supplementary materials


gw2124 scheme

Acta Cryst. (2012). E68, m1214    [ doi:10.1107/S1600536812036112 ]

(2,3,7,8,12,13,17,18-Octaethylporphyrinato-[kappa]4N)cobalt(II)-2-nitrobenzaldehyde (1/2)

A. Mansour, J.-C. Daran and H. Nasri

Abstract top

The asymmetric unit of the title compound, [Co(C36H44N4)]·2C7H5NO3, is composed of one half of the complex, arranged about an inversion center, and a complete 2-nitrobenzaldehyde (NBA) molecule. The structure consists of columns that contain interleaved molecules of NBA and [CoII(OEP)] (OEP is 2,3,7,8,12,13,17,18-octaethylporphyrin), which are stacked along the a axis. The CoII atom is involved in a [pi] interaction with the ring of the NBA molecule with a centroid-metal distance of 3.508 (6) Å. There is an intramolecular C-H...O hydrogen bond in the NBA molecule.

Comment top

In continuation of our research on the crystal structures of porphyrin complexes (Ben Moussa et al., 2011; Dhifet et al., 2010) we herein report the synthesis and crystal structure of the title compound. The x unit contains one half molecule of [CoII(OEP)] and a whole molecule of nitrobenzaldehyde.

For our derivative, the average equatorial cobalt-pyrrole nitrogen atoms distance Co—Np [1.972 (4) Å] is typical for a Co(II) octaethylporphyrin where the porphyrin core is nearly planar (Figure 1) (Scheidt & Tyrk, 1994) and similar to the value of 1.969 (2) Å found in the [CoII(OEP)].TNFM (TNFM = (2, 4, 7-trinitrofluoreylidene)malontrile) (Smirnov et al., 1998) and 1.986 (14) Å in the [Co(F28TPP)].2tol complex (Tol = toluene and F28TPP = tetrakis(pentafluorophenyl)porphyrin) (Olmstead et al., 2003).

It is known that OEP metalloporphyrins can be dimerized as is the case of the [FeIII(OEP)(NO)]+ complex (Ellison et al., 2000). For this species the distance between two adjacent porphyrinato mean plans is 3.41 Å which indicated a strong π-π interaction. This complex forms a tight cofacial π-π dimer in the solid state.The most interesting feature of (I), is the rather strong π-interaction between the cobalt metal of the [CoII(OEP)] and the centroid of the phenyl rings of the nitrobenzaldehyde molecule (Figure 1) where the Co···Cg intermolecular distance is 3.508 Å (Cg is the centroid of the phenyl ring of the NBA molecule) and the angle between this distance and the perpendicular from the cobalt to the plane of the phenyl is 23.39 ° (Table 2). The cobalt atom is nearly perpendicular to the C101 atom (Figure 2). This structure present a striking resemblance with the one of the [CoII(F28TPP)].2tol complex (Olmstead et al., 2003) where the cobalt atom is centered roughly at the midpoint at the two adjacent carbons bonds in the toluene rings and the Co—C distances are 3.05 and 3.13 Å. It is noteworthy that the structure of (I) consists of columns that contain interleaved molecules of NBA and [CoII(OEP)] which are stacked a long the crystallographic a axis (Figure 3).

A unique C—H···O (nitrobenzaldehyde) intramoleculair hydrogen bond of 1.82 (7) Å is found in the structure (Table 1).

Related literature top

For the synthesis, see: Scheidt & Tyrk (1994). For related structures, see: Olmstead et al. (2003); Smirnov et al. (1998); Ben Moussa et al. (2011); Dhifet et al. (2010); Ellison et al. (2000).

Experimental top

[CoII(OEP)] (Scheidt & Tyrk, 1994) (100 mg, 0.17 mmol) and nitrobenzaldehyde (190 mg, 1.26 mmol) in 25 ml of chlorobenzene were stirred over night at room temperature. The color changes from red-pink to dark red and crystals of complex (I) were prepared by slow diffusion of hexanes into the chlorobenzene solution.

Refinement top

All H atoms attached to C atoms were fixed geometrically and treated as riding with C—H = 0.96 Å (methyl), 0.97 Å (methylene) or 0.93 Å (aromatic) with Uiso(H) = 1.2Ueq(Caromatic, methylene) or Uiso(H) = 1.5Ueq(Cmethyl). The coordinates of the H atom attached to the aldehyde function have been refined freely with Uiso(H) = 1.2Ueq(C).

Computing details top

Data collection: CrysAlis PRO (Agilent, 2012); cell refinement: CrysAlis PRO (Agilent, 2012); data reduction: CrysAlis PRO (Agilent, 2012); program(s) used to solve structure: SIR2004 (Burla et al., 2005); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEPIII (Burnett & Johnson, 1996) and ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999) and SHELXL97 (Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. Perspective drawings from the X-ray crystal structure determination of (I) that highlights π-interraction between the [CoII(OEP)] complex and the 2-nitrobenzaldehyde molecule. H atoms have been omitted for clarity.
[Figure 2] Fig. 2. An ORTEP drawing of the structure of [CoII(OEP)].NBA, with the atom-numbering scheme. Dislacement ellipsoids are drawing at 35% and H atoms have been omitted for clarity.Symmetry code: ('): -x, -y, -z.
[Figure 3] Fig. 3. Drawing showing the packing in lattice of [CoII(OEP)].NBA, viewed down the b axis.
(2,3,7,8,12,13,17,18-Octaethylporphyrinato- κ4N)cobalt(II)–2-nitrobenzaldehyde (1/2) top
Crystal data top
[Co(C36H44N4)]·2C7H5NO3F(000) = 942
Mr = 893.92Dx = 1.375 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 4505 reflections
a = 10.1952 (11) Åθ = 3.1–28.3°
b = 21.2230 (17) ŵ = 0.46 mm1
c = 10.1601 (10) ÅT = 180 K
β = 100.771 (9)°Prism, purple
V = 2159.6 (4) Å30.52 × 0.26 × 0.14 mm
Z = 2
Data collection top
Agilent Xcalibur Sapphire1 long-nozzle
diffractometer
3782 independent reflections
Radiation source: fine-focus sealed tube2969 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.038
Detector resolution: 8.2632 pixels mm-1θmax = 25.0°, θmin = 3.2°
ω scansh = 1212
Absorption correction: multi-scan
(CrysAlis PRO; Agilent, 2012)
k = 2522
Tmin = 0.797, Tmax = 0.939l = 1211
11654 measured reflections
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.079Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.197H atoms treated by a mixture of independent and constrained refinement
S = 1.13 w = 1/[σ2(Fo2) + (0.0484P)2 + 9.9571P]
where P = (Fo2 + 2Fc2)/3
3782 reflections(Δ/σ)max < 0.001
272 parametersΔρmax = 0.99 e Å3
0 restraintsΔρmin = 0.45 e Å3
Crystal data top
[Co(C36H44N4)]·2C7H5NO3V = 2159.6 (4) Å3
Mr = 893.92Z = 2
Monoclinic, P21/cMo Kα radiation
a = 10.1952 (11) ŵ = 0.46 mm1
b = 21.2230 (17) ÅT = 180 K
c = 10.1601 (10) Å0.52 × 0.26 × 0.14 mm
β = 100.771 (9)°
Data collection top
Agilent Xcalibur Sapphire1 long-nozzle
diffractometer
3782 independent reflections
Absorption correction: multi-scan
(CrysAlis PRO; Agilent, 2012)
2969 reflections with I > 2σ(I)
Tmin = 0.797, Tmax = 0.939Rint = 0.038
11654 measured reflectionsθmax = 25.0°
Refinement top
R[F2 > 2σ(F2)] = 0.079H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.197Δρmax = 0.99 e Å3
S = 1.13Δρmin = 0.45 e Å3
3782 reflectionsAbsolute structure: ?
272 parametersFlack parameter: ?
0 restraintsRogers parameter: ?
Special details top

Experimental. Absorption correction: empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm. CrysAlisPro (Agilent Technologies,2012)

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

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > 2σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Co0.50000.00001.00000.0223 (3)
N10.3667 (4)0.06811 (18)0.9652 (4)0.0219 (8)
N20.6428 (4)0.06272 (18)1.0557 (4)0.0241 (9)
C10.5113 (5)0.1592 (2)1.0282 (4)0.0284 (11)
H10.51420.20291.03620.034*
C20.8358 (5)0.0066 (2)1.1098 (4)0.0278 (11)
H20.92790.00841.13840.033*
C110.2321 (5)0.0628 (2)0.9185 (4)0.0249 (10)
C120.1692 (5)0.1241 (2)0.9020 (5)0.0294 (11)
C130.2667 (5)0.1669 (2)0.9403 (5)0.0298 (11)
C140.3887 (5)0.1319 (2)0.9805 (4)0.0235 (10)
C210.6293 (5)0.1270 (2)1.0647 (4)0.0237 (10)
C220.7556 (5)0.1565 (2)1.1157 (5)0.0289 (11)
C230.8479 (5)0.1099 (2)1.1354 (5)0.0294 (11)
C240.7768 (4)0.0520 (2)1.0987 (4)0.0220 (10)
C1210.0251 (5)0.1352 (3)0.8455 (5)0.0366 (13)
H12A0.00040.17640.87340.044*
H12B0.02820.10390.88130.044*
C1220.0048 (6)0.1315 (3)0.6913 (5)0.0425 (14)
H12C0.04670.16280.65540.064*
H12D0.09810.13900.65910.064*
H12E0.01850.09050.66330.064*
C1310.2557 (5)0.2373 (2)0.9361 (5)0.0356 (12)
H13A0.31610.25491.01240.043*
H13B0.16550.24940.94320.043*
C1320.2888 (7)0.2648 (3)0.8080 (7)0.0515 (16)
H13C0.37670.25160.79870.077*
H13D0.28570.30990.81180.077*
H13E0.22500.25010.73250.077*
C2210.7747 (5)0.2255 (2)1.1470 (5)0.0346 (12)
H22A0.71750.24971.07800.041*
H22B0.86650.23691.14510.041*
C2220.7430 (6)0.2430 (3)1.2831 (6)0.0454 (15)
H22C0.65080.23411.28380.068*
H22D0.75970.28711.29940.068*
H22E0.79840.21891.35170.068*
C2310.9941 (5)0.1149 (3)1.1924 (5)0.0351 (12)
H23A1.02500.15671.17440.042*
H23B1.04220.08471.14780.042*
C2321.0261 (3)0.10290 (19)1.3431 (2)0.0475 (15)
H23C0.97770.13231.38780.071*
H23D1.12010.10821.37520.071*
H23E1.00050.06071.36120.071*
N30.4262 (3)0.10463 (13)0.6484 (2)0.0731 (19)
O10.7932 (3)0.01832 (13)0.7585 (2)0.0880 (18)
O310.3191 (3)0.12778 (13)0.6159 (2)0.109 (2)
O320.5322 (3)0.13821 (13)0.6534 (2)0.112 (2)
C1000.4442 (2)0.03814 (12)0.6568 (2)0.0412 (14)
C1010.5620 (3)0.00702 (11)0.7012 (2)0.0372 (12)
C1020.5715 (3)0.05699 (11)0.7001 (2)0.0581 (19)
H1020.65250.07670.73260.070*
C1030.4612 (7)0.0916 (3)0.6509 (6)0.0528 (16)
H1030.46790.13520.64660.063*
C1040.3390 (6)0.0629 (3)0.6070 (5)0.0442 (15)
H1040.26430.08770.57660.053*
C1050.3263 (7)0.0006 (4)0.6076 (6)0.0558 (17)
H1050.24410.01970.57720.067*
C1060.6934 (6)0.0416 (4)0.7524 (6)0.0517 (17)
H1060.683 (7)0.097 (3)0.732 (6)0.062*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Co0.0218 (5)0.0259 (5)0.0186 (4)0.0027 (4)0.0019 (3)0.0006 (4)
N10.020 (2)0.029 (2)0.0165 (18)0.0002 (16)0.0020 (15)0.0001 (15)
N20.031 (2)0.030 (2)0.0122 (18)0.0023 (17)0.0055 (16)0.0010 (15)
C10.036 (3)0.026 (2)0.022 (2)0.004 (2)0.002 (2)0.0014 (19)
C20.024 (2)0.040 (3)0.019 (2)0.004 (2)0.0026 (18)0.000 (2)
C110.031 (3)0.030 (3)0.014 (2)0.002 (2)0.0063 (19)0.0008 (18)
C120.031 (3)0.036 (3)0.023 (2)0.008 (2)0.009 (2)0.002 (2)
C130.033 (3)0.037 (3)0.019 (2)0.005 (2)0.005 (2)0.000 (2)
C140.022 (3)0.030 (3)0.019 (2)0.0018 (19)0.0042 (18)0.0004 (19)
C210.025 (3)0.029 (3)0.016 (2)0.004 (2)0.0028 (19)0.0007 (18)
C220.031 (3)0.035 (3)0.021 (2)0.012 (2)0.005 (2)0.001 (2)
C230.032 (3)0.039 (3)0.018 (2)0.012 (2)0.007 (2)0.002 (2)
C240.018 (2)0.032 (3)0.015 (2)0.0056 (19)0.0013 (18)0.0001 (18)
C1210.031 (3)0.044 (3)0.035 (3)0.012 (2)0.006 (2)0.002 (2)
C1220.039 (3)0.053 (4)0.032 (3)0.007 (3)0.003 (2)0.001 (3)
C1310.031 (3)0.036 (3)0.039 (3)0.010 (2)0.005 (2)0.003 (2)
C1320.057 (4)0.038 (3)0.061 (4)0.005 (3)0.013 (3)0.011 (3)
C2210.033 (3)0.035 (3)0.035 (3)0.017 (2)0.003 (2)0.001 (2)
C2220.050 (4)0.042 (3)0.044 (3)0.012 (3)0.007 (3)0.012 (3)
C2310.026 (3)0.050 (3)0.028 (3)0.017 (2)0.002 (2)0.003 (2)
C2320.031 (3)0.078 (4)0.029 (3)0.008 (3)0.005 (2)0.001 (3)
N30.088 (5)0.068 (4)0.067 (4)0.020 (4)0.023 (4)0.003 (3)
O10.058 (4)0.108 (5)0.094 (4)0.016 (3)0.005 (3)0.016 (4)
O310.099 (5)0.085 (4)0.138 (6)0.051 (4)0.005 (4)0.016 (4)
O320.109 (6)0.104 (5)0.126 (6)0.037 (4)0.033 (5)0.041 (4)
C1000.052 (4)0.050 (4)0.025 (3)0.008 (3)0.017 (3)0.008 (2)
C1010.047 (3)0.044 (3)0.025 (3)0.008 (3)0.017 (2)0.008 (2)
C1020.088 (6)0.049 (4)0.045 (4)0.003 (4)0.033 (4)0.003 (3)
C1030.052 (4)0.069 (4)0.043 (3)0.005 (3)0.023 (3)0.005 (3)
C1040.043 (4)0.062 (4)0.029 (3)0.023 (3)0.010 (3)0.000 (3)
C1050.060 (4)0.080 (5)0.031 (3)0.001 (4)0.017 (3)0.005 (3)
C1060.028 (3)0.085 (5)0.041 (3)0.006 (3)0.005 (3)0.015 (3)
Geometric parameters (Å, º) top
Co—N11.970 (4)C131—H13B0.9700
Co—N1i1.970 (4)C132—H13C0.9600
Co—N21.976 (4)C132—H13D0.9600
Co—N2i1.976 (4)C132—H13E0.9600
N1—C111.370 (6)C221—C2221.524 (8)
N1—C141.376 (6)C221—H22A0.9700
N2—C241.373 (6)C221—H22B0.9700
N2—C211.376 (6)C222—H22C0.9600
C1—C211.373 (7)C222—H22D0.9600
C1—C141.381 (7)C222—H22E0.9600
C1—H10.9300C231—C2321.526 (5)
C2—C241.376 (7)C231—H23A0.9700
C2—C11i1.383 (7)C231—H23B0.9700
C2—H20.9300C232—H23C0.9600
C11—C2i1.383 (7)C232—H23D0.9600
C11—C121.445 (7)C232—H23E0.9600
C12—C131.350 (7)N3—O311.1858
C12—C1211.492 (7)N3—O321.2882
C13—C141.441 (7)N3—C1001.4235
C13—C1311.499 (7)O1—C1061.123 (7)
C21—C221.438 (7)C100—C1011.3708
C22—C231.353 (7)C100—C1051.451 (7)
C22—C2211.503 (7)C101—C1021.3620
C23—C241.442 (7)C101—C1061.531 (7)
C23—C2311.499 (7)C102—C1031.357 (7)
C121—C1221.542 (7)C102—H1020.9300
C121—H12A0.9700C103—C1041.383 (9)
C121—H12B0.9700C103—H1030.9300
C122—H12C0.9600C104—C1051.354 (9)
C122—H12D0.9600C104—H1040.9300
C122—H12E0.9600C105—H1050.9300
C131—C1321.520 (8)C106—H1061.19 (7)
C131—H13A0.9700
N1—Co—N1i180.000 (1)C13—C131—H13B109.1
N1—Co—N290.21 (16)C132—C131—H13B109.1
N1i—Co—N289.79 (16)H13A—C131—H13B107.9
N1—Co—N2i89.79 (16)C131—C132—H13C109.5
N1i—Co—N2i90.21 (16)C131—C132—H13D109.5
N2—Co—N2i180.00 (16)H13C—C132—H13D109.5
C11—N1—C14104.5 (4)C131—C132—H13E109.5
C11—N1—Co127.9 (3)H13C—C132—H13E109.5
C14—N1—Co127.5 (3)H13D—C132—H13E109.5
C24—N2—C21104.4 (4)C22—C221—C222112.9 (4)
C24—N2—Co127.9 (3)C22—C221—H22A109.0
C21—N2—Co127.6 (3)C222—C221—H22A109.0
C21—C1—C14125.2 (5)C22—C221—H22B109.0
C21—C1—H1117.4C222—C221—H22B109.0
C14—C1—H1117.4H22A—C221—H22B107.8
C24—C2—C11i124.6 (4)C221—C222—H22C109.5
C24—C2—H2117.7C221—C222—H22D109.5
C11i—C2—H2117.7H22C—C222—H22D109.5
N1—C11—C2i124.9 (4)C221—C222—H22E109.5
N1—C11—C12111.2 (4)H22C—C222—H22E109.5
C2i—C11—C12123.9 (5)H22D—C222—H22E109.5
C13—C12—C11106.6 (5)C23—C231—C232112.7 (4)
C13—C12—C121128.6 (5)C23—C231—H23A109.0
C11—C12—C121124.8 (5)C232—C231—H23A109.0
C12—C13—C14106.5 (4)C23—C231—H23B109.0
C12—C13—C131128.1 (5)C232—C231—H23B109.0
C14—C13—C131125.3 (5)H23A—C231—H23B107.8
N1—C14—C1124.8 (4)C231—C232—H23C109.5
N1—C14—C13111.2 (4)C231—C232—H23D109.5
C1—C14—C13124.0 (4)H23C—C232—H23D109.5
C1—C21—N2124.6 (4)C231—C232—H23E109.5
C1—C21—C22124.1 (4)H23C—C232—H23E109.5
N2—C21—C22111.2 (4)H23D—C232—H23E109.5
C23—C22—C21106.6 (4)O31—N3—O32120.2
C23—C22—C221128.4 (5)O31—N3—C100122.0
C21—C22—C221124.9 (5)O32—N3—C100116.6
C22—C23—C24106.4 (4)C101—C100—N3126.4
C22—C23—C231128.3 (5)C101—C100—C105117.9 (3)
C24—C23—C231125.2 (5)N3—C100—C105115.7 (3)
N2—C24—C2124.8 (4)C102—C101—C100122.5
N2—C24—C23111.3 (4)C102—C101—C106115.0 (3)
C2—C24—C23123.9 (4)C100—C101—C106122.5 (3)
C12—C121—C122112.1 (4)C103—C102—C101119.2 (3)
C12—C121—H12A109.2C103—C102—H102120.4
C122—C121—H12A109.2C101—C102—H102120.4
C12—C121—H12B109.2C102—C103—C104121.0 (6)
C122—C121—H12B109.2C102—C103—H103119.5
H12A—C121—H12B107.9C104—C103—H103119.5
C121—C122—H12C109.5C105—C104—C103121.2 (6)
C121—C122—H12D109.5C105—C104—H104119.4
H12C—C122—H12D109.5C103—C104—H104119.4
C121—C122—H12E109.5C104—C105—C100118.3 (6)
H12C—C122—H12E109.5C104—C105—H105120.9
H12D—C122—H12E109.5C100—C105—H105120.9
C13—C131—C132112.3 (4)O1—C106—C101122.3 (7)
C13—C131—H13A109.1O1—C106—H106120 (3)
C132—C131—H13A109.1C101—C106—H106112 (3)
Symmetry code: (i) x+1, y, z+2.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C106—H106···O321.19 (7)1.82 (7)2.701 (7)126 (5)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C106—H106···O321.19 (7)1.82 (7)2.701 (7)126 (5)
Interaction between the Co atom and the phenyl ring of the nitrobenzaldehyde. top
Cg1 is the centroid of the C100-C101-C102-C103-C104-C105 phenyl ring. Symmetry codes: (i) 1/2-X, -1/2+Y, 1-Z ; (ii) -1/2+X, 1/2-Y, Z
Cg···Co (Å)Co-Perp (Å)Beta (°)
Co···Cg1i3.508-3.21923.39
Co···Cg1ii3.508-3.21923.39
Acknowledgements top

The authors gratefully acknowledge financial support from the Ministry of Higher Education, Scientific Research and Technology of Tunisia.

references
References top

Agilent (2012). CrysAlis PRO. Agilent Technologies Ltd, Yarnton, England.

Ben Moussa, I., Belkhiria, M. S., Najmudin, S., Bonifacio, C. & Nasri, H. (2011). Acta Cryst. E67, m903–m904.

Burla, M. C., Caliandro, R., Camalli, M., Carrozzini, B., Cascarano, G. L., De Caro, L., Giacovazzo, C., Polidori, G. & Spagna, R. (2005). J. Appl. Cryst. 38, 381–388.

Burnett, M. N. & Johnson, C. K. (1996). ORTEPIII. Report ORNL-6895. Oak Ridge National Laboratory, Tennessee, USA.

Dhifet, M., Belkhiria, M. S., Daran, J. C., Schulz, C. E. & Nasri, H. (2010). Inorg. Chim. Acta, 363, 3208–3213.

Ellison, M. K., Schulz, C. E. & Scheidt, W. R. (2000). Inorg. Chem. 39, 5102–5110.

Farrugia, L. J. (1997). J. Appl. Cryst. 30, 565.

Farrugia, L. J. (1999). J. Appl. Cryst. 32, 837–838.

Olmstead, M. M., Bettencourt-Dias, A., Lee, H. M., Pham, D. & Balch, A. L. (2003). Dalton Trans. pp. 3227–3232.

Scheidt, W. R. & Tyrk, I. T. (1994). Inorg. Chem. 33, 1314–1318.

Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122.

Smirnov, V. V., Woller, E. K. & DiMagno, S. G. (1998). Inorg. Chem. 37, 4971–4978.