ArH), 7.09 (d,
JHH ¼ 8.1 Hz, 2 H, ArH), 7.15 (d, JHH ¼ 7.8 Hz, 2 H, ArH), 7.26 (d,
JHH ¼ 7.8 Hz, 2 H, ArH), 7.35 (d, JHH ¼ 7.8 Hz, 2 H, ArH), 7.40 (s, 1 H,
(CDCl3, 400 MHz):
3 ꢂ 3 H, CH3), 5.66 (s, 1 H, ArH), 6.12 (br, 1 H, NH), 6.35 (d,
JHH ¼ 7.8 Hz, 2 H, ArH), 6.38 (s, 1 H, ArH), 6.71 (d, JHH ¼ 7.8 Hz, 2 H,
ArH), 6.78 (d, JHH ¼ 7.8 Hz, 2 H, ArH), 6.90 (d, JHH ¼ 7.8 Hz, 1 H, ArH),
7.05 (d, JHH ¼ 8.2 Hz, 2 H, ArH), 7.40 (s, 1 H, NH). 13C NMR
NH). 13C NMR (100.5 MHz, CDCl3):
d 20.8, 20.9 (CH3), 51.0 (d,
3
1JCP ¼ 14.4 Hz, PCH2N), 73.1 (d, JCP ¼ 6.7 Hz, NCH2N), 115.9 (ArC/
(100.5 MHz, CDCl3):
d 20.9, 21.1 (CH3), 28.0 (C(CH3)3), 39.6
ArC), 116.3 (q, 1JCF ¼ 291.9 Hz, CF3), 125.3, 125.6, 125.9, 130.0, 130.7,
3
(C(CH3)3), 112.1, 122.4, 124.3, 124.7, 126.6, 129.5, 130.6, 130.7, 133.9,
134.1, 134.7, 136.4, 137.1, 142.5, 144.6 (ArC/ArCH, and C]N), 185.2
(OC(O)). Anal. Calcd for C54H62N6O4Pd2 (Mw: 1071.96): C, 60.51; H,
5.83; N, 7.84%. Found: C, 60.55; H, 5.69; N, 7.83.
132.3 (d, JPC ¼ 7.7 Hz), 133.6, 135.4, 136.0, 137.2, 139.8 (d,
2JPC ¼ 23.2 Hz), 141.1, 148.3 (ArC/ArCH, and C]N), 161.2 (q,
3JCF ¼ 35.1 Hz, OC(O)). 19F NMR (CDCl3, 282.4 MHz):
d
ꢀ74.4. 31P
NMR (CDCl3, 161.8 MHz):
d
e 51.3. MS (TOF-ESþ), m/z (intensity %),
[ion]: 706 (18), [M þ H]þ; 482 (100), [LH34-tolyl þ OC(O)CF3 þ K]þ.
Anal. Calcd for C30H34N6O2PF3Pd (Mw: 705.03): C, 51.11; H, 4.86; N,
11.92%. Found: C, 51.05; H, 4.66; N, 11.70. Crystals suitable for X-ray
diffraction were grown from CH2Cl2/MeOH mixture over a period of
several days at ambient condition.
3.2.3. Palladacycle 3
Palladacycle 3 was prepared from 1 (500 mg, 0.420 mmol) and
excess of LiBr (198 mg, 2.280 mmol) in ethanol: water (27/3, v/v)
mixture following the procedure previously published for the
related palladacycle [11]. Yield: 94% (405 mg, 0.393 mmol). FTꢀIR
(KBr, cmꢀ1):
400 MHz):
n
(NH) 3404 (br);
n
(C]N) 1625 (vs). 1H NMR (CDCl3,
2.22, 2.30, 2.34 (each s, 3 ꢂ 3 H, CH3), 6.15 (s, 1 H, NH),
3.2.6. Palladacycle 6
d
Palladacycle 6 was prepared from 3 (100 mg, 0.097 mmol) and
2,6-lutidine (23.0 mg, 0.215 mmol) in CH2Cl2 (7 mL) and purified by
a procedure analogous to that described previously for 4. Yield: 97%
6.18 (d, JHH ¼ 7.8 Hz, 1 H, ArH), 6.34 (s, 1 H, ArH), 6.69 (d,
JHH ¼ 7.8 Hz,1 H, ArH), 6.90 (d, JHH ¼ 8.0 Hz, 2 H, ArH), 7.13 (br s, 2 H,
ArH), 7.17 (d, JHH ¼ 8.3 Hz, 2 H, ArH), 7.27 (br, 3 H, ArH and NH). 13
C
(117 mg, 0.188 mmol). FTꢀIR (KBr, cmꢀ1):
n
(NH) 3401 (w); 3272 (br
NMR (100.5 MHz, CDCl3):
d
20.9, 21.1, 21.2 (CH3), 113.6, 113.7 124.4,
m); n d 1.97, 2.32, 2.36
(C]N) 1622 (s). 1H NMR (CDCl3, 300 MHz):
125.4,125.6,127.1,127.5,129.7,130.1,130.8,132.0,133.5,133.9,135.4,
135.7, 137.3, 140.1, 143.4, 147.2 (ArC/ArCH, and C]N). MS (TOF-ESþ),
m/z (intensity %), [ion]: 516 (97) [(C,N)PdBr þ H]þ; 475 (77), [(C,N)
Pd þ K]þ; 329 (100), [LH42-tolyl]þ. Anal. Calcd for C44H44N6Br2Pd2
(Mw: 1029.52): C, 51.33; H, 4.31; N, 8.16%. Found: C, 51.32; H, 4.34;
N, 8.12. Greenish yellow crystals of 3$2CHCl3 suitable for X-ray
diffraction were grown from chloroform/toluene mixture at
ambient temperature over a period of several days.
(each s, 3 ꢂ 3 H, CH3), 3.14 (s, 6 H, NC5H3(CH3)2-2,6), 5.76 (s,1 H, ArH
or NH), 6.29 (d, JHH ¼ 7.8 Hz, 1 H, ArH), 6.38, 6.44 (each s, 2 ꢂ 1 H,
ArH or NH), 6.71 (d, JHH ¼ 7.8 Hz, 1 H, ArH), 6.94 (d, JHH ¼ 7.5 Hz, 2 H,
ArH), 7.08 (d, JHH ¼ 7.8 Hz, 2 H, ArH), 7.20 (d, JHH ¼ 7.8 Hz, 4 H, ArH),
7.29 (d, JHH ¼ 7.8 Hz, 2 H, C5H3N(CH3)2e2,6), 7.52 (t, JHH ¼ 7.6 Hz, 1
H, C5H3N(CH3)2e2,6). 13C NMR (100.5 MHz, CDCl3):
d 20.9, 21.0, 21.2
(CH3), 28.3 (NC5H3(CH3)2-2,6), 113.6, 122.6, 125.2, 125.5, 125.6,
127.3, 129.7, 130.7, 131.7, 134.0, 135.0, 135.4, 137.1, 137.6, 143.9, 147.4,
159.6 (ArC/ArCH, and C]N). MS (TOF-ESþ), m/z (intensity %), [ion]:
623 (53), [M þ H]þ; 622 (39), [M]þ; 554 (26), [M e L þ K]þ; 352
(100), [LH42-tolyl þ Na]þ. Anal. Calcd for C29H31N4BrPd (Mw: 621.91):
C, 56.00; H, 5.02; N, 9.01%. Found: C, 55.89; H, 4.70; N, 8.99. Crystals
suitable for X-ray diffraction were grown from CH2Cl2/MeOH
mixture over a period of several days at ambient condition.
3.2.4. Palladacycle 4
A 25 mL round bottom flask was charged with 1 (100 mg,
0.091 mmol) and CH2Cl2 (7 mL) solution of 2,6-lutidine (21 mg,
0.20 mmol). The suspension was stirred for 12 h at room temper-
ature to afford a clear pale yellow solution. The solution was
concentrated under vacuum to about 2 mL and layered with
methanol to afford 4$0.5H2O as pale yellow crystals in 96% (0.115 g,
3.2.7. Palladacycle 7
0.175 mmol) yield. FTꢀIR (KBr, cmꢀ1):
n
(NH) 3399 (w); 3277 (br);
(CF3) 1198
1.98, 2.33, 2.38 (each s,
3 ꢂ 3 H, CH3), 3.23 (s, 6 H, NC5H3(CH3)2-2,6), 5.86 (s,1 H, ArH or NH),
Palladacycle 7 was prepared from 3 (100 mg, 0.097 mmol) and
PTA (0.032 g, 0.204 mmol) in CH2Cl2 (7 mL) and purified by a
procedure analogous to that described previously for 4. Yield: 86%
na(OCO) 1681 (vs); n(C]N) 1628 (s); ns(OCO) 1470 (m); n
(vs); 1132 (s). 1H NMR (CDCl3, 300 MHz):
d
(126 mg, 0.083 mmol). FTꢀIR (KBr, cmꢀ1):
n(NH) 3390 (m); 3232 (br

146
P. Elumalai et al. / Journal of Organometallic Chemistry 741-742 (2013) 141e147
Table 4
Crystallographic data for 1$3S(O)Me2, 2, 4$0.5H2O, and 5$CH2Cl2.
1$3S(O)Me2
2
4$0.5H2O
5$CH2Cl2
Formula
fw
Temp (K)
Wavelength (
C54H62F6N6O7Pd2S3
1330.08
100(2)
0.71073
Monoclinic
P21/c
20.4129(14)
12.9294(8)
23.3913(16)
90
110.388(2)
90
5786.8(7)
4
1.527
2712
0.804
1.06e26.37
92,379
11,843
710
0.0555
0.1484
1.166
1.872/e1.348
C54H62N6O4Pd2
1071.90
298(2)
0.71073
Monoclinic
C2/c
19.011(5)
15.548(5)
17.710(5)
90
97.418(5)
90
5191(3)
4
1.372
2208
C124H124F12N16O9Pd4
2635.99
100(2)
0.71073
Monoclinic
C2/c
36.595(4)
12.6104(13)
27.708(3)
90
113.386(5)
90
11,736(2)
4
1.492
5376
0.687
1.21e26.37
60,985
11,991
745
0.0557
0.1486
1.112
3.811/e1.062
C61H68ClF6N12O4P2Pd2
1457.46
100(2)
0.71073
Monoclinic
C2/c
26.002(3)
10.3808(12)
24.601(3)
90
112.176(5)
90
6149.1(12)
4
1.574
2972
0.757
1.69e26.37
47,447
6306
398
0.0425
0.1125
1.167
1.646/e1.073
l
)
Crystal system
Space group
ꢀ
a (A)
ꢀ
b (A)
ꢀ
c (A)
a
b
g
(ꢁ)
(ꢁ)
(ꢁ)
3
ꢀ
Volume (A )
Z
rcalcd (g cmꢀ3
F(000)
)
m
(Mo K
a
) (mmꢀ1
)
0.742
q
range (ꢁ)
2.96e26.37
22,446
5312
No. of reflns collected
No. of reflns used
Parameters
317
R1 [I > 2
s
(I)]a
0.0373
0.0936
1.148
wR2 (all reflns)b
GooFc
ꢀꢀ3
Largest diff peak/hole (e$A
)
0.688/e0.585
a
R1 ¼ SjjFoj ꢀ jFcjj/SjFoj.
b
wR2 ¼ {S[w(F2o ꢀ F2c)2]/S[w(Fo2)2]}1/2
.
c
S ¼ {S[w(F2o ꢀ F2c)2]/(nep)}1/2
.
m);
n
(C]N) 1600 (vs). 1H NMR (CDCl3, 300 MHz):
d
2.30, 2.34, 2.36
diffractometer with
chromator. The frames were collected by
10 s per frame with SMART [20]. The measured intensities were
reduced to F2 and corrected for absorption with SADABS [21]. In-
tensity data of suitably sized crystals of 2, and 3$2CHCl3 were
a
CCD area detector, graphite mono-
, 4, and 2 rotation at
(each s, 3 ꢂ 3 H, CH3), 4.30 (s, 3 ꢂ 2 H, CH2, PTA), 4.44 (s, 3 ꢂ 2 H,
CH2, PTA), 6.31 (s, 2 H, NH), 6.40 (d, JHH ¼ 7.8 Hz, 1 H, ArH), 6.80 (d,
JHH ¼ 7.2 Hz,1 H, ArH), 6.92 (d, JHH ¼ 8.1 Hz, 2 H, ArH), 7.04e7.08 (m,
3 H, ArH), 7.15 (d, JHH ¼ 8.1 Hz, 2 H, ArH), 7.24 (d, JHH ¼ 8.1 Hz, 2 H,
u
q
ArH). 31P NMR (161.8 MHz, CDCl3):
d
e 49.7. MS (TOF-ESþ), m/z
collected on an Oxford Xcalibur S diffractometer (4-circle
ometer, Sapphire-3 CCD detector, scans, graphite mono-
chromator, and a single wavelength enhanced X-ray source with
MoK radiation) [22]. Pre-experiment, data collection, data
k goni-
(intensity %), [ion]: 673 (15), [M þ H]þ; 457 (100), [(C,N)Pd þ Na]þ.
Anal. Calcd for C28H34N6PBrPd$CH2Cl2 (Mw: 671.9 þ 84.94): C,
46.02; H, 4.79; N, 11.10%. Found: C, 46.15; H, 4.76; N, 11.29.
u
a
reduction, and absorption corrections were performed with the
CrysAlisPro software suite [23]. The structures were solved by
direct methods using SIR 92 [24], which revealed the atomic po-
sitions, and refined using the SHELX-97 program package [25] and
SHELXL97 (within the WinGX program package) [26]. Non-
hydrogen atoms were refined anisotropically. CeH/NeH hydrogen
atoms were placed in geometrically calculated positions by using a
riding model. The molecular structures were created with Olex2
program [27]. Details of data collections, structure solutions and
refinements are presented in Table 4.
3.2.8. Palladacycle 8
A 25 mL round bottom flask was charged with 3 (100 mg,
0.097 mmol) and subsequently dissolved in CH2Cl2 (7 mL). Na(acac)
(25.0 mg, 0.205 mmol) was added in portion to the above-
mentioned solution and the resulting suspension was stirred. The
suspension slowly turned into a clear colourless solution after
15 min and subsequently NaBr precipitated out. The solution was
filtrated and the filtrate was concentrated under vacuum to about
2 mL, layered with n-hexane and stored at ambient temperature
over a period of several hours to afford 8 in 97% (0.101 g,
0.094 mmol) yield. FTꢀIR (KBr, cmꢀ1):
n
(NH) 3403 (w); 3340 (w);
Acknowledgements
n
(C]N) 1630 (m); n
(CeO) 1588 (vs). 1H NMR (CDCl3, 400 MHz):
d
1.56, 1.98 (each s, 2 ꢂ 3 H, acacCH3), 2.31, 2.33, 2.36 (each s,
The authors acknowledge the (i) Department of Science and
Technology, New Delhi, for a research grant (grant no. SR/S1/IC-04/
2010), (ii) University Science Instrumentation Center, University of
Delhi for elemental analyses, spectroscopic, and X-ray diffraction
measurements, (iii) Indian Institute of Technology Roorkee for X-
ray diffraction measurements for 1$3S(O)Me2, 4$0.5H2O, 5$CH2Cl2,
and 6.
3 ꢂ 3 H, CH3), 5.17 (s, 1 H, acacCH), 5.91 (s, 1 H, NH), 6.25 (d,
JHH ¼ 7.8 Hz, 1 H, ArH), 6.50 (s, 1 H, NH), 6.77 (dd, JHH ¼ 7.8; 3.1 Hz,
1 H, ArH), 6.96 (d, JHH ¼ 8.2 Hz, 2 H, ArH), 7.16 (br, 4 H, ArH), 7.19 (d,
JHH ¼ 7.8 Hz, 2 H, ArH), 7.48 (br, 1 H, ArH). 13C NMR (100.5 MHz,
CDCl3):
d 21.0, 21.1, 21.2 (CH3), 27.2, 27.6 (acacCH3), 99.6 (acacCH),
113.2, 123.5, 125.4, 125.5, 127.7, 129.5, 130.8, 131.2, 134.0, 134.2,
134.7, 135.4, 137.1, 141.6, 146.4 (ArC/ArCH, and C]N), 185.7, 187.6
(acac-C]O). Anal. Calcd for C27H29N3O2Pd (Mw: 533.97): C, 60.73;
H, 5.47; N, 7.87%. Found: C, 60.70; H, 5.67; N, 7.82.
Appendix A. Supplementary material
CCDC 921726e921731 (1e6) contain the supplementary crys-
tallographic data for this paper. These data can be obtained free of
charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or
from the Cambridge Crystallographic Data Centre, 12 Union Road,
3.2.9. X-ray crystallography
Intensity data of suitably sized crystals of 1$3S(O)Me2, 4$0.5H2O,
5$CH2Cl2, and 6 were collected on a Bruker AXS SMART-APEX

P. Elumalai et al. / Journal of Organometallic Chemistry 741-742 (2013) 141e147
147
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Appendix B. Supplementary material
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Supplementary material related to this article can be found
at http://dx.doi.org/10.1016/j.jorganchem.2013.05.030. These data
include MOL files and InChiKeys of the most important compounds
described in this article.
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