Tetra-μ3-tert-butano­lato-tetra­thallium(I)

Blasberg, F.; Lerner, H.-W.; Bolte, M.

doi:10.1107/S1600536810047550

metal-organic compounds

CRYSTALLOGRAPHIC
COMMUNICATIONS

ISSN: 2056-9890

Volume 66| Part 12| December 2010| Page m1621

https://doi.org/10.1107/S1600536810047550

Open

access

Tetra-μ₃-tert-butanolato-tetrathallium(I)

Florian Blasberg,^a Hans-Wolfram Lerner ^a and Michael Bolte ^a ^*

^aInstitut für Anorganische Chemie, J. W. Goethe-Universität Frankfurt, Max-von-Laue-Strasse 7, 60438 Frankfurt/Main, Germany
^*Correspondence e-mail: bolte@chemie.uni-frankfurt.de

(Received 2 November 2010; accepted 16 November 2010; online 20 November 2010)

The title compound, [Tl₄(C₄H₉O)₄], featuring a (Tl—O)₄ cube, crystallizes with a quarter-molecule (located on a special position of site symmetry $[\overline{4}]$ ..) and a half-molecule (located on a special position of site symmetry 23.) in the asymmetric unit. The Tl—O bond distances range from 2.463 (12) to 2.506 (12) Å. All O—Tl—O bond angles are smaller than 90° whereas the Tl—O—Tl angles are wider than a rectangular angle.

Related literature

For the use of bulky silyl chalcogenolate ligands of the type ESiR₃⁻ and alkyl chalcogenolates E(alkyl)⁻ (E = O, S, Se, Te) with especially bulky alkoxides to stabilize transition metal centres, see: Wolczanski (2009 ); Kückmann et al. (2005 , 2008 , 2010 ). For substitution reactions of transition metal atoms, see: Kern et al. (2008 ); Lerner et al. (2002 , 2005 ). The title compound was prepared according to a slightly changed published procedure, see: Schmidbaur et al. (1968 ).

Experimental

Crystal data

[Tl₄(C₄H₉O)₄]
M_r = 1109.93
Cubic, $[P \overline 43n ]$
a = 17.1500 (15) Å
V = 5044.2 (8) Å³
Z = 8
Mo Kα radiation
μ = 25.49 mm⁻¹
T = 173 K
0.21 × 0.18 × 0.10 mm

Data collection

Stoe IPDS II two-circle diffractometer
Absorption correction: multi-scan (MULABS; Spek, 2009 ; Blessing, 1995 ) T_min = 0.075, T_max = 0.185
13612 measured reflections
1489 independent reflections
1226 reflections with I > 2σ(I)
R_int = 0.084

Refinement

R[F² > 2σ(F²)] = 0.042
wR(F²) = 0.083
S = 1.00
1489 reflections
73 parameters
6 restraints
H-atom parameters constrained
Δρ_max = 1.77 e Å⁻³
Δρ_min = −1.01 e Å⁻³
Absolute structure: Flack (1983 ), 711 Friedel pairs
Flack parameter: 0.00 (7)

Data collection: X-AREA (Stoe & Cie, 2001 ); cell refinement: X-AREA; data reduction: X-AREA; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: XP (Sheldrick, 2008); software used to prepare material for publication: SHELXL97.

Supporting information

Crystal structure: contains datablocks I, global. DOI: https://doi.org/10.1107/S1600536810047550/kj2165sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536810047550/kj2165Isup2.hkl

checkCIF report

Comment top

In a number of recent studies bulky silyl chalcogenolate ligands of the type ESiR₃^- and alkyl chalcogenolates E(alkyl)^- (E = O, S, Se, Te) with especially bulky alkoxides have been used to stabilize transition metal centers (Wolczanski, 2009; Kückmann et al. 2005, 2008, 2010). In macromolecular chemistry, these ligands have also found application. Chalcogen-based ligands offer a variety of possible binding modes. Chalcogenolates are often found bridging two or more metal ions. Normally, transition metal complexes possess 6 e^- thiolate ligands in a µ₃-binding mode. Recently, however, we have shown that the anion of the mixed-valence Mn(I/II) complex Na(thf)₆[(OC)₃Mn(µ-SSitBu₃)₃MnSSitBu₃] contains a terminal thiolate ligand with a linear Mn—S—Si unit (Kückmann et al. 2008). The prerequisite for six-electron donation (2 σ- and 4 π-electrons) comparable with Cp^- is thus fulfilled. One approach is to create such complexes by substitution reactions of transition metal halogenides with alkali metal alkoxides as M⁺[OC(CH₃)₃]^- or alkali metal siloxides M⁺[OSiR₃]- (Kern et al. 2008; Lerner et al. 2005, 2002). In most cases the reactions that occur between alkali metal alkoxides and transition metal halides are not quantitative. Another approach to complexes with chalcogen coordination is to start from thallium alkoxides which react almost quantitatively with transition metal chlorides due to the poor solubility of TlCl. In this paper we report the synthesis and the crystal structure of [TlOtBu]₄. The title compound [TlOtBu]₄ was prepared according to a slightly changed published procedure (Schmidbaur et al. 1968), as shown in Fig. 2. The following modifications have been made in our approach: thallium ethoxide was used instead of thallium methoxide and potassium tert-butoxide was substituted for sodium tert-butoxide.

Related literature top

For the use of bulky silyl chalcogenolate ligands of the type ESiR₃^- and alkyl chalcogenolates E(alkyl)^- (E = O, S, Se, Te) with especially bulky alkoxides to stabilize transition metal centers, see: Wolczanski (2009); Kückmann et al. (2005, 2008, 2010). For substitution reactions of transition metal halogenides with alkali metal alkoxides as M⁺[OC(CH₃)₃]^- or alkali metal siloxides M⁺[OSiR₃]^-, see: Kern et al. (2008); Lerner et al. (2002, 2005). The title compound was prepared according to a slightly changed published procedure, see: Schmidbaur et al. (1968).

Experimental top

In a flame-dried vial 1.1 ml thallium ethoxide (3.77 g, 15.1 mmol) was added to 1.70 g potassium tert-butoxide (15.1 mmol) in 50 ml benzene. After flame-sealing, the vial was heated to 80 °C for four days. The vial was opened, the crude reaction mixture filtered hot under an nitrogen atmosphere, the solid residue was washed with 20 ml benzene and the combined filtrates evaporated to dryness. The remaining colorless solid was suspended in ether and allowed to settle. A sample of the supernatant was transferred to a flame-dried Schlenk vessel and stored at -35°C. After two days colorless crystals of the composition [TlOtBu]₄ deposited and were separated from the mother liquor (Yield 15%).

Structure description top

Computing details top

Data collection: X-AREA (Stoe & Cie, 2001); cell refinement: X-AREA (Stoe & Cie, 2001); data reduction: X-AREA (Stoe & Cie, 2001); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: XP (Sheldrick, 2008); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures top

	Fig. 1. Perspective view of one of the two independent molecules of the title compound with the atom numbering scheme for the symmetry independent atoms; displacement ellipsoids are at the 50% probability level; H atoms are omitted for clarity.
	Fig. 2. Preparation of the title compound.

Tetra-µ₃-tert-butanolato-tetrathallium(I) top

Crystal data top

[Tl₄(C₄H₉O)₄]	D_x = 2.923 Mg m⁻³
M_r = 1109.93	Mo Kα radiation, λ = 0.71073 Å
Cubic, P43n	Cell parameters from 7201 reflections
Hall symbol: P -4n 2 3	θ = 3.4–25.9°
a = 17.1500 (15) Å	µ = 25.49 mm⁻¹
V = 5044.2 (8) Å³	T = 173 K
Z = 8	Plate, colourless
F(000) = 3904	0.21 × 0.18 × 0.10 mm

Data collection top

Stoe IPDS II two-circle diffractometer	1489 independent reflections
Radiation source: fine-focus sealed tube	1226 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.084
ω scans	θ_max = 25.0°, θ_min = 3.4°
Absorption correction: multi-scan (MULABS; Spek, 2009; Blessing, 1995)	h = −18→20
T_min = 0.075, T_max = 0.185	k = −19→20
13612 measured reflections	l = −20→18

Refinement top

Refinement on F²	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.042	H-atom parameters constrained
wR(F²) = 0.083	w = 1/[σ²(F_o²) + (0.037P)²] where P = (F_o² + 2F_c²)/3
S = 1.00	(Δ/σ)_max = 0.001
1489 reflections	Δρ_max = 1.77 e Å⁻³
73 parameters	Δρ_min = −1.01 e Å⁻³
6 restraints	Absolute structure: Flack (1983), 711 Friedel pairs
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.00 (7)

Crystal data top

[Tl₄(C₄H₉O)₄]	Z = 8
M_r = 1109.93	Mo Kα radiation
Cubic, P43n	µ = 25.49 mm⁻¹
a = 17.1500 (15) Å	T = 173 K
V = 5044.2 (8) Å³	0.21 × 0.18 × 0.10 mm

Data collection top

Stoe IPDS II two-circle diffractometer	1489 independent reflections
Absorption correction: multi-scan (MULABS; Spek, 2009; Blessing, 1995)	1226 reflections with I > 2σ(I)
T_min = 0.075, T_max = 0.185	R_int = 0.084
13612 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.042	H-atom parameters constrained
wR(F²) = 0.083	Δρ_max = 1.77 e Å⁻³
S = 1.00	Δρ_min = −1.01 e Å⁻³
1489 reflections	Absolute structure: Flack (1983), 711 Friedel pairs
73 parameters	Absolute structure parameter: 0.00 (7)
6 restraints

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
Tl1	0.66760 (4)	0.91953 (4)	0.57229 (3)	0.02168 (17)
O1	0.8130 (7)	0.9310 (7)	0.5635 (7)	0.022 (2)
C1	0.8550 (13)	0.8777 (10)	0.6115 (13)	0.029 (4)
C2	0.9386 (12)	0.8950 (18)	0.6078 (19)	0.059 (8)
H2A	0.9478	0.9485	0.6256	0.088*
H2B	0.9569	0.8895	0.5539	0.088*
H2C	0.9671	0.8586	0.6414	0.088*
C3	0.8400 (19)	0.7958 (10)	0.583 (2)	0.059 (7)
H3A	0.7839	0.7853	0.5844	0.089*
H3B	0.8669	0.7588	0.6177	0.089*
H3C	0.8596	0.7901	0.5301	0.089*
C4	0.8261 (16)	0.8852 (14)	0.6961 (12)	0.041 (6)
H4A	0.8368	0.9380	0.7153	0.061*
H4B	0.8533	0.8472	0.7290	0.061*
H4C	0.7698	0.8753	0.6980	0.061*
Tl1A	0.42129 (4)	0.42129 (4)	0.42129 (4)	0.0223 (2)
O1A	0.5652 (6)	0.4348 (6)	0.4348 (6)	0.020 (4)
C1A	0.6118 (13)	0.3882 (13)	0.3882 (13)	0.020 (7)
C2A	0.6960 (12)	0.3942 (13)	0.4110 (14)	0.035 (5)
H2A1	0.7125	0.4488	0.4086	0.053*
H2A2	0.7277	0.3631	0.3751	0.053*
H2A3	0.7027	0.3746	0.4643	0.053*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Tl1	0.0231 (3)	0.0211 (3)	0.0208 (3)	−0.0047 (3)	0.0036 (3)	0.0011 (3)
O1	0.031 (6)	0.020 (6)	0.015 (6)	0.005 (5)	−0.005 (5)	0.009 (5)
C1	0.036 (10)	0.016 (9)	0.034 (12)	0.012 (8)	−0.009 (9)	0.003 (8)
C2	0.023 (10)	0.065 (16)	0.09 (2)	0.006 (12)	0.006 (13)	0.040 (14)
C3	0.09 (2)	0.007 (8)	0.08 (2)	0.007 (11)	−0.018 (18)	0.008 (12)
C4	0.063 (16)	0.041 (13)	0.019 (10)	0.018 (11)	0.007 (10)	0.003 (8)
Tl1A	0.0223 (2)	0.0223 (2)	0.0223 (2)	−0.0035 (3)	−0.0035 (3)	−0.0035 (3)
O1A	0.020 (4)	0.020 (4)	0.020 (4)	0.005 (5)	0.005 (5)	−0.005 (5)
C1A	0.020 (7)	0.020 (7)	0.020 (7)	0.003 (8)	0.003 (8)	−0.003 (8)
C2A	0.025 (8)	0.041 (8)	0.041 (9)	0.011 (6)	0.007 (7)	−0.010 (7)

Geometric parameters (Å, º) top

Tl1—O1ⁱ	2.463 (12)	C4—H4A	0.9800
Tl1—O1ⁱⁱ	2.493 (11)	C4—H4B	0.9800
Tl1—O1	2.506 (12)	C4—H4C	0.9800
O1—C1	1.42 (2)	Tl1A—O1A	2.490 (8)
O1—Tl1ⁱⁱ	2.463 (12)	Tl1A—O1Aⁱⁱⁱ	2.490 (8)
O1—Tl1ⁱ	2.492 (11)	Tl1A—O1A^iv	2.490 (8)
C1—C2	1.47 (3)	O1A—C1A	1.38 (4)
C1—C3	1.51 (3)	O1A—Tl1Aⁱⁱⁱ	2.490 (8)
C1—C4	1.54 (3)	O1A—Tl1A^iv	2.490 (8)
C2—H2A	0.9800	C1A—C2A^v	1.50 (2)
C2—H2B	0.9800	C1A—C2A^vi	1.50 (2)
C2—H2C	0.9800	C1A—C2A	1.50 (2)
C3—H3A	0.9800	C2A—H2A1	0.9800
C3—H3B	0.9800	C2A—H2A2	0.9800
C3—H3C	0.9800	C2A—H2A3	0.9800

O1ⁱ—Tl1—O1ⁱⁱ	81.0 (4)	H3B—C3—H3C	109.5
O1ⁱ—Tl1—O1	78.3 (4)	C1—C4—H4A	109.5
O1ⁱⁱ—Tl1—O1	77.8 (4)	C1—C4—H4B	109.5
O1ⁱ—Tl1—Tl1^vii	41.8 (3)	H4A—C4—H4B	109.5
O1ⁱⁱ—Tl1—Tl1^vii	41.2 (3)	C1—C4—H4C	109.5
O1—Tl1—Tl1^vii	84.3 (2)	H4A—C4—H4C	109.5
C1—O1—Tl1ⁱⁱ	119.7 (10)	H4B—C4—H4C	109.5
C1—O1—Tl1ⁱ	119.3 (11)	O1A—Tl1A—O1Aⁱⁱⁱ	78.9 (6)
Tl1ⁱⁱ—O1—Tl1ⁱ	97.0 (4)	O1A—Tl1A—O1A^iv	78.9 (6)
C1—O1—Tl1	114.7 (11)	O1Aⁱⁱⁱ—Tl1A—O1A^iv	78.9 (6)
Tl1ⁱⁱ—O1—Tl1	101.8 (4)	C1A—O1A—Tl1Aⁱⁱⁱ	117.7 (11)
Tl1ⁱ—O1—Tl1	101.0 (4)	C1A—O1A—Tl1A^iv	117.7 (11)
O1—C1—C2	109.8 (17)	Tl1Aⁱⁱⁱ—O1A—Tl1A^iv	100.1 (5)
O1—C1—C3	109.2 (17)	C1A—O1A—Tl1A	117.7 (11)
C2—C1—C3	110 (2)	Tl1Aⁱⁱⁱ—O1A—Tl1A	100.1 (5)
O1—C1—C4	109.1 (16)	Tl1A^iv—O1A—Tl1A	100.1 (5)
C2—C1—C4	110 (2)	O1A—C1A—C2A^v	111.4 (15)
C3—C1—C4	109 (2)	O1A—C1A—C2A^vi	111.4 (15)
C1—C2—H2A	109.5	C2A^v—C1A—C2A^vi	107.4 (16)
C1—C2—H2B	109.5	O1A—C1A—C2A	111.4 (15)
H2A—C2—H2B	109.5	C2A^v—C1A—C2A	107.4 (16)
C1—C2—H2C	109.5	C2A^vi—C1A—C2A	107.4 (16)
H2A—C2—H2C	109.5	C1A—C2A—H2A1	109.5
H2B—C2—H2C	109.5	C1A—C2A—H2A2	109.5
C1—C3—H3A	109.5	H2A1—C2A—H2A2	109.5
C1—C3—H3B	109.5	C1A—C2A—H2A3	109.5
H3A—C3—H3B	109.5	H2A1—C2A—H2A3	109.5
C1—C3—H3C	109.5	H2A2—C2A—H2A3	109.5
H3A—C3—H3C	109.5

O1ⁱ—Tl1—O1—C1	−137.9 (13)	Tl1—O1—C1—C4	−53.8 (18)
O1ⁱⁱ—Tl1—O1—C1	139.0 (13)	O1Aⁱⁱⁱ—Tl1A—O1A—C1A	139.7 (13)
Tl1^vii—Tl1—O1—C1	−179.8 (12)	O1A^iv—Tl1A—O1A—C1A	−139.7 (13)
O1ⁱ—Tl1—O1—Tl1ⁱⁱ	91.4 (5)	O1Aⁱⁱⁱ—Tl1A—O1A—Tl1Aⁱⁱⁱ	10.8 (5)
O1ⁱⁱ—Tl1—O1—Tl1ⁱⁱ	8.2 (4)	O1A^iv—Tl1A—O1A—Tl1Aⁱⁱⁱ	91.49 (15)
Tl1^vii—Tl1—O1—Tl1ⁱⁱ	49.5 (3)	O1Aⁱⁱⁱ—Tl1A—O1A—Tl1A^iv	−91.49 (15)
O1ⁱ—Tl1—O1—Tl1ⁱ	−8.2 (4)	O1A^iv—Tl1A—O1A—Tl1A^iv	−10.8 (5)
O1ⁱⁱ—Tl1—O1—Tl1ⁱ	−91.4 (5)	Tl1Aⁱⁱⁱ—O1A—C1A—C2A^v	68.4 (10)
Tl1^vii—Tl1—O1—Tl1ⁱ	−50.1 (3)	Tl1A^iv—O1A—C1A—C2A^v	−171.6 (10)
Tl1ⁱⁱ—O1—C1—C2	−53 (2)	Tl1A—O1A—C1A—C2A^v	−51.6 (10)
Tl1ⁱ—O1—C1—C2	66 (2)	Tl1Aⁱⁱⁱ—O1A—C1A—C2A^vi	−171.6 (10)
Tl1—O1—C1—C2	−174.2 (19)	Tl1A^iv—O1A—C1A—C2A^vi	−51.6 (10)
Tl1ⁱⁱ—O1—C1—C3	−173.5 (18)	Tl1A—O1A—C1A—C2A^vi	68.4 (10)
Tl1ⁱ—O1—C1—C3	−55 (2)	Tl1Aⁱⁱⁱ—O1A—C1A—C2A	−51.6 (10)
Tl1—O1—C1—C3	65 (2)	Tl1A^iv—O1A—C1A—C2A	68.4 (10)
Tl1ⁱⁱ—O1—C1—C4	67.6 (19)	Tl1A—O1A—C1A—C2A	−171.6 (10)
Tl1ⁱ—O1—C1—C4	−173.7 (14)

Symmetry codes: (i) −x+3/2, −z+3/2, y−1/2; (ii) −x+3/2, z+1/2, −y+3/2; (iii) −x+1, y, −z+1; (iv) −x+1, −y+1, z; (v) −z+1, −x+1, y; (vi) −y+1, z, −x+1; (vii) x, −y+2, −z+1.

Experimental details

Crystal data
Chemical formula	[Tl₄(C₄H₉O)₄]
M_r	1109.93
Crystal system, space group	Cubic, P43n
Temperature (K)	173
a (Å)	17.1500 (15)
V (Å³)	5044.2 (8)
Z	8
Radiation type	Mo Kα
µ (mm⁻¹)	25.49
Crystal size (mm)	0.21 × 0.18 × 0.10

Data collection
Diffractometer	Stoe IPDS II two-circle
Absorption correction	Multi-scan (MULABS; Spek, 2009; Blessing, 1995)
T_min, T_max	0.075, 0.185
No. of measured, independent and observed [I > 2σ(I)] reflections	13612, 1489, 1226
R_int	0.084
(sin θ/λ)_max (Å⁻¹)	0.595

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.042, 0.083, 1.00
No. of reflections	1489
No. of parameters	73
No. of restraints	6
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	1.77, −1.01
Absolute structure	Flack (1983), 711 Friedel pairs
Absolute structure parameter	0.00 (7)

Computer programs: X-AREA (Stoe & Cie, 2001), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), XP (Sheldrick, 2008).

References

Blessing, R. H. (1995). Acta Cryst. A51, 33–38. CrossRef CAS Web of Science IUCr Journals Google Scholar
Flack, H. D. (1983). Acta Cryst. A39, 876–881. CrossRef CAS Web of Science IUCr Journals Google Scholar
Kern, B., Vitze, H., Bolte, M., Wagner, M. & Lerner, H.-W. (2008). Z. Anorg. Allg. Chem. 634, 1830–1832. Web of Science CSD CrossRef CAS Google Scholar
Kückmann, T. I., Hermsen, M., Bolte, M., Wagner, M. & Lerner, H.-W. (2005). Inorg. Chem. 44, 3449–3458. Web of Science PubMed Google Scholar
Kückmann, T. I., Schödel, F., Sänger, I., Bolte, M., Wagner, M. & Lerner, H.-W. (2008). Organometallics, 27, 3272–3278. Google Scholar
Kückmann, T. I., Schödel, F., Sänger, I., Bolte, M., Wagner, M. & Lerner, H.-W. (2010). Eur. J. Inorg. Chem. pp. 468–475. Web of Science CSD CrossRef Google Scholar
Lerner, H.-W., Scholz, S. & Bolte, M. (2002). Organometallics, 21, 3827–3830. Web of Science CSD CrossRef CAS Google Scholar
Lerner, H.-W., Scholz, S., Wiberg, N., Polborn, K., Bolte, M. & Wagner, M. (2005). Z. Anorg. Allg. Chem. 631, 1863–1870. Web of Science CSD CrossRef CAS Google Scholar
Schmidbaur, H., Bergfeld, M. & Schindler, F. (1968). Z. Anorg. Allg. Chem. 363, 73–83. CrossRef 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 (2001). X-AREA. Stoe & Cie, Darmstadt, Germany. Google Scholar
Wolczanski, P. T. (2009). Chem. Commun. pp. 740–757. Web of Science CrossRef Google Scholar