Dioxidobis{2-[(E)-p-tolyl­imino­meth­yl]phenolato}molybdenum(VI)

Hatefi, M.; Sheikhshoaie, I.; Mirkhani, V.; Moghadam, M.; Kia, R.

doi:10.1107/S1600536810032836

metal-organic compounds

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ISSN: 2056-9890

Volume 66| Part 9| September 2010| Page m1137

https://doi.org/10.1107/S1600536810032836

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Dioxidobis{2-[(E)-p-tolyliminomethyl]phenolato}molybdenum(VI)

Mehdi Hatefi,^a Iran Sheikhshoaie,^a ^* Valiollah Mirkhani,^b Majid Moghadam ^b and Reza Kia ^c,^d ‡

^aChemistry Department, Shahid Bahonar University, Kerman, Iran, ^bDepartment of Chemistry, University of Isfahan, Isfahan 81746-73441, Iran, ^cDepartment of Chemistry, Science and Research Branch, Islamic Azad University, Tehran, Iran, and ^dX-ray Crystallography Laboratory, Plasma Physics Research Center, Science and Research Branch, Islamic Azad University, Tehran, Iran
^*Correspondence e-mail: i_shoaie@yahoo.com

(Received 28 July 2010; accepted 16 August 2010; online 21 August 2010)

The asymmetric unit of the title compound, [Mo(C₁₄H₁₂NO)₂O₂], comprises half of the complex with the full molecule generated by the application of twofold symmetry. The Mo^VI atom is surrounded by two oxide O atoms and the two sets of N,O-donor atoms of the bidentate Schiff base ligands. The resulting N₂O₄ donor set defines a distorted octahedral coordination geometry. Intermolecular C—H⋯O contacts link molecules into chains along the b axis. The crystal structure is further stabilized by intermolecular π–π interactions [ring centroid–centroid distance = 3.724 (6) Å].

Related literature

For related structures with MoO₂ units and for the synthesis, see: Arnaiz et al. (2000 ); Holm et al. (1996 ); Syamal & Maurya (1989 ).

Experimental

Crystal data

[Mo(C₁₄H₁₂NO)₂O₂]
M_r = 548.43
Monoclinic, C 2/c
a = 26.375 (8) Å
b = 6.8095 (8) Å
c = 15.648 (10) Å
β = 116.94 (2)°
V = 2505.4 (18) Å³
Z = 4
Mo Kα radiation
μ = 0.56 mm⁻¹
T = 296 K
0.21 × 0.11 × 0.08 mm

Data collection

Stoe IPDS II diffractometer
Absorption correction: multi-scan [MULABS in PLATON (Spek, 2009 ; Blessing, 1995 )] T_min = 0.892, T_max = 0.957
4305 measured reflections
2006 independent reflections
761 reflections with I > 2σ(I)
R_int = 0.144

Refinement

R[F² > 2σ(F²)] = 0.079
wR(F²) = 0.168
S = 0.83
2006 reflections
124 parameters
H-atom parameters constrained
Δρ_max = 0.55 e Å⁻³
Δρ_min = −0.81 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C9—H9A⋯O2ⁱ	0.93	2.34	3.237 (18)	163
C13—H13A⋯O2ⁱⁱ	0.93	2.42	3.164 (17)	136
Symmetry codes: (i) $[-x, y+1, -z+{\script{1\over 2}}]$ ; (ii) $[-x, y, -z+{\script{1\over 2}}]$ .

Data collection: X-AREA (Stoe & Cie, 2005 ); cell refinement: X-AREA; data reduction: X-AREA; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009).

Supporting information

Crystal structure: contains datablocks global, I. DOI: https://doi.org/10.1107/S1600536810032836/tk2696sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536810032836/tk2696Isup2.hkl

checkCIF report

Comment top

Numerous chemical reactions are catalyzed by complexes containing the dioxomolybdenum(VI) unit, MoO₂ (Arnaiz et al. 2000). Moreover, Schiff base compounds containing molybdenum play a significant role in the chemistry of molybdoenzymes (Holm et al. 1996; Syamal & Maurya, 1989).

The asymmetric unit of the title compound, Fig. 1, comprises half of the complex. The Mo atom is located on a crystallographic 2-fold axis. The Mo^VI atom is surrounded by two oxo-O atoms and the N₂O₂ donor atoms of two bidentate Schiff base ligands to define a distorted octahedral coordination geometry. Intermolecular C—H···O contacts link molecules into chains along the b axis, Table 1 and Fig. 2. The crystal structure is further stabilized by intermolecular π–π interactions with the ring centroid(C1– C6) to centroid(C8–C13)ⁱ distance being 3.724 (6) Å for i: -x, y, 1/2-z.

Related literature top

For related structures with MoO₂ units and for the synthesis, see: Arnaiz et al. (2000); Holm et al. (1996); Syamal & Maurya (1989).

Experimental top

The title complex was prepared by adding MoO₂(acac)₂ and the ligand (molar ratio 1:1) to dry methanol (30 ml), followed by refluxing for 1 h. Small, light-yellow crystals were filtered off and recrystallized from acetonitrile. The quality of the crystal was not optimal and it was weakly diffracting. Although recrystallization was attempted repeatedly, better crystals were not obtained.

Structure description top

For related structures with MoO₂ units and for the synthesis, see: Arnaiz et al. (2000); Holm et al. (1996); Syamal & Maurya (1989).

Computing details top

Data collection: X-AREA (Stoe & Cie, 2005); cell refinement: X-AREA (Stoe & Cie, 2005); data reduction: X-AREA (Stoe & Cie, 2005); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).

Figures top

	Fig. 1. The molecular structure of the title complex showing the atom-labelling scheme and displacement ellipsoids at the 35% probability level. Symmetry code for the unlabeled atoms: -x, y, 1/2 - z.
	Fig. 2. A view of the crystal packing of the title compound down the a axis showing connections of molecules through C—H···O interactions (shown as dashed lines) along the b axis.

Dioxidobis{2-[(E)-p-tolyliminomethyl]phenolato}molybdenum(VI) top

Crystal data top

[Mo(C₁₄H₁₂NO)₂O₂]	F(000) = 1120
M_r = 548.43	D_x = 1.454 Mg m⁻³
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 2560 reflections
a = 26.375 (8) Å	θ = 1.7–29.6°
b = 6.8095 (8) Å	µ = 0.56 mm⁻¹
c = 15.648 (10) Å	T = 296 K
β = 116.94 (2)°	Block, colourless
V = 2505.4 (18) Å³	0.21 × 0.11 × 0.08 mm
Z = 4

Data collection top

Stoe IPDS II diffractometer	2006 independent reflections
Radiation source: fine-focus sealed tube	761 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.144
Detector resolution: 0.15 mm pixels mm^-1	θ_max = 25.5°, θ_min = 2.6°
φ and ω scans	h = −31→22
Absorption correction: multi-scan (MULABS in PLATON; Blessing, 1995)	k = −7→8
T_min = 0.892, T_max = 0.957	l = −18→18
4305 measured reflections

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.079	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.168	H-atom parameters constrained
S = 0.83	w = 1/[σ²(F_o²) + (0.0476P)²] where P = (F_o² + 2F_c²)/3
2006 reflections	(Δ/σ)_max < 0.001
124 parameters	Δρ_max = 0.55 e Å⁻³
0 restraints	Δρ_min = −0.81 e Å⁻³

Crystal data top

[Mo(C₁₄H₁₂NO)₂O₂]	V = 2505.4 (18) Å³
M_r = 548.43	Z = 4
Monoclinic, C2/c	Mo Kα radiation
a = 26.375 (8) Å	µ = 0.56 mm⁻¹
b = 6.8095 (8) Å	T = 296 K
c = 15.648 (10) Å	0.21 × 0.11 × 0.08 mm
β = 116.94 (2)°

Data collection top

Stoe IPDS II diffractometer	2006 independent reflections
Absorption correction: multi-scan (MULABS in PLATON; Blessing, 1995)	761 reflections with I > 2σ(I)
T_min = 0.892, T_max = 0.957	R_int = 0.144
4305 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.079	0 restraints
wR(F²) = 0.168	H-atom parameters constrained
S = 0.83	Δρ_max = 0.55 e Å⁻³
2006 reflections	Δρ_min = −0.81 e Å⁻³
124 parameters

Special details top

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 > σ(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

	x	y	z	U_iso*/U_eq
Mo1	0.0000	−0.2892 (2)	0.2500	0.0502 (7)
O1	−0.0423 (3)	−0.2223 (11)	0.3209 (4)	0.053 (2)
O2	−0.0486 (4)	−0.4409 (11)	0.1680 (6)	0.079 (3)
N1	0.0559 (5)	−0.0212 (13)	0.3428 (5)	0.037 (3)
C1	−0.0533 (6)	−0.061 (2)	0.3573 (8)	0.0479 (18)
C2	−0.1029 (5)	−0.0625 (17)	0.3693 (7)	0.0479 (18)
H2A	−0.1260	−0.1733	0.3541	0.057*
C3	−0.1165 (5)	0.1058 (16)	0.4047 (7)	0.0479 (18)
H3A	−0.1493	0.1052	0.4127	0.057*
C4	−0.0846 (5)	0.2697 (19)	0.4278 (6)	0.0479 (18)
H4A	−0.0957	0.3798	0.4503	0.057*
C5	−0.0345 (5)	0.2726 (19)	0.4176 (6)	0.054 (4)
H5A	−0.0118	0.3845	0.4333	0.065*
C6	−0.0187 (5)	0.1007 (18)	0.3827 (6)	0.037 (3)
C7	0.0360 (5)	0.1081 (16)	0.3804 (6)	0.041 (3)
H7A	0.0589	0.2167	0.4087	0.049*
C8	0.1129 (6)	0.013 (2)	0.3551 (7)	0.044 (3)
C9	0.1308 (6)	0.198 (2)	0.3415 (7)	0.063 (2)
H9A	0.1063	0.3049	0.3253	0.075*
C10	0.1856 (6)	0.219 (2)	0.3524 (7)	0.067 (4)
H10A	0.1972	0.3429	0.3429	0.081*
C11	0.2243 (6)	0.063 (2)	0.3771 (8)	0.063 (2)
C12	0.2048 (6)	−0.115 (2)	0.3891 (7)	0.063 (2)
H12A	0.2294	−0.2217	0.4054	0.075*
C13	0.1500 (5)	−0.144 (2)	0.3781 (7)	0.063 (2)
H13A	0.1384	−0.2690	0.3861	0.075*
C14	0.2838 (6)	0.095 (3)	0.3862 (11)	0.120 (6)
H14A	0.3085	−0.0083	0.4239	0.181*
H14B	0.2984	0.2193	0.4169	0.181*
H14C	0.2821	0.0955	0.3236	0.181*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Mo1	0.0830 (15)	0.0203 (8)	0.0809 (12)	0.000	0.0666 (11)	0.000
O1	0.056 (6)	0.046 (5)	0.080 (5)	0.015 (5)	0.050 (5)	0.018 (5)
O2	0.110 (10)	0.039 (5)	0.138 (8)	−0.036 (6)	0.099 (7)	−0.043 (5)
N1	0.045 (9)	0.033 (6)	0.037 (6)	0.027 (6)	0.022 (6)	0.014 (4)
C1	0.043 (5)	0.055 (4)	0.049 (4)	0.005 (4)	0.024 (4)	0.007 (3)
C2	0.043 (5)	0.055 (4)	0.049 (4)	0.005 (4)	0.024 (4)	0.007 (3)
C3	0.043 (5)	0.055 (4)	0.049 (4)	0.005 (4)	0.024 (4)	0.007 (3)
C4	0.043 (5)	0.055 (4)	0.049 (4)	0.005 (4)	0.024 (4)	0.007 (3)
C5	0.064 (10)	0.060 (9)	0.034 (6)	0.006 (9)	0.018 (6)	−0.006 (6)
C6	0.031 (9)	0.064 (9)	0.017 (6)	0.010 (7)	0.012 (6)	0.002 (6)
C7	0.053 (11)	0.037 (7)	0.029 (6)	0.010 (7)	0.015 (7)	0.018 (5)
C8	0.029 (9)	0.075 (10)	0.034 (7)	0.010 (8)	0.020 (6)	0.004 (6)
C9	0.053 (6)	0.079 (5)	0.062 (4)	0.031 (6)	0.031 (4)	0.015 (4)
C10	0.072 (11)	0.063 (9)	0.073 (8)	−0.010 (10)	0.038 (8)	−0.020 (8)
C11	0.053 (6)	0.079 (5)	0.062 (4)	0.031 (6)	0.031 (4)	0.015 (4)
C12	0.053 (6)	0.079 (5)	0.062 (4)	0.031 (6)	0.031 (4)	0.015 (4)
C13	0.053 (6)	0.079 (5)	0.062 (4)	0.031 (6)	0.031 (4)	0.015 (4)
C14	0.070 (14)	0.165 (18)	0.150 (14)	−0.014 (12)	0.071 (11)	−0.031 (12)

Geometric parameters (Å, º) top

Mo1—O2	1.694 (9)	C5—H5A	0.9300
Mo1—O2ⁱ	1.694 (9)	C6—C7	1.459 (14)
Mo1—O1ⁱ	1.950 (6)	C7—H7A	0.9300
Mo1—O1	1.950 (6)	C8—C13	1.385 (15)
Mo1—N1	2.382 (9)	C8—C9	1.394 (17)
Mo1—N1ⁱ	2.382 (9)	C9—C10	1.384 (15)
O1—C1	1.330 (12)	C9—H9A	0.9300
N1—C7	1.293 (12)	C10—C11	1.400 (16)
N1—C8	1.446 (14)	C10—H10A	0.9300
C1—C6	1.367 (15)	C11—C12	1.363 (17)
C1—C2	1.405 (16)	C11—C14	1.528 (18)
C2—C3	1.388 (14)	C12—C13	1.391 (16)
C2—H2A	0.9300	C12—H12A	0.9300
C3—C4	1.344 (14)	C13—H13A	0.9300
C3—H3A	0.9300	C14—H14A	0.9600
C4—C5	1.402 (14)	C14—H14B	0.9600
C4—H4A	0.9300	C14—H14C	0.9600
C5—C6	1.432 (14)

O2—Mo1—O2ⁱ	104.8 (6)	C4—C5—H5A	120.5
O2—Mo1—O1ⁱ	98.2 (3)	C6—C5—H5A	120.5
O2ⁱ—Mo1—O1ⁱ	98.2 (4)	C1—C6—C5	119.7 (12)
O2—Mo1—O1	98.2 (4)	C1—C6—C7	123.9 (11)
O2ⁱ—Mo1—O1	98.2 (3)	C5—C6—C7	116.3 (12)
O1ⁱ—Mo1—O1	153.0 (4)	N1—C7—C6	126.5 (11)
O2—Mo1—N1	167.6 (4)	N1—C7—H7A	116.7
O2ⁱ—Mo1—N1	87.6 (3)	C6—C7—H7A	116.7
O1ⁱ—Mo1—N1	79.2 (3)	C13—C8—C9	119.4 (13)
O1—Mo1—N1	80.2 (3)	C13—C8—N1	118.7 (12)
O2—Mo1—N1ⁱ	87.6 (3)	C9—C8—N1	121.9 (12)
O2ⁱ—Mo1—N1ⁱ	167.6 (4)	C10—C9—C8	118.9 (14)
O1ⁱ—Mo1—N1ⁱ	80.2 (3)	C10—C9—H9A	120.5
O1—Mo1—N1ⁱ	79.2 (3)	C8—C9—H9A	120.5
N1—Mo1—N1ⁱ	80.0 (4)	C9—C10—C11	122.9 (14)
C1—O1—Mo1	136.7 (7)	C9—C10—H10A	118.6
C7—N1—C8	116.2 (10)	C11—C10—H10A	118.6
C7—N1—Mo1	122.2 (9)	C12—C11—C10	116.2 (14)
C8—N1—Mo1	121.5 (7)	C12—C11—C14	123.3 (15)
O1—C1—C6	122.9 (12)	C10—C11—C14	120.5 (14)
O1—C1—C2	116.5 (12)	C11—C12—C13	123.1 (14)
C6—C1—C2	120.6 (12)	C11—C12—H12A	118.4
C3—C2—C1	118.0 (12)	C13—C12—H12A	118.4
C3—C2—H2A	121.0	C8—C13—C12	119.5 (13)
C1—C2—H2A	121.0	C8—C13—H13A	120.2
C4—C3—C2	123.4 (12)	C12—C13—H13A	120.2
C4—C3—H3A	118.3	C11—C14—H14A	109.5
C2—C3—H3A	118.3	C11—C14—H14B	109.5
C3—C4—C5	119.2 (12)	H14A—C14—H14B	109.5
C3—C4—H4A	120.4	C11—C14—H14C	109.5
C5—C4—H4A	120.4	H14A—C14—H14C	109.5
C4—C5—C6	119.0 (12)	H14B—C14—H14C	109.5

O2—Mo1—O1—C1	−136.1 (11)	C2—C1—C6—C5	−3.0 (15)
O2ⁱ—Mo1—O1—C1	117.6 (11)	O1—C1—C6—C7	−5.2 (16)
O1ⁱ—Mo1—O1—C1	−9.2 (10)	C2—C1—C6—C7	174.4 (9)
N1—Mo1—O1—C1	31.5 (11)	C4—C5—C6—C1	1.9 (14)
N1ⁱ—Mo1—O1—C1	−50.1 (11)	C4—C5—C6—C7	−175.7 (8)
O2—Mo1—N1—C7	62 (2)	C8—N1—C7—C6	−176.2 (9)
O2ⁱ—Mo1—N1—C7	−119.5 (8)	Mo1—N1—C7—C6	7.8 (13)
O1ⁱ—Mo1—N1—C7	141.7 (8)	C1—C6—C7—N1	10.1 (16)
O1—Mo1—N1—C7	−20.8 (7)	C5—C6—C7—N1	−172.5 (9)
N1ⁱ—Mo1—N1—C7	59.9 (7)	C7—N1—C8—C13	137.6 (10)
O2—Mo1—N1—C8	−113.4 (19)	Mo1—N1—C8—C13	−46.3 (11)
O2ⁱ—Mo1—N1—C8	64.6 (8)	C7—N1—C8—C9	−44.5 (13)
O1ⁱ—Mo1—N1—C8	−34.2 (7)	Mo1—N1—C8—C9	131.6 (9)
O1—Mo1—N1—C8	163.4 (8)	C13—C8—C9—C10	−0.7 (15)
N1ⁱ—Mo1—N1—C8	−116.0 (8)	N1—C8—C9—C10	−178.7 (8)
Mo1—O1—C1—C6	−25.2 (17)	C8—C9—C10—C11	−0.3 (16)
Mo1—O1—C1—C2	155.2 (7)	C9—C10—C11—C12	0.8 (16)
O1—C1—C2—C3	−178.3 (9)	C9—C10—C11—C14	178.8 (10)
C6—C1—C2—C3	2.1 (16)	C10—C11—C12—C13	−0.2 (17)
C1—C2—C3—C4	0.0 (16)	C14—C11—C12—C13	−178.1 (11)
C2—C3—C4—C5	−1.0 (15)	C9—C8—C13—C12	1.3 (15)
C3—C4—C5—C6	0.1 (14)	N1—C8—C13—C12	179.3 (9)
O1—C1—C6—C5	177.4 (9)	C11—C12—C13—C8	−0.9 (16)

Symmetry code: (i) −x, y, −z+1/2.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C9—H9A···O2ⁱⁱ	0.93	2.34	3.237 (18)	163
C13—H13A···O2ⁱ	0.93	2.42	3.164 (17)	136

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

Experimental details

Crystal data
Chemical formula	[Mo(C₁₄H₁₂NO)₂O₂]
M_r	548.43
Crystal system, space group	Monoclinic, C2/c
Temperature (K)	296
a, b, c (Å)	26.375 (8), 6.8095 (8), 15.648 (10)
β (°)	116.94 (2)
V (Å³)	2505.4 (18)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.56
Crystal size (mm)	0.21 × 0.11 × 0.08

Data collection
Diffractometer	Stoe IPDS II
Absorption correction	Multi-scan (MULABS in PLATON; Blessing, 1995)
T_min, T_max	0.892, 0.957
No. of measured, independent and observed [I > 2σ(I)] reflections	4305, 2006, 761
R_int	0.144
(sin θ/λ)_max (Å⁻¹)	0.606

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.079, 0.168, 0.83
No. of reflections	2006
No. of parameters	124
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.55, −0.81

Computer programs: X-AREA (Stoe & Cie, 2005), SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C9—H9A···O2ⁱ	0.93	2.34	3.237 (18)	163
C13—H13A···O2ⁱⁱ	0.93	2.42	3.164 (17)	136

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

Footnotes

‡Additional corresponding author, e-mail: zsrkk@yahoo.com, rkia@srbiau.ac.ir.

Acknowledgements

This work was supported by grants from the University of Kerman and the University of Tehran. RK thanks the Islamic Azad University for the X-ray diffractometer facility.

References

Arnaiz, F. J., Aguado, R., Pedrosa, M. R., De Cian, A. & Fischer, A. (2000). Polyhedron, 19, 2141–2147. Web of Science CSD CrossRef CAS Google Scholar
Blessing, R. H. (1995). Acta Cryst. A51, 33–38. CrossRef CAS Web of Science IUCr Journals Google Scholar
Holm, R. H., Kennepohl, P. & Solomon, E. I. (1996). Chem. Rev. 96, 2239–2314. CrossRef PubMed CAS Web of Science Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Spek, A. L. (2009). Acta Cryst. D65, 148–155. Web of Science CrossRef CAS IUCr Journals Google Scholar
Stoe & Cie (2005). X-AREA. Stoe & Cie, Darmstadt, Germany. Google Scholar
Syamal, A. & Maurya, M. R. (1989). Coord. Chem. Rev. 95, 183–238. CrossRef CAS Web of Science Google Scholar