Cobalt(II) complexes containing N′-substituted N,N′,N-bis((1H-pyrazol-1-yl)methyl)amine ligands: The formation of four-coordinate or five-coordinate complexes as a function of the N′-substitution group in N,N′,N-bis((1H-pyrazol-1-yl)methyl)amine

Article abstract of DOI:10.1016/j.ica.2015.09.008

N,N-bis((1H-pyrazol-1-yl)methyl)(cyclohexyl)methanamine (L_A), N,N-bis((1H-pyrazol-1-yl)methyl)-2,6-diethylbenzenamine (L_B), N,N-bis((1H-pyrazol-1-yl)methyl)-4-bromobenzenamine (L_C), N,N-bis((1H-pyrazol-1-yl)methyl)cyclohex

Full text of DOI:10.1016/j.ica.2015.09.008

Accepted Manuscript
Cobalt(II) Complexes Containing N ’-Substituted N,N′,N-bis((1H-pyrazol-1-
yl)methyl)amine Ligands: The Formation of Four-Coordinate or Five-Coordi-
nate Complexes as a Function of the N ’-Substitution group in N,N′,N-bis((1H-
pyrazol-1-yl)methyl)amine
Sunghye Choi, Saira Nayab, Jongho Jeon, Sang Hyun Park, Hyosun Lee
PII:
S0020-1693(15)00446-6
http://dx.doi.org/10.1016/j.ica.2015.09.008
ICA 16683
DOI:
Reference:
Inorganica Chimica Acta
To appear in:
Received Date:
Revised Date:
Accepted Date:
25 August 2015
5 September 2015
7 September 2015
Please cite this article as: S. Choi, S. Nayab, J. Jeon, S.H. Park, H. Lee, Cobalt(II) Complexes Containing N ’-
Substituted N,N′,N-bis((1H-pyrazol-1-yl)methyl)amine Ligands: The Formation of Four-Coordinate or Five-
Coordinate Complexes as a Function of the N ’-Substitution group in N,N′,N-bis((1H-pyrazol-1-yl)methyl)amine,
Inorganica Chimica Acta (2015), doi: http://dx.doi.org/10.1016/j.ica.2015.09.008
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Cobalt(II) Complexes Containing N'-Substituted N,N′,N-bis((1H-pyrazol-1-
yl)methyl)amine Ligands: The Formation of Four-Coordinate or Five-
Coordinate Complexes as a Function of the N'-Substitution group in
N,N′,N-bis((1H-pyrazol-1-yl)methyl)amine
Sunghye Choia, Saira Nayabb, Jongho Jeonc, Sang Hyun Parkc,*, 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
bDepartment of Chemistry, Shaheed Benazir Bhutto University, Sheringal, Dir Upper, Khyber
Pakhtunkhwa, Pakistan
cResearch Division for Biotechnology, Advanced Radiation Technology Institute, Korea
Atomic Energy Research Institute(KAERI), Jeongeup, Jeonbuk, 580-185, 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
N,N-bis((1H-pyrazol-1-yl)methyl)(cyclohexyl)methanamine (LA), N,N-bis((1H-pyrazol-1-
yl)methyl)-2,6-diethylbenzenamine
bromobenzenamine (LC), N,N-bis((1H-pyrazol-1-yl)methyl)cyclohexanamine (LD), N,N-
bis((1H-pyrazol-1-yl)methyl)(furan-2-yl)methanamine (LE), N,N-bis((1H-pyrazol-1-
yl)methyl)-2-methoxyethanamine (LF), and N,N-bis((1H-pyrazol-1-yl)methyl)-3-
(LB),
N,N-bis((1H-pyrazol-1-yl)methyl)-4-
.
(methylthio)propan-1-amine (LG) with [CoCl2 6H2O] in ethanol yield a novel series of Co(II)
chloride complexes; i.e. [LnCoCl2] (Ln = LA – LG), respectively. The molecular structures of
[LnCoCl2] (Ln = LA – LC) and [LnCoCl2] (Ln = LD – LG) exist as monomeric four-
coordinated and five-coordinated complexes, respectively. [LnCoCl2] (Ln = LA – LC) showed
a distorted tetrahedral geometry involving non-coordination of the nitrogen atom of the N′-
substitution amine moiety and the Co(II) centre, resulting in the formation of an eight-
membered chelate ring. The geometry at each Co(II) centre in [LnCoCl2] (Ln = LD – LG) were
best described as a distorted trigonal bipyramid involving coordination of the nitrogen atom
of the N′-substitution amine group and the Co(II) centre. Specifically, a distorted trigonal
bipyramid was achieved in [LDCoCl2] through a coordinative interaction of the nitrogen atom
of the cyclohexylamine unit and the Co(II) atom with an σ plane of symmetry based on the
bond length of Co-Ncyclcohexylamine [2.466(4) Å]. Moreover, [LDCoCl2] showed the highest
activity for methyl methacrylate (MMA) polymerization in the presence of modified
methylaluminoxane (MMAO) at 60°C and yielded poly(methylmethacrylate) (PMMA) with a
high molecular weight (Mw) and narrower polydispersity index (PDI) compared to the other
Co(II) complexes. However, all Co(II) complexes produced syndiotactic (PMMA),
characterised using 1H-NMR spectroscopy, with ca. 0.70.
Keywords: N′-substituted N,N′,N-bis((1H-pyrazol-1-yl)methyl)amine, Co(II) complexes,
Molecular structures, Methyl methacrylate Polymerization, Syndiotacticity
2

Introduction
The coordination chemistry of pyrazole-based ligands has been extensively studied [1-
4]. Specifically, the bonding properties of pyrazole derivatives of simple amines have been
well-documented and show furnished metal complexes of varying coordination geometries
and nuclearity [1,4,5]. The versatility of the N-alkylaminopyrazole ligands is found not only
regarding the ability to prepare both bi- and tri-dentate ligands but also in the variability of
substituents of the amine and pyrazolyl rings [6-9]. Since the pioneering work of Driessen in
1982 [10,11], pyrazolyl-based chelating ligands and their transition metal complexes, due to
their structural stability and catalytic ability, have been synthesised and applied as supra-
molecules for metal-organic frames (MOF) [12,13], as catalysts for organic transformation
[14-17], as biological agents [18-20], as cancer sensors, and as hydrolysis and oxidation
agents [21-24].
More recently, N-alkylaminopyrazole ligands [25] ligated to transition metals including
Rh(I), Ru(II), Pd(II), Pt(II), Zn(II), and Co(II) have exhibited a variety of potentially useful
chemical properties [26-30], and are used as catalysts for olefin polymerisation [31-33] and
methyl methacrylate (MMA) polymerisation [34-40]. Particularly, cobalt complexes in which
we are interested as precatalyst for MMA polymerisation, extensively were used for catalysts
for ethylene polymerisation [41,42]. Previous work from our group applied Co(II), Zn(II),
and Pd(II) complexes with N,N-bis(1H-pyrazolyl-1-methyl)aniline and their derivatives for
MMA polymerisations [43-45]. These results and potential merit of pyrazole-amine based
ligands, that show fine tuning of the reactivity of the metal centre to which they are bound,
prompted us to explore the complexing properties of N,N′,N-bis((1H-pyrazol-1-
yl)methyl)amine ligands to the Co(II) centre and its catalytic capabilities.
The current study describes the synthesis and structural characterisation of four-
3

coordinated and five-coordinated monomeric Co(II) complexes supported with N′-substituted
N,N′,N-bis((1H-pyrazol-1-yl)methyl)amine ligand and its derivative serving as bi- and tri-
dentate ancillary ligands. The structural aspects of the synthesised Co(II) complexes and the
effects of various substituents attached to the N′-substituted amine moiety on catalytic
activity of MMA polymerisation in the presence of MMAO were further investigated.
2. Experimental Section
2.1. Chemicals and Physical Measurement
98% [CoCl2·6H2O], pyrazole, cyclohexylmethanamine, 2,6-diethylbenzenamine, 4-
bromobenzenamine and 2-methoxyethanamine, 95% para-formaldehyde, 99%
cyclohexylamine and (furan-2-yl)methanamine, 97% 3-(methylthio)propan-1-amine, 99.5%
MgSO4, and 99% MMA were purchased from Aldrich. Anhydrous solvents, such as methanol
(MeOH), ethanol (EtOH), acetone, dimethylformamine (DMF), diethyl ether (Et2O), and
dichloromethane (CH2Cl2) of HPLC grade were purchased from Merck and used without
further purification. Modified methylaluminoxane (MMAO) was purchased from Tosoh
Finechem Corporation as 6.9% weight aluminium in a toluene solution and used without
further purification. The 1H-pyrazolyl-1-methanol as starting material was prepared
according to reported method [10,11].
2.2. Instrumentation
1H-NMR (400.01 MHz) and 13C NMR (100.61 MHz) spectra were recorded on a
Bruker Advance Digital 400 NMR spectrometer and chemical shifts were recorded in parts-
per-million (ppm) using SiMe4 as an internal standard. Elemental analysis (C, H, N) of the
prepared complexes were carried out on an elemental analyser (EA 1108; Carlo-Erba, Milan,
4

Italy). The molecular weight and molecular weight distribution of the obtained PMMA were
determined by gel permeation chromatography (GPC) (CHCl3, Alliance e2695; Waters Corp.,
Milford, MA). Glass transition temperatures (Tg) were determined using a thermal analyser
(Q2000; TA Instruments, New Castle, DE). X-ray crystallography was carried by Western
Seoul Center of Korea Basic Science Institute.
2.3. Preparation of ligands and corresponding Co(II) complexes
2.3.1. N-((1H-pyrazol-1-yl)methyl)-N-(cyclohexylmethyl)(1H-pyrazol-1-yl)methanamine (LA)
LA was prepared by a similar procedure as described in the literature [46]. The
CH2Cl2 solution (10.0 mL) of cyclohexylmethanamine (2.26 g, 0.0200 mol) was added to
CH2Cl2 solution (30.0 mL) of 1H-1-pyrazolyl-1-methanol (3.92 g, 0.0400 mol). The reaction
solution was dried over MgSO4 after stirring at room temperature for 3 days. The filtrate
solvent under reduced pressure to give a colorless and transparent oil product was obtained
(4.38 g, 80.2%). Analysis calculated for C15H23N5: C, 65.9, H, 8.48, N, 25.6. Found: C, 65.8,
H, 8.62, N, 25.0%. 1H-NMR (CDCl3, 400 MHz): δ 7.51 (d, 2H, J = 1.2 Hz, -N=CH-CH=CH-
N-), 7.50 (d, 2H, J = 2.4 Hz, -N=CH-CH=CH-N-), 6.26 (dd, 2H, J = 1.2 Hz, J = 2.0 Hz, -
N=CH-CH=CH-N-), 4.97 (s, 4H, -N-CH2-N-), 2.45 (d, 2H, J = 2.8 Hz, -C6H11-CH2-N-),
1.72-1.65 (m, 5H, -C6H11-), 1.53-1.50 (m, 1H, ipso-C6H11-), 1.24-1.07 (m, 3H, -C6H11-),
13
0.81-0.73 (m, 2H, -C6H11-). C-NMR (CDCl3, 100 MHz): δ 140.69 (d, 2C, J = 176 Hz, -
N=CH-CH=CH-N-), 130.92 (d, 2C, J = 177 Hz, -N=CH-CH=CH-N-), 107.13 (d, 2C, J = 185
Hz, -N=CH-CH=CH-N-), 68.62 (t, 2C, J = 150 Hz, -N-CH2-N-), 56.97 (t, 1C, J = 132 Hz, -
C6H11-CH2-N-), 36.64 (d, 1C, J = 123 Hz, ipso-C6H11-), 31.60 (t, 2C, J = 123 Hz, o-C6H11-),
27.06 (t, 1C, J = 124 Hz, p-C6H11-), 26.32 (t, 2C, J = 125 Hz, m-C6H11-). IR (liquid neat; cm-
5

1): 3110 (w), 2922 (s), 2850 (m), 1512 (m), 1387 (m), 1251 (m), 1124 (w), 1084 (m), 1044 (s),
962 (m), 859 (w), 746 (s), 614 (m).
2.3.2. N,N-bis((1H-pyrazol-1-yl)methyl)-2,6-diethylbenzenamine (LB)
Analogous method is applied for synthesis of LB as described for LA. The CH2Cl2
solution (10.0 mL) of 2,6-diethylbenzenamine (3.29 mL, 0.0200 mol) was added a CH2Cl2
solution (30.0 mL) of 1H-1-pyrazolyl-1-methanol (3.92 g, 0.0400 mol). The reaction solution
was dried over the MgSO4 after stirring the reaction mixture at room temperature for 3 days.
The filtrate solvent was removed under reduced pressure to give bright yellow oil (5.54 g,
89.5%). Analysis calculated for C18H23N5: C, 69.8; H, 7.49; N, 22.6. Found: C, 68.1; H, 7.41;
N, 21.6%. 1H-NMR (CDCl3, 400 MHz): δ 7.57 (d, 2H, J = 2.0 Hz, -N=CH-CH=CH-N-), 7.28
(d, 2H, J = 2.0 Hz, -N=CH-CH=CH-N-), 7.19 (t, 1H, J = 7.2 Hz, p-NC6H3(CH2CH3)2-), 7.09
(d, 2H, J = 7.6 Hz, m-NC6H3(CH2CH3)2-), 6.24 (t, 2H, J = 2.0 Hz, -N=CH-CH=CH-N-), 5.40
(s, 4H, -N-CH2-N-), 2.10 (q, 4H, J = 7.6 Hz, -NC6H3(CH2CH3)2-), 1.05 (t, 6H, J = 7.6 Hz, -
13
NC6H3(CH2CH3)2-). C-NMR (CDCl3, 100 MHz): δ 142.94 (s, 1C, ipso-NC6H3(CH2CH3)2),
142.41 (s, 2C, o-NC6H3(CH2CH3)2-), 139.90 (d, 2C, J = 183 Hz, -N=CH-CH=CH-N-),
129.27 (d, 2C, J = 184 Hz, -N=CH-CH=CH-N-), 127.25 (d, 2C, J = 158 Hz, m-
NC6H3(CH2CH3)2-), 126.42 (d, 1C, J = 156 Hz, p-NC6H3(CH2CH3)2-), 105.95 (d, 2C, J =
176 Hz, -N=CH-CH=CH-N-), 68.85 (t, 2C, J = 149 Hz, -N-CH2-N-), 23.00 (t, 2C, J = 125
Hz, -NC6H3(CH2CH3)2-), 14.75 (q, 2C, J = 125 Hz, -NC6H3(CH2CH3)2-). IR (liquid neat; cm-
1): 3845 (w), 3743 (w), 3617 (w), 3110 (w), 2967 (m), 1702 (w), 1151 (m), 1457 (m), 1392
(m), 1264 (s), 1159 (s), 1083 (s), 1042 (s), 962 (m), 873 (w), 812 (w), 744 (s), 653 (w), 616
(m), 581 (w).
6

2.3.3. N,N-bis((1H-pyrazol-1-yl)methyl)-4-bromobenzenamine (LC)
LC was prepared by analogous method as described for LA except utilizing 4-
bromobenzenamine (3.44 g, 0.0200 mol). A bright green solid product was obtained (4.47 g,
88.7%). Analysis calculated for C14H14N5: C, 50.6; H, 4.25; N, 21.1. Found: C, 50.7; H, 4.23;
N, 21.9%. 1H-NMR (CDCl3, 400 MHz): δ 7.58 (d, 2H, J = 1.6 Hz, -N=CH-CH=CH-N-), 7.44
(d, 2H, J = 2.4 Hz, -N=CH-CH=CH-N-), 7.38 (d, 2H, J = 9.2 Hz, m-NC6H4Br-), 7.05 (d, 2H,
J = 9.2 Hz, o-NC6H4Br-), 6.28 (dd, 2H, J = 1.6 Hz, J = 2.0 Hz, -N=CH-CH=CH-N-), 5.69 (s,
13
4H, -N-CH2-N-). C-NMR (CDCl3, 100 MHz): δ 144.84 (s, 1C, ipso-NC6H4Br-), 140.11 (d,
2C, J = 176 Hz, -N=CH-CH=CH-N-), 132.32 (d, 2C, J = 165 Hz, m-NC6H4Br-), 128.89 (d,
2C, J = 175 Hz, -N=CH-CH=CH-N-), 117.51 (d, 2C, J = 164 Hz, o-NC6H4Br-), 113.64 (s, 1C,
p-NC6H4Br-), 106.43 (d, 2C, J = 176 Hz, -N=CH-CH=CH-N-), 66.24 (t, 2C, J = 151 Hz, -N-
CH2-N-). IR (liquid neat; cm-1): 3108 (m), 1594 (m), 1495 (s), 1364 (s), 1296 (s), 1263 (s),
1188 (s), 1082 (s), 1044 (s), 951 (m), 971 (s), 881 (m), 822 (s), 741 (s), 632 (s), 589 (m).
2.3.4. N,N-bis((1H-pyrazol-1-yl)methyl)cyclohexanamine (LD)
LD was prepared by analogous method as described for LA except utilizing
cyclohexanamine (2.28 mL, 0.0200 mol). A colorless oil product was obtained (4.44 g, 85.7%)
Analysis calculated for C14H21N5: C, 64.8, H, 8.16, N, 27.0. Found: C, 66.2, H, 8.27, N,
27.5%. 1H-NMR (CDCl3, 400 MHz): δ 7.53 (d, 2H, J = 1.6 Hz, -N=CH-CH=CH-N-), 7.51 (d,
2H, J = 2.4 Hz, -N=CH-CH=CH-N-), 6.27 (dd, 2H, J = 2.0 Hz, J = 2.4 Hz, -N=CH-CH=CH-
N-), 5.13 (s, 4H, -N-CH2-N-), 2.86-2.79 (m, 1H, ipso-C6H11-), 1.73-1.71 (m, 2H, -C6H11-),
1.63-1.56 (m, 3H, -C6H11-), 1.24-1.16 (m, 4H, -C6H11-), 1.08-0.98 (m, 1H, -C6H11-). 13C-
NMR (CDCl3, 100 MHz): δ 139.35 (d, 2C, J = 175 Hz, -N=CH-CH=CH-N-), 129.02 (d, 2C,
J = 185 Hz, -N=CH-CH=CH-N-), 105.94 (d, 2C, J = 175 Hz, -N=CH-CH=CH-N-), 65.92 (t,
7

2C, J = 144 Hz, -N-CH2-N-), 59.82 (d, 1C, J = 130 Hz, ipso-C6H11-), 30.98 (t, 2C, J = 125
Hz, o-C6H11-), 25.93 (t, 1C, J = 128 Hz, p-C6H11-), 25.71 (t, 2C, J = 127 Hz, m-C6H11-). IR
(liquid neat; cm-1): 3111 (w), 2928 (m), 2855 (w), 1510 (w), 1449 (w), 1387 (m), 1258 (m),
1130 (m), 1084 (m), 1042 (s), 966 (m), 882 (w), 745 (s), 653 (w), 614 (m).
2.3.5. N,N-bis((1H-pyrazol-1-yl)methyl)(furan-2-yl)methanamine (LE)
LE was prepared by analogous method as described for LA except utilizing (furan-2-
yl)methanamine (1.76 mL, 0.0200 mol). A colorless oil product was obtained (4.28 g, 83.2%).
Analysis calculated for C13H15N5: C, 60.6, H, 5.88, N, 27.2. Found: C, 60.1, H, 5.87, N,
26.2%. 1H-NMR (CDCl3, 400 MHz): δ 7.55 (d, 2H, J = 2.0 Hz, -N=CH-CH=CH-N-),7.54 (d,
2H, J = 2.0 Hz, -N=CH-CH=CH-N-), 7.40 (d, 1H, J = 2.0 Hz, -O-CH=CH-CH=C-), 6.34 (dd,
1H, J = 2.0 Hz, J = 1.6 Hz, -O-CH=CH-CH=C-), 6.29 (t, 2H, J = 1.6 Hz, -N=CH-CH=CH-
N-), 6.27 (d, 1H, J = 1.6 Hz, -O-CH=CH-CH=C-), 5.02 (s, 4H, -N-CH2-N-), 3.83 (s, 2H, -O-
CH=CH-CH=C-CH2-N-). 13C-NMR (CDCl3, 100 MHz): δ 150.96 (s, 1C, ipso-O-CH=CH-
CH=C-), 142.52 (d, 1C, J = 201 Hz, -O-CH=CH-CH=C-), 139.71 (d, 2C, J = 198 Hz, -
N=CH-CH=CH-N-), 129.97 (d, 2C, J = 199 Hz, -N=CH-CH=CH-N-), 110.35 (d, 1C, J = 178
Hz, -O-CH=CH-CH=C-), 109.23 (d, 1C, J = 173 Hz, -O-CH=CH-CH=C-), 105.95 (d, 2C, J
= 177 Hz, -N=CH-CH=CH-N-), 66.83 (t, 1C, J = 149 Hz, -N-CH2-N-), 46.72 (t, 1C, J = 136
Hz, -O-CH=CH-CH=C-CH2-N-). IR (liquid neat; cm-1): 3116 (w), 2949 (w), 1693 (w), 1510
(w), 1443 (w), 1384 (w), 1285 (w), 1139 (s), 1082 (w), 1046 (w), 1007 (w), 962 (w), 743 (s),
609 (s).
2.3.6. N,N-bis((1H-pyrazol-1-yl)methyl)-2-methoxyethanamine (LF)
LF was prepared by analogous method as described for LA except utilizing 2-
8

methoxyethanamine (1.74 mL, 0.0200 mol). A colorless oily product was obtained (4.10 g,
87.1%). Analysis calculated for C11H17N5: C, 56.1, H, 7.28, N, 29.7. Found: C, 55.0, H, 7.22,
N, 29.4%. 1H-NMR (CDCl3, 400 MHz): δ 7.48 (d, 2H, J = 2.4 Hz, -N=CH-CH=CH-N-), 7.43
(d, 2H, J = 2.0 Hz, -N=CH-CH=CH-N-), 6.17 (t, 2H, J = 2.4 Hz, -N=CH-CH=CH-N-), 5.00
(s, 4H, -N-CH2-N-), 3.34 (t, 2H, J = 5.6 Hz, CH3-O-CH2-CH2-N-), 3.20 (s, 3H, CH3-O-CH2-
CH2-N-), 2.79 (t, 2H, CH3-O-CH2-CH2-N-). 13C-NMR (CDCl3, 100 MHz): δ 138.53 (d, 2C, J
= 181 Hz, -N=CH-CH=CH-N-), 128.91 (d, 2C, J = 185 Hz, -N=CH-CH=CH-N-), 104.80 (d,
2C, J = 186 Hz, -N=CH-CH=CH-N-), 70.75 (t, 2C, J = 139 Hz, -N-CH2-N-), 67.31 (t, 1C, J
= 149 Hz, CH3-O-CH2-CH2-N-), 57.71 (q, 1C, J = 140 Hz, CH3-O-CH2-CH2-N-), 48.44 (t,
1C, J = 133 Hz, CH3-O-CH2-CH2-N-). IR (liquid neat; cm-1): 3113 (w), 2926 (w), 2885 (w),
1489 (w), 1457 (w), 1394 (m), 1280 (m), 1252 (m), 1113 (s), 1084 (s), 1046 (s), 962 (m), 750
(s), 653 (m), 616 (s).
2.3.6. N,N-bis((1H-pyrazol-1-yl)methyl)-3-(methylthio)propan-1-amine (LG)
LG was prepared by analogous method as described for LA except utilizing 3-
(methylthio)propan-1-amine (2.24 mL, 0.0200 mol). A colorless oil product was obtained
(4.98 g, 93.8%). Analysis calculated for C12H19N5: C, 54.3, H, 7.22, N, 26.4. Found: C, 54.0,
H, 7.32, N, 26.9%. 1H-NMR (CDCl3, 400 MHz): δ 7.54 (d, 4H, J = 2.4 Hz, -N=CH-CH=CH-
N-), 6.29 (t, 2H, J = 2.4 Hz, -N=CH-CH=CH-N-), 5.02 (s, 4H, -N-CH2-N-), 2.77 (t, 2H, J =
7.2 Hz, CH3-S-CH2-CH2-CH2-N-), 2.45 (t, 2H, J = 7.2 Hz, CH3-S-CH2-CH2-CH2-N-), 2.05 (s,
3H, CH3-S-CH2-CH2-CH2-N-), 1.76 (m, 2H, CH3-S-CH2-CH2-CH2-N-). 13C-NMR (CDCl3,
100 MHz): δ 138.65 (d, 2C, J = 184 Hz, -N=CH-CH=CH-N-), 128.75 (d, 2C, J = 184 Hz, -
N=CH-CH=CH-N-), 104.96 (d, 2C, J = 176 Hz, -N=CH-CH=CH-N-), 66.73 (t, 2C, J = 149
Hz, -N-CH2-N-), 47.67 (t, 1C, J = 137 Hz, -CH3-S-CH2-CH2-CH2-N-), 30.43 (t, 1C, J = 137
9

Hz, CH3-S-CH2-CH2-CH2-N-), 25.73 (t, 1C, J = 127 Hz, CH3-S-CH2-CH2-CH2-N-), 14.43 (q,
1C, J = 137 Hz, CH3-S-CH2-CH2-CH2-N-). IR (liquid neat; cm-1): 3110 (w), 2915 (w), 2859
(w), 1512 (m), 1439 (m), 1393 (s), 1349 (m), 1277 (m), 1247 (s), 1128 (s), 1084 (s), 1044 (s),
961 (s), 917 (m), 878 (w), 749 (s), 652 (m), 616 (s).
2.3.7.N-((1H-pyrazol-1-yl)methyl)-N-(cyclohexylmethyl)(1H-pyrazol-1-yl)methanamine Co(II)
chloride [LACoCl2]
A solution of LA (0.273 g, 1.00 mmol) in dried EtOH (10.0 mL) was added to EtOH
(10.0 mL) solution of CoCl2·6H2O (0.237 g, 1.00 mmol) at room temperature. The blue
powder obtained after stirring at 12 h was filtered and washed with ethanol (50.0 mL × 2),
followed by washing with Et2O (50.0 mL × 2) to yield final product (0.360 g, 89.3%).
Crystals suitable for the X-ray study of [LACoCl2] were obtained within five days from
mixture of n-hexane (10.0 mL) and CH2Cl2 (10.0 mL) of [LACoCl2] (0.100 g). Analysis
calculated for C15H23Cl2CoN5: C, 44.6, H, 5.75, N, 17.3. Found: C, 44.9, H, 5.81, N, 17.1%.
IR (solid neat; cm-1): 3743 (w), 3104 (w), 2926 (w), 2850 (w), 1698 (w), 1649 (w), 1514 (w),
1453 (m), 1408 (m), 1317 (w), 1248 (m), 1165 (s), 1068 (s), 986 (m), 913 (w), 776 (s), 722
(s), 645 (w), 611 (m).
2.3.8. N,N-bis((1H-pyrazol-1-yl)methyl)-2,6-diethylbenzenamine Co(II) chloride [LBCoCl2]
The [LBCoCl2] was prepared according to the similar procedure described for
[LACoCl2] except utilizing LB (0.309 g, 1.00 mmol). The blue powder was filtered and
washed with EtOH (50.0 mL × 2), followed by washing with Et2O (50.0 mL × 2) (0.380 g,
86.8%). Crystals suitable for the X-ray study of [LBCoCl2] were obtained within five days
from Et2O (10.0 mL) diffusion into DMF solution (10.0 mL) of [LBCoCl2] (0.100 g).
10

Analysis calculated for C18H23Cl2CoN5: C, 49.2, H, 5.28, N, 15.9. Found: C, 48.8, H, 5.45, N,
15.1%. IR (solid neat; cm-1): 3854 (s), 3743 (s), 3616 (m), 3120 (w), 2969 (w), 1835 (w),
1745 (m), 1695 (s), 1649 (s), 1517 (s), 1460 (s), 1409 (s), 1303 (m), 1254 (m), 1173 (s), 1067
(s), 982 (m), 773 (s), 643 (w).
2.3.9.N,N-bis((1H-pyrazol-1-yl)methyl)-4-bromobenzenamine Co(II) chloride [LCCoCl2]
The [LCCoCl2] was prepared according to the similar procedure described for
[LACoCl2] except utilizing LC (0.332 g, 33.2 mg, 1.00 mmol). The blue powder was filtered
and washed with EtOH (50.0 mL × 2), followed by washing with Et2O (50.0 mL × 2) (0.370
g, 80.0%). Crystals suitable for the X-ray study of [LCCoCl2] were obtained within five days
from Et2O (10.0 mL) diffusion into DMF solution (10.0 mL) of [LCCoCl2] (0.100 g).
Analysis calculated for C14H14BrCl2CoN5: C, 36.3, H, 3.05, N, 15.1. Found: C, 35.7, H, 2.97,
N, 14.9%. IR (solid neat; cm-1): 3845 (w), 3743 (m), 3616 (w), 3107 (w), 1835 (w), 1694 (m),
1648 (m), 1496 (m), 1406 (m), 1309 (m), 1247 (m), 1165 (s), 1101 (s), 992 (m), 767 (s), 613
(m), 575 (w).
2.3.10. N,N-bis((1H-pyrazol-1-yl)methyl)cyclohexanamine Co(II) chloride [LDCoCl2]
The [LDCoCl2] was prepared according to the similar procedure described for
[LACoCl2] except utilizing LD (0.259 g, 1.00 mmol). The blue powder was filtered and
washed with EtOH (50.0 mL × 2), followed by washing with Et2O (50.0 mL × 2) (0.310 g,
80.0%). Crystals suitable for the X-ray study of [LDCoCl2] were obtained within five days
from Et2O (10.0 mL) diffusion into DMF solution (10.0 mL) of [LDCoCl2] (0.100 g).
Analysis calculated for C14H21Cl2CoN5: C, 43.2, H, 5.44, N, 18.0. Found: C, 43.1, H, 5.46, N,
18.1%. IR (solid neat; cm-1): 3127 (w), 3111 (w), 2934 (w), 2859 (w), 1750 (w), 1518 (w),
11

1454 (m), 1402 (s), 1279 (s), 1196 (m), 1167 (m), 1117 (s), 1098 (m), 924 (w), 843 (w), 777
(s), 759 (s), 611 (s).
2.3.11. N,N-bis((1H-pyrazol-1-yl)methyl)(furan-2-yl)methanamine Co(II) chloride [LECoCl2]
The [LECoCl2] was prepared according to the similar procedure described for
[LACoCl2] except utilizing LE (0.257 g, 1.00 mmol). The blue powder was filtered and
washed with EtOH (50.0 mL × 2), followed by washing with Et2O (50.0 mL × 2) (0.310 g,
75.6%). Crystals suitable for the X-ray study of [LECoCl2] were obtained within five days
from Et2O (10.0 mL) diffusion into DMF solution (10.0 mL) of [LECoCl2] (0.100 g).
Analysis calculated for C15H15Cl2CoN5O: C, 40.3, H, 3.91, N, 18.1. Found: C, 40.2, H, 3.89,
N, 17.9%. IR (solid neat; cm-1): 3824 (w), 3746 (w), 3126 (w), 1649 (w), 1511 (w), 1458 (w),
1396 (m), 1340 (w), 1277 (m), 1195 (w), 1107 (m), 1067 (m), 1016 (m), 988 (w), 845 (w),
764 (s), 645 (w), 605 (m).
2.3.12. N,N-bis((1H-pyrazol-1-yl)methyl)-2-methoxyethanamine Co(II) chloride [LFCoCl2]
The [LFCoCl2] was prepared according to the similar procedure described for
[LACoCl2] except utilizing LF (0.235 g, 1.00 mmol). The blue powder was filtered and
washed with EtOH (50.0 mL × 2), followed by washing with Et2O (50.0 mL × 2) (0.209 g,
57.4%). Crystals suitable for the X-ray study of [LFCoCl2] were obtained within five days
from Et2O (10.0 mL) diffusion into MeOH solution (10.0 mL) of [LFCoCl2] (0.100 g).
Analysis calculated for C11H17Cl2CoN5O: C, 36.2, H, 4.69, N, 19.1. Found: C, 36.7, H, 4.85,
N, 19.1%. IR (solid neat; cm-1): 3123 (w), 2397 (w), 2872 (w), 2819 (w), 1684 (w), 1541 (m),
1438 (s), 1405 (s), 1351 (w), 1317 (m), 1283 (m), 1245 (m), 1140 (s), 992 (w), 923 (w), 781
(s), 766 (s), 647 (m), 609 (s), 570 (w).
12

2.3.13. N,N-bis((1H-pyrazol-1-yl)methyl)-3-(methylthio)propan-1-amine Co(II) chloride
[LGCoCl2]
The [LGCoCl2] was prepared according to the similar procedure described for
[LACoCl2] except utilizing LG (0.265 g, 1.00 mmol). The blue powder was filtered and
washed with EtOH (50.0 mL × 2), followed by washing with Et2O (50.0 mL × 2) (0.320 g,
81.0%). Crystals suitable for the X-ray study of [LGCoCl2] were obtained within five days
from Et2O (10.0 mL) diffusion into DMF solution (10.0 mL) of [LGCoCl2] (0.100 g).
Analysis calculated for C12H19Cl2CoN5S: C, 36.4, H, 4.85, N, 17.7. Found: C, 36.2, H, 4.85,
N, 16.6%. IR (solid neat; cm-1): 3134 (w), 1510 (w), 1468 (m), 1453 (m), 1403 (s), 1388 (m),
1280 (s), 1235 (m), 1138 (m), 1096 (w), 1063 (s), 1019 (m), 962 (m), 795 (s), 773 (s), 648
(w), 610 (s), 566 (w).
2.4. X-ray crystallographic studies
A blue crystal was picked up with paraton oil and mounted on a Bruker SMART
CCD diffractometer equipped with a graphite-monochromated Mo-Kα (λ= 0.71073 Å)
radiation source under nitrogen cold stream (200 K). Data collection and integration were
performed with SMART and SAINT-Plus software packages [47]. Semi-empirical absorption
corrections based on equivalent reflections were applied by SADABS [48]. Structures were
solved by direct methods and refined using a full-matrix least-squares method on F2 using
SHELXTL [49]. All non-hydrogen atoms were refined anisotropically. Hydrogen atoms were
added to their geometrically ideal positions. Crystallographic data and refinement parameters
are listed in Table 1.
2.5. General Polymerization procedure of methyl methacrylate
13

In a Schlenk line, 15.0 µmol of initiators, (5.77 mg for [LACoCl2], 6.59 mg for
[LBCoCl2], 6.93 mg for [LCCoCl2], 5.84 mg for [LDCoCl2], 5.81 mg for [LECoCl2], 5.48 mg
for [LFCoCl2] or 5.93 mg for [LGCoCl2]) was dissolved in dried toluene (10.0 mL) followed
by the addition of modified methylaluminoxane (MMAO) (3.25 mL, 7.50 mmol) as a co-
catalyst. The solution was stirred for 20 min at 60 °C. The MMA (5.00 mL, 47.10 mmol) was
added to the above reaction mixture and stirred for 2 h at 60 °C to obtain a viscous solution.
Polymerization was terminated by adding MeOH (2.00 mL). The reaction mixture was
poured into a large quantity of MeOH (500 mL), and 35% HCl (5.00 mL) was injected to
remove the remaining co-catalyst (MMAO). White PMMA was obtained by filtration,
washed by MeOH (250 mL × 2), and dried under vacuum at a mild temperature for 24 h.
3. Results and Discussion
3.1. Synthesis and chemical properties
The synthesis of ligands used in the current study was accomplished by treating
various substituted amines with 1H-pyrazolyl-1-methanol in CH2Cl2, showing high yields of
80% to 94%. The corresponding Co(II) complexes [LnCoCl2] (Ln = LA – LG) were obtained
by treating [CoCl2.6H2O] with ligands in anhydrous EtOH (approximately 80% to 89% yields)
(Scheme 1). The synthesised ligands and resultant complexes were structurally characterised
using various spectroscopic techniques and their results are consistent with the ligands and
molecular formulae of the Co(II) complexes. All synthesised Co(II) are stable to both heat
and moisture and are paramagnetic, preventing NMR analysis. In addition, these ligands
show bidentate coordination (N,N′) and tridentate coordination (N,N′,N) depending on the
14

orientation of the various N′-substituents of the amine moiety to the plane of the pyrazole and
metal centre.
3.2. Description of X-ray structures
Structural determination by X-ray diffraction revealed monomeric structures for
[LnCoCl2] (Ln = LA – LG) (Fig. 1 − 7). The selected bond distances and angles are presented
in Table 2. It is worth noting that the metal centre in [LnCoCl2] (Ln = LA – LC) is bonded to
their corresponding ligands through the nitrogen atoms of the pyrazolyl moiety in a bidentate
manner, forming an eight-membered chelate ring. The resultant geometry around the Co(II)
centre exhibited slightly distorted tetrahedral configuration. Geometric distortion from ideal
angles can be explained by the need to accommodate the bulky eight-membered chelate ring.
Such bulky chelate rings are rare due to the destabilisation caused by non-bonding
interactions within the eight-membered rings due to unfavourable torsion angles imposed by
the ring size. The presence of sterically demanding substituents and hetero-atoms may
contribute to the stability of the eight-membered chelate ring. The geometry around the Co(II)
centre in [LnCoCl2] (Ln = LD – LG) complexes can be best described as distorted trigonal
bipyramid with an σ plane of symmetry. These complexes adopted a five-coordinated
geometry through coordination of Npyrazole and Namine atoms to the metallic centre. The
orientation of N′-substituents attached to amine with respect to the plane of the pyrazole ring
depends on the nature of the attached moiety.
The average Co–Npyrazole bond lengths for [LnCoCl2] (Ln = LA – LC) and [LnCoCl2]
(Ln = LD – LG) are 2.017Å and 2.028 Å, respectively, and are comparable to Co(II)
complexes [41]. Similarly, the average Co–Clterminal bond lengths range from 2.239(1) Å to
2.243(1) Å for [LnCoCl2] (Ln = LA – LC), while for [LnCoCl2] (Ln = LD – LG) it ranges from
15

2.257(1) Å to 2.309(1) Å. Monomeric [LnCoCl2] (Ln = LA – LC) complexes exhibit a four-
coordinated geometry due to the steric effect of the ligand; the bond length of Co–Namine are
3.575(3) Å, 3.437(6) Å, and 3.292(5) Å, which indicates a non-coordinative interaction
between the N atom of the N′-substituted amine moiety and Co(II) atom [50,51]. On the other
hand, [LnCoCl2] (Ln = LD – LG) adopted a five-coordinated geometry due to weak
interactions between the N of the cyclohexyl/furan/3-(methylthio)propan-1-amine and the
cobalt metal atom based on the Co-Namine bond length of 2.466(4) Å to 2.522 (6) Å.
The bite angles Npyrazole-Co-Npyrazole were 108.1(1)°, 115.3(2)°, and 114.9(2)°, while Clterminal
-
Co-Clterminal angles were 117.28(5)°, 119.48(5)°, and 116.15(5)° for [LACoCl2], [LBCoCl2],
and [LCCoCl2], respectively. Similarly, the Npyrazole-Co-Npyrazole angles were 108.3(2)°,
109.1(2)°, 115.0(1)°, and 113.1(1)°, and the Clterminal-Co-Clterminal angles were 103.18(5)°,
103.13(5)°, 106.76(4)°, and 108.12(5)° for [LDCoCl2], [LECoCl2], [LFCoCl2] and
[LGCoCl2], respectively [43]. Although, we have not done the calculation on the electronic
stability of two different coordinated Co(II) complexes, we carefully suggest by judging from
the molecular structures of Co(II) complexes that the substituent R1 is oriented toward
coordination sphere around Co(II) metal, hampers geometrically the coordination of nitrogen
in R1 substituted amine moiety to cobalt metal center. For example, the substituent R1 in
ligands LA – LC occupy the inside coordination space thus producing tetrahedral [LnCoCl2]
(Ln = LA – Lc). However, in case of ligands LD – LG, the substituent R1 is located in out of
coordination sphere around metal and allowing the coordination of nitrogen in R1 substituted
amine unit to cobalt metal center, thus giving distorted trigonal bipyramidal [LnCoCl2] (Ln =
LD – LG). It seems that the occupation of coordination sphere around Co(II) metal by
substituent R1 in ligands was not obviously irrelevant to the functionality of substituent R1.
3.3. Discussion of MMA polymerisation
16

Methyl methacrylate (MMA) polymerisation was investigated with the synthesised
Co(II) complexes. The representative results are shown in Table 3. All Co(II) complexes
could be activated with modified methylaluminoxane (MMAO) to polymerise MMA,
yielding poly(methylmethacrylate) (PMMA) with glass transition temperatures (Tg) ranging
from 123°C to 132°C [52-54]. The polymers were isolated as white solids and characterised
using gel permeation chromatography (GPC) in THF using standard polystyrene as a
reference.
To confirm the catalytic activity of Co(II) complexes for MMA polymerisation, blank
tests were performed with anhydrous metal starting material [CoCl2] (4.03 × 104 g
PMMA/mol·Co·h) or MMAO (1.40 × 104 g PMMA/mol·Al·h) alone at a specific
temperature. It has been found that amongst the four-coordinated complexes, i.e. [LACoCl2]
(Ln = LA – LC), [LACoCl2] (5.77 × 104 g PMMA/mol·Co·h) with a cyclohexyl pendent group
exhibited higher activity at 60°C and resulted in PMMA with a greater yield, which may be
due to better solubility of the resultant catalytic species compared to the counterparts. Among
the five-coordinated Co(II) complexes, i.e. [LnCoCl2] (Ln= LD – LG), the MMA
polymerisation activity of complex [LDCoCl2] (8.33 × 104 g PMMA/mol Co.h) at 60°C,
which contains a cyclohexyl pendent group at the N atom of the amine moiety that tilted
towards the pyrazole ring and located near the cobalt metal (Fig. 4), was significantly higher
than the counterparts (Table 3, entries 6 ─ 9). To explore the effect of temperature on the
activity of MMA polymerisation, MMA polymerisation was performed at various
temperatures; i.e. 30, 60, 90°C, and the maximum yield and activity were observed at 60°C.
Thus, this optimised temperature was used for further polymerisation reactions. In addition,
[LDCoCl2] yielded the narrowest PDI and the highest molecular weight of PMMA compared
to the other five-coordinated Co(II) complexes in the current study. This high activity may
17

have resulted from the increased solubility of [LDCoCl2] in toluene compared to other Co(II)
complexes. Specifically, [LGCoCl2] showed the lowest activity (2.53 × 104 g PMMA/mol
Co.h) due to its poor solubility in reaction media. Since Co(II) complexes themselves have
poor solubility in toluene, the co-catalyst MMAO was applied to the Co(II) complex to form
a soluble cationic catalyst species. The amount of MMAO was decreased to 250 volumes of
MMAO for MMA polymerisation, but the yield of PMMA also decreased. Moreover, PDI
and tacticity were not affected by the amount of MMAO. Thus, additional MMAO may
function as a scavenger from 500 volumes of MMAO used during MMA polymerisation.
Relative to previously reported cobalt complexes with N,N-bis(1H-pyrazolyl-1-
methyl)aniline [43], the Co(II) complexes exhibited higher molecular weights (12.6 × 105
g/mol for [LDCoCl2]) of syndiotactic PMMA, narrower PDIs, and higher catalytic activities
(8.33 × 104 g PMMA/mol·Co·h) at 60°C. The PDIs of the Co(II) complexes ranged from 1.33
to 1.97. In general, the PDI range narrowed with increasing molecular weight of PMMA
(Table 3, entries 6 – 9) [55,56].
The triad microstructure of PMMA was analysed using 1H-NMR spectroscopy [57,58]. The
tacticity of PMMA ranged around syndiotactic (rr, δ 0.85), atactic (mr, δ 1.02), and isotactic
(mm, δ 1.21). The syndiotacticity ranged from 0.68 to 0.70 in almost all cases, irrespective of
their coordination mode and catalytic activities, but was higher than the starting materials
(Table 3, entries 1 and 2). This also indicated that syndiotacticity was only slightly affected
by substituents on the ligand architecture. A higher Tg typically represents higher optical
quality and syndiotacticity content of PMMA. The Tg of isotactic PMMA, which is produced
by radical commercial processes, is around 65ºC. Thus, the non-radical-mediated
polymerisation of MMA using complex catalysts achieves a high Tg for high content of
syndiotactic PMMA [59-62]. However, catalytic activity was affected to a greater extent by
steric influences of the substituents at the amine moiety, as determined by the relative
amounts of PMMA product yielded. The MMA polymerisation activity of Co(II) complexes
should be considered a function of the electron density around the metal centre. However, the
molecular weight of PMMA was affected by the steric influences of N′-substitution at the
18

amine moiety, where the direction was with respect to the plane of the two pyrazole rings. In
addition, when MMA polymerization was done using five equivalents of radical inhibitor
TEMPO (2,2,6,6-tetramethylpiperidinyloxy), the yield of PMMA did not much reduce (ca. 2
5% yield). It was an indirect evidence that the mechanism of coordination polymerization is
not a radical mechanism, although the moderate syndiotacticity of Co(II) complexes around
ca. 70% was not sufficient to confer a mechanism of coordination polymerization [63].
̶
4. Conclusion
Novel Co(II) complexes [LnCoCl2] (Ln = LA – LG) were prepared by reaction of
[CoCl2·6H2O] with N′-substituted N,N-bis(1-pyrazolyl)methylamine and its derivatives. The
coordination of these ligands to the Co(II) metal revealed that [LnCoCl2] (Ln = LA – LC)
exists in four-coordinated and [LnCoCl2] (Ln = LD – LG) exists in five-coordinated
geometries, respectively, depending on the interactions between the nitrogen atom of the N′-
substitution in the amine moiety and the metal centre. The formation of four-coordinate or
five-coordinate monomers was determined based on steric effects of N′-substituents on the
amine residue around the cobalt centre. The catalytic activity of [LnCoCl2] (Ln = LA – LG) for
MMA polymerisation in the presence of MMAO were investigated: the five-coordinated
[LDCoCl2] (8.33 × 104 g PMMA/mol Co·h) showed higher catalytic activity than the other
Co(II) complexes in this study. The PDIs of the resultant PMMA did not strongly depend on
the substituent effects of the catalyst. However, the molecular weight of the obtained PMMA
and the catalytic activities of Co(II) complexes were influenced by the steric encumbrance of
the N′-substitution amine moiety depending on the orientation of substituents with respect to
the plane of the two pyrazole rings.
Supplementary materials
19

CCDC 1055572–1055578 contains the supplementary crystallographic data for [LACoBr2],
[LBCoBr2], [LCCoBr2], [LDCoBr2], [LECoBr2], [LFCoBr2] and [LGCoBr2], respectively.
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, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail:
deposit@ccdc.cam.ac.uk.
Acknowledgment
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. 2014-
R1A1A3049750). This research was supported by the Korea Atomic Energy Research
Institute (KAERI) grant (Grant No. 79085-13) funded by Korea government (Ministry of
Science, ICT and Future Planning).
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22

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23

Scheme 1. Synthesis of ligands (Ln = LA – LG) and their corresponding Co(II) complexes.
24

Table 1. Crystal data and Structure refinement for [LnCoCl2] (Ln = LA – LG).
[LACoCl2]
[LBCoCl2]
[LCCoCl2]
[LDCoCl2]
[LECoCl2]
[LFCoCl2]
[LGCoCl2]
Empirical formula
Formula weight
Crystal system
C15H23Cl2CoN5
2(C18H23Cl2CoN5),O
894.49
C14H14Cl2BrCoN5
462.04
C14H21Cl2CoN5
389.19
C15H15Cl2CoN5O
387.13
C11H17Cl2CoN5O
365.13
C12H19Cl2CoN5S
395.21
403.21
Monoclinic
P21/c
Rhombohedral
R-3
Monoclinic
P21/c
Monoclinic
P21/c
Monoclinic
P21/c
Orthorhombic
Pna2(1)
Monoclinic
P21/c
Space group
Unit cell dimensions
a = 8.148(1) Å
b = 13.626(2) Å
c = 16.539(2) Å
α = 90°
a = 17.932(1) Å
b = 17.932(1) Å
c = 17.932(1) Å
α = 114.05°
β = 114.05°
γ = 114.05°
3490.9(4)
a = 8.6341(4) Å
b = 14.9323(7) Å
c = 13.8870(6) Å
α = 90°
a = 8.468(2) Å
b = 13.194(3) Å
c = 15.270(3) Å
α = 90°
a = 8.4122(9) Å
b = 12.517(1) Å
c = 14.636(2) Å
α = 90°
a = 17.1336(7) Å
b = 7.7035(3) Å
c = 23.576(1) Å
α = 90°
a = 8.9428(6) Å
b = 8.2289(5) Å
c = 23.365(2) Å
α = 90°
β = 95.353(3)°
γ = 90°
β = 98.664(1) °
γ = 90°
β = 90.542(4)°
γ = 90°
β = 93.411(2)°
γ = 90°
β = 90°
β = 92.681(1)°
γ = 90°
γ = 90°
Volume (Å3)
1828.1(4)
4
1770.0(1)
4
1706.0(6)
4
1538.3(3)
4
3111.7(2)
8
1717.5(2)
4
Z
3
Density (calculated) (g/cm3)
Absorption coefficient mm-1
F(000)
1.465
1.276
1.734
1.515
1.762
1.559
1.528
1.236
0.980
3.533
1.322
1.471
1.448
1.431
836
1386
916
804
788
1496
812
Crystal size (mm3)
Theta range for data
collection
0.19 × 0.18 × 0.14
0.28 × 0.28 × 0.19
0.27 × 0.14 × 0.07
0.30 × 0.23 × 0.18
0.19 × 0.17 × 0.14
0.18 × 0.16 × 0.08
0.23 × 0.20 × 0.12
1.94 to 28.29°
13479
1.35 to 28.30°
26254
2.02 to 28.29°
12675
2.04 to 28.33°
12428
2.14 to 28.32°
11255
2.38 to 28.45°
88656
2.28 to 28.29°
11814
Reflections collected
Independent reflections
No. parameters
4535 [Rint = 0.0787]
208
5774 [Rint = 0.0886]
246
4372 [Rint = 0.0249]
208
4234 [Rint = 0.0517]
199
3820 [Rint = 0.0441]
199
7803 [Rint = 0.0896]
363
4190 [Rint = 0.0221]
191
Goodness-of-fit on F2
Final R and wR2 indices
[I>2σ(I)]
0.807
0.843
1.136
1.137
1.131
1.068
1.201
R1 = 0.0428, wR2 =
0.0699
R1 = 0.0552, wR2 =
0.1478
R1 = 0.0353, wR2 =
0.0671
R1 = 0.0491, wR2 =
0.0880
R1 = 0.0409, wR2 =
0.0819
R1 = 0.0350, wR2 =
0.0670
R1 = 0.0369, wR2 =
0.0818
R indices (all data)
R1 = 0.1246, wR2 =
0.1016
R1 = 0.1381, wR2 =
0.1923
R1 = 0.0637, wR2 =
0.1152
R1 = 0.1020, wR2 =
0.1413
R1 = 0.0952, wR2 =
0.1457
R1 = 0.0604, wR2 =
0.0768
R1 = 0.0576, wR2 =
0.1458
Largest diff. peak and hole
(e.Å-3)
0.642 and -0.793
0.953 and -0.585
0.816 and -0.913
0.915 and -1.167
1.054 and -1.313
0.454 and -0.293
0.840 and -0.987
25

Table 2. The selected bond lengths (Å) and angles (°) of [LnCoCl2] (Ln = LA – LG).
[LACoCl2] [LBCoCl2] [LCCoCl2]
Co(1)-N(4)
2.008(3)
Co(1)-N(1)
2.018(4)
Co(1)-N(1)
2.009(4)
Co(1)-N(1)
2.019(3)
3.575(3)
2.241 (1)
2.243 (1)
1.333(4)
1.348(4)
1.335(4)
1.476(4)
1.378(5)
108.1(1)
104.8 (1)
104.71(9)
110.47(9)
110.93(9)
117.28(5)
105.8(3)
125.7(3)
128.1(2)
111.0(3)
Co(1)-N(4)
2.024(4)
3.437(6)
2.239 (1)
2.243 (1)
1.344(6)
1.368(5)
1.329(6)
1.471(5)
1.383(7)
115.4 (2)
107.1(1)
107.9 (1)
103.8 (1)
103.7(1)
119.48(5)
105.1(4)
126.7(3)
128.1(3)
111.0(4)
Co(1)-N(5)
2.021(4)
3.292(5)
2.242 (1)
2.243 (1)
1.329(6)
1.359(5)
1.350(6)
1.457(5)
1.381(7)
114.9(2)
109.2 (1)
106.4(1)
103.2 (1)
107.3 (1)
116.15(5)
105.4(4)
130.2(3)
124.3(3)
111.0(4)
Co(1)-N(5)
Co(1)-N(5)
Co(1)-N(3)
Co(1)-Cl(2)
Co(1)-Cl(1)
Co(1)-Cl(1)
Co(1)-Cl(1)
Co(1)-Cl(2)
Co(1)-Cl(2)
N(1)-C(1)
N(1)-C(1)
N(1)-C(1)
N(1)-N(2)
N(1)-N(2)
N(1)-N(2)
N(2)-C(3)
N(2)-C(3)
N(2)-C(3)
N(2)-C(4)
N(2)-C(4)
N(2)-C(4)
C(1)-C(2)
C(1)-C(2)
C(1)-C(2)
N(4)-Co(1)-N(1)
N(4)-Co(1)-Cl(2)
N(1)-Co(1)-Cl(2)
N(4)-Co(1)-Cl(1)
N(1)-Co(1)-Cl(1)
Cl(2)-Co(1)-Cl(1)
C(1)-N(1)-N(2)
C(1)-N(1)-Co(1)
N(2)-N(1)-Co(1)
C(3)-N(2)-N(1)
N(1)-Co(1)-N(4)
N(1)-Co(1)-Cl(1)
N(4)-Co(1)-Cl(1)
N(1)-Co(1)-Cl(2)
N(4)-Co(1)-Cl(2)
Cl(1)-Co(1)-Cl(2)
C(1)-N(1)-N(2)
C(1)-N(1)-Co(1)
N(2)-N(1)-Co(1)
C(3)-N(2)-N(1)
N(1)-Co(1)-N(5)
N(1)-Co(1)-Cl(1)
N(5)-Co(1)-Cl(1)
N(1)-Co(1)-Cl(2)
N(5)-Co(1)-Cl(2)
Cl(1)-Co(1)-Cl(2)
C(1)-N(1)-N(2)
C(1)-N(1)-Co(1)
N(2)-N(1)-Co(1)
C(3)-N(2)-N(1)
26

[LDCoCl2]
[LECoCl2]
[LFCoCl2]
[LGCoCl2]
Co(1)-N(1)
2.021(4)
Co(1)-N(4)
2.030(4)
Co(1)-N(1)
2.017(2)
Co(1)-N(5)
2.032(5)
Co(1)-N(3)
2.035(4)
2.466(4)
2.286 (1)
2.295(1)
1.328(6)
1.353(5)
1.343(6)
1.452(6)
1.377(7)
108.3(2)
108.1(1)
133.6(1)
101.2(1)
97.0(1)
Co(1)-N(1)
2.031(4)
2.507(4)
2.257(1)
2.305(1)
1.337(6)
1.358(5)
1.345(6)
1.459(6)
1.395(7)
109.1(2)
121.2(1)
119.3(1)
98.5(1)
Co(1)-N(5)
2.024(3)
2.514(4)
2.268(1)
2.306(1)
1.331(4)
1.344(4)
1.337(4)
1.466(4)
1.450(4)
115.0(1)
109.89(8)
124.68(8)
100.11(8)
95.67(8)
106.76(4)
105.5(2)
132.6(2)
121.5(2)
111.3(3)
Co(1)-N(1)
2.035(5)
2.522(6)
2.281(2)
2.286(2)
1.337(7)
1.361(6)
1.359(7)
1.453(7)
1.400(9)
115.7(2)
99.7(2)
Co(1)-N(5)
Co(1)-N(5)
Co(1)-N(3)
Co(1)-N(4)
Co(1)-Cl(1)
Co(1)-Cl(1)
Co(1)-Cl(2)
Co(1)-Cl(2)
Co(1)-Cl(2)
Co(1)-Cl(2)
Co(1)-Cl(1)
Co(1)-Cl(1)
N(1)-C(1)
N(1)-C(1)
N(1)-C(1)
N(1)-C(1)
N(1)-N(2)
N(1)-N(2)
N(1)-N(2)
N(1)-N(2)
N(2)-C(3)
N(2)-C(3)
N(2)-C(3)
N(2)-C(3)
N(2)-C(4)
N(2)-C(4)
N(2)-C(4)
N(2)-C(4)
C(1)-C(2)
C(1)-C(2)
N(3)-C(4)
C(1)-C(2)
N(1)-Co(1)-N(3)
N(1)-Co(1)-Cl(1)
N(3)-Co(1)-Cl(1)
N(1)-Co(1)-Cl(2)
N(3)-Co(1)-Cl(2)
Cl(1)-Co(1)-Cl(2)
C(1)-N(1)-N(2)
C(1)-N(1)-Co(1)
N(2)-N(1)-Co(1)
C(3)-N(2)-N(1)
N(4)-Co(1)-N(1)
N(4)-Co(1)-Cl(1)
N(1)-Co(1)-Cl(1)
N(4)-Co(1)-Cl(2)
N(1)-Co(1)-Cl(2)
Cl(1)-Co(1)-Cl(2)
C(1)-N(1)-N(2)
C(1)-N(1)-Co(1)
N(2)-N(1)-Co(1)
C(3)-N(2)-N(1)
N(1)-Co(1)-N(5)
N(1)-Co(1)-Cl(2)
N(5)-Co(1)-Cl(2)
N(1)-Co(1)-Cl(1)
N(5)-Co(1)-Cl(1)
Cl(2)-Co(1)-Cl(1)
C(1)-N(1)-N(2)
C(1)-N(1)-Co(1)
N(2)-N(1)-Co(1)
C(3)-N(2)-N(1)
N(4)-Co(1)-N(1)
N(4)-Co(1)-Cl(2)
N(1)-Co(1)-Cl(2)
N(4)-Co(1)-Cl(1)
N(1)-Co(1)-Cl(1)
Cl(2)-Co(1)-Cl(1)
C(1)-N(1)-N(2)
C(1)-N(1)-Co(1)
N(2)-N(1)-Co(1)
C(3)-N(2)-N(1)
98.6(1)
119.8(2)
111.1(1)
108.63(7)
106.5(5)
132.3(4)
121.2(3)
110.3(5)
100.7(1)
103.13(5)
105.4(4)
133.3(3)
120.3(3)
110.7(4)
103.18(5)
105.8(4)
135.1(4)
119.0(3)
110.6(4)
27

Table 3. Polymerization of MMA by [LnCoCl2] (Ln = LA – LG) in the presence of MMAO.
d
Tg
e
Temp. Yieldb
Activityc
Tacticity
Mw
f
Entry
Catalysta
Mw/Mn
×104
(g/molCat·h)
×105
(g/mol)
(%)
%mm %mr %rr
(℃)
(℃)
1
2
3
4
5
6
7
8
9
[CoCl2]g
MMAOh
60
60
60
60
60
60
60
60
60
25.9
8.97
37.0
23.9
20.5
53.4
32.7
26.7
16.2
4.03
1.40
5.77
3.73
3.20
8.33
5.10
4.17
2.53
125 7.70 24.6 51.9 8.15
120 37.2 10.9 51.9 0.61
131 7.69 23.8 68.5 10.6
123 6.49 22.7 70.8 9.03
129 7.29 21.8 70.8 11.8
128 6.80 23.1 70.0 12.6
131 6.67 24.0 69.3 10.4
132 7.19 23.0 69.8 10.6
129 9.00 23.4 67.6 9.70
1.97
2.20
1.74
1.90
1.68
1.33
1.75
1.86
1.97
[LACoCl2]
[LBCoCl2]
[LCCoCl2]
[LDCoCl2]
[LECoCl2]
[LFCoCl2]
[LGCoCl2]
a[Co(II) catalyst]0 = 15 µmol, [MMA]0/[MMAO]0/[Co(II) catalyst]0 = 3100:500:1.
bYield defined as mass of dried polymer recovered/mass of monomer used.
cActivity is (gPMMA)·(molCo·h)–1.
dTg is the glass transition temperature determined using a thermal analyzer.
eDetermined using gel permeation chromatography (GPC) eluted with THF at room temperature by filtration
with polystyrene calibration.
fMn refers to the number average of molecular weights of PMMA.
gBlank polymerisation in which anhydrous [CoCl2] was also activated by MMAO.
hBlank polymerisation with MMAO alone.
28

Fig. 1. ORTEP drawing of [LACoCl2] with displacement at 30% probability. All hydrogen
atoms are omitted for clarity. Symmetry codes are #1 -x+1,-y+1,-z+2; #2 -x+1,-y,-z; #3 -x+1,-
y+1,-z; #4 x,-y+1/2, z.
29