1,2-Bis{bis­[4-(trifluoro­meth­yl)phen­yl]phosphino}ethane

Bork, M.A.; Krueger, A.M.; Tanke, R.S.; Brummer, J.G.

doi:10.1107/S1600536807068547

organic compounds

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ISSN: 2056-9890

Volume 64| Part 2| February 2008| Page o421

doi:10.1107/S1600536807068547

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1,2-Bis{bis[4-(trifluoromethyl)phenyl]phosphino}ethane

Matthew A. Bork,^a Aaron M. Krueger,^a Robin S. Tanke ^a ^* and James G. Brummer ^a

^aDepartment of Chemistry, University of Wisconsin – Stevens Point, Stevens Point, WI 54481, USA
^*Correspondence e-mail: rtanke@uwsp.edu

(Received 28 November 2007; accepted 27 December 2007; online 11 January 2008)

Crystals of the title compound, C₃₀H₂₀F₁₂P₂ or R₂PCH₂CH₂PR₂ (R = 4-C₆H₄CF₃), were inadvertently prepared while attempting to recrystallize a crude sample of trans-Re(Cl)(N₂)(R₂PCH₂CH₂PR₂)₂ from diethyl ether. The molecule lies on a center of inversion. One of the rings lies approximately in the P—C—C—P plane; the dihedral angle is 174.53°.The other ring is not quite perpendicular; the dihedral angle is 71.1°. The compound is isostructural with the R = Ph, 4-C₆H₄CH₃ and 4-C₆H₄CH₂CH₃ analogues. It is well known that the basicity of phosphines and diphosphines can be altered by changing the electron-donating ability of R; however, the structural parameters for the title compound do not significantly differ from those of the aforementioned substituted-phenyl compounds.

Related literature

For the synthesis of the title compound, see: Chatt et al. (1985 ). For the crystal structures of similar 1,2-bis(diphenylphosphino)ethane structures, see: Tiekink (2001 ); Zeller et al. (2003 ); Zeller & Hunter (2004 ). For related literature, see: Allman & Goel (1982 ); Larson (1970 ); Nordwig et al. (2006 ); Streuli (1960 ); Tolman (1970 ).

Experimental

Crystal data

C₃₀H₂₀F₁₂P₂
M_r = 670.41
Monoclinic, P 2₁ /n
a = 15.188 (11) Å
b = 5.402 (4) Å
c = 18.123 (13) Å
β = 99.044 (9)°
V = 1468.3 (19) Å³
Z = 2
Mo Kα radiation
μ = 0.24 mm⁻¹
T = 208 K
0.40 × 0.10 × 0.10 mm

Data collection

Bruker SMART APEXII diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 2006 ) T_min = 0.91, T_max = 0.98
9947 measured reflections
3240 independent reflections
2616 reflections with I > 2σ(I)
R_int = 0.044

Refinement

R[F² > 2σ(F²)] = 0.061
wR(F²) = 0.162
S = 0.95
3229 reflections
208 parameters
H-atom parameters constrained
Δρ_max = 0.73 e Å⁻³
Δρ_min = −0.43 e Å⁻³

Data collection: APEX2 (Bruker, 2006 ); cell refinement: APEX2; data reduction: APEX2; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: CRYSTALS (Betteridge et al., 2003 ); molecular graphics: CAMERON (Watkin et al., 1996 ); software used to prepare material for publication: CRYSTALS.

Supporting information

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536807068547/om2196sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536807068547/om2196Isup2.hkl

checkCIF report

Comment top

1,2-Bis{bis[4-(trifluoromethyl)phenyl]phosphino}ethane was obtained accidently during the recrystallization of trans-Re(Cl)(N₂)(R₂PCH₂CH₂PR₂)₂[R = 4-Ph—CF₃] from diethyl ether. We were interested in preparing this complex in order to measure its luminescent properties and then compare them to those for the analogous R = Ph, 4-Ph-OCH₃, and CH₂CH₃complexes. Our preliminary results indicate that these complexes show simultaneous emission from two excited levels of different orbital parentage. Our intent is to investigate how changes in diphosphine basicity brought about by variations in R influence the bandshape and lifetimes of these emissions thereby allowing us to assign the excited states responsible for luminescence.

The title compound resides on a center of inversion. It is isostructural to its R = Ph, 4-Ph—CH₃, and 4-Ph—CH₂CH₃ analogues. It is well known that the basicity of phosphines and diphosphines can be altered by changing the electron donating ability of R; however, the structural parameters for the title compound do not significantly differ from the aforementioned phenyl substituted compounds.

A summary of the C—P bond distances, C—P—C bond angles, and sums of the C—P—C angles is given in Table 1 for this work and several related diphosphines that contain aromatic and aliphatic substituents. The title compound has nearly identical geoemtric parameters about phosphorus as the other phenyl diphosphines and there appears to be no experimentally significant trends that parallel the electron donating ability of the para-substituent, which follows the order CH₃CH₂> CH₃> H > CF₃(Nordwig et al., 2006; Allman & Goel, 1982; Tolman, 1970; Streuli, 1960). The aromatic diphosphines display Σ C—P—C values of about 303.5° which indicates a pyramidal arrangement of the bonds about phosphorus. The aliphatic diphosphines are more electron donating with the less sterically demanding R = CH₃and CH₂CH₃cases giving rise to lower ΣC—P—C values. The R = CH(CH₃)₂ and C(CH₃)₃compounds display larger ΣC—P—C values and longer C—P bond distances due to increased space requirements for these bulkier substituents. Substituent effects for the alkyl substituted compounds have been discussed previously (Bruckmann & Kruger, 1997; Eisentrager et al., 2003).

One of the rings lines approximately in the P—C—C—P plane; the dihedral angle is 174.53°.The other ring is not quite perpendicular; the dihedral angle is 71.1°.

Related literature top

For the synthesis of the title compound, see Chatt et al. (1985) For the crystal structures of similar 1,2-bis(diphenylphosphino)ethane structures, see Tiekink (2001); Zeller et al. (2003); Zeller & Hunter (2004). For related literature, see: Allman & Goel (1982); Larson (1970); Nordwig et al. (2006); Streuli (1960); Tolman (1970).

Experimental top

A non-crystalline sample of R₂PCH₂CH₂PR₂ [R = 4-Ph—CF₃] and a crude sample of trans-Re(Cl)(N₂)(R₂PCH₂CH₂PR₂)₂ [R = 4-Ph—CF₃] were prepared according to previously reported methods (Chatt, et al., 1985). Crude trans-Re(Cl)(N₂)(R₂PCH₂CH₂PR₂)₂was dissolved in a minimum of diethyl ether at 20° C. The yellow-orange solution was filtered and ether was gradually evaporated by passing a slow stream of nitrogen gas through the flask. A mixture of microcrystalline orange solid and pale yellow-orange crystals formed over the course of 4 h. A pale crystal from this mixture was analyzed.

Computing details top

Data collection: APEX2 (Bruker, 2006); cell refinement: APEX2 (Bruker, 2006); data reduction: APEX2 (Bruker, 2006); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: CRYSTALS (Betteridge et al., 2003); molecular graphics: CAMERON (Watkin et al., 1996); software used to prepare material for publication: CRYSTALS (Betteridge et al., 2003).

Figures top

Fig. 1. The title compound with displacement ellipsoids drawn at the 50% probability level. Symmetry code: i = -x + 2, -y + 2, -z.

1,2-Bis{bis[4-(trifluoromethyl)phenyl]phosphino}ethane top

Crystal data top

C₃₀H₂₀F₁₂P₂	F(000) = 676
M_r = 670.41	D_x = 1.516 Mg m⁻³
Monoclinic, P2₁/n	Melting point: 471 K
Hall symbol: -P 2yn	Mo Kα radiation, λ = 0.71073 Å
a = 15.188 (11) Å	Cell parameters from 4592 reflections
b = 5.402 (4) Å	θ = 2.3–27.2°
c = 18.123 (13) Å	µ = 0.25 mm⁻¹
β = 99.044 (9)°	T = 208 K
V = 1468.3 (19) Å³	Block, colorless
Z = 2	0.40 × 0.10 × 0.10 mm

Data collection top

Bruker SMART APEXII diffractometer	3240 independent reflections
Radiation source: fine-focus sealed tube	2616 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.044
ω scans	θ_max = 27.2°, θ_min = 1.6°
Absorption correction: multi-scan (SADABS; Sheldrick, 2006)	h = −19→19
T_min = 0.91, T_max = 0.98	k = −4→6
9947 measured reflections	l = −23→17

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.061	H-atom parameters constrained
wR(F²) = 0.162	Method = Modified Sheldrick w = 1/[σ²(F²) + ( 0.07P)² + 1.82P] , where P = (max(F_o²,0) + 2F_c²)/3
S = 0.95	(Δ/σ)_max = 0.001
3229 reflections	Δρ_max = 0.73 e Å⁻³
208 parameters	Δρ_min = −0.43 e Å⁻³
0 restraints	Extinction correction: Larson (1970), Equation 22
0 constraints	Extinction coefficient: 100 (30)

Crystal data top

C₃₀H₂₀F₁₂P₂	V = 1468.3 (19) Å³
M_r = 670.41	Z = 2
Monoclinic, P2₁/n	Mo Kα radiation
a = 15.188 (11) Å	µ = 0.25 mm⁻¹
b = 5.402 (4) Å	T = 208 K
c = 18.123 (13) Å	0.40 × 0.10 × 0.10 mm
β = 99.044 (9)°

Data collection top

Bruker SMART APEXII diffractometer	3240 independent reflections
Absorption correction: multi-scan (SADABS; Sheldrick, 2006)	2616 reflections with I > 2σ(I)
T_min = 0.91, T_max = 0.98	R_int = 0.044
9947 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.061	0 restraints
wR(F²) = 0.162	H-atom parameters constrained
S = 0.95	Δρ_max = 0.73 e Å⁻³
3229 reflections	Δρ_min = −0.43 e Å⁻³
208 parameters

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

	x	y	z	U_iso*/U_eq
F1	1.27583 (17)	0.8551 (5)	0.42720 (14)	0.0973
F2	1.22595 (19)	0.5004 (4)	0.40090 (12)	0.0933
F3	1.15394 (18)	0.7552 (7)	0.45867 (12)	0.1188
F4	0.58890 (16)	0.7965 (6)	0.11270 (19)	0.1126
F5	0.56328 (18)	1.1552 (8)	0.0760 (3)	0.1601
F6	0.59438 (18)	1.0822 (8)	0.19080 (19)	0.1525
C1	1.02538 (17)	0.9577 (5)	0.03782 (13)	0.0376
C2	1.06731 (16)	1.0281 (5)	0.19636 (13)	0.0366
C3	1.12029 (18)	0.8196 (5)	0.19746 (14)	0.0432
C4	1.16363 (19)	0.7219 (6)	0.26452 (15)	0.0474
C5	1.15250 (17)	0.8323 (5)	0.33151 (14)	0.0422
C6	1.1999 (2)	0.7337 (7)	0.40384 (16)	0.0566
C7	1.0996 (2)	1.0400 (6)	0.33167 (15)	0.0501
C8	1.05801 (19)	1.1393 (6)	0.26470 (15)	0.0466
C9	0.89383 (17)	1.1273 (5)	0.11969 (14)	0.0375
C10	0.8645 (2)	0.9282 (6)	0.15831 (18)	0.0531
C11	0.7744 (2)	0.8957 (7)	0.16050 (19)	0.0600
C12	0.71295 (19)	1.0603 (6)	0.12370 (17)	0.0530
C13	0.6158 (2)	1.0234 (9)	0.1269 (3)	0.0781
C14	0.7406 (2)	1.2566 (7)	0.08562 (19)	0.0587
C15	0.83094 (19)	1.2916 (6)	0.08420 (17)	0.0488
P1	1.01119 (4)	1.18369 (12)	0.11177 (3)	0.0363
H11	1.0876	0.9429	0.0344	0.0451*
H12	1.0028	0.7998	0.0503	0.0451*
H31	1.1270	0.7433	0.1527	0.0513*
H41	1.2006	0.5845	0.2647	0.0539*
H71	1.0918	1.1122	0.3768	0.0578*
H81	1.0232	1.2810	0.2648	0.0543*
H101	0.9059	0.8154	0.1819	0.0610*
H111	0.7548	0.7643	0.1868	0.0685*
H141	0.6989	1.3674	0.0614	0.0680*
H151	0.8499	1.4260	0.0587	0.0563*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
F1	0.0832 (16)	0.114 (2)	0.0773 (15)	−0.0152 (14)	−0.0410 (12)	0.0092 (14)
F2	0.135 (2)	0.0749 (15)	0.0578 (13)	0.0188 (14)	−0.0231 (13)	0.0109 (11)
F3	0.0998 (19)	0.211 (3)	0.0491 (12)	0.057 (2)	0.0224 (12)	0.0483 (17)
F4	0.0612 (14)	0.128 (2)	0.155 (3)	−0.0417 (15)	0.0383 (15)	−0.065 (2)
F5	0.0438 (14)	0.213 (4)	0.219 (4)	0.0033 (19)	0.0043 (19)	0.058 (3)
F6	0.0792 (17)	0.252 (4)	0.143 (3)	−0.069 (2)	0.0692 (18)	−0.128 (3)
C1	0.0375 (12)	0.0447 (14)	0.0301 (12)	−0.0025 (11)	0.0036 (9)	−0.0012 (10)
C2	0.0352 (12)	0.0416 (13)	0.0321 (11)	−0.0035 (10)	0.0022 (9)	−0.0015 (10)
C3	0.0476 (14)	0.0499 (15)	0.0306 (12)	0.0024 (12)	0.0015 (10)	−0.0059 (11)
C4	0.0480 (15)	0.0504 (16)	0.0419 (14)	0.0086 (12)	0.0012 (11)	−0.0001 (12)
C5	0.0368 (13)	0.0543 (16)	0.0338 (12)	−0.0062 (11)	0.0003 (10)	0.0016 (11)
C6	0.0545 (17)	0.076 (2)	0.0371 (14)	0.0052 (16)	−0.0006 (13)	0.0024 (14)
C7	0.0527 (16)	0.0644 (19)	0.0323 (13)	0.0042 (14)	0.0036 (11)	−0.0087 (12)
C8	0.0488 (15)	0.0506 (16)	0.0396 (14)	0.0089 (12)	0.0043 (11)	−0.0060 (12)
C9	0.0380 (12)	0.0408 (13)	0.0330 (12)	−0.0019 (10)	0.0041 (10)	−0.0020 (10)
C10	0.0447 (15)	0.0549 (18)	0.0584 (17)	−0.0033 (13)	0.0041 (13)	0.0165 (14)
C11	0.0525 (17)	0.066 (2)	0.0627 (19)	−0.0154 (15)	0.0142 (15)	0.0084 (16)
C12	0.0403 (14)	0.068 (2)	0.0514 (16)	−0.0054 (14)	0.0108 (12)	−0.0176 (15)
C13	0.0438 (18)	0.106 (3)	0.087 (3)	−0.011 (2)	0.0157 (18)	−0.029 (2)
C14	0.0437 (16)	0.067 (2)	0.0638 (19)	0.0105 (15)	0.0027 (14)	0.0007 (16)
C15	0.0469 (15)	0.0491 (16)	0.0507 (16)	0.0045 (13)	0.0090 (12)	0.0101 (13)
P1	0.0368 (4)	0.0389 (4)	0.0320 (3)	−0.0041 (3)	0.0022 (2)	0.0012 (2)

Geometric parameters (Å, º) top

F1—C6	1.336 (4)	C2—C3	1.383 (4)
F2—C6	1.324 (4)	C2—C8	1.403 (4)
F3—C6	1.307 (4)	C2—P1	1.836 (3)
F4—C13	1.305 (5)	C3—C4	1.392 (4)
F5—C13	1.328 (6)	C3—H31	0.930
F6—C13	1.290 (5)	C4—C5	1.387 (4)
H101—C10	0.930	C5—C6	1.492 (4)
H111—C11	0.930	C5—C7	1.380 (4)
H141—C14	0.930	C7—C8	1.385 (4)
H151—C15	0.930	C9—C10	1.394 (4)
H41—C4	0.930	C9—C15	1.386 (4)
H71—C7	0.930	C9—P1	1.836 (3)
H81—C8	0.930	C10—C11	1.386 (4)
C1—C1ⁱ	1.533 (5)	C11—C12	1.383 (5)
C1—P1	1.850 (3)	C12—C13	1.499 (5)
C1—H11	0.960	C12—C14	1.367 (5)
C1—H12	0.960	C14—C15	1.389 (4)

C1ⁱ—C1—P1	110.6 (2)	C7—C8—H81	119.9
C1ⁱ—C1—H11	109.3	C10—C9—C15	118.4 (3)
P1—C1—H11	109.2	C10—C9—P1	123.9 (2)
C1ⁱ—C1—H12	109.1	C15—C9—P1	117.7 (2)
P1—C1—H12	109.2	C9—C10—H101	119.3
H11—C1—H12	109.5	C9—C10—C11	120.5 (3)
C3—C2—C8	118.3 (2)	H101—C10—C11	120.2
C3—C2—P1	125.28 (19)	C10—C11—H111	120.6
C8—C2—P1	116.3 (2)	C10—C11—C12	120.0 (3)
C2—C3—C4	121.0 (2)	H111—C11—C12	119.4
C2—C3—H31	119.5	C11—C12—C13	119.3 (3)
C4—C3—H31	119.5	C11—C12—C14	120.3 (3)
C3—C4—H41	120.6	C13—C12—C14	120.4 (3)
C3—C4—C5	119.7 (3)	C12—C13—F5	112.9 (4)
H41—C4—C5	119.7	C12—C13—F4	113.4 (3)
C4—C5—C6	120.5 (3)	F5—C13—F4	103.3 (4)
C4—C5—C7	120.2 (2)	C12—C13—F6	113.0 (3)
C6—C5—C7	119.3 (3)	F5—C13—F6	106.4 (4)
C5—C6—F1	112.1 (3)	F4—C13—F6	107.0 (4)
C5—C6—F2	114.2 (3)	H141—C14—C12	119.8
F1—C6—F2	103.4 (3)	H141—C14—C15	120.4
C5—C6—F3	113.2 (3)	C12—C14—C15	119.8 (3)
F1—C6—F3	104.7 (3)	C14—C15—C9	121.0 (3)
F2—C6—F3	108.3 (3)	C14—C15—H151	119.9
C5—C7—H71	119.8	C9—C15—H151	119.1
C5—C7—C8	119.9 (3)	C1—P1—C2	102.20 (13)
H71—C7—C8	120.3	C1—P1—C9	99.93 (12)
C2—C8—C7	120.8 (3)	C2—P1—C9	100.83 (13)
C2—C8—H81	119.3

C2—P1—C1—C1ⁱ	174.53 (18)	C7—C5—C6—F2	160.7 (3)
C9—P1—C1—C1ⁱ	71.1 (2)	C4—C5—C6—F3	−146.1 (3)
C2—P1—C9—C10	−25.8 (3)	C7—C5—C6—F1	−82.2 (3)
C1—P1—C2—C3	11.2 (3)	C7—C5—C6—F3	36.0 (4)
C9—P1—C2—C3	113.9 (2)	C5—C7—C8—C2	1.4 (5)
C1—P1—C2—C8	−171.8 (2)	P1—C9—C10—C11	−178.7 (2)
C9—P1—C2—C8	−69.1 (2)	C15—C9—C10—C11	0.4 (4)
C1—P1—C9—C15	−100.4 (2)	P1—C9—C15—C14	177.9 (2)
C1—P1—C9—C10	78.8 (3)	C10—C9—C15—C14	−1.3 (4)
C2—P1—C9—C15	155.1 (2)	C9—C10—C11—C12	0.5 (5)
P1—C1—C1ⁱ—P1ⁱ	179.98 (16)	C10—C11—C12—C13	−179.7 (4)
P1—C2—C3—C4	176.8 (2)	C10—C11—C12—C14	−0.6 (5)
C3—C2—C8—C7	−1.1 (4)	C11—C12—C13—F4	−47.9 (5)
C8—C2—C3—C4	−0.1 (4)	C11—C12—C13—F5	−165.0 (4)
P1—C2—C8—C7	−178.4 (2)	C11—C12—C13—F6	74.1 (5)
C2—C3—C4—C5	1.1 (4)	C14—C12—C13—F4	133.0 (4)
C3—C4—C5—C7	−0.8 (4)	C14—C12—C13—F5	15.8 (6)
C3—C4—C5—C6	−178.7 (3)	C14—C12—C13—F6	−105.0 (5)
C4—C5—C6—F1	95.7 (4)	C11—C12—C14—C15	−0.3 (5)
C4—C5—C6—F2	−21.5 (4)	C13—C12—C14—C15	178.8 (3)
C4—C5—C7—C8	−0.4 (4)	C12—C14—C15—C9	1.3 (5)
C6—C5—C7—C8	177.5 (3)

Symmetry code: (i) −x+2, −y+2, −z.

Experimental details

Crystal data
Chemical formula	C₃₀H₂₀F₁₂P₂
M_r	670.41
Crystal system, space group	Monoclinic, P2₁/n
Temperature (K)	208
a, b, c (Å)	15.188 (11), 5.402 (4), 18.123 (13)
β (°)	99.044 (9)
V (Å³)	1468.3 (19)
Z	2
Radiation type	Mo Kα
µ (mm⁻¹)	0.25
Crystal size (mm)	0.40 × 0.10 × 0.10

Data collection
Diffractometer	Bruker SMART APEXII diffractometer
Absorption correction	Multi-scan (SADABS; Sheldrick, 2006)
T_min, T_max	0.91, 0.98
No. of measured, independent and observed [I > 2σ(I)] reflections	9947, 3240, 2616
R_int	0.044
(sin θ/λ)_max (Å⁻¹)	0.644

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.061, 0.162, 0.95
No. of reflections	3229
No. of parameters	208
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.73, −0.43

Computer programs: APEX2 (Bruker, 2006), SHELXS97 (Sheldrick, 2008), CRYSTALS (Betteridge et al., 2003), CAMERON (Watkin et al., 1996).

Comparison of structural parameters (Å, °) for R₂PCH₂CH₂PR₂ top

R	C-P-C	Σ C-P-C	P-C_ethyl	P-C_R
p-Ph-CF₃^a	100.79, 102.15,99.96	302.90	1.854	1.838
Ph^b	100.219,102.369,101.047	303.64	1.844	1.832
p-Ph-CH₃^c	98.668,101.864,102.985	303.52	1.849	1.821
p-Ph-CH₂CH₃^d	99.719,102.754,101.37	303.84	1.85	1.83
CH₃^e	98.869,99.665,98.872	297.3	1.848	1.836
CH₂CH₃^e	99.272,99.491,100.206	298.5	1.845	1.843
CH(CH₃)₂^e	101.184,100.805,102.235	304.2	1.86	1.86
C(CH₃)₃^f	100.990,103.197,110.350	314.5	1.86	1.89

Notes: (a) This work; (b) Tiekink (2001); (c) Zeller et al. (2003); (d) Zeller & Hunter (2004); (e) Bruckmann & Kruger (1997); (f) Eisentrager et al. (2003).

Acknowledgements

RST acknowledges the Small Molecule X-ray Crystallography Summer School hosted by Professor Arnold Rheingold at the University of California – San Diego and the University of Wisconsin – Stevens Point Letters and Science Foundation and Chemistry Department.

References

Allman, T. & Goel, R. G. (1982). Can. J. Chem. 60, 716–722. CrossRef CAS Web of Science Google Scholar
Betteridge, P. W., Carruthers, J. R., Cooper, R. I., Prout, K. & Watkin, D. J. (2003). J. Appl. Cryst. 36, 1487. Web of Science CrossRef IUCr Journals Google Scholar
Bruckmann, J. & Kruger, C. (1997). J. Organomet. Chem. 536–537, 465–472. CSD CrossRef Web of Science Google Scholar
Bruker (2006). APEX2. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Chatt, J., Hussain, W., Leigh, G. J., Modh Ali, H., Pickett, C. J. & Rankin, D. A. (1985). J. Chem. Soc. Dalton Trans. pp. 1131–1136. CrossRef Web of Science Google Scholar
Eisentrager, F., Gothlich, A., Gruber, I., Heiss, H., Kiener, C. A., Kruger, C., Ulrich Notheis, J., Rominger, F., Scherhag, G., Schultz, M., Straub, B. F., Volland, M. A. O. & Hofmann, P. (2003). New J. Chem. 27, 540–550. Web of Science CSD CrossRef Google Scholar
Larson, A. C. (1970). Crystallographic Computing, edited by F. R. Ahmed, S. R. Hall & C. P. Huber, pp. 291–294. Copenhagen: Munksgaard. Google Scholar
Nordwig, B. L., Ohlsen, D. J., Beyer, K. D., Wruck, A. S. & Brummer, J. G. (2006). Inorg. Chem. 45, 858–867. Web of Science CrossRef PubMed CAS Google Scholar
Sheldrick, G. M. (2006). SADABS. University of Göttingen, Germany. Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Streuli, C. A. (1960). Anal. Chem. 32, 985–987. CrossRef CAS Web of Science Google Scholar
Tiekink, E. R. T. (2001). Z. Kristallogr. 216, 69–70. CrossRef CAS Google Scholar
Tolman, C. A. (1970). J. Am. Chem. Soc. 92, 2953–2956. CrossRef CAS Web of Science Google Scholar
Watkin, D. J., Prout, C. K. & Pearce, L. J. (1996). CAMERON. Chemical Crystallography Laboratory, Oxford, UK. Google Scholar
Zeller, M. & Hunter, A. D. (2004). Private communication (refcode FOGGAK). CCDC, Union Road, Cambridge, England. Google Scholar
Zeller, M., Lazich, E., Wagner, T. R. & Hunter, A. D. (2003). Acta Cryst. E59, o1721–o1722. Web of Science CSD CrossRef IUCr Journals Google Scholar