Cadmium(II) complexes containing N′-substituted N,N-di(2-picolyl)amine: The formation of monomeric versus dimeric complexes is affected by the N′-substitution group on the amine moiety

Article abstract of DOI:10.1016/j.jorganchem.2015.02.011

The reaction of [CdBr₂·4H₂O] with N′-substituted N,N-di(2-picolyl)amine ligands such as 1-cyclohexyl-N,N-bis(pyridin-2-ylmethyl)methanamine (L_A), N,N-bis(pyridin-2-ylmethyl)aniline (L_B), 2-methoxy-N,N-bis(pyridin-2-ylmethyl)ethan-1-amine (L_C) and 3-methoxy-N,N-bis(pyridin-2-ylmethyl)propan-1-amine (L_D) in ethanol yielded cadmium(II) [Cd(II)] complexes, i.e. [L_nCdBr₂]_m (L_n = L_A, m = 2; L_B, m = 1; L_C, m = 1; L_D, m = 2, respectively). The molecular structures of Cd(II) complexes revealed that 6-coordinate dimeric [L_ACd(μ-Br)Br]₂ and [L_DCd(μ-Br)Br]₂ showed a distorted octahedral geometry through coordination of nitrogen in the N′-substituted amine moiety (cyclohexylmethylamine and 3-methoxypropylamine, respectively) to the Cd metal centre and a bromide bridge ligand. However, the 5-coordinate monomeric [L_BCdBr₂] was square pyramidal through the coordination of nitrogen in the N′-phenyl-substituted amine residue to the Cd metal centre. The molecular structure of 6-coordinate monomeric [L_CCdBr₂] had a distorted octahedral geometry achieved through bidentate coordination of nitrogen and oxygen in the N′-methoxyethylamine group to the Cd metal centre. However, for dimeric [L_DCd(μ-Br)Br]₂, although L_D has a bidentate coordination ability in the N′-methoxypropylamine group, it generated a distorted octahedral geometry through coordination of nitrogen and non-coordination of oxygen in the N′-methoxyethylamine moiety to the Cd metal centre. Monomeric complex [L_BCdBr₂] [6.70 × 10⁴ gPMMA·(molCd·h)^-1] showed higher catalytic activity for the polymerisation of methyl methacrylate (MMA) in the presence of modified methylaluminoxane (MMAO) than the rest of Cd(II) complexes in this study. The catalytic activity of dimeric complex [L_ACd(μ-Br)Br]₂ [7.00 × 10⁴ gPMMA·(molCd·h)^-1] and [L_DCd(μ-Br)Br]₂ [7.07 × 10⁴ gPMMA·(molCd·h)^-1] increased by twofold due to the presence of two Cd metal centres compared to the corresponding reference complex [CdBr₂·4H₂O] [2.85 × 10⁴ gPMMA·(molCd·h)^-1] or anhydrous [CdCl₂] [3.53 × 10⁴ gPMMA·(molCd·h)^-1]. All Cd(II) complexes resulted in syndiotactic poly(methylmethacrylate) (PMMA) with ca. 0.70.

Full text of DOI:10.1016/j.jorganchem.2015.02.011

Accepted Manuscript
Cadmium(II) complexes containing N'-substituted N,N-di(2-picolyl)amine: The
formation of monomeric versus dimeric complexes is affected by the N'-substitution
group on the amine moiety
Yujin Song, Saira Nayab, Jongho Jeon, Sang Hyun Park, Hyosun Lee
PII:
S0022-328X(15)00079-0
10.1016/j.jorganchem.2015.02.011
JOM 18911
DOI:
Reference:
To appear in: Journal of Organometallic Chemistry
Received Date: 14 November 2014
Revised Date: 30 January 2015
Accepted Date: 10 February 2015
Please cite this article as: Y. Song, S. Nayab, J. Jeon, S.H. Park, H. Lee, Cadmium(II) complexes
containing N'-substituted N,N-di(2-picolyl)amine: The formation of monomeric versus dimeric complexes
is affected by the N'-substitution group on the amine moiety, Journal of Organometallic Chemistry
(2015), doi: 10.1016/j.jorganchem.2015.02.011.
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ACCEPTED MANUSCRIPT
Graphical Abstract (Synopsis)
Cadmium(II) complexes containing N'-substituted N,N-di(2-
picolyl)amine: The formation of monomeric versus dimeric complexes
is affected by the N'-substitution group on the amine moiety
Yujin Songa, Saira Nayabb, Jongho Jeonc, Sang Hyun Parkc,*, Hyosun Leea,*
A new series of N,N',N-tridentate complexes, [LACd(µ-Br)Br]2, [LBCdBr2], [LDCd(µ-Br)Br]2 and
N,N',N, O-tetradentate complex, [LCCdBr2] containing N'-substituted N,N-di(2-picolyl)amine ligands (Ln
= LA ̶ LD) were synthesized and characterized by X-ray crystallography. These Cd(II) complexes showed
diverse co-ordination geometry around the cadmium centre from 5-coordinated monomeric structure to 6-
coordinated monomeric and dimeric structures. The catalytic activity of Cd(II) complexes for methyl
methacrylate polymerisation was investigated.

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Cadmium(II) complexes containing N'-substituted N,N-di(2-picolyl)amine:
The formation of monomeric versus dimeric complexes is affected by the
N'-substitution group on the amine moiety
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Yujin Songa, 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 (U), Khyber
Pakhtunkhwa, Republic of Pakistan.
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cResearch Division for Biotechnology, Advanced Radiation Technology Institute, Korea
Atomic Energy Research Institute(KAERI), Jeongeup, Jeonbuk, 580-185, Republic of Korea
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*Corresponding authors. Tel: +82-53-950-5337; fax: +82-53-950-6330
E-mail address: hyosunlee@knu.ac.kr (H. Lee)
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Abstract
The reaction of [CdBr2 4H2O] with N'-substituted N,N-di(2-picolyl)amine ligands such as 1-
cyclohexyl-N,N-bis(pyridin-2-ylmethyl)methanamine (LA), N,N-bis(pyridin-2-
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ylmethyl)aniline (LB), 2-methoxy-N,N-bis(pyridin-2-ylmethyl)ethan-1-amine (LC) and 3-
methoxy-N,N-bis(pyridin-2-ylmethyl)propan-1-amine (LD) in ethanol yielded cadmium(II)
[Cd(II)] complexes, i.e. [LnCdBr2]m (Ln = LA, m = 2; LB, m = 1; LC, m = 1; LD, m = 2,
respectively). The molecular structures of Cd(II) complexes revealed that 6-coordinate
dimeric [LACd(µ−Br)Br]2 and [LDCd(µ−Br)Br]2 showed a distorted octahedral geometry
through coordination of nitrogen in the N'-substituted amine moiety (cyclohexylmethylamine
and 3-methoxypropylamine, respectively) to the Cd metal centre and a bromide bridge ligand.
However, the 5-coordinate monomeric [LBCdBr2] was square pyramidal through the
coordination of nitrogen in the N'-phenyl-substituted amine residue to the Cd metal centre.
The molecular structure of 6-coordinate monomeric [LCCdBr2] had a distorted octahedral
geometry achieved through bidentate coordination of nitrogen and oxygen in the N'-
methoxyethylamine group to the Cd metal centre. However, for dimeric [LDCd(µ−Br)Br]2,
although LD has a bidentate coordination ability in the N'-methoxypropylamine group, it
generated a distorted octahedral geometry through coordination of nitrogen and non-
coordination of oxygen in the N'-methoxyethylamine moiety to the Cd metal centre.
Monomeric complex [LBCdBr2] [6.70 × 104 gPMMA·(molCd·h)–1] showed higher catalytic
activity for the polymerisation of methyl methacrylate (MMA) in the presence of modified
methylaluminoxane (MMAO) than the rest of Cd(II) complexes in this study. The catalytic
activity of dimeric complex [LACd(µ−Br)Br]2 [7.00 × 104 gPMMA·(molCd·h)–1] and
[LDCd(µ−Br)Br]2 [7.07 × 104 gPMMA·(molCd·h)–1] increased by twofold due to the
presence of two Cd metal centres compared to the corresponding reference complex
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[CdBr2 4H2O] [2.85 × 104 gPMMA·(molCd·h)–1] or anhydrous [CdCl2] [3.53 × 104
gPMMA·(molCd·h)–1].
poly(methylmethacrylate) (PMMA) with ca. 0.70.
All
Cd(II)
complexes
resulted
in
syndiotactic
Keywords: Dimeric Cd(II) complex, N'-substituted N,N-di(2-picolyl)amine, MMA
polymerization, Syndiotacticity
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1. Introduction
Ligand architecture with N,N-di(2-picolyl)amine and its N'-substituted derivatives have been
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widely studied in transition metal complexes [1]. This is likely due to their diverse structural
variations in coordination mode from N,N-bidentate and N,N',N-tridentate to N,Nꢀ,N,X-
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tetradentate, in which coordination of the X atom is derived from substitution on the pyridine
ring or amine residue (and possibly on both residues) [2]. In particular, the coordination
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complexes of Zn, Cd and Hg with N,N-bidentate and N,Nꢀ,N-tridentate di(2-picolyl)amine
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ligands are known to form diverse coordination geometries from mononuclear to poly-
nuclear complexes [3,4]. The aforementioned complexes have been studied for important
synthetic, kinetic and spectroscopic applications [1a-k, 2a-h, 3a-h, 4a-e], as well as for photo-
luminescent materials and supramolecular materials [2i-l, 3i-l, 4f-i], biological enzymatic
applications [1l, 1m, 2m-o, 3m-r, 4j-m], catalysis of organic transformation and catalysts for
the polymerisation of α-olefins and polar olefins [1n-q, 2p-s]. Recently few reports are
documented regarding the use of various transition metal complexes, especially Pd(II), Pt(II),
Zn(II) and Cu(II) with N'-substituted N,N-di(2-picolyl)amine, as a catalyst in the
polymerisation of methyl methacrylate (MMA) [5] due to the fact that transition-metal
complexes influence all of the steps of polymerization such as initiation, propagation and
termination [6].
Thus the development of new highly active catalysts is still an extremely attractive yet
challenging goal to get high molecular weight PMMA with better tacticity. In this regard our
success in the first ever reported examples of Cd(II) complexes with N'-substituted N,N-di(2-
picolyl)amines [7], prompted us to develop and extend our research investigations towards
the design and synthesis of new Cd(II) catalysts with such type of ligands diverse structural
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variations on amine moiety of N,N-di(2-picolyl)amine architecture. In addition steric and
electronic properties can be fine-tuned around the metal centre by appropriate choice of
substitution on N atom of these N,N',N-tridentate.
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The current study describes the synthesis and structural characterization of monomeric and
dimeric Cd(II) complexes bearing N'-substituted N,N-di(2-picolyl)amine ligand framework
with various N'-substituted groups at amine moiety. Further investigations involved the
structural aspects of these complexes and the effect of various substitutions on amine moiety
on their catalytic ability towards MMA polymerization in the presence of MMAO at 60 oC.
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2. Results and discussion
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2.1. Synthesis and chemical properties
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The ligands and their corresponding Cd(II) complexes were prepared using the synthetic
procedure illustrated in Scheme 1. The previously reported ligands were obtained in yields of
LA [2f, 2h] (88%), LB [1e, 1f] (81%), LC [8] (87%) and LD [8] (86%) from the starting
materials cyclohexylmethylamine, aniline, 2-methoxyethanamine, and 3-methoxypropan-1-
amine, respectively, and 2-picolylchloride hydrochloride in water. The complexation reaction
proceeded smoothly by treating [CdBr2·4H2O] with ligands precursors in anhydrous EtOH
and resultant complexes are obtained in high yields (85 -88%) (Scheme 1).
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Scheme 1
1
The results of H-NMR, 13C-NMR and elemental analyses were consistent with ligand
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and Cd(II) complex formation. The resonance of CH2–pyridine protons in complexes shifted
up field compared to the ligands due to a shielding effect of the interaction between Cd metal
and the N'-substitution group in the amine moiety, i.e. pyridine–CH2–N'–X (X = cyclohexyl,
1
phenyl, 2-methoxyethyl, 3-methoxypropyl). For example, H-NMR peaks for CH2–pyridine
in ligands showed a singlet peak at δ 3.76 (LA), δ 4.67 (LB), δ 3.79 (LC) and δ 3.72 (LD),
respectively. However, the CH2–pyridine proton peaks for dimeric [LDCd(µ−Br)Br]2
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appeared as two doublet peaks (e.g. at δ 4.12 and δ 3.89), indicating that H-NMR peaks for
CH2–pyridine were affected by the symmetrical location of pyridine–CH2–N'–X (X = 3-
methoxypropyl) with respect to the Cd centre. This appearance of two doublet in
[LDCd(µ−Br)Br]2 can be attributed to larger JAB = 92 Hz that split the peak. However, in the
case of cyclohexyl backbone the J value might not be enough high to split the peak in to
doublet so it appeared as broad singlet for -CH2 protons. Furthermore various interactions
that exist in the crystal packing of the complex [LDCd(µ−Br)Br]2, i.e. H6a…C4 (2.850 Å),
H7a…O1 (2.632 Å), and H7b…Br1 (2.865 Å) also supports the appearance of doublet, which
are not present in [LACd(µ-Br)Br]2.
2.2. Molecular structures
A single crystal suitable for X-ray crystallography was obtained from Et2O or hexane
diffusion into CH2Cl2 or DMF. Crystal data and structural refinements for Cd(II) complexes
are summarized in Table 1. The molecular structures of Cd(II) complexes are shown in Fig. 1
([LACd(µ−Br)Br]2), Fig. 2 ([LBCdBr2]), Fig. 3 ([LcCdBr2]), and Fig. 4 ([LDCd(µ−Br)Br]2).
The selected bond lengths and angles are listed in Table 2. The molecular structures revealed
that the Cd atom in 6-coordinate dimeric complexes, [LACd(µ−Br)Br]2 and
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[LDCd(µ−Br)Br]2 showed a distorted octahedral geometry through coordination of nitrogen
in the N'-substituted amine moiety (cyclohexylmethyl and 3-methoxypropyl, respectively) to
the Cd metal centre and a bromide bridge ligand. However, the 5-coordinate monomeric
[LBCdBr2] had a square pyramidal geometry through only coordination of the nitrogen in the
N'-phenyl-substituted amine moiety to the Cd metal centre. The 6-coordinate monomeric
[LCCdBr2] had a distorted octahedral structure, achieved through bidentate coordination of
nitrogen and oxygen in the N'-methoxyethyl moiety to the Cd metal centre.
The bond lengths of Cd–Namine [Cd(1)–N(2) and Cd(2)–N(5)] in dimeric
[LACd(µ−Br)Br]2 were 2.472(7) Å, and 2.488(7) Å, respectively. The bond length of Cd–
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Namine [Cd(1)–N(2) and Cd(1#)–N(2#)] in dimeric [LDCd(µ−Br)Br]2 was 2.462(2) Å. Those
of monomeric [LBCdBr2] and [LcCdBr2] were 2.523(6) Å and 2.438 (2) Å, respectively.
Table 1
Fig. 1
Fig. 2
Fig. 3
Fig. 4
Table 2
Bond lengths of Cd–Npyridine [Cd(1)–N(1), Cd(1)–N(3), Cd(2)–N(4) and Cd(2)–N(6)] for
dimeric [LACd(µ−Br)Br]2 ranged from 2.382(8) Å to 2.419(8) Å. Those of
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[LDCd(µ−Br)Br]2 [Cd(1)–N(1), Cd(1)–N(3), Cd(1#)–N(1#) and Cd(1#)–N(3#)] were 2.375(2)
Å and 2.350(2) Å, respectively. The bond lengths of Cd–Npyridine for [LBCdBr2] and
[LcCdBr2] were 2.310(6) and 2.303(6) Å, and 2.346(2) and 2.329(2) Å, respectively.
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Specifically, the bond length of Cd(1)–O(1) in [LCCdBr2] was 2.580(2) Å, which was
acceptable for regular covalent bonds of Cd and oxygen [9]. Bond lengths of Cd–Brterminal
[2.615 (1) Å and 2.693 (1) Å] in dimeric [LACd(µ−Br)Br] were shorter than the two bonds
of the Cd–Brbridge [2.704(1) Å and 2.837(1) Å]. Similar patterns were observed in dimeric
[LDCd(µ−Br)Br] [2.6311(5) Å vs. 2.7670(7) Å and 2.7911(5) Å]. The bond lengths of
Cd(1)–Br(1) and Cd(1)–Br(2) for [LBCdBr2] and [LCCdBr2] ranged from 2.585 (1) Å to
2.6817(5) Å.
The four Namine–Cd–Npyridine bond angles for dimeric [LACd(µ−Br)Br]2 were 69.1(3)°,
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70.9(3)°, 69.9(2)°, and 71.8(3)°. Dimeric [LACd(µ−Br)Br]2 showed a 6-coordinated distorted
octahedral geometry based on N(3)-Cd(1)-N(1), N(2)-Cd(1)-Br(3), N(3)-Cd(1)-Br(3), Br(3)-
Cd(1)-Br(2), Br(2)-Cd(1)-Br(1), N(1)-Cd(1)-Br(1), Br(3)-Cd(1)-Br(1), and N(2)-Cd(1)-Br(1)
angles of 103.3(3)°, 82.3(2)°, 86.3(2)°, 108.63(4)°, 97.24(4)°, 82.6(2)°, 83.55(4)°, and 103.6
(2)°, respectively.
The two Namine–Cd–Npyridine bond angles for dimeric [LDCd(µ−Br)Br]2 were 70.31(5)°
and 71.57(5)°. The N(2)-Cd(1)-N(1), N(2)-Cd(1)-Br(2), Br(2)-Cd(1)-Br(1), Br(2#)-Cd(1)-
Br(1), N(1)-Cd(1)-Br(2#), Br(2)-Cd(1)-Br(2#) and N(3)-Cd(1)-Br(2) angles in the
[LDCd(µ−Br)Br] complex were 70.31(5)°, 93.09(4)°, 103.89 (2)°, 94.95(2)°, 168.44(4)°,
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86.38(3)°, and 163.44(4)°, respectively. Thus, [LDCd(µ−Br)Br] showed a distorted
octahedral geometry with N,N'N-tridentate di(2-picolyl)amine, two bridge bromides and one
terminal bromide, achieving a 6-coordinated complex. [LBCdBr2], which contains a phenyl
group substituent on the di(2-picolyl)amine residue, adopts a square pyramidal geometry
through only coordination of nitrogen in the N'-phenyl di(2-picolyl)amine moiety to the Cd
metal centre. The two Namine–Cd–Npyridine bond angles for [LBCdBr2] were 71.0(2)° and
70.4(2)°. However, the bond angles of Namine–Cd–Npyridine in [LCCdBr2] were 70.92(7)° and
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71.29(7)°. [LCCdBr2] showed a distorted octahedral geometry, achieved through
coordination of the N,N-tridentate di(2-picolyl)amine unit, two bromides and the N',O-
bidentate of nitrogen and oxygen in N'-methoxyethylamine to the Cd metal centre. Note that
the N',O-bidentate of nitrogen and oxygen in N'-methoxypropylamine did not form a N',O-
bidentate mode in dimeric [LDCd(µ −Br)Br]2. Instead, a 6-coordinate octahedral geometry
formed through the adoption of bromide-bridged dimeric structures and through the
coordination of nitrogen in the N'-methoxypropyl di(2-picolyl)amine moiety to the Cd metal
centre. These observations were comparable to the Zn(II), Cu(II), Ni(II), and Mn(II)
complexes, in which differentiation of the N',O-bidentate mode of 2-methoxy-N,N-
bis(pyridin-2-ylmethyl)ethanamine (LC) and 3-methoxy-N,N-bis(pyridin-2-ylmethyl)propan-
1-amine (LD) to the metal centre was achieved [2j, 3a, 3m, 8].
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2.3. Methyl methacrylate (MMA) polymerisation
All Cd(II) complexes activated with MMAO were examined for their catalytic activities in
MMA polymerization to get poly(methyl methacrylate) (PMMA). The Cd(II) complexes in
current study yielded PMMA, with a glass transition temperature (Tg) ranging from 121 °C to
132 °C. A higher Tg represents higher optical quality and syndiotacticity of PMMA. Isotactic
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PMMA, which is commercially produced by radical processes, has a Tg around 65 C [10].
Thus, non-radical-mediated polymerisation of MMA is commonly used to achieve a high Tg
for PMMA, i.e. MMA polymerisation through coordination complexes [10,11]. The resultant
PMMA was isolated as white solids and characterised using gel permeation chromatography
(GPC) in tetrahydrofuran (THF) using standard polystyrene as a reference. The molecular
weight (Mw) ranged from 66,700 g·mol–1 to 882,000 g·mol–1, with a polydispersity index
(PDI) value of ca. 2. The microstructure analysis of the resultant PPMA was carried out using
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1H-NMR spectroscopy, and different triads were identified in the range around syndiotactic
(rr,
δ 0.85), heterotactic (mr, δ 1.02) and isotactic (mm, δ 1.21) (Fig. 5). The results of
polymerisation, including tacticity and PDI as the average degree of polymerisation in terms
of the number of structural units and molecules [12], are summarized in Table 3.
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Fig. 5
Table 3
To confirm the catalytic activity of Cd(II) complexes in MMA polymerisation, blank test
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was performed with metal starting material [CdBr2 4H2O], anhydrous [CdCl2] or MMAO
alone at a specific temperature. Monomeric [LBCdBr2] [6.70 × 104 gPMMA·(molCd·h)–1]
had the highest activity and provided PMMA with a PDI value of 1.98 and Mw of 702,000
g·mol–1 at 60 °C. As it is clear from polymerization data (Table 3) that maximum yield and
activity was observed at 60 °C, i.e. for LBCdBr2 the activity is 0.28, 6.70, and 1.16 at 30, 60,
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90 °C, respectively. So this optimized temperature has been used for further polymerization
reactions. In addition, the catalytic activity of dimeric [LACd(µ−Br)Br]2 [7.00 × 104
gPMMA·(molCd·h)–1] and [LDCd(µ−Br)Br]2 [7.07 × 104 gPMMA·(molCd·h)–1] increased
by twofold due to the two Cd metal centres compared to the corresponding reference complex
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[CdBr2 4H2O] [2.85 × 104 gPMMA·(molCd·h)–1] and anhydrous [CdCl2] [3.53 × 104
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gPMMA·(molCd·h)–1], respectively. Presumably, dimeric Cd(II) complexes were dissociated
to monomeric Cd(II) species in solution during MMA polymerisation. In total, 500 volumes
of MMAO with respect to the amount of catalyst were used. MMAO acts as a co-catalyst and
scavenger in the polymerisation solution. Due to the poor solubility of Cd(II) complexes in
toluene, MAO was applied to the Cd(II) complex to form a cationic catalyst. We next used
250 volumes of MMAO for MMA polymerization, but the yield of PMMA decreased.
Moreover, PDI and tacticity were not affected. Thus, the additional MMAO can be used as a
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scavenger during MMA polymerisation [11a, 11c,d].
The syndiotacticity of PMMA by monomeric [LBCdBr2] was ca. 0.70, which was similar
to the other complexes including [LCCdBr2], [LACd(µ−Br)Br]2 and [LDCd(µ−Br)Br]2, and
even the reference materials [CdCl2] and [CdBr2(H2O)4] regardless of the polymerisation
temperature. Thus, the polymerization temperature has no pronounce effect on tacticity of
obtained PMMA. However, a difference was noted in the syndiotacticity of PMMA compared
to the co-catalyst, MMAO. For comparison, Cu(II) complexes with ligand N-(2-
furanylmethyl)-N-(1-3,5-dimethyl-1H-pyrazolylmethyl)-N-(phenylmethyl)amines [10], which
are known to be active catalysts for MMA polymerisation to yield syndiotactic PMMA,
yielded an rr value of up to 0.78. However, the conversion of MMA to PMMA was only 30%.
In addition, Ni(II) complexes [11a, 11d, 13] with ligands such as pentane-2,4-diol and
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phenoxy-imine showed syndiotacticity ranging from 0.73 to 0.82 with an activity of 4.20 ꢁ
104 gPMMA.(molNiꢂh)–1. Co(II) complexes with phenoxy-imine [11b] were also used as
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catalysts for MMA polymerisation with moderate activity and syndiotacticity. At this time,
the lanthanide metal organosamarium(II) [LSm(II)] complex with a bispyrrolylaldiminato
ligand is known to produce isotactic PMMA with an mm value of 98% [14].
Although the moderate syndiotacticity was not sufficient to confer a coordination
polymerisation mechanism for all complexes, we clearly observed stronger steric or
electronic effects of monomeric [LBCdBr2] compared to monomeric [LCCdBr2], dimeric
[LACd(µ−Br)Br]2 and [LDCd(µ−Br)Br]2 for MMA polymerisation. In addition, the
experiment using five equivalents of the radical inhibitor 2,2,6,6-tetramethylpiperidinyloxy
(TEMPO) during MMA polymerisation did not significantly decrease the yield of PMMA,
showing a minimum 2% and maximum 5% yield reduction, supporting that the mechanism of
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coordination polymerisation is not a radical mechanism.
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3. Conclusions
We investigated the synthesis and molecular structures of binuclear [LACd(µ−Br)Br]2 and
[LDCd(µ−Br)Br]2 and mononuclear [LBCdBr2] and [LCCdBr2] complexes, which were
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prepared through the substitution reaction of [CdBr2 4H2O] with N'-substituted N,N-di(2-
picolyl)amino ligands. The 5-coordinate monomeric [LBCdBr2] was square pyramidal
through the coordination of nitrogen in the N'-phenyl substitution of the amine moiety to the
Cd metal centre. The 6-coordinate monomeric [LCCdBr2] had a distorted octahedral
geometry achieved through bidentate coordination of nitrogen and oxygen in the N'-
methoxyethylamine moiety to the Cd metal centre. Binuclear [LACd(µ−Br)Br]2 and
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[LDCd(µ−Br)Br]2 showed a 6-coordinate octahedral geometry around the Cd centre, which
was achieved through the N,N',N-tridentate ligand, two terminal bromides and two bridged
bromides. Finally, the complex [LBCdBr2] showed the highest catalytic activity in the
presence of MMAO for MMA polymerisation with syndiotacticity of ca. 0.7 at 60 °C.
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4. Experimental
4.1. Physical measurement
[CdBr2·4H2O], 2-picolylchloride hydrochloride, aniline, cyclohexylmethylamine, 2-
methoxyethanamine, 3-methoxypropan-1-amine, NaOH, and methyl methacrylate (MMA)
were purchased from Sigma-Aldrich (St. Louis, MO) and anhydrous solvents such as
C2H5OH, DMF, diethyl ether, and dichloromethane were purchased from Merck (Darmstadt,
Germany) and used without further purification. The deionized water was prepared using a
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Millipore Milli-Q water system (Bedford, MA). Modified methylaluminoxane (MMAO) was
purchased from Tosoh Finechem Corporation (Tokyo, Japan) as 6.9% aluminum (by weight)
in a toluene solution and used without further purification. Elemental analyses (C, H, N) of
the prepared complexes were performed on an elemental analyzer (EA 1108; Carlo-Erba,
1
Milan, Italy). H-NMR (operating at 400 MHz) and 13C-NMR (operating at 100 MHz)
spectra were recorded on an Advance Digital 400 NMR spectrometer (Bruker, Billerica, MA);
chemical shifts were recorded in ppm units (δ) relative to SiMe4 as the internal standard.
Infrared (IR) spectra were recorded on a Bruker FT/IR-Alpha (neat) and the data were
reported in reciprocal centimeters. The molecular weight and molecular weight distribution of
the obtained poly(methylmethacrylate) (PMMA) were determined using gel permeation
chromatography (GPC) (CHCl3, Alliance e2695; Waters Corp., Milford, MA). Glass
transition temperature (Tg) was determined using a thermal analyzer (Q2000; TA Instruments,
New Castle, DE). X-ray crystallography was carried by Western Seoul Center of Korea Basic
Science Institute.
4.2. Preparation of ligand and Cd(II) Complexes
Ligands
N,N-di(2-picolyl)cyclohexylmethylamine
(LA),
N,N-bis(pyridin-
2ylmethyl)benzenamine (LB), 2-methoxy-N,N-bis(pyridin-2-ylmethyl)ethanamine (LC), 3-
methoxy-N,N-bis(pyridin-2-ylmethyl)propan-1-amine (LD) have been re-synthesized by
literature procedures [1e, 1f, 2f, 2h, 2j, 3a, 3m, 8].
4.2.1. [N,N-di(2-picolyl)cyclohexylmethylamine]cadmium(II) bromide([LACd(µ−Br)Br]2).
A solution of LA (148 mg, 0.500 mmol) in dried ethanol (10.0 mL) was added to a solution
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of [CdBr2·4H2O] (172 mg, 0.500 mmol) in dried ethanol (10.0 mL) at room temperature.
Precipitation of white material occurred while stirring at room temperature for 12 hours. The
powder was filtered and washed with EtOH (25.0 mL × 2), followed by washing with Et2O
(25.0 mL × 2) to get final product (0.250 g, 88.1%). The X-ray crystals of [LACd(µ−Br)Br]2
were obtained within five days from hexane diffusion into a CH2Cl2 solution of
[LACd(µ−Br)Br]2 (0.0500 g). Analysis calculated for C38H50Br4Cd2N6: C, 40.2%; H, 4.44%;
N, 7.40%. Found: C, 41.0%; H, 4.56%; N, 7.57%. 1H-NMR (DMSO-d6, 400 MHz): δ 8.74 (d,
4H, J = 4.0 Hz, -NC5H4-), 8.00 (t, 4H, J = 7.0 Hz, -NC5H4-), 7.57 (d, 8H, J = 7.6 Hz, -
NC5H4-), 4.05 (s, 8H, -CH2NC5H4-), 2.50 (d, 4H, J= 5.6 Hz, -CH2C6H11-), 1.64 (m, 12H, -
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C6H11-), 1.08 (m, 6H, -C6H11-), 0.79 (m, 4H, -C6H11-). C-NMR (DMSO-d6, 125 MHz): δ
154.18 (s, 4C, ipso-NC5H4-), 150.00 (d, 4C, J = 172 Hz, -NC5H4-), 139.79 (d, 4C, J = 164 Hz,
-NC5H4-), 124.59 (d, 4C, J = 164 Hz, -NC5H4-), 124.25 (d, 4C, J = 169 Hz, -NC5H4-), 59.24
(t, 4C, J = 139 Hz, -CH2NC5H4-), 57.90 (t, 2C, J = 139 Hz, -CH2C6H11-), 33.53(d, 2C, J =
125 Hz, ipso-C6H11-), 33.41 (t, 4C, J = 123 Hz, o-C6H11-), 25.54 (t, 6C, J = 123 Hz, p,m-
C6H11-). IR (Solid neat; cm-1): 3145 (w), 2920 (w), 2851 (w), 1601 (m), 1559 (m), 1444 (s),
1048 (m), 1012 (m), 957 (m), 841 (s), 762 (s), 712 (s), 641 (s).
4.2.2. [N,N-bis(pyridin-2ylmethyl)benzenamine]cadmium(II) bromide([LBCdBr2]).
[LBCdBr2] was prepared according to the procedure described for [LACd(µ−Br)Br]2, except
utilizing LB (140 mg, 0.500 mmol) and [CdBr2·4H2O] (172 mg, 0.500 mmol). The white
solid was filtered and washed with EtOH (25.0 mL × 2), followed by washing with Et2O
(25.0 mL × 2) (0.240 g, 88.3%). Crystals suitable for the X-ray study of [LBCdBr2] were
obtained within five days from Et2O (10.0 mL) diffusion into a DMF solution (10.0 mL) of
[LBCdBr2] (0.0500 g). Analysis calculated for C18H17Br2CdN3: C, 39.4%; H, 3.13%; N,
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7.67%. Found: C, 39.6%; H, 3.16%; N, 7.84%. H-NMR (DMSO-d6, 400 MHz): δ 8.62 (d,
2H, J = 4.8 Hz, -NC5H4-), 7.82 (t, 2H, J = 7.6 Hz, -NC5H4-), 7.38 (d, 2H, J = 8.0 Hz, -
NC5H4-), 7.36 (t, 2H, J = 6.8 Hz, -NC5H4-), 7.11 (t, 2H, J = 7.6 Hz, m-C6H5-), 6.78 (d, 2H, J
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=7.2 Hz,o-C6H5-), 6.69 (t, 1H, J = 7.2 Hz, p-C6H5-), 4.77 (s, 4H, -CH2NC5H4-). C-NMR
(DMSO-d6, 125 MHz): δ 163.19 (s, 2C, ipso-NC5H4-), 158.11 (s, 1C, ipso-C6H5-), 149.94 (d,
2C, J = 167 Hz, -NC5H4-), 139.10 (d, 2C, J = 163 Hz, -NC5H4-), 129.76 (d, 2C, J = 150 Hz,
m-C6H5-), 123.92 (d, 2C, J = 164 Hz, -NC5H4-), 123.41 (d, 2C, J = 161 Hz, -NC5H4-), 116.66
(d, 1C, J = 165 Hz p-C6H5-), 113.49 (d, 2C, J = 165, o-C6H5-), 58.43 (t, 2C, J = 137 Hz -
CH2NC5H4-). IR (solid neat; cm-1): 3112 (w), 3040 (w), 2897 (w), 2657 (w), 1773 (m), 1667
(m), 1524 (s), 1178 (m), 1087 (m), 898 (m), 833 (m), 758 (s), 674 (s).
4.2.3. [2-methoxy-N,N-bis(pyridin-2-ylmethyl)ethanamine]cadmium(II) bromide([LCCdBr2]).
[LcCdBr2] was prepared according to the procedure described for [LACd(µ−Br)Br]2, except
utilizing LC (260 mg, 1.00 mmol) and [CdBr2·4H2O] (344 mg, 1.00 mmol). The white solid
was filtered and washed with EtOH (25.0 mL × 2), followed by washing with Et2O (25.0 mL
× 2) (0.450 g, 85.0%). Crystals suitable for the X-ray study of [LcCdBr2] were obtained
within three days from hexane (10.0 mL) diffusion into a CH2Cl2 solution (10.0 mL) of
[LcCdBr2] (0.0500 g). Analysis calculated for C15H19Br2CdN3O: C, 34.02%; H, 3.62%; N,
1
7.94%. Found: C, 34.48%; H, 3.68%; N, 8.02%. H-NMR (DMSO-d6, 400 MHz): δ 8.69 (d,
2H, J = 4.4 Hz, -NC5H4-), 8.04 (t, 2H, J = 7.6 Hz, -NC5H4-), 7.62 (d, 2H, J = 6.0 Hz, -
NC5H4-), 7.57 (t, 2H, J = 8.0 Hz, -NC5H4-), 4.19 (s, 4H, -CH2NC5H4-), 2.96 (s, 3H, -
CH3OCH2CH2N-), 2.78 (t, 2H, J =5.0 Hz, -CH3OCH2CH2N-), 2.51 (t, 2H, J = 5.6 Hz, -
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CH3OCH2CH2N-). C-NMR (DMSO-d6, 100 MHz): δ 155.12 (s, 2C, ipso-NC5H4-), 148.35
(d, 2C, J = 177 Hz, -NC5H4-), 140.21 (d, 2C, J = 172 Hz, -NC5H4-), 124.87 (d, 2C, J = 165
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Hz, -NC5H4-), 124.62 (d, 2C, J = 167 Hz, -NC5H4-), 67.67 (t, 1C, J = 151 Hz, -
CH3OCH2CH2N-), 59.01 (t, 2C, J = 137 Hz, -CH2NC5H4-), 58.19 (q, 1C, J = 142 Hz, -
CH3OCH2CH2N-), 55.19 (t, 1C, J = 133 Hz, -CH3OCH2CH2N-). IR (Solid neat; cm-1): 3123
(w), 3002 (w), 2802 (w), 1695 (m), 1598 (m), 1544 (w), 1439 (s), 1306 (m), 1144 (m), 1097
(s), 1019 (s), 835 (m), 772 (s), 643 (m).
4.2.4.
[3-methoxy-N,N-bis(pyridin-2-ylmethyl)propan-1amine]cadmium(II)
bromide
([LDCd(
µ-Br)Br]2).
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[LDCd(µ−Br)Br]2 was prepared according to the procedure described for [LACd(µ−Br)Br]2,
except utilizing LD (130 mg, 0.500 mmol) and [CdBr2·4H2O] (172 mg, 0.500 mmol). The
white solid was filtered and washed with EtOH (25.0 mL × 2), followed by washing with
Et2O (25.0 mL × 2) (0.240 g, 88.3%). Crystals suitable for the X-ray study of
[LDCd(µ−Br)Br]2 were obtained within three days from Et2O (10.0 mL) diffusion into a
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DMF solution (10.0 mL) of [LDCd(µ−Br)Br]2 (0.0500 g). Analysis calculated for
C32H42Br4Cd2N6O2: C, 35.35%; H, 3.89%; N, 7.73%. Found: C, 34.84%; H, 3.85%; N,
7.44%. 1H-NMR (DMSO-d6, 400 MHz): δ 8.78 (d, 4H, J = 4.0 Hz, -NC5H4-), 8.00 (t, 4H, J =
7.2 Hz, -NC5H4-), 7.57 (t, 4H, J = 6.4 Hz, -NC5H4-), 7.53 (d, 4H, J = 8.0 Hz, -NC5H4-), 4.12
(s, 4H, -CH2NC5H4-), 3.89 (s, 4H, -CH2NC5H4-), 3.21 (t, 4H, J = 12.4 Hz, -
CH3OCH2CH2CH2N-), 3.13 (s, 6H, -CH3OCH2CH2CH2N-), 2.73 (t, 4H, J = 12.0 Hz, -
CH3OCH2CH2CH2N-), 1.71 (m, 4H, -CH3OCH2CH2CH2N-). 13C-NMR (DMSO-d6, 100
MHz): δ 155.24 (s, 4C, ipso-NC5H4-), 148.99 (d, 4C, J = 169 Hz, -NC5H4-), 140.15 (d, 4C, J
= 161 Hz, -NC5H4-), 124.81 (d, 4C, J = 160 Hz, -NC5H4-),124.44 (d, 4C, J = 167 Hz, -
NC5H4-), 70.43 (t, 2C, J = 120 Hz, -CH3OCH2CH2CH2N-), 58.14 (t, 4C, J = 139 Hz, -
CH2NC5H4-), 57.06 (q, 2C, J = 139 Hz, -CH3OCH2CH2CH2N-), 52.83 (t, 2C, J = 136 Hz, -
CH3OCH2CH2CH2N-), 24.29 (t, 2C, J = 123 Hz, -CH3OCH2CH2CH2N-). IR (solid neat; cm-
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1): 3146 (w), 2977 (w), 2808 (w), 1694 (m), 1602 (w), 1524 (w), 1438 (w), 1380 (m), 1089
(m), 837 (w), 771 (s), 640 (s).
4.3. X-Ray crystallographic studies
A crystal was isolated 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 a nitrogen cold stream (200 K). Data collection and integration were performed
with SMART and SAINT-Plus software packages [15]. Semi-empirical absorption
corrections based on equivalent reflections were applied using SADABS [16]. Structures
were solved using direct methods and refined using a full-matrix least-squares method on F2
using SHELXTL [17]. All non-hydrogen atoms were refined anisotropically. Hydrogen
atoms were added to their geometrically ideal positions. Crystallographic and structural data
are summarized in Table 1.
4.4. Catalytic activity for MMA polymerization
The methyl methacrylate (MMA) was extracted with 10% sodium hydroxide, washed with
water, dried over magnesium sulfate, and distilled over calcium hydride under reduced
pressure before use. In a Schlenk line, complex (15.0 µmol, 8.50 mg for [LACd(µ−Br)Br]2;
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8.20 mg for [LBCdBr2]; 7.90 mg for [LCCdBr2]; 8.20 mg for [LDCd(µ−Br)Br]2) was
dissolved in dried toluene (10.0 mL) followed by the addition of modified MMAO (6.90 wt%
in toluene, 3.25 mL, 7.50 mmol, and [MMAO]0/[Pd(II) catalyst]0=500) as a co-catalyst. The
solution was stirred at 60 °C for 20 min. The MMA (5.00 mL, 47.1 mmol, [MMA]0/[Pd(II)
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catalyst]0=3100) was added to the above reaction mixture and stirred at 60 °C for 2 h to
obtain a viscous solution. MeOH (2.00 mL) was added to terminate the polymerization. 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). The resulting polymer was
filtered and washed with MeOH (250 mL × 2) to yield poly(methylmethacrylate) (PMMA),
which was vacuum-dried at 60 °C.
Supplementary materials
CCDC 1033592 ̶ 1033595 contains the supplementary crystallographic data for complexes
[LACd(µ−Br)Br]2, [LBCdBr2], [LCCdBr2], and [LDCd(µ−Br)Br]2, 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.
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). 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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Scheme 1. Synthesis of [LnCdBr2]m (Ln = LA, m = 2; LB, m = 1; LC, m = 1; LD, m = 2).
25

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Table 1
Crystal data and structural refinement for [LnCdBr2]m (Ln = LA, m = 2; LB, m = 1; LC, m = 1; LD, m = 2).
[LBCdBr2]
[LCCdBr2]
[LACd(µ−Br)Br]2
[LDCd(µ−Br)Br]2
Empirical formula
Formula weight
Temperature
C38H50Br4Cd2N6
C18H17Br2CdN3
C15H19Br2CdN3O
C32H42Br4Cd2N6O
1135.28
547.57
529.55
1087.14
200(2) K
200(2)K
100(2)K
100(2)K
Wavelength
0.71073 Å
0.71073 Å
0.630 Å
0.630 Å
Crystal system
Space group
Monoclinic
P21/c
Monoclinic
P21/n
Monoclinic
P21/c
Monoclinic
P21/n
Unit cell dimensions
a = 14.249(1) Å
b = 18.443(2) Å
c = 17.123(1) Å
α = 90°.
a = 8.5180(3) Å
b = 14.6435(6) Å
c = 15.0213(6) Å
α = 90°.
a = 8.372(2) Å
b = 26.397(5) Å
c = 9.020(2) Å
α = 90°.
a = 9.771(2) Å
b = 15.510(3) Å
c = 12.513(3) Å
α = 90°.
β = 111.826(2)°
γ = 90°
β =100.268(1)°
γ = 90°
β =116.89(3)°
γ = 90°
β =103.12(3)°
γ = 90°
Volume, Z
4177.0(6) Å3, 4
1.805 g/cm3
4.879 mm-1
2224
1843.65(12) Å3, 4
1.973 g/cm3
5.523 mm-1
1056
1777.9 (7) Å3, 4
1.978 g/cm3
4.161 mm-1
1024
1846.8 (7) Å3, 2
1.955 g/cm3
4.008 mm-1
1056
Density (calculated)
Absorption coefficient
F(000)
Crystal size
0.17× 0.11× 0.04 mm3
0.20× 0.13× 0.04 mm3
0.10× 0.05× 0.05 mm3
0.10× 0.05× 0.03 mm3
Theta range for data 1.54 to 26.02°
collection
1.96 to 28.31°
2.346 to 29.482°
2.423 to 29.513°
Index ranges
-17≤h≤17
-22≤k≤11
-11≤h≤11
-15≤k≤19
-13≤h≤13
-41≤k≤41
-15≤h≤15
-24≤k≤24
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-20≤l≤21
-19≤l≤20
-14≤l≤14
-19≤l≤19
Reflections collected
Independent reflections
Completeness to theta
22.210°
25723
12958
25574
26452
=
8229 [R(int) = 0.0643]
99.9 %
4501 [R(int) = 0.0205]
97.9%
7053 [R(int) = 0.0529]
99.6%
7368 [R(int) = 0.0570]
99.7%
Absorption correction
Semi-empirical
equivalents
from Semi-empirical
from Empirical
Empirical
Refinement method
equivalents
Full-matrix least-
squares on F2
8229 / 18 / 451
1.098
Full-matrix least-
squares on F2
4501 / 0 / 217
1.212
Full-matrix least-
squares on F2
7053 / 0 / 210
1.079
Full-matrix least-
squares on F2
7368 / 0 / 210
1.034
Data / restraints / parameters
Goodness-of-fit on F2
Final
R
indices
[I>2sigma(I)]
R1 = 0.0582
R1 = 0.0359
R1 = 0.0350
R1 = 0.0381
R indices (all data)
wR2 = 0.1537
R1 = 0.1018
wR2 = 0.0695
R1 = 0.0626
wR2 = 0.0900
R1 = 0.0397
wR2 = 0.0955
R1 = 0.0444
Largest diff. peak and hole
wR2 = 0.2278
3.058 and -1.758 e.Å-3
wR2 = 0.1297
1.865 and -1.831 e.Å-3
wR2 = 0.0918
3.513 and -3.878 e.Å-3
wR2 = 0.0976
1.995 and -3.461 e.Å-3
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1
2
3
Table 2
Selected bond lengths (Å) and angles (°) of [LnCdBr2]m (Ln = LA, m = 2; LB, m = 1; LC, m =
1; LD, m = 2).
[LBCdBr2]
[LCCdBr2]
[LACd(µ−Br)Br]2
[LDCd(µ−Br)Br]2
Bond Lengths (Å)
Cd(1)-N(1)
2.382(8)
2.472(7)
2.419(8)
2.837(1)
2.615(1)
2.704(1)
2.382(8)
2.488(7)
2.389(8)
2.716(1)
2.820(1)
2.639(1)
Cd(1)-N(1)
2.303(6)
Cd(1)-N(1)
2.346(2)
2.438(2)
2.329(2)
2.5564(5)
2.6817(5)
2.580(2)
1.459(3)
1.467(3)
1.479(4)
1.333(7)
1.491(6)
1.407(7)
Cd(1)-N(1)
2.3
2.4
2.3
2.6
2.7
2.7
2.3
2.4
2.3
2.6
2.7
2.7
Cd(1)-N(2)
Cd(1)-N(3)
Cd(1)-Br(1)
Cd(1)-Br(2)
Cd(1)-Br(3)
Cd(2)-N(4)
Cd(2)-N(5)
Cd(2)-N(6)
Cd(2)-Br(1)
Cd(2)-Br(3)
Cd(2)-Br(4)
Cd(1)-N(2)
Cd(1)-N(3)
Cd(1)-Br(1)
Cd(1)-Br(2)
N(1)-C(5)
N(2)-C(6)
N(2)-C(7)
N(2)-C(13)
N(3)-C(8)
N(5)-C(6)
N(7)-C(8)
2.523(6)
2.310(6)
2.585(1)
2.538(1)
1.348(9)
1.475(9)
1.479(9)
1.454(9)
1.318(9)
1.49(1)
Cd(1)-N(2)
Cd(1)-N(3)
Cd(1)-Br(1)
Cd(1)-Br(2)
Cd(1)-O(1)
N(2)-C(6)
Cd(1)-N(2)
Cd(1)-N(3)
Cd(1)-Br(1)
Cd(1)-Br(2)
Cd(1)-Br(2#)
Cd(1#)-N(1#)
Cd(1#)-N(2#)
Cd(1#)-N(3#)
Cd(1#)-Br(1#)
Cd(1#)-Br(2)
Cd(1#)-Br(2#)
N(2)-C(7)
N(2)-C(13)
C(13)-C(14a)
C(14a)-O(1)
C(15a)-O(1)
1.52(1)
Bond Angles (°)
N(1)-Cd(1)-N(2)
N(1)-Cd(1)-N(3)
N(1)-Cd(1)-Br(1)
N(1)-Cd(1)-Br(2)
N(1)-Cd(1)-Br(3)
N(2)-Cd(1)-Br(1)
N(2)-Cd(1)-Br(2)
N(2)-Cd(1)-Br(3)
N(3)-Cd(1)-N(2)
N(3)-Cd(1)-Br(2)
N(3)-Cd(1)-Br(3)
Br(2)-Cd(1)-Br(3)
70.9(3)
103.3(3)
82.6(2)
98.9(2)
150.4(2)
103.6(2)
155.1(2)
87.3(2)
69.1(3)
92.4(2)
86.3(2)
108.63(4)
N(1)-Cd(1)-N(2)
N(1)-Cd(1)-N(3)
N(1)-Cd(1)-Br(1)
N(1)-Cd(1)-Br(2)
N(2)-Cd(1)-Br(1)
N(2)-Cd(1)-Br(2)
N(3)-Cd(1)-N(2)
N(3)-Cd(1)-Br(1)
N(3)-Cd(1)-Br(2)
Br(1)-Cd(1)-Br(2)
C(1)-N(1)-Cd(1)
C(12)-N(3)-Cd(1)
70.4(2)
N(1)-Cd(1)-N(2)
N(1)-Cd(1)-N(3)
N(1)-Cd(1)-Br(1)
N(1)-Cd(1)-O(1)
N(2)-Cd(1)-N(3)
N(2)-Cd(1)-Br(1)
N(2)-Cd(1)-O(1)
N(3)-Cd(1)-Br(1)
N(3)-Cd(1)-Br(2)
N(3)-Cd(1)-O(1)
Br(1)-Cd(1)-Br(2)
Br(1)-Cd(1)-O(1)
71.29(7)
141.56(6)
108.25(5)
81.19(8)
70.92(7)
160.84(5)
69.87(8)
105.09(4)
98.18(5)
79.61(7)
106.48(2)
91.03(5)
N(1)-Cd(1)-N(2)
N(1)-Cd(1)-N(3)
N(1)-Cd(1)-Br(1)
N(1)-Cd(1)-Br(2#)
N(2)-Cd(1)-N(3)
N(2)-Cd(1)-Br(1)
N(2)-Cd(1)-Br(2#)
N(3)-Cd(1)-Br(1)
N(3)-Cd(1)-Br(2#)
Br(1)-Cd(1)-Br(2)
Br(1)-Cd(1)-Br(2#)
Br(2)-Cd(1)-Br(2#)
70
94
95
16
71
15
10
92
94
10
94
86
141.4(2)
96.0(2)
101.8(2)
115.1(1)
125.1(1)
71.0(2)
100.1(2)
100.1(2)
119.75(4)
122.3(5)
120.6(5)
4
5
28