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Logo of actae2this articlesearchopen accesssubmitActa Crystallographica Section E: Crystallographic CommunicationsActa Crystallographica Section E: Crystallographic Communications
 
Acta Crystallogr E Crystallogr Commun. 2017 April 1; 73(Pt 4): 640–643.
Published online 2017 March 31. doi:  10.1107/S2056989017004492
PMCID: PMC5382640

Crystal structure of [Cu(tmpen)](BF4)2 {tmpen is N,N,N′,N′-tetra­kis­[(6-methyl­pyridin-2-yl)meth­yl]ethane-1,2-di­amine}

Abstract

The mononuclear copper title complex {N,N,N′,N′-tetra­kis­[(6-methyl­pyridin-2-yl)meth­yl]ethane-1,2-di­amine-κ6 N}copper(II) bis­(tetra­fluorido­borate), [Cu(C30H36N6)](BF4)2, is conveniently prepared from the reaction of Cu(BF4)2·6H2O with N,N,N′,N′-tetra­kis­[(6-methyl­pyridin-2-yl)meth­yl]ethane-1,2-di­amine (tmpen) in aceto­nitrile at room temperature in air. The complex shows a distorted octa­hedral environment around the CuII cation (site symmetry 2) and adopts the centrosymmetric space group C2/c. The presence of the 6-methyl substituent hinders the approach of the pyridine group to the CuII core. The bond lengths about the CuII atom are significantly longer than those of analogues without the 6-methyl substituents.

Keywords: crystal structure, copper, catalysis, CO2 reduction, electrochemistry

Chemical context  

Copper complexes with polypyridine ligands are of great inter­est in catalytic reactions. For example, the copper-based complex CuBr[N,N,N′,N′-tetra­kis­(2-pyridyl­meth­yl)ethyl­ene­di­amine] (TPEN) is reported as a versatile and highly active catalyst for acrylic, methacrylic and styrenic monomers (Tang et al., 2006  ). Copper(II) N-benzyl-N,N′,N′-tris­(pyridin-2-ylmeth­yl)ethyl­enedi­amine (bztpen) displays high catalytic activity for electrochemical proton reduction in acidic aqueous solutions, with a calculated hydrogen-generation rate constant (kobs) of over 10000 s−1 (Zhang et al., 2014  ). [Cu2(m-xpt)2(NO3)2](PF6)2 [m-xpt = m-xylylenebis(pyridyl­triazole)] can selectively capture CO2 from air and reduce it to oxalate, in the form of an oxalate-bridged complex (Pokharel et al., 2014  ). Generally, the reduction of a metal complex is accompanied by ligand dissociation (reductive dissociation), which is able to give the appearance of an open site for catalytic reaction. Herein, we describe the structure of the title complex, 1.

An external file that holds a picture, illustration, etc.
Object name is e-73-00640-scheme1.jpg

Structural commentary  

In the title complex (Fig. 1  ), the coordination sphere of the copper(II) atom is distorted octa­hedral, presumably as a result of the introduction of the 6-methyl substituent. Two pyridine nitro­gen atoms (N1, N1′) and two amino nitro­gen atoms (N2, N2′) form the equatorial planar coordination, while the apical positions are occupied by the other two pyridine nitro­gen atoms (N3, N3′). The CuII ion lies almost in the equatorial plane. The Cu—N bond lengths for the two axial pyridine-nitro­gen atoms [Cu—N3 = 2.5742 (13) Å] are significantly longer than those for the other four nitro­gen atoms [Cu—N1 = 2.0571 (13), Cu—N2 = 2.0311 (13) Å]. The long Cu—N3 distance indicates a weak connection between copper and pyridine, which is apt to dissociate under reductive conditions (Tang et al., 2006  ). As a result of steric hindrance from the methyl group, the N3—Cu1—N3′ bond angle is not linear but rather 164.94 (5)°. The pyridine rings in the equatorial plane (N1/C2–C6 and N1′/C2′–C6′) subtend a dihedral angle of 35.03 (9)°.

Figure 1
The molecular entities in the structure of complex 1. Atoms N1A, N2A and N3A are generated by the symmetry operation −x, y, An external file that holds a picture, illustration, etc.
Object name is e-73-00640-efi7.jpg − z.

The distortion about the CuII atom is in favour of the reductive dissociation of one pyridine group. On a cathodic scan under Ar, complex 1 features one reversible couple based on copper at 0.26 V (vs Fc+/0), assigned to CuII/I (Fig. 2  ). The free ligand tmpen is electrochemically silent in the potential range (Fig. 3  ). The good reversibility of the couple indicates negligible change in the configuation of 1 under reductive conditions.

Figure 2
Cyclic voltammograms of complex 1 (1 mM) under Ar in CH3CN with 0.1 M nBu4NBF4 as the supporting electrolyte.
Figure 3
Cyclic voltammograms of the TMPEN ligand (1 mM) under Ar in CH3CN with 0.1 M nBu4NBF4 as the supporting electrolyte.

Supramolecular features  

While there are no classical hydrogen bonds in the crystal structure, C—H(...)N and C—H(...)F inter­actions are observed (Fig. 4  , Table 1  ).

Figure 4
The crystal packing showing the C—H(...)F hydrogen bonds.
Table 1
Hydrogen-bond geometry (Å, °)

Database survey  

There are four published reports of polypyridine copper complexes (Kaur et al., 2015  ; Meyer et al., 2015  ; Bania & Deka, 2012  ; Yoon et al., 2005  ) , but to the best of our knowledge, the title compound has not been reported previously. Among the earliest reports, the copper complex with an N,N,N′,N′-tetra­kis­(2-pyridyl­meth­yl)ethyl­enedi­amine (TPEN) ligand is most similar to title complex in configuration. In the presence of ascorbic acid as a reducing agent, Cu2+(TPEN) displays high activity in atom-transfer radical addition (ATRA) reactions (Kaur et al., 2015  ). In contrast to Cu2+(TPEN), the title complex exhibits greater steric hindrance, which results in an evident Jahn–Teller effect on the configuration. In the title complex, the axial Cu—N bonds to pyridyl nitro­gen atoms [2.5742 (13) Å)] are significantly longer than in Cu2+(TPEN) [2.377 (3) and 2.308 (2) Å] while the differences in the equatorial Cu—N distances are negligible (Yoon et al., 2005  ). The other two reported polypyridine copper complexes show similar distorted octa­hedral coordination spheres around the Cu2+ cation, but the ligands are evidently different from the title complex.

Synthesis and crystallization  

The tetra­pyridinedi­amine ligand N,N,N′,N′-tetra­kis­[(6-methyl­pyridin-2-yl)meth­yl]ethane-1,2-di­amine (tmpen) was prepared according to literature procedures (Mikata et al., 2005  ). 1H NMR (CDCl3, 600 MHz): δ 7.44 (d, 4H), 7.31 (m, 4H), 6.94 (d, 4H), 3.74 (s, 8H), 2.75 (s, 4H), 2.48 (s, 12H). ESI–MS: calculated for [M + H]+: m/z 481.65.19; found: 481.31.

For the preparation of [Cu(tmpen)](BF4)2 (1), Cu(BF4)2·H2O (0.16 g, 0.5 mmol) was added to an aceto­nitrile solution (5 ml) of tmpen (0.2 g, 0.5 mmol). The mixture was stirred at room temperature for 6 h. The blue solution was then transferred to tubes, which were placed in a flask containing ether. Block-shaped crystals were obtained in a yield of 85% (0.25 g). Analysis calculated for C30H36B2CuF8N6 (%): C, 50.52; H, 5.09; N, 11.78; found: 50.51; H, 5.08; N, 11.75; MS (TOF–ES): m/z =272.6641 {[M − 2(BF4)]/2}+, 579.3025 [M − 2(BF4)+Cl]+.

Refinement  

Crystal data, data collection and structure refinement details are summarized in Table 2  . All F atoms of the BF4 group were split into two groups and their ccupancies determined via a free variable refinement. All hydrogen atoms were refined in riding mode with C—H= 0.93–0.97 and U iso(H) = 1.2U eq(C) or 1.5U eq(C) for methyl H atoms.

Table 2
Experimental details

Supplementary Material

Crystal structure: contains datablock(s) I. DOI: 10.1107/S2056989017004492/pj2042sup1.cif

Structure factors: contains datablock(s) I. DOI: 10.1107/S2056989017004492/pj2042Isup2.hkl

CCDC reference: 1440025

Additional supporting information: crystallographic information; 3D view; checkCIF report

supplementary crystallographic information

Crystal data

[Cu(C30H36N6)](BF4)2F(000) = 1476
Mr = 717.81Dx = 1.487 Mg m3Dm = 1.485 Mg m3Dm measured by none
Monoclinic, C2/cMo Kα radiation, λ = 0.71073 Å
a = 18.670 (2) ÅCell parameters from 5092 reflections
b = 12.8309 (15) Åθ = 2.3–27.5°
c = 14.0146 (16) ŵ = 0.76 mm1
β = 107.193 (2)°T = 296 K
V = 3207.2 (6) Å3Block, purple
Z = 40.30 × 0.20 × 0.10 mm

Data collection

Bruker APEXII CCD area detector diffractometer3334 reflections with I > 2σ(I)
Radiation source: sealed tubeRint = 0.023
phi and ω scansθmax = 27.5°, θmin = 2.0°
Absorption correction: multi-scan (SADABS; Bruker, 2013)h = −12→24
Tmin = 0.833, Tmax = 0.927k = −16→16
10330 measured reflectionsl = −18→16
3676 independent reflections

Refinement

Refinement on F240 restraints
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.034H-atom parameters constrained
wR(F2) = 0.097w = 1/[σ2(Fo2) + (0.0549P)2 + 2.078P] where P = (Fo2 + 2Fc2)/3
S = 1.06(Δ/σ)max = 0.002
3676 reflectionsΔρmax = 0.97 e Å3
254 parametersΔρmin = −0.25 e Å3

Special details

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2)

xyzUiso*/UeqOcc. (<1)
Cu10.00000.23649 (2)0.25000.02731 (10)
N10.08743 (7)0.15031 (11)0.33863 (10)0.0289 (3)
N20.07204 (7)0.35197 (10)0.31608 (10)0.0286 (3)
N30.07474 (8)0.26278 (11)0.12413 (11)0.0333 (3)
C10.08575 (13)0.00170 (16)0.22917 (16)0.0537 (6)
H1A0.03580.02420.19450.081*
H1B0.0863−0.07260.23720.081*
H1C0.11900.02090.19140.081*
C20.11081 (9)0.05237 (13)0.32937 (13)0.0336 (4)
C30.16060 (10)0.00215 (15)0.40983 (15)0.0401 (4)
H3A0.1747−0.06650.40360.048*
C40.18899 (10)0.05447 (16)0.49875 (14)0.0429 (4)
H4A0.21950.02010.55440.052*
C50.17170 (10)0.15836 (16)0.50451 (13)0.0387 (4)
H5B0.19380.19670.56200.046*
C60.12094 (9)0.20416 (14)0.42312 (12)0.0302 (3)
C70.09995 (10)0.31833 (13)0.42177 (12)0.0325 (3)
H7A0.06130.32800.45450.039*
H7B0.14340.35930.45690.039*
C80.02775 (10)0.45062 (13)0.30188 (13)0.0359 (4)
H8A0.06110.51010.30960.043*
H8B0.00120.45560.35170.043*
C90.13719 (9)0.36030 (14)0.27541 (13)0.0351 (4)
H9A0.17510.31080.31070.042*
H9B0.15850.42950.29030.042*
C100.12107 (9)0.34140 (14)0.16498 (13)0.0328 (4)
C110.15943 (12)0.39957 (17)0.11282 (16)0.0485 (5)
H11A0.18960.45520.14290.058*
C120.15162 (15)0.3728 (2)0.01508 (17)0.0619 (6)
H12A0.17700.4098−0.02200.074*
C130.10602 (14)0.2910 (2)−0.02692 (16)0.0550 (6)
H13A0.10080.2714−0.09250.066*
C140.06769 (11)0.23748 (15)0.02882 (15)0.0394 (4)
C150.01701 (13)0.14901 (19)−0.01745 (17)0.0551 (6)
H15A0.00110.11360.03310.083*
H15B0.04350.1012−0.04750.083*
H15C−0.02600.1755−0.06760.083*
B10.31688 (17)0.1726 (2)0.2629 (2)0.0555 (6)
F10.3874 (4)0.1486 (8)0.3288 (7)0.124 (2)0.639 (19)
F20.3115 (7)0.2722 (5)0.2310 (10)0.101 (3)0.639 (19)
F30.2668 (5)0.1626 (7)0.3154 (7)0.091 (2)0.639 (19)
F40.3036 (5)0.1037 (4)0.1872 (4)0.0811 (16)0.639 (19)
F1A0.3844 (7)0.1315 (12)0.2879 (15)0.122 (3)0.361 (19)
F4A0.2738 (11)0.1220 (13)0.1767 (8)0.119 (4)0.361 (19)
F3A0.2862 (10)0.1559 (10)0.3370 (10)0.083 (3)0.361 (19)
F2A0.3273 (13)0.2753 (11)0.2471 (18)0.107 (4)0.361 (19)

Atomic displacement parameters (Å2)

U11U22U33U12U13U23
Cu10.02415 (15)0.02360 (15)0.02934 (16)0.0000.00043 (11)0.000
N10.0245 (6)0.0307 (7)0.0284 (6)0.0006 (5)0.0030 (5)−0.0015 (5)
N20.0284 (6)0.0289 (7)0.0272 (6)−0.0029 (5)0.0063 (5)−0.0041 (5)
N30.0315 (7)0.0364 (8)0.0341 (7)−0.0066 (6)0.0127 (6)−0.0055 (6)
C10.0595 (13)0.0401 (11)0.0500 (12)0.0127 (9)−0.0017 (10)−0.0144 (9)
C20.0275 (8)0.0323 (8)0.0385 (9)0.0028 (6)0.0058 (7)−0.0014 (7)
C30.0311 (8)0.0348 (9)0.0503 (11)0.0071 (7)0.0061 (8)0.0059 (8)
C40.0303 (9)0.0528 (11)0.0395 (9)0.0074 (8)0.0008 (7)0.0110 (8)
C50.0310 (8)0.0518 (11)0.0294 (8)0.0013 (8)0.0031 (7)−0.0006 (7)
C60.0251 (7)0.0361 (8)0.0280 (8)−0.0007 (6)0.0056 (6)−0.0023 (6)
C70.0340 (8)0.0359 (9)0.0255 (8)−0.0018 (7)0.0054 (6)−0.0055 (6)
C80.0412 (9)0.0254 (8)0.0396 (9)−0.0019 (7)0.0095 (8)−0.0048 (7)
C90.0292 (8)0.0410 (9)0.0343 (8)−0.0108 (7)0.0083 (7)−0.0063 (7)
C100.0295 (8)0.0365 (9)0.0332 (8)−0.0044 (6)0.0108 (7)−0.0036 (7)
C110.0513 (11)0.0490 (11)0.0486 (11)−0.0181 (9)0.0199 (9)−0.0020 (9)
C120.0711 (15)0.0762 (16)0.0472 (12)−0.0258 (13)0.0311 (11)0.0008 (11)
C130.0630 (14)0.0714 (15)0.0368 (10)−0.0142 (12)0.0243 (10)−0.0099 (10)
C140.0370 (9)0.0468 (10)0.0359 (9)−0.0035 (7)0.0134 (8)−0.0100 (7)
C150.0571 (13)0.0637 (14)0.0487 (12)−0.0175 (11)0.0222 (10)−0.0265 (10)
B10.0770 (18)0.0415 (12)0.0585 (15)−0.0006 (12)0.0363 (14)−0.0085 (11)
F10.090 (3)0.132 (5)0.130 (5)0.017 (3)−0.001 (3)−0.019 (3)
F20.130 (5)0.043 (2)0.123 (6)−0.001 (3)0.026 (4)0.012 (3)
F30.086 (3)0.109 (4)0.105 (5)−0.009 (2)0.067 (3)−0.023 (3)
F40.143 (4)0.0526 (17)0.0577 (18)0.016 (2)0.045 (2)−0.0101 (15)
F1A0.089 (5)0.102 (5)0.193 (10)0.023 (4)0.068 (6)−0.033 (7)
F4A0.169 (9)0.102 (6)0.085 (5)−0.024 (6)0.036 (5)−0.057 (4)
F3A0.146 (9)0.059 (4)0.061 (4)−0.017 (5)0.056 (5)−0.011 (3)
F2A0.166 (9)0.057 (5)0.097 (6)−0.053 (5)0.034 (7)0.000 (4)

Geometric parameters (Å, º)

Cu1—N2i2.0311 (13)C7—H7B0.9700
Cu1—N22.0312 (13)C8—C8i1.516 (3)
Cu1—N12.0571 (13)C8—H8A0.9700
Cu1—N1i2.0571 (13)C8—H8B0.9700
Cu1—N32.5742 (13)C9—C101.506 (2)
Cu1—N3i2.5742 (13)C9—H9A0.9700
N1—C21.349 (2)C9—H9B0.9700
N1—C61.354 (2)C10—C111.384 (3)
N2—C71.482 (2)C11—C121.378 (3)
N2—C91.492 (2)C11—H11A0.9300
N2—C81.493 (2)C12—C131.370 (3)
N3—C101.342 (2)C12—H12A0.9300
N3—C141.343 (2)C13—C141.387 (3)
C1—C21.492 (3)C13—H13A0.9300
C1—H1A0.9600C14—C151.497 (3)
C1—H1B0.9600C15—H15A0.9600
C1—H1C0.9600C15—H15B0.9600
C2—C31.390 (2)C15—H15C0.9600
C3—C41.376 (3)B1—F1A1.315 (11)
C3—H3A0.9300B1—F3A1.343 (10)
C4—C51.379 (3)B1—F41.347 (6)
C4—H4A0.9300B1—F21.347 (7)
C5—C61.380 (2)B1—F31.356 (6)
C5—H5B0.9300B1—F2A1.360 (12)
C6—C71.515 (2)B1—F4A1.398 (10)
C7—H7A0.9700B1—F11.401 (6)
N2i—Cu1—N286.31 (8)H7A—C7—H7B108.4
N2i—Cu1—N1165.41 (5)N2—C8—C8i108.82 (11)
N2—Cu1—N179.43 (6)N2—C8—H8A109.9
N2i—Cu1—N1i79.43 (6)C8i—C8—H8A109.9
N2—Cu1—N1i165.41 (5)N2—C8—H8B109.9
N1—Cu1—N1i114.97 (8)C8i—C8—H8B109.9
N1—Cu1—N389.43 (5)H8A—C8—H8B108.3
N1—Cu1—N3i98.67 (5)N2—C9—C10116.30 (13)
N2—Cu1—N378.28 (5)N2—C9—H9A108.2
N2—Cu1—N3i90.69 (5)C10—C9—H9A108.2
N3—Cu1—N3i164.94 (5)N2—C9—H9B108.2
C2—N1—C6118.72 (14)C10—C9—H9B108.2
C2—N1—Cu1131.62 (11)H9A—C9—H9B107.4
C6—N1—Cu1109.44 (11)N3—C10—C11123.31 (16)
C7—N2—C9108.49 (13)N3—C10—C9117.86 (15)
C7—N2—C8113.42 (13)C11—C10—C9118.59 (16)
C9—N2—C8111.74 (13)C12—C11—C10118.13 (19)
C7—N2—Cu1103.48 (10)C12—C11—H11A120.9
C9—N2—Cu1112.51 (10)C10—C11—H11A120.9
C8—N2—Cu1106.97 (10)C13—C12—C11119.23 (19)
C10—N3—C14117.87 (15)C13—C12—H12A120.4
C2—C1—H1A109.5C11—C12—H12A120.4
C2—C1—H1B109.5C12—C13—C14119.71 (19)
H1A—C1—H1B109.5C12—C13—H13A120.1
C2—C1—H1C109.5C14—C13—H13A120.1
H1A—C1—H1C109.5N3—C14—C13121.70 (18)
H1B—C1—H1C109.5N3—C14—C15118.54 (17)
N1—C2—C3120.78 (16)C13—C14—C15119.76 (18)
N1—C2—C1118.43 (15)C14—C15—H15A109.5
C3—C2—C1120.68 (17)C14—C15—H15B109.5
C4—C3—C2119.65 (17)H15A—C15—H15B109.5
C4—C3—H3A120.2C14—C15—H15C109.5
C2—C3—H3A120.2H15A—C15—H15C109.5
C3—C4—C5119.35 (17)H15B—C15—H15C109.5
C3—C4—H4A120.3F1A—B1—F3A108.9 (10)
C5—C4—H4A120.3F4—B1—F2112.5 (7)
C4—C5—C6118.58 (17)F4—B1—F3111.6 (5)
C4—C5—H5B120.7F2—B1—F3105.9 (6)
C6—C5—H5B120.7F1A—B1—F2A105.1 (10)
N1—C6—C5122.16 (16)F3A—B1—F2A113.3 (10)
N1—C6—C7115.57 (13)F1A—B1—F4A107.8 (6)
C5—C6—C7122.26 (15)F3A—B1—F4A109.0 (8)
N2—C7—C6107.90 (12)F2A—B1—F4A112.5 (12)
N2—C7—H7A110.1F4—B1—F1107.0 (4)
C6—C7—H7A110.1F2—B1—F1113.0 (7)
N2—C7—H7B110.1F3—B1—F1106.6 (5)
C6—C7—H7B110.1
C6—N1—C2—C39.0 (2)C7—N2—C8—C8i−152.37 (17)
Cu1—N1—C2—C3−165.01 (13)C9—N2—C8—C8i84.61 (19)
C6—N1—C2—C1−167.28 (18)Cu1—N2—C8—C8i−38.93 (19)
Cu1—N1—C2—C118.7 (3)C7—N2—C9—C10151.06 (15)
N1—C2—C3—C4−2.9 (3)C8—N2—C9—C10−83.17 (18)
C1—C2—C3—C4173.28 (19)Cu1—N2—C9—C1037.18 (18)
C2—C3—C4—C5−4.6 (3)C14—N3—C10—C112.4 (3)
C3—C4—C5—C65.7 (3)C14—N3—C10—C9−171.80 (17)
C2—N1—C6—C5−7.8 (2)N2—C9—C10—N3−41.5 (2)
Cu1—N1—C6—C5167.40 (14)N2—C9—C10—C11143.95 (18)
C2—N1—C6—C7171.25 (15)N3—C10—C11—C12−2.4 (3)
Cu1—N1—C6—C7−13.52 (17)C9—C10—C11—C12171.8 (2)
C4—C5—C6—N10.5 (3)C10—C11—C12—C130.6 (4)
C4—C5—C6—C7−178.54 (16)C11—C12—C13—C140.9 (4)
C9—N2—C7—C6−73.22 (16)C10—N3—C14—C13−0.7 (3)
C8—N2—C7—C6162.00 (13)C10—N3—C14—C15179.19 (19)
Cu1—N2—C7—C646.47 (14)C12—C13—C14—N3−0.9 (4)
N1—C6—C7—N2−22.45 (19)C12—C13—C14—C15179.2 (2)
C5—C6—C7—N2156.64 (16)

Symmetry code: (i) −x, y, −z+1/2.

Hydrogen-bond geometry (Å, º)

D—H···AD—HH···AD···AD—H···A
C1—H1B···F2Aii0.962.503.296 (17)140
C4—H4A···F4Aiii0.932.503.394 (15)161
C5—H5B···F3iv0.932.453.355 (9)164
C5—H5B···F3Aiv0.932.333.194 (13)155
C7—H7A···N3i0.972.593.212 (2)122
C8—H8A···F1Av0.972.483.298 (16)142
C9—H9A···F30.972.553.436 (10)152
C9—H9B···F4v0.972.343.303 (6)173
C12—H12A···F4vi0.932.453.198 (7)137

Symmetry codes: (i) −x, y, −z+1/2; (ii) −x+1/2, y−1/2, −z+1/2; (iii) x, −y, z+1/2; (iv) −x+1/2, −y+1/2, −z+1; (v) −x+1/2, y+1/2, −z+1/2; (vi) −x+1/2, −y+1/2, −z.

References

  • Bania, K. K. & Deka, R. C. (2012). J. Phys. Chem. C, 116, 14295–14310.
  • Bruker (2013). APEX2, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.
  • Kaur, A., Gorse, E. E., Ribelli, T. G., Jerman, C. C. & Pintauer, T. (2015). Polymer, 72, 246–252.
  • Meyer, A., Schnakenburg, G., Glaum, R. & Schiemann, O. (2015). Inorg. Chem. 54, 8456–8464. [PubMed]
  • Mikata, Y.-J., Wakamatsu, M. & Yano, S. (2005). Dalton Trans. pp. 545–550. [PubMed]
  • Pokharel, U. R., Fronczek, F. R. & Maverick, A. W. (2014). Nature Comm. 5, 5883–5887.
  • Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. [PubMed]
  • Sheldrick, G. M. (2015). Acta Cryst. C71, 3–8. [PMC free article] [PubMed]
  • Tang, H., Arulsamy, N., Radosz, M., Shen, Y.-Q., Tsarevsky, N. V., Braunecker, W. A., Tang, W. & Matyjaszewski, K. (2006). J. Am. Chem. Soc. 128, 16277–16285. [PubMed]
  • Yoon, D. C., Lee, U., Lee, D. J. & Oh, C. E. (2005). Bull. Korean Chem. Soc. 26, 1097–1100.
  • Zhang, P.-L., Wang, M., Yang, Y., Yao, T.-Y. & Sun, L.-C. (2014). Angew. Chem. Int. Ed. 53, 13803–13807. [PubMed]

Articles from Acta Crystallographica Section E: Crystallographic Communications are provided here courtesy of International Union of Crystallography