Synthesis and characterisation of palladium(II) and platinum(II) complexes with N,N′,N-tridentate ligands based on N, N-di(2-picolyl) cycloalkylamine and polymerisation of methyl methacrylate

Article abstract of DOI:10.1016/j.poly.2013.07.021

The reaction of Pd(CH₃CN)₂Cl2 and NaClO₄ with the ancillary ligands N, N-di(2-picolyl)cyclopentylamine (L1), N, N-di(2-picolyl)cyclohexylamine (L₂) and N, N-di(2-picolyl) cycloheptylamine (L₃) in ethanol yielded a new series of [(N,N′,N)-PdCl]ClO₄ complexes, i.e., [PdL₁]ClO ₄, [PdL₂]ClO₄ and [PdL₃]ClO ₄, respectively. The reaction of Pt(CH₃CN) ₂Cl₂ and NaClO₄ with the ancillary ligands L1-L3 gave only the stable [PtL₂]ClO₄ complex. The Pd and Pt atoms of all of the complexes had an almost square-planar geometry involving three nitrogen atoms and a chloro ligand. Moreover, the unit cell included a ClO4 anion as the counterion. The bond lengths between the metal and nitrogen atoms are a little affected by the substituted cycloalkyl group, however those between the metal and the chloro ligand are not affected. The catalytic activity of the Pd(II) and Pt(II) complexes toward the polymerisation of methyl methacrylate in the presence of modified methylaluminoxane resulted in a high molecular weight and a narrow polydispersity index; the highest activity was measured for [PdL₃]ClO₄ at 60 °C.

Full text of DOI:10.1016/j.poly.2013.07.021

Accepted Manuscript
Synthesis and characterization of palladium(II) and platinum(II) complexes with
N,N’ ,N-tridentate ligands based on N,N-di(2-picolyl)cycloalkylamine and pol‐
ymerization of methyl methacrylate
Dongil Kim, Sunghoon Kim, Eunhee Kim, Ha-Jin Lee, Hyosun Lee
PII:
S0277-5387(13)00546-9
DOI:
http://dx.doi.org/10.1016/j.poly.2013.07.021
POLY 10252
Reference:
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Polyhedron
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9 April 2013
10 July 2013
Please cite this article as: D. Kim, S. Kim, E. Kim, H-J. Lee, H. Lee, Synthesis and characterization of palladium(II)
and platinum(II) complexes with N,N’ ,N-tridentate ligands based on N,N-di(2-picolyl)cycloalkylamine and
polymerization of methyl methacrylate, Polyhedron (2013), doi: http://dx.doi.org/10.1016/j.poly.2013.07.021
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Synthesis and Characterization of Palladium(II) and Platinum(II) Complexes with
N,N’,N-Tridentate Ligands Based on N,N-Di(2-picolyl)cycloalkylamine and
Polymerization of Methyl Methacrylate
Dongil Kima, Sunghoon Kima, Eunhee Kima, Ha-Jin Leeb, Hyosun Leea,*
aDepartment of Chemistry and Green-Nano Materials Research Center, Kyungpook National
University, 1370 Sankyuk-dong, Buk-gu, Daegu-city, 702-701, Republic of Korea
bJeonju Center, Korea Basic Science Institute (KBSI), 634-18 Keumam-dong, Dukjin-gu,
Jeonju, 561-180, Republic of Korea
----------------------------------
*Corresponding author. Tel: +82-53-950-5337; fax: +82-53-950-6330
E-mail address: hyosunlee@knu.ac.kr (H. Lee)
1

Abstract
The reaction of Pd(CH3CN)2Cl2 and NaClO4 with the ancillary ligands N,N-di(2-
picolyl)cyclopentylamine (L1), N,N-di(2-picolyl)cyclohexylamine (L2) and N,N-di(2-
picolyl)cycloheptylamine (L3) in ethanol yielded a new series of [(N,N´,N)-PdCl]ClO4
complexes, i.e. [PdL1]ClO4, [PdL2]ClO4 and [PdL3]ClO4, respectively. The reaction of
Pt(CH3CN)2Cl2 and NaClO4 with the ancillary ligands L1–L3 gave only the stable
[PtL2]ClO4 complex. The Pd and Pt atoms of all of the complexes had an almost square-
planar geometry involving three nitrogen atoms and a chloro ligand. Moreover, the unit cell
−
included a ClO4 anion as the counterion. The bond lengths between the metal and nitrogen
atoms are a little affected by the substituted cycloalkyl group, however those between the
metal and the chloro ligand are not affected. The catalytic activity of the Pd(II) and Pt(II)
complexes toward the polymerisation of methyl methacrylate in the presence of modified
methylaluminoxane resulted in a high molecular weight and a narrow polydispersity index;
the highest activity was measured for [PdL3]ClO4 at 60 °C.
Keywords: palladium, platinum, N,N-di(2-picolyl)cycloalkylamine, MMA
1. Introduction
2

The chemistry of transition metal complexes with the N,N-bidentate ligand 2,2´-
dipyridylamine (dpa) and its derivatives has been extensively studied because of the potential
applications as new luminescent materials for sensors [1-4], anticancer agents [5-10] and
catalysts [11,12], including the polymerisation of α-olefins and polar olefins [13-15].
Specifically, various transition metal complexes with N-substituted picolyl derivatives such
as N,N,N´,N´-tetrakis(2-pyridylmethylbenzene)-1,4-diamine (1,4-tpbd) [16], bis(2-
pyridylmethyl)amine (bpma) [17-20], bis[2-(2-pyridylethyl)]-(2-pyridylmethyl)amine (pmap)
[21], 1,2-bis(dipyridylaminomethyl)benzene [22], tris[2-(2-pyridyl)alkyl]amine [23] and
bis(2,2’-dipicolyl)benzylamine [24] have been extensively studied for chemical and
biological applications. Ni(II), Zn(II), Cu(II) and Pd(II) complexes with N-substituted di(2-
picolyl)amine derivatives [25-29] were prepared to investigate their enzymatic activities in
biological systems, i.e. with respect to hydrolysis, catalytic CO2 conversion to oxalate,
photoluminescence, cytotoxic activity and kinetics [30-39]. The coordination compounds of
Pd(II) and Pt(II) with tridentate ligands form very stable mononuclear square-planar
complexes. However, the structures of Pd(II) and Pt(II) complexes with N,N´,N-tridentate
picolyl-based ligands containing N,N-dipicolylcycloalkyl and their utility in the
polymerisation of methyl methacrylate (MMA) have not been established.
Accordingly, we describe here the synthesis and characterisation of complexes of Pd(II)
and Pt(II) with the N,N´,N-tridentate ligands N,N-di(2-picolyl)cyclopentylamine (L1), N,N-
di(2-picolyl)cyclohexylamine (L2) and N,N-di(2-picolyl)cycloheptylamine (L3). The Pd(II)
1
complexes were characterised by H and 13C NMR spectroscopy, Fourier transform infrared
(FTIR) spectroscopy and elemental analysis; the Pd(II) complexes [PdL1]ClO4, [PdL2]ClO4
and [PdL3]ClO4 and the Pt(II) complex [PtL2]ClO4 were also structurally characterised. The
catalytic activities of the synthesized Pd(II) and Pt(II) complexes toward MMA
polymerisation in toluene at 0, 25 and 60 °C were also investigated.
2. Experimental
2.1. Materials and physical measurements
PdCl2, PtCl2, 2-picolylchloride hydrochloride, cyclopentylamine, cyclohexylamine,
cycloheptylamine, NaClO4·H2O, NaOH and MMA were purchased from Sigma-Aldrich.
Anhydrous solvents, such as ethanol, dimethylformamide (DMF), diethyl ether, acetonitrile
and dichloromethane, were purchased from Merck KGaA and were used without further
3

purification. Deionised water was prepared using a Millipore Milli-Q system. Modified
methylaluminoxane (MMAO) was purchased from Tosoh Finechem Corporation as a toluene
solution (6.9 wt% aluminium) and was used without further purification. Elemental analyses
(C, H, N) of the prepared complexes were carried out using an elemental analyser (EA 1108;
1
Carlo-Erba). H NMR (400 MHz) and 13C NMR (400 MHz) spectra were recorded on a
Bruker Advance Digital 400 NMR spectrometer; chemical shifts were recorded in ppm units
( relative to SiMe4 as the internal standard. Infrared (IR) spectra were recorded on a Bruker
FT/IR-Alpha (neat) and the data are reported in reciprocal centimeters. The molecular
weights and molecular weight distributions of the obtained poly(methyl methacrylate)
(PMMA) were determined using gel permeation chromatography (GPC) (CHCl3, Alliance
e2695; Waters Corp.). The glass transition temperature (Tg) was determined using a thermal
analyser (Q2000; TA Instruments).
2.2. Preparation of the ligands
2.2.1. N,N-di(2-picolyl)cyclopentylamine (L1)
L1 was prepared by a similar procedure as described in the literature [24,40-42]. A water
solution (15.0 mL) of cyclopentylamine (1.70 g, 0.020 mol) was added to a water solution
(15.0 mL) of 2-picolylchloride hydrochloride (6.58 g, 0.040 mol) and an added NaOH pellet
(3.20 g, 0.080 mol). After 5 days of stirring at rt, the product was extracted with
dichloromethane. The reaction solution was dried over MgSO4, then the filtrate solvent was
removed under reduced pressure to give a brown oil (4.01 g, 75.0%). Analysis calculated for
1
C17H21N3: C, 76.37; H, 7.92; N, 15.72. Found: C, 73.50; H, 7.72; N, 15.17%. H NMR
(DMSO-d6, 400 MHz) δ: 8.44 (d, 2H, J = 2.4 Hz, pyridine), 7.70 (t, 2H, J = 7.6 Hz, pyridine),
7.17 (d, 2H, J = 7.6 Hz, pyridine), 7.18 (t, 2H, J = 4.8 Hz, pyridine), 3.77 (s, 4H, CH2-
pyridine), 3.12 (m, 1H, -NCH-), 1.72 (m, 2H, cyclopentyl), 1.55 (m, 2H, cyclopentyl), 1.42
(m, 4H, cyclopentyl). 13C NMR (DMSO-d6, 400 MHz) δ: 162.34 (pyridine), 148.76
(pyridine), 136.78 (pyridine), 122.79 (pyridine), 120.44 (pyridine), 70.91 (N-C, cyclopentyl),
57.92 (-CH2-pyridine), 28.96 (cyclopentyl), 23.90 (cyclopentyl). IR (liquid neat; cm-1):
2950(w), 2866(w), 1588(w), 1471(w), 1433(w), 1355(s), 1124(w), 987(s), 755(w), 617(w).
2.2.2. N,N-di(2-picolyl)cyclohexylamine (L2)
L2 [43] was prepared by an analogous method as described for L1, except utilizing
cyclohexylamine. The product was obtained as a brown powder (4.61 g, 82.0%). Analysis
4

calculated for C18H23N3: C, 40.14; H, 4.16; N, 8.26. Found: C, 40.10; H, 4.16; N, 8.33%. 1H
NMR (DMSO-d6, 400 MHz) δ: 8.42 (d, 2H, J = 4.8 Hz, pyridine), 7.70 (t, 2H, J = 7.6 Hz,
pyridine), 7.52 (d, 2H, J = 7.6 Hz, pyridine), 7.19 (t, 2H, J = 7.2 Hz, pyridine), 3.78 (s, 4H,
CH2-pyridine), 2.41 (m, 1H, -NCH-), 1.83 (m, 2H, cyclohexyl), 1.71 (m, 2H, cyclohexyl),
1.53 (m, 1H, cyclohexyl), 1.30 (m, 1H, cyclohexyl), 1.10 (m, 4H, cyclohexyl). 13C NMR
(DMSO-d6, 400 MHz) δ: 162.28 (pyridine), 148.89 (pyridine), 136.81 (pyridine), 122.37
(pyridine), 122.22 (pyridine), 59.72 (N-C, cyclohexyl), 56.39 (-CH2-pyridine), 32.70
(cyclohexyl), 26.08 (cyclohexyl), 24.42 (cyclohexyl). IR (solid neat; cm-1): 2923(w),
2851(w), 1587(w), 1440(w), 1359(s), 1127(w), 754(s), 620(s).
2.2.3. N,N-di(2-picolyl)cycloheptylamine (L3)
L3 was prepared by an analogous method as described for L1, except utilizing
cycloheptylamine. The product was obtained as a yellow oil (4.02 g, 68.0%). Analysis
calculated for C18H23N3: C, 76.83; H, 8.24; N, 14.93. Found: C, 70.53; H, 8.64; N, 13.64%.
1H NMR (DMSO-d6, 400 MHz) δ: 8.46 (d, 2H, J = 4.8 Hz, pyridine), 7.58 (t, 2H, J = 7.2 Hz,
pyridine), 7.55 (d, 2H, J = 10.4 Hz, pyridine), 7.18 (t, 2H, J = 6.4 Hz, pyridine), 3.84 (s, 4H,
CH2-pyridine), 2.66 (m, 1H, -NCH-), 1.99 (m, 2H, cycloheptyl), 1.67 (m, 2H, cycloheptyl),
1.57 (m, 2H, cycloheptyl), 1.47 (m, 4H, cycloheptyl), 1.34 (m, 2H, cycloheptyl). 13C NMR
(DMSO-d6, 400 MHz) δ: 161.87 (pyridine), 148.93 (pyridine), 136.89 (pyridine), 122.64
(pyridine), 121.42 (pyridine), 61.46 (N-C, cyclohexyl), 57.19 (-CH2-pyridine), 30.98
(cycloheptyl), 28.74 (cycloheptyl), 26.30 (cycloheptyl). IR (liquid neat; cm-1): 2921(w),
2853(w), 1587(w), 1436(w), 1361(s), 1124(w), 1048(s), 750(w), 618(s).
2.3. Preparation of the Pd(II) and Pt(II) complexes
2.3.1. N,N-di(2-picolyl)cyclopentylamino(chloro)palladium(II) perchlorate ([PdL1]ClO4)
A solution of L1 (0.14 g, 0.50 mmol) and NaClO4·H2O (0.071 g, 0.50 mmol) in dried ethanol
(10.0 mL) was added to a solution of anhydrous Pd(CH3CN)2Cl2 [44-46] (0.13 g, 0.50 mmol)
in dried ethanol (10.0 mL) at room temperature. Precipitation of a white material occurred
while stirring at room temperature for 12 hours. A yellow powder was filtered and washed
with ethanol (50.0 mL), followed by washing with diethyl ether (50.0 mL) (0.21 g, 83%).
Crystals of [PdL1]ClO4, suitable for X-ray analysis, were obtained within three days from a
diethyl ether (10.0mL) diffusion into a DMF solution (10.0 mL) of [PdL1]ClO4 (0.050 g).
Analysis calculated for [C17H21ClN3Pd]ClO4: C, 40.14; H, 4.16; N, 8.26. Found: C, 40.10; H,
5

4.16; N, 8.33%. 1H NMR (DMSO-d6, 400 MHz) δ: 8.57 (d, 2H, J = 4.8 Hz, pyridine), 8.19 (t,
2H, J = 7.8 Hz, pyridine), 7.74 (d, 2H, J = 10.0 Hz, pyridine), 7.62 (t, 2H, J = 6.4 Hz,
pyridine), 5.52(d, 2H, J = 16.2 Hz, CH2-pyridine), 4.65 (d, 2H, J = 16.2 Hz, CH2-pyridine),
3.39 (m, 1H, -NCH-), 1.77 (m, 2H, cyclopentyl), 1.60 (m, 2H, cyclopentyl), 1.34 (m, 4H,
cyclopentyl). 13C NMR (DMSO-d6, 400 MHz): δ: 166.11 (pyridine), 150.32 (pyridine),
142.03 (pyridine), 125.30 (pyridine), 123.26 (pyridine), 73.62 (N-C, cyclopentyl), 66.39 (-
CH2-pyridine), 29.83 (cyclopentyl), 22.22 (cyclopentyl). IR (solid neat; cm-1): 3745(w),
3618(w), 1747(w), 1701(w), 1649(s), 1612(s), 1541(w), 1075(w), 760(s), 620(s).
2.3.2. N,N-di(2-picolyl)cyclohexylamino(chloro)palladium(II) perchlorate ([PdL2]ClO4)
[PdL2]ClO4 was prepared according to a similar procedure as described for [PdL1]ClO4. The
yellow powder was filtered and washed with ethanol (50.0 mL), followed by washing with
diethyl ether (50.0 mL) (0.24 g, 90%). X-ray quality crystals of [PdL2]ClO4 were obtained
within five days from a diethyl ether (10.0mL) diffusion into a DMF solution (10.0 mL) of
[PdL2]ClO4 (0.05 g). Analysis calculated for [C18H23ClN3Pd]ClO4: C, 41.36; H, 4.44; N,
8.04. Found: C, 41.20; H, 4.43; N, 8.00%. 1H NMR (DMSO-d6, 400 MHz) δ: 8.56 (d, 2H, J =
6.0 Hz, pyridine), 8.19 (t, 2H, J = 8.0 Hz, pyridine), 7.73 (d, 2H, J = 7.8 Hz, pyridine), 7.61
(t, 2H, J = 6.4 Hz, pyridine), 5.47 (d, 2H, J = 16.4 Hz, CH2-pyridine), 4.76 (d, 2H, J = 16.4
Hz, CH2-pyridine), 2.88 (m, 1H, -NCH-), 2.23 (m, 2H, cyclohexyl), 1.65 (m, 2H,
cyclohexyl), 1.49 (m, 1H, cyclohexyl), 1.23 (m, 5H, cyclohexyl). 13C NMR (DMSO-d6, 400
MHz) δ: 166.09 (pyridine), 150.38 (pyridine), 142.01 (pyridine), 125.31 (pyridine), 123.15
(pyridine), 70.14 (N-C, cyclohexyl), 64.18 (-CH2-pyridine), 30.33 (cyclohexyl), 25.34
(cyclohexyl), 24.91 (cyclohexyl). IR (solid neat; cm-1) ; 3199(w), 2939(w), 2862(s), 1616(w),
1491(s), 1443(w), 1076(w), 917(s), 765(s), 620(s).
2.3.3. N,N-di(2-picolyl)cycloheptylamino(chloro)palladium(II) perchlorate ([PdL3]ClO4)
[PdL3]ClO4 was prepared according to a similar procedure as described for [PdL1]ClO4. The
yellow powder was filtered and washed with ethanol (50.0 mL), followed by washing with
diethyl ether (50.0 mL) (0.24 g, 88%). X-ray quality crystals of [PdL3]ClO4 were obtained
within five days from a diethyl ether (10.0mL) diffusion into a DMF solution (10.0 mL) of
[PdL3]ClO4 (0.05 g). Analysis calculated for [C19H25ClN3Pd]ClO4: C, 42.52; H, 4.69; N,
7.83. Found: C, 42.30; H, 4.71; N, 7.88%. 1H NMR (DMSO-d6, 400 MHz) δ: 8.57 (d, 2H, J =
4.8 Hz, pyridine), 8.20 (t, 2H, J = 7.2 Hz, pyridine), 7.74 (d, 2H, J = 7.5 Hz, pyridine), 7.62
6

(t, 2H, J = 6.8 Hz, pyridine), 5.36 (d, 2H, J = 16.6 Hz, CH2-pyridine), 4.63 (d, 2H, J = 16.6
Hz, CH2-pyridine), 2.95 (m, 1H, -NCH-), 1.63 (m, 2H, cycloheptyl), 1.46 (m, 3H,
cycloheptyl), 1.37 (m, 7H, cycloheptyl). 13C NMR (DMSO-d6, 400 MHz) δ: 165.75
(pyridine), 150.52 (pyridine), 141.99 (pyridine), 125.42 (pyridine), 123.53 (pyridine), 70.79
(N-C, cyclohexyl), 63.63 (-CH2-pyridine), 31.46 (cycloheptyl), 27.03 (cycloheptyl), 24.71
(cycloheptyl). IR (solid neat; cm-1) ; 3054(w), 2927(w), 2861(s), 1612(s), 1478(s), 1427(w),
1288(s), 1256(s), 1051(w), 846(s), 737(w), 707(w), 613(s).
2.3.4. N,N-di(2-picolyl)cyclohexylamino(chloro)platinum(II) perchlorate ([PtL2]ClO4).
A solution of L2 (0.14 g, 0.50 mmol) and NaClO4·H2O (0.071 g, 0.50 mmol) in dried ethanol
(10.0 mL) was added to a solution of anhydrous Pt(CH3CN)2Cl2 (0.17 g, 0.50 mmol) in dried
ethanol (10.0mL) at room temperature. Precipitation of a yellow material occurred while
stirring at room temperature for 12 hours. The yellow powder was filtered and washed with
ethanol (50.0 mL), followed by washing with diethyl ether (50.0 mL) (0.27 g, 88%). X-ray
quality crystals of [PtL2]ClO4 [43] were obtained within three days from a diethyl ether
diffusion into a DMF solution of [PtL2]ClO4. Analysis calculated for [C18H23ClN3Pt]ClO4:
1
C, 35.36; H, 3.79; N, 6.87. Found: C, 35.31; H, 3.90; N, 6.99%. H NMR (DMSO-d6, 400
MHz) δ: 8.61 (d, 2H, J = 4.8 Hz, pyridine), 8.11 (t, 2H, J = 7.8 Hz, pyridine), 7.61 (d, 2H, J =
7.6 Hz, pyridine), 7.48 (t, 2H, J = 6.4 Hz, pyridine), 5.10 (d, 2H, 16.4 Hz, CH2-pyridine),
4.86 (d, 2H, 16.4 Hz, CH2-pyridine), 2.65 (m, 1H, -NCH-), 1.97 (m, 1H, cyclohexyl), 1.50
(m, 2H, cyclohexyl), 1.30 (m, 1H, cyclohexyl), 1.04 (m, 5H, cyclohexyl), 0.86 (m, 1H,
cyclohexyl). 13C NMR (DMSO-d6, 400 MHz) δ: 165.43 (pyridine), 147.63 (pyridine), 140.27
(pyridine), 124.07 (pyridine), 121.60 (pyridine), 70.74 (-NCH-, cyclohexyl), 64.24 (-NCH2-
pyridine), 28.57 (cyclohexyl), 23.64 (cyclohexyl), 23.37 (cyclohexyl). IR (solid neat; cm-1) ;
3744(w), 3297(w), 2941(w), 1699(s), 1649(w), 1587(w), 1524(s), 1453(w), 1308(s), 1101(w),
1067(w), 923(s), 779(s), 623(s), 580(s).
2.4. X-ray crystallographic studies
A yellow cubic-shaped crystal was picked up with paraffin oil and mounted on a Bruker
SMART CCD diffractometer equipped with a graphite-monochromated Mo Kα (λ = 0.71073
Å) radiation source and a nitrogen cold stream (-100 °C). Data collection and integration
were performed with SMART (Bruker, 2000) and SAINT-Plus (Bruker, 2001) software [47].
Semi-empirical absorption corrections based on equivalent reflections were applied by
7

SADABS [48]. The structure was solved by direct methods and refined by full-matrix least-
squares on F2 using SHELXTL [49]. All non-hydrogen atoms were refined anisotropically,
and hydrogen atoms were added in their geometrically ideal positions. The crystal and
structure refinement data for all of the structures are summarised in Table 1. The final cycle
of the refinement converged with R1 [I > 2σ(I)] = 0.0506, wR2 [I > 2σ(I)] = 0.1087 for
[PdL1]ClO4 , R1 [I > 2σ(I)] = 0.0398, wR2 [I > 2σ(I)] = 0.0803 for [PdL2]ClO4, R1 [I > 2σ(I)]
= 0.0448, wR2 [I > 2σ(I)] = 0.1000 for [PdL3]ClO4 and R1 [I > 2σ(I)] = 0.0365, wR2 [I >
2σ(I)] = 0.0766 for [PtL1]ClO4.
Table 1
2.5 Catalytic activity of MMA polymerization
In a Schlenk line, the complex (7.6 mg for [PdL1]ClO4, 7.8 mg for [PdL2]ClO4, 8.0 mg
for [PdL3]ClO4 and 9.1 mg for [PtL2]ClO4) was dissolved in dry toluene (2.3 mL), and then
MMAO (3.25 mL, 7.50 mmol) was added as a co-catalyst. The solution was stirred for 20
min at 0, 25 or 60 °C. MMA (5.0 mL, 47.1 mmol) was added to the reaction mixture and
stirred for 10 min to 2 h, as required, to obtain a viscous solution. Methanol (50.0 mL) was
added to terminate the polymerisation. The reaction mixture was poured into a large quantity
of MeOH (500 mL), and then 35% HCl (5.0 mL) was injected to remove the remaining
MMAO co-catalyst. The PMMA was obtained by filtration and dried under vacuum at a mild
temperature for 24 h.
3. Results and discussion
3.1. Synthesis and chemical properties
Scheme 1 shows the synthesis of the ligands and their Pd(II) and Pt(II) complexes. The
ligands were obtained in yields of 75 (L1), 82 (L2) and 68% (L3) from the cyclo(X)amine (X
= pentyl, hexyl, heptyl) and 2-picolylchloride hydrochloride in water. The [PdL1]ClO4
(83%), [PdL2]ClO4 (90%), [PdL3]ClO4 (88%) and [PtL2]ClO4 (88%) complexes were
obtained from the corresponding ligands and Pd(CH3CN)2Cl2 and Pt(CH3CN)2Cl2,
respectively, in anhydrous ethanol. Attempts to synthesise [PtL1]ClO4 and [PtL3]ClO4 were
not successful, despite changing the solvent, temperature and counter anion. The synthesis
and DFT calculations of [PtL2]ClO4 were reported previously [43], however its molecular
structure was not determined.
Scheme 1
8

The 1H and 13C NMR and elemental analysis results were consistent with the formulation of
1
the Pd(II) and Pt(II) complexes. The H NMR peaks of the Pd(II) complexes were shifted to
1
lower field by about 0.1-0.5 relative to the signals for the free ligands. Specifically, the H
NMR peaks for CH2–pyridine appeared as a singlet at 3.77 (L1), 3.78 (L2) and 3.84 (L3),
whilst the CH2–pyridine signal for the Pd(II) complexes appeared as two doublets centred at
5.52 (2JH-H = 16.2 Hz) and 4.65 (2JH-H =16.2 Hz) for [PdL1]ClO4, 5.47 (2JH-H = 16.4 Hz)
and 4.76 (2JH-H = 16.4 Hz) for [PdL2]ClO4 and 5.36 (2JH-H = 16.6 Hz) and 4.63 (2JH-H = 16.6
1
Hz) for [PdL3]ClO4. The H NMR peaks of the Pt(II) complex were shifted by about 0.1-
1
1.5 to lower field relative to the signals for the free ligands. In particular, the H NMR peak
for CH2–pyridine in the Pt(II) complex appeared as two doublets centred at 5.10 (2JH-H
=
16.4 Hz) and 4.86 (2JH-H = 16.4 Hz). This indicates that the 1H NMR peaks for CH2–pyridine
in the Pd(II) and Pt(II) complexes are affected by the cyclo(X) (X = pentyl, hexyl, heptyl) N-
substituent. This is because the cyclo(X) group is not coplanar with the planar pyridine group.
The 13C NMR peaks of both the Pd(II) and Pt(II) complexes were found at lower field (by
about 2-10) relative to the signals for the free ligands. The 13C NMR peaks for CH2–
pyridine in the Pd(II) complexes appeared as a singlet because the two pyridine groups are
coplanar; the signal moved downfield on increasing the ring size of the cycloalkyl moiety
[cyclopentyl ( 66.39) > cyclohexyl ( 64.18) > cycloheptyl ( 63.63)].
3.2. Discussion of the X-ray crystal structures
The ORTEP drawings of the complexes are shown in Figs. 1-4 for [PdL1]ClO4, [PdL2]ClO4,
[PdL3]ClO4 and [PtL2]ClO4, respectively. Fundamental crystal data and experimental
structure refinement for the Pd(II) and Pt(II) complexes are given Table 1. Selected bond
lengths and angles are listed in Table 2. A single crystal suitable for X-ray crystallography
was obtained by diffusing diethyl ether (10.0 mL) into a DMF solution (10.0 mL). The
coordination geometry around the Pd(II) and Pt(II) centres is almost square planar, consisting
of the three N atoms of the Ln ligands and one Cl atom ligand. Additionally, the unit cell of
−
the Pd(II) and Pt(II) complexes includes a ClO4 anion as the counterion.
Fig. 1
Fig. 2
9

Fig. 3
Fig. 4
Table 2
The N atom of the cycloalkyl that is connected by three carbon atoms and a Pd or Pt atom
nearly has the angle of an sp3 hybrid orbital. The y–z plane of the cycloalkyl group is
perpendicular to the x–y plane of the Pd(II) and Pt(II) centre. This explains why the 1H NMR
CH2–pyridine signals for the Pd(II) and Pt(II) complexes appeared as two doublets. The Pd–
N(cycloalkyl) bond lengths of the synthesised complexes are 2.028(6) Å for [PdL1]ClO4,
2.043(5) Å for [PdL2]ClO4 and 2.056(4) Å for [PdL3]ClO4, and these are slightly affected
by steric hindrance from the cycloalkyl group. The bond lengths are longer for the Pd(II)
complexes, which has larger rings. However, the other bond lengths are little affected by the
presence of the cycloalkyl substituent compared to those of chloro{methyldi-[(6-methyl-2-
pyridyl)methyl]amine}palladium chloride, having a Pd-N(1) bond length of 2.018(8) Å [50].
Four of the cyclopentyl carbon atoms (C14, C15, C16, C17) of [PdL1]ClO4 are
approximately coplanar, with the fifth carbon atom (C13) out of plane. The cyclohexyl group
of [PdL2]ClO4 is in a stable chair formation. The cycloheptyl group of [PdL3]ClO4 appears
in the stable twist-chair formation. The N(3)–Pd(1)–Cl(1) angles for the complexes are nearly
linear and are 178.30(19)° for [PdL1]ClO4, 178.03(14)° for [PdL2]ClO4 and 178.94(14)° for
[PdL3]ClO4. The average [N(3)–Pd(1)–N(2) and N(3)–Pd(1)–N(1)] bond angles of the two
five-membered rings are 83.55° for [PdL1]ClO4, 83.85° for [PdL2]ClO4 and 84.01° for
[PdL3]ClO4. These rings are bent because of ring strain, and are somewhat affected by the
cycloalkyl ring size. In contrast, the Pt(1)–N(3) bond length in the complex [PtL2]ClO4 is
2.021(8) Å and the average of the Pt(1)–N(1) and Pt(1)–N(2) bond lengths is 2.008 Å.
The cyclohexyl groups in [PtL2]ClO4 and [PdL2]ClO4 are also in the stable chair
formation. The N(3)–Pt(1)–Cl(1) angle for [PtL2]ClO4 is nearly linear (177.5°). The average
of the N(3)–Pt(1)–N(1) and N(3)–Pt(1)–N(2) bond angles for the two five-membered rings is
83.4°; the rings are distorted because of ring strain. All of the bond distances and bond angles
in [PtL2]ClO4 are very similar to those recently reported for [Pt{bis(2-
pyridylmethyl)amine)}Cl]Cl·H2O [51].
Intramolecular Pd(II) or Pt(II)···C-H( and ) weak interactions between a side chain of an
N-cycloalkyl group and Pd(II) or Pt(II) are attributable to the location of the cycloalkyl group
in the ligand structure. Compared to Pd complexes containing an N-alkyl substituted N,N-
10

di(2-picolyl)alkyl amine [26], these Pd(II) and Pt(II) complexes with N-cycloalkyl substituted
N,N-di(2-picolyl)cycloalkylamine have similar C–H( and )···M and C( )···M interactions
(Table 3).
Table 3
[PdL1]ClO4, [PdL2]ClO4 and [PtL2]ClO4, with N-cyclopentyl and N-cyclohexyl
substituents (Figs. 1, 2 and 4) exhibit weak C-H( and )···M contacts (Pd(II)···C = 2.926 and
2.964 Å, Pt(II) ···C = 2.967 Å) that involve the second methylene group (C13 position) from
the tertiary nitrogen atom (Table 3). The results indicate that the metal ion and the methylene
group are weakly bonding [52-56].
2.4. Discussion of MMA polymerization
All of the Pd(II) complexes and [PtL2]ClO4 could be activated with MMAO to polymerise
MMA. Since Pd(II) and Pt(II) complexes are cationic, their polymerizations of MMA were
also carried out without MMAO. However, a tracee amount of PMMA was obtained.
The obtained PMMA had a Tg value ranging from 120 to 145 °C [57-59]. The polymers were
isolated as white solids and characterised by GPC in THF using standard polystyrene as the
1
reference. The triad microstructure of the PMMA was analysed by H NMR spectroscopy.
The results of the polymerisations are summarised in Table 4 and include tacticity (isotactic
(mm), heterotactic (mr), syndiotactic (rr)) and the polydispersity index (PDI) as the average
degree of polymerisation in terms of the numbers of structural units and of molecules [60].
Table 4
To confirm the catalytic activity toward MMA polymerisation, a blank polymerisation of
MMA was performed with Pd(CH3CN)2Cl2, Pt(CH3CN)2Cl2 and MMAO at a specified
1
temperature. The tacticity of the PMMA was identified by the H NMR peaks present at
0.85 (syndiotactic), 1.02 (heterotactic) and 1.21 (isotactic) [61]. The catalytic activities and
PDIs for the Pd(II) complexes increased with the increasing ring size of the cycloalkyl group
(cyclopentyl < cyclohexyl < cycloheptyl) and with increasing temperature (0 < 25 < 60 °C).
Presumably, the electron-rich cloud around the Pd metal in [PdL3]ClO4 provided increased
activity compared to the electronic effects with [PdL1]ClO4 and [PdL2]ClO4. The PDIs of
the Pd(II) complexes were observed similarly in the range 1.92–2.41. The PDI range
11

decreased slightly with increasing PMMA molecular weight. These results are explained by
the narrower PDI range of the higher-molecular-weight polymer [62,63]. [PdL3]ClO4 had the
highest activity and provided PMMA with the narrowest PDI and highest molecular weight at
60 °C. This results is comparable to previous cobalt complexes with N,N-bis(1H-pyrazolyl-1-
methyl)aniline [64]. The activity of [PtL2]ClO4 towards the polymerisation of MMA at 60 °C
was very low compared with the corresponding Pd(II) complex [PdL2]ClO4. However, the
opposite was observed at 0 and 25 °C, i.e. higher activity was found for [PtL2]ClO4 than for
[PdL2]ClO4. The syndiotacticity was not sufficiently high to infer a coordination
polymerisation mechanism, but it was similar in all of the synthesised Pd(II) complexes.
However, if it was considered that there was some contribution of a coordination
polymerisation mechanism, the syndiotacticity was only slightly affected by the cycloalkyl
ring size and the polymerisation temperature. Thus, the activity of these Pd(II) complexes
toward MMA polymerisation should be considered in reference to the steric effect of the
metal and the polymerisation temperature.
4. Conclusion
We have investigated the synthesis and X-ray crystallographic structures of [PdL1]ClO4,
[PdL2]ClO4, [PdL3]ClO4 and [PtL2]ClO4, which were prepared by the substitution reaction
of Pd(CH3CN)2Cl2 and Pt(CH3CN)2Cl2 with N,N-di(2-picolyl)cycloalkylamino ligands
containing cycloalkyl bridging units. The coordination geometry around the Pd(II) and Pt(II)
centres were almost square-planar. The catalytic activities of the Pd(II) complexes toward
MMA polymerisation were determined: the PDI and molecular weight increased with
increasing ring size of the substituent cycloalkyl bridge (cyclopentyl < cyclohexyl <
cycloheptyl).
Acknowledgments
This research was supported by the National Research Foundation of Korea (NRF), funded
by the Ministry of the Education, Science, and Technology (MEST) (Grant No. 2012-
R1A2A2A01045730).
Appendix A. Supplementary materials
CCDC 929887~929890 contain the supplementary crystallographic data for [PdL1]ClO4,
[PdL2]ClO4 [PdL3]ClO4 and [PtL2]ClO4, respectively. These data can be obtained free of
charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge
12

Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-
336-033; or e-mail: deposit@ccdc.cam.ac.uk.
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15

R
NH2
+
+
M(CH3CN)2Cl2
+
R
N
-
ClO4
NaClO4
EtOH
2
4
R
N
H2O, rt, 5days
.
N
Cl HCl
N
N
M
Cl
NaOH
N
N
M
[ML1]ClO4 (M = Pd, R = cyclopentyl)
[ML2]ClO4 (M = Pd, R = cyclohexyl)
4 (M = Pd, R = cycloheptyl)
[ML2]ClO4 (M = Pt, R = cyclohexyl)
= Pd, Pt
L
1 (R = cyclopentyl)
[ML3]ClO
L2 (R = cyclohexyl)
L
3 (R = cycloheptyl)
Scheme 1. Synthesis of the ligands and the Pd(II) and Pt(II) complexes.
16

Table 1. Crystal data and structure refinement for the Pd(II) and Pt(II) complexes.
[PdL1]ClO4
[PdL2]ClO4
[PdL3]ClO4
[PtL2]ClO4
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
Unit cell dimensions
a (Å)
C17H21ClN3Pd, ClO4
508.67
C18H23ClN3Pd, ClO4
522.69
C19H25ClN3Pd, ClO4
536.72
C18H23ClN3Pt, ClO4
611.38
200(2)
200(2)
200(2)
200(2)
0.71073
0.71073
0.71073
0.71073
Monoclinic
P21/c
Monoclinic
P21/c
Monoclinic
P21/c
Monoclinic
P21/c
7.6306(3)
12.0847(4)
20.5565(8)
90
7.9172(3)
12.3689(5)
20.4344(7)
90
7.9255(3)
12.7413(5)
20.4875(8)
90
7.9631(4)
12.2958(6)
20.4364(9)
90
b (Å)
c (Å)
α (°)
β (°)
97.1580(10)
90
97.8260(10)
90
95.5860(10)
90
97.8630(10)
90
γ (°)
Volume (Å3), Z
Density (calculated) (Mg/m3)
Absorption coefficient (mm-1)
F(000)
1880.81(12), 4
1.796
1982.44(13), 4
1.751
2059.03(14), 4
1.731
1982.17(16), 4
2.049
1.300
1.236
1.193
7.379
1024
1056
1088
1184
Crystal size (mm3)
0.23 x 0.23 x 0.18
0.27 x 0.25 x 0.24
1.93 to 28.28
0.32 x 0.24 x 0.21
1.88 to 28.28
0.28 x 0.21 x 0.19
1.94 to 28.30
Theta range for data collection (°) 1.96 to 28.28
Index ranges
-10
-16
-25
h
k
l
8
-10
-15
-27
h
k
l
10
16
20
-10
-14
h
k
10
16
-10
-15
h
k
8
14
27
16
-21 l 27
-27 l 27
13531
14511
14402
13907
Reflections collected
4650 [R(int) = 0.0370]
99.8 %
4926 [R(int) = 0.0495]
99.8 %
5021 [R(int) = 0.0279]
98.5 %
4808 [R(int) = 0.0281]
97.4%
Independent reflections
Completeness to theta = 28.30°
Absorption correction
Refinement method
None
None
None
None
Full-matrix least-
squares on F2
4650 / 0 / 244
1.196
Full-matrix least-
squares on F2
4926 / 0 / 253
1.165
Full-matrix least-
squares on F2
5021 / 0 / 262
1.182
Full-matrix least-
squares on F2
4808 / 0 / 253
1.189
Data / restraints / parameters
Goodness-of-fit on F2
R1 = 0.0506
wR2 = 0.1087
R1 = 0.0928
wR2 = 0.1880
2.823 and -4.138
R1 = 0.0398
wR2 = 0.0803
R1 = 0.0849
wR2 = 0.1449
1.517 and -2.321
R1 = 0.0448
wR2 = 0.1000
R1 = 0.0720
wR2 = 0.1620
1.510 and -2.062
R1 = 0.0365
wR2 = 0.0766
R1 = 0.0677
wR2 = 0.1427
2.837 and -3.908
Final R indices [I>2sigma(I)]
R indices (all data)
Largest diff. peak and hole (e Å-3)
17

Table 2. Selected bond lengths (Å) and angles (°) of all the Pd(II) and Pt(II) complexes.
[PdL1]ClO4
[PdL2]ClO4
[PdL3]ClO4
[PtL2]ClO4
Bond lengths
2.008(5)
Pd(1)-N(1)
Pd(1)-N(2)
Pd(1)-N(3)
Pd(1)-Cl(1)
N(3)-C(6)
N(3)-C(7)
N(3)-C(13)
2.009(8)
2.024(6)
2.028(6)
2.293(2)
1.507(9)
1.485(10)
1.521(9)
Pd(1)-N(1)
Pd(1)-N(2)
Pd(1)-N(3)
Pd(1)-Cl(1)
N(3)-C(6)
N(3)-C(7)
N(3)-C(13)
Pd(1)-N(1)
Pd(1)-N(2)
Pd(1)-N(3)
Pd(1)-Cl(1)
N(3)-C(6)
N(3)-C(7)
N(3)-C(13)
2.009(5)
2.009(5)
2.056(4)
Pt(1)-N(1)
Pt(1)-N(2)
Pt(1)-N(3)
2.012(9)
2.004(9)
2.021(8)
2.297(3)
1.562(12)
1.496(13)
1.509(12)
2.022(5)
2.043(5)
2.2977(15)
1.506(7)
1.509(7)
1.530(7)
2.2926(15) Pt(1)-Cl(1)
1.496(7)
1.499(7)
1.514(7)
N(3)-C(6)
N(3)-C(7)
N(3)-C(13)
Bond angles
N(1)-Pd(1)-N(3)
N(3)- Pd(1)-N(2)
N(1)-Pd(1)-Cl(1)
N(2)-Pd(1)-Cl(1)
N(1)-Pd(1)-N(2)
N(3)-Pd(1)-Cl(1)
C(7)-N(3)-C(6)
C(7)-N(3)-C(13)
C(6)-N(3)-C(13)
C(7)-N(3)-Pd(1)
C(6)-N(3)-Pd(1)
C(13)-N(3)-Pd(1)
84.2(3)
N(1)-Pd(1)-N(3)
N(3)- Pd(1)-N(2)
N(1)-Pd(1)-Cl(1)
N(2)-Pd(1)-Cl(1)
N(1)-Pd(1)-N(2)
N(3)-Pd(1)-Cl(1)
C(7)-N(3)-C(6)
C(6)-N(3)-C(13)
C(7)-N(3)-C(13)
C(7)-N(3)-Pd(1)
C(6)-N(3)-Pd(1)
C(13)-N(3)-Pd(1)
83.02(19)
84.59(19)
95.49(14)
97.04(2)
165.7(2)
178.03(14)
111.9(4)
112.0(4)
113.5(4)
107.2(3)
101.3(3)
110.2(3)
N(1)-Pd(1)-N(3) 83.23(18) N(1)-Pt(1)-N(3)
N(3)- Pd(1)-N(2) 84.8(2) N(3)-Pt(1)-N(2)
84.7(3)
82.1(4)
82.9(3)
97.2(2)
N(1)-Pd(1)-Cl(1) 95.75(14) N(1)-Pt(1)-Cl(1) 97.3(3)
95.8(2)
N(2)-Pd(1)-Cl(1) 96.20(2)
N(1)-Pd(1)-N(2) 166.1(2)
N(2)-Pt(1)-Cl(1) 96.1(3)
N(1)-Pt(1)-N(2) 165.3(4)
165.7(3)
178.30(19)
112.3(6)
110.4(6)
112.6(6)
102.0(5)
108.7(5)
110.2(4)
N(3)-Pd(1)-Cl(1) 178.94(14) N(3)-Pt(1)-Cl(1) 177.5(2)
C(7)-N(3)-C(6) 113.0(4) C(7)-N(3)-C(6) 110.6(7)
C(6)-N(3)-C(13) 110.3(4)
C(7)-N(3)-C(13) 113.0(4)
C(7)-N(3)-Pd(1) 107.7(3)
C(6)-N(3)-Pd(1) 100.1(3)
C(13)-N(3)-Pd(1) 112.0(3)
C(6)-N(3)-C(13) 111.0(7)
C(7)-N(3)-C(13) 110.9(8)
C(7)-N(3)-Pt(1)
C(6)-N(3)-Pt(1)
102.5(6)
107.9(6)
C(13)-N(3)-Pt(1) 113.6(6)
18

Table 3. Selected C–H( and )···M and C( )··· M bond distances (Å).
[PdL1]ClO4
[PdL2]ClO4
[PdL3]ClO4
[PtL2]ClO4
Pd(1)···C(13)
2.924
2.926
3.126
3.722
Pd(1)···C(13)
2.945
2.964
2.806
3.713
Pd(1)···C(13)
2.975
3.075
2.767
3.475
Pt(1)···C(13)
2.967
2.988
2.823
Pd(1)···H(13)
Pd(1)···H(14a)
Pd(1)··· H(14b)
Pd(1)···H(13)
Pd(1)···H(18a)
Pd(1)··· H(18b)
Pd(1)···H(13)
Pd(1)···H(19a)
Pd(1)··· H(19b)
Pt(1)···H(13)
Pt(1)···H(14a)
Pt(1)··· H(14b) 3.735
19

Table 4. Polymerisation of MMA by the Pd(II) and Pt(II) complexes in the presence of
MMAO.
Yield
Entry Catalysta Temp.(time)
Activityc
Tg
Tacticity
%mr
Mw
Mw/Mn
d
b
(g/mol-
(g)
%mm
7.66
%rr
(g/mol)×105
0.66
(℃)
(℃)
Cat·h)×104
e
Pd(AN)2Cl2
60(2hr)
60(2hr)
60(2hr)
60(2hr)
0.88
2.93
1.20
1.40
3.63
12.8
19.2
1.3
131.47
22.81 69.53
23.87 66.44
10.92 51.88
29.71 62.09
20.11 73.14
22.06 69.58
24.83 65.64
19.73 71.43
27.37 57.48
28.36 56.18
29.51 56.96
29.43 57.27
18.94 73.29
19.04 73.11
18.91 71.87
23.70 64.15
28.78 59.63
30.37 58.34
28.96 69.78
29.34 60.44
22.81 68.07
2.90
1.88
2.09
2.06
1.97
1.92
6.02
2.97
3.15
3.95
2.25
2.14
1.93
7.54
1.70
4.13
2.56
2.41
2.04
2.41
2.93
1
2
e
Pt(AN)2Cl2
0.36
0.42
1.09
0.96
1.44
0.40
0.55
0.15
0.14
0.21
0.24
0.47
0.64
0.38
0.17
0.12
0.01
0.14
0.07
0.26
128.31
119.61
128.46
129.83
128.58
127.25
129.93
124.23
125.29
121.40
120.31
122.27
126.29
129.05
127.25
129.50
123.60
125.63
123.74
128.81
9.69
37.20
8.20
9.66
6.78
2.76
8.15
8.42
4.58
0.72
0.97
1.12
0.41
0.35
0.39
2.46
9.93
2.73
3.25
0.91
0.51
0.70
1.58
MMAOf
3
[PdL1]ClO4
4
[PdL2]ClO4 60(30min)
[PdL3]ClO4 60(10min)
6.75
5
7.36
6
[PtL2]ClO4
Pd(AN)2Cl2
60(2hr)
25(2hr)
25(2hr)
25(2hr)
25(2hr)
25(2hr)
25(2hr)
25(2hr)
0(2hr)
9.53
7
e
1.83
0.5
8.84
8
e
Pt(AN)2Cl2
15.15
15.46
13.53
13.30
7.77
9
MMAOf
0.47
0.70
0.80
1.57
2.1
10
11
12
13
14
15
16
17
18
19
20
21
[PdL1]ClO4
[PdL2]ClO4
[PdL3]ClO4
[PtL2]ClO4
7.85
e
Pd(AN)2Cl2
1.27
0.57
0.40
0.03
0.47
0.23
0.86
9.22
e
Pt(AN)2Cl2
0(2hr)
12.15
11.59
11.29
10.26
10.22
9.12
MMAOf
0(2hr)
[PdL1]ClO4
[PdL2]ClO4
[PdL3]ClO4
[PtL2]ClO4
0(2hr)
0(2hr)
0(2hr)
0(2hr)
a [Mt (II) catalyst]0 = 15 μmol, and [MMA]0/[MMAO]0/[Mt (II) catalyst]0 = 3100:500:1.
b Yield defined as the mass of dried polymer recovered/mass of monomer used. c Activity is g of
PMMA/(mol-Pd·h). d Determined by GPC eluted with THF at room temperature by filtration with
polystyrene calibration. e A blank polymerization in which Pd(AN)2Cl2 and Pt(AN)2Cl2 were also
activated by MMAO. f A blank polymerization which was done solely by MMAO.
20

Fig. 1. ORTEP drawing of [PdL1]ClO4 with thermal ellipsoids at 50% probability. Some
hydrogen atoms have been omitted for clarity.
21

Fig. 2. ORTEP drawing of [PdL2]ClO4 with thermal ellipsoids at 50% probability, showing
two different views. Some hydrogen atoms have been omitted for clarity.
22

Fig. 3. ORTEP drawing of [PdL3]ClO4 with thermal ellipsoids at 50% probability. Some
hydrogen atoms have been omitted for clarity.
23

Fig. 4. ORTEP drawing of [PtL2]ClO4 with thermal ellipsoids at 50% probability. All
hydrogen atoms have been omitted for clarity.
24

Palladium(II) and Platinum(II) Complexes with N,N’,N-Tridentate Ligands
Based on N,N-Di(2-Picolyl)Cycloalkylamine: Synthesis, Characterisation
and Polymerisation of Methyl Methacrylate
Dongil Kima, Sunghoon Kima, Eunhee Kima, Ha-Jin Leeb, Hyosun Leea,*
The complexes [PdL1]ClO4, [PdL2]ClO4, [PdL3]ClO4 and [PtL2]ClO4, where, for
example, L1 is N,N-di(2-picolyl)cyclopentylamine, were synthesized and characterized by X-
ray crystallography. The coordination geometry around the Pd(II) and Pt(II) centres were
almost square-planar and the catalytic activities of the Pd(II) complexes toward MMA
polymerisation were moderate.
25

Palladium(II) and Platinum(II) Complexes with N,N’,N-Tridentate Ligands
Based on N,N-Di(2-Picolyl)Cycloalkylamine: Synthesis, Characterisation
and Polymerisation of Methyl Methacrylate
Dongil Kima, Sunghoon Kima, Eunhee Kima, Ha-Jin Leeb, Hyosun Leea,*
The complexes [PdL1]ClO4, [PdL2]ClO4, [PdL3]ClO4 and [PtL2]ClO4, where, for
example, L1 is N,N-di(2-picolyl)cyclopentylamine, were synthesized and characterized by X-
ray crystallography. The coordination geometry around the Pd(II) and Pt(II) centres were
almost square-planar and the catalytic activities of the Pd(II) complexes toward MMA
polymerisation were moderate.
Graphical Abstract
26

Research Highlights
¾ The synthesis and molecular structures of [PdLn]ClO4 with N,N-di(2-
picolyl)cycloalkylamino ligands are reported.
−
¾ A square-planar geometry around Pd(II) and Pt(II) included a ClO4 anion in the unit
cell.
¾ [PdLn]ClO4 proved to be moderate for MMA polymerisation.
27