1,4-Bis(4-bromo-2,6-diisopropyl­phen­yl)-1,4-diaza­buta-1,3-diene

Guzei, I.A.; Hill, N.J.; Van Hout, M.R.

doi:10.1107/S1600536809050843

organic compounds

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ISSN: 2056-9890

Volume 66| Part 1| January 2010| Pages o40-o41

doi:10.1107/S1600536809050843

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1,4-Bis(4-bromo-2,6-diisopropylphenyl)-1,4-diazabuta-1,3-diene

Ilia A. Guzei,^a ^* Nicholas J. Hill ^a and Matthew R. Van Hout ^a

^aDepartment of Chemistry, University of Wisconsin-Madison, 1101 University Ave, Madison, WI 53706, USA
^*Correspondence e-mail: iguzei@chem.wisc.edu

(Received 11 November 2009; accepted 25 November 2009; online 4 December 2009)

The molecule of the title compound, C₂₆H₃₄Br₂N₂, lies on a crystallographic inversion center and hence the two imine groups are s-trans. The dihedral angle between the central 1,4-diazabuta-1,3-diene unit and the attached substituted phenyl ring is 88.4 (7)°. The structure features a C—H⋯N close contact. The crystal selected for this study proved to be a non-merohedral twin with a minor component of 21.8 (3)%.

Related literature

1,4-diaza-1,3-butadiene (DAB) ligands containing sterically demanding N-substituents have proved to be versatile platforms for stabilizing s- and p-block atoms in unusual oxidation states or coordination geometries, see: Baker et al. (2008 ); Hill et al. (2009 ); Liu et al. (2009 ); Martin et al. (2009 ); Segawa et al. (2008 ). The title compound was prepared as part of our continuing studies on the chemistry of N-heterocyclic silylenes and germylenes, see: Hill et al. (2005 ); Naka et al. (2004 ); Tomasik et al. (2009 ). For the use of DAB ligands in olefin polymerization catalysis, see: Ittel et al. (2000 ); Jung et al. (2007 ). For related structures, see: (2003); Müller et al. (2003 ); Schaub et al. (2006 ); Berger et al. (2001 ); Laine et al. (1999 ). For the preparation of 4-bromo-2,6-di-iso-propyl aniline, see: Liu et al. (2005 ). For a description of the Cambridge Structural Database, see: Allen (2002 ).

Experimental

Crystal data

C₂₆H₃₄Br₂N₂
M_r = 534.37
Monoclinic, P 2₁ /c
a = 8.961 (3) Å
b = 17.848 (7) Å
c = 8.620 (3) Å
β = 104.260 (11)°
V = 1336.2 (8) Å³
Z = 2
Mo Kα radiation
μ = 3.05 mm⁻¹
T = 300 K
0.43 × 0.35 × 0.29 mm

Data collection

Bruker SMART X2S diffractometer
Absorption correction: multi-scan (TWINABS; Bruker, 2007 ) T_min = 0.103, T_max = 0.428
2286 measured reflections
2286 independent reflections
1585 reflections with I > 2σ(I)
R_int = 0.110

Refinement

R[F² > 2σ(F²)] = 0.069
wR(F²) = 0.199
S = 1.04
2286 reflections
142 parameters
H-atom parameters constrained
Δρ_max = 0.53 e Å⁻³
Δρ_min = −0.60 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C8—H8⋯N1	0.98	2.40	2.880 (9)	109

Data collection: GIS (Bruker, 2009 ); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ); program(s) used to refine structure: SHELXTL and OLEX2 (Dolomanov et al., 2009 ); molecular graphics: SHELXTL and OLEX2; software used to prepare material for publication: SHELXTL, OLEX2 (Dolomanov et al., 2009), publCIF (Westrip, 2009 ) and modiCIFer (Guzei, 2007 ).

Supporting information

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536809050843/bx2248sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536809050843/bx2248Isup2.hkl

checkCIF report

Comment top

1,4-diaza-1,3-butadiene (DAB) ligands bearing bulky aryl or alkyl groups on the nitrogen atoms have proven to be versatile platforms for stabilizing s- and p-block atoms in unusual oxidation states or coordination geometries (Baker et al. (2008); Hill et al. (2009); Liu et al. (2009); Martin et al. (2009); Segawa et al. (2008)). The title compound, (I), was prepared as part of our continuing studies upon the chemistry of N-heterocyclic silylenes and germylenes (Hill et al. (2005); Naka et al. (2004); Tomasik et al. (2009)), the silicon(II) and germanium(II) analogues of the well known Arduengo N-heterocyclic carbenes. DAB ligands are ideal in this regard since their stereo-electronic properties are easily tuned by alteration of the N– and C-substituents.

DAB ligands have also been used extensively in d-block coordination chemistry, particularly within the field of olefin polymerization catalysis (Ittel et al. 2000). Jung et al. (2007) recently used the title compound as a precursor to an N-heterocyclic carbene in the synthesis of a catalytically active cationic (η³-allyl)(NHC)palladium complex.

The molecule of (I) resides on a crystallographic inversion center and hence the two imine groups are s-trans. The dihedral angle between the central 1,4-diazabuta-1,3-diene moiety and the attached substituted phenyl ring is 88.4 (7)°. The molecular symmetry approaches C_2h, however, the positions of the isopropyl groups break the mirror plane symmetry: both H atoms on the tertiary C atoms of the two symmetry-independent ⁱPr groups point toward atom N1, but reside on the opposite sides of the phenyl ring. This is illustrated with two disparate but "would be equivalent" torsion angles, one for each ⁱPr group: C2—C3—C8—C9 (-96.5 (8)°) and C2—C7—C11—C13 (163.6 (7)°). This geometry differs from that of the unbrominated congener of (I), 1,4-bis(2,6-diisopropyl-phenyl)-1,4-diazabuta-1,3-diene, (II). For related structures, see: Müller et al. (2003), Schaub et al. (2006). Compound (II), structurally characterized at 173 K by Berger et al. (2001) and at 193 K by Laine et al.(1999), crystallizes with the molecule of (II) on an inversion center. The H atoms of the tertiary C atom of the isopropyl groups point toward the N atom and, in contrast to (I), are located on the same side of the phenyl ring. The overall symmetry of (II) is much closer to C_2h as the ⁱPr groups are oriented very similarly: in the 193 K structure of (II) two "would be equivalent" Me—C(H)—C—C(N) torsion angles measured 144.6 and 145.4°. The C—Br distance of 1.897 (6) Å is in excellent agreement with the value of 1.899 (11) Å obtained by averaging 2303 C—Br bond lengths from 1736 relevant compounds reported to the Cambridge Structural Database (Allen, 2002).

Related literature top

1,4-diaza-1,3-butadiene (DAB) ligands containing sterically demanding N-substituents have proved to be versatile platforms for stabilizing s- and p-block fragments in unusual oxidation states or coordination geometries, see: Baker et al. (2008); Hill et al. (2009); Liu et al. (2009); Martin et al. (2009); Segawa et al. (2008). The title compound was prepared as part of our continuing studies on the chemistry of N-heterocyclic silylenes and germylenes, see: Hill et al. (2005); Naka et al. (2004); Tomasik et al. (2009). For the use of DAB ligands in olefin polymerization catalysis, see: Ittel et al. (2000); Jung et al. (2007). For related structures, see: (2003); Müller et al. (2003); Schaub et al. (2006);Berger et al. (2001); Laine et al. (1999). For the preparation of 4-bromo-2,6-di-iso-propyl aniline, see: Liu et al. (2005). For a description of the Cambridge Structural Database, see: Allen (2002).

Experimental top

4-Bromo-2,6-di-iso-propyl aniline was prepared according to the literature procedure (Liu et al. 2005). To a stirred solution of 4-bromo-2,6-di-iso-propyl aniline (3.0 g,11.71 mmol) in methanol (40 cm³) containing 4 drops of formic acid was added glyoxal (0.85 g, 5.80 mmol, 40% aqueous soln.) slowly dropwise. The reaction mixture was stirred for 24 h at room temperature, filtered, and the precipitate washed with cold MeOH (2 x 10 mL). This yellow solid was dried in vacuo and recrystallized from EtOH to give a crop of pale yellow needles suitable for X-ray diffraction analysis. Yield 3.53 g, 56%.

¹H-NMR (CD₂Cl₂, 300 MHz): δ 1.19 (d, ³J = 6.9 Hz, 24H, CH₃), 2.91 (sept, ³J = 6.8 Hz, 4H, CH), 7.31 (s, 4H, aromatic), 8.07 (s, 2H, CH); ¹³C{¹H}-NMR (CD₂Cl₂, 75 MHz): δ 22.80, 28.43, 119.42, 126.79, 139.29, 147.52, 163.97.

Computing details top

Data collection: GIS (Bruker, 2009); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT (Bruker, 2007); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008) and OLEX2 (Dolomanov et al., 2009); molecular graphics: SHELXTL (Sheldrick, 2008) and OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: SHELXTL (Sheldrick, 2008) and OLEX2 (Dolomanov et al., 2009) publCIF (Westrip, 2009) and modiCIFer (Guzei, 2007).

Figures top

Fig. 1. Molecular structure of (I). The thermal ellipsoids are shown at 30% probability level. Atoms labeled with the suffixes A and unlabeled are generated by the symmetry operation (-x+1, -y+1, -z+1).

1,4-Bis(4-bromo-2,6-diisopropylphenyl)-1,4-diazabuta-1,3-diene top

Crystal data top

C₂₆H₃₄Br₂N₂	F(000) = 548
M_r = 534.37	D_x = 1.328 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 999 reflections
a = 8.961 (3) Å	θ = 2.3–24.8°
b = 17.848 (7) Å	µ = 3.05 mm⁻¹
c = 8.620 (3) Å	T = 300 K
β = 104.260 (11)°	Block, yellow
V = 1336.2 (8) Å³	0.43 × 0.35 × 0.29 mm
Z = 2

Data collection top

Bruker SMART X2S diffractometer	2286 independent reflections
Radiation source: micro-focus sealed tube	1585 reflections with I > 2σ(I)
Doubly curved silicon crystal monochromator	R_int = 0.110
ω scans	θ_max = 24.8°, θ_min = 2.3°
Absorption correction: multi-scan (TWINABS; Bruker, 2007)	h = 0→10
T_min = 0.103, T_max = 0.428	k = −21→0
2286 measured reflections	l = −10→9

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)] = 0.069	H-atom parameters constrained
wR(F²) = 0.199	w = 1/[σ²(F_o²) + (0.0949P)² + 1.843P] where P = (F_o² + 2F_c²)/3
S = 1.04	(Δ/σ)_max = 0.001
2286 reflections	Δρ_max = 0.53 e Å⁻³
142 parameters	Δρ_min = −0.60 e Å⁻³
0 restraints	Extinction correction: SHELXTL (Sheldrick, 2008), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.038 (5)

Crystal data top

C₂₆H₃₄Br₂N₂	V = 1336.2 (8) Å³
M_r = 534.37	Z = 2
Monoclinic, P2₁/c	Mo Kα radiation
a = 8.961 (3) Å	µ = 3.05 mm⁻¹
b = 17.848 (7) Å	T = 300 K
c = 8.620 (3) Å	0.43 × 0.35 × 0.29 mm
β = 104.260 (11)°

Data collection top

Bruker SMART X2S diffractometer	2286 independent reflections
Absorption correction: multi-scan (TWINABS; Bruker, 2007)	1585 reflections with I > 2σ(I)
T_min = 0.103, T_max = 0.428	R_int = 0.110
2286 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.069	0 restraints
wR(F²) = 0.199	H-atom parameters constrained
S = 1.04	Δρ_max = 0.53 e Å⁻³
2286 reflections	Δρ_min = −0.60 e Å⁻³
142 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
Br1	1.14981 (9)	0.69711 (6)	0.27272 (12)	0.0957 (6)
N1	0.6097 (6)	0.5812 (3)	0.5079 (7)	0.0523 (14)
C1	0.5657 (8)	0.5148 (3)	0.4744 (8)	0.0513 (17)
H1	0.6173	0.4847	0.4166	0.062*
C2	0.7381 (6)	0.6090 (3)	0.4544 (7)	0.0395 (14)
C3	0.7094 (7)	0.6469 (3)	0.3074 (7)	0.0409 (14)
C4	0.8336 (7)	0.6738 (3)	0.2564 (7)	0.0456 (15)
H4	0.8179	0.6992	0.1595	0.055*
C5	0.9804 (7)	0.6630 (4)	0.3489 (8)	0.0500 (16)
C6	1.0083 (7)	0.6289 (4)	0.4968 (8)	0.0529 (16)
H6	1.1086	0.6245	0.5591	0.063*
C7	0.8860 (8)	0.6012 (3)	0.5528 (8)	0.0485 (16)
C8	0.5477 (7)	0.6575 (4)	0.2044 (9)	0.0536 (16)
H8	0.4780	0.6500	0.2746	0.064*
C9	0.5079 (12)	0.5984 (6)	0.0770 (14)	0.119 (4)
H9C	0.5672	0.6062	−0.0004	0.179*
H9B	0.4002	0.6013	0.0251	0.179*
H9A	0.5309	0.5498	0.1247	0.179*
C10	0.5185 (9)	0.7356 (5)	0.1375 (14)	0.088 (3)
H10C	0.5496	0.7714	0.2224	0.132*
H10A	0.4108	0.7416	0.0883	0.132*
H10B	0.5766	0.7436	0.0590	0.132*
C11	0.9157 (9)	0.5652 (4)	0.7203 (8)	0.0626 (18)
H11	0.8533	0.5195	0.7090	0.075*
C12	0.8601 (13)	0.6152 (5)	0.8316 (10)	0.101 (3)
H12B	0.8573	0.5880	0.9269	0.151*
H12A	0.7586	0.6327	0.7808	0.151*
H12C	0.9285	0.6572	0.8591	0.151*
C13	1.0834 (11)	0.5415 (5)	0.7895 (10)	0.087 (3)
H13A	1.1158	0.5093	0.7148	0.131*
H13B	1.0915	0.5152	0.8884	0.131*
H13C	1.1478	0.5852	0.8086	0.131*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Br1	0.0555 (5)	0.1428 (10)	0.0961 (8)	−0.0228 (5)	0.0324 (5)	0.0295 (6)
N1	0.067 (3)	0.034 (3)	0.065 (4)	−0.011 (2)	0.036 (3)	−0.001 (2)
C1	0.068 (4)	0.035 (3)	0.063 (4)	−0.014 (3)	0.040 (4)	−0.007 (3)
C2	0.053 (3)	0.027 (3)	0.046 (4)	−0.006 (2)	0.026 (3)	−0.004 (3)
C3	0.046 (3)	0.033 (3)	0.046 (4)	−0.005 (3)	0.015 (3)	−0.003 (3)
C4	0.053 (4)	0.046 (3)	0.039 (3)	−0.006 (3)	0.014 (3)	0.002 (3)
C5	0.046 (4)	0.059 (4)	0.050 (4)	−0.011 (3)	0.021 (3)	0.000 (3)
C6	0.052 (3)	0.057 (4)	0.050 (4)	−0.006 (3)	0.014 (3)	0.006 (3)
C7	0.064 (4)	0.042 (3)	0.043 (4)	−0.006 (3)	0.020 (3)	0.002 (3)
C8	0.046 (3)	0.052 (4)	0.063 (4)	−0.005 (3)	0.014 (3)	0.007 (3)
C9	0.093 (7)	0.119 (8)	0.117 (9)	−0.024 (6)	−0.030 (6)	−0.045 (7)
C10	0.063 (5)	0.080 (5)	0.115 (8)	0.008 (4)	0.013 (6)	0.039 (6)
C11	0.083 (5)	0.059 (4)	0.052 (4)	−0.003 (4)	0.027 (4)	0.014 (4)
C12	0.161 (10)	0.094 (6)	0.063 (6)	0.043 (6)	0.058 (6)	0.026 (5)
C13	0.109 (7)	0.081 (6)	0.072 (6)	0.025 (5)	0.025 (5)	0.019 (5)

Geometric parameters (Å, º) top

Br1—C5	1.897 (6)	C8—H8	0.9800
N1—C1	1.260 (7)	C9—H9C	0.9600
N1—C2	1.429 (7)	C9—H9B	0.9600
C1—C1ⁱ	1.455 (11)	C9—H9A	0.9600
C1—H1	0.9300	C10—H10C	0.9600
C2—C7	1.393 (9)	C10—H10A	0.9600
C2—C3	1.403 (8)	C10—H10B	0.9600
C3—C4	1.380 (8)	C11—C12	1.483 (11)
C3—C8	1.513 (9)	C11—C13	1.533 (12)
C4—C5	1.374 (9)	C11—H11	0.9800
C4—H4	0.9300	C12—H12B	0.9600
C5—C6	1.379 (9)	C12—H12A	0.9600
C6—C7	1.393 (9)	C12—H12C	0.9600
C6—H6	0.9300	C13—H13A	0.9600
C7—C11	1.542 (9)	C13—H13B	0.9600
C8—C9	1.501 (12)	C13—H13C	0.9600
C8—C10	1.507 (10)

C1—N1—C2	118.9 (5)	C8—C9—H9B	109.5
N1—C1—C1ⁱ	120.3 (7)	H9C—C9—H9B	109.5
N1—C1—H1	119.9	C8—C9—H9A	109.5
C1ⁱ—C1—H1	119.9	H9C—C9—H9A	109.5
C7—C2—C3	122.3 (5)	H9B—C9—H9A	109.5
C7—C2—N1	119.3 (5)	C8—C10—H10C	109.5
C3—C2—N1	118.4 (5)	C8—C10—H10A	109.5
C4—C3—C2	118.2 (5)	H10C—C10—H10A	109.5
C4—C3—C8	120.0 (5)	C8—C10—H10B	109.5
C2—C3—C8	121.8 (5)	H10C—C10—H10B	109.5
C5—C4—C3	119.9 (6)	H10A—C10—H10B	109.5
C5—C4—H4	120.1	C12—C11—C13	111.5 (8)
C3—C4—H4	120.1	C12—C11—C7	110.3 (6)
C4—C5—C6	121.9 (6)	C13—C11—C7	114.0 (6)
C4—C5—Br1	119.2 (5)	C12—C11—H11	106.9
C6—C5—Br1	118.9 (5)	C13—C11—H11	106.9
C5—C6—C7	119.9 (6)	C7—C11—H11	106.9
C5—C6—H6	120.1	C11—C12—H12B	109.5
C7—C6—H6	120.1	C11—C12—H12A	109.5
C6—C7—C2	117.7 (6)	H12B—C12—H12A	109.5
C6—C7—C11	120.2 (6)	C11—C12—H12C	109.5
C2—C7—C11	122.1 (6)	H12B—C12—H12C	109.5
C9—C8—C10	112.5 (8)	H12A—C12—H12C	109.5
C9—C8—C3	111.2 (6)	C11—C13—H13A	109.5
C10—C8—C3	113.0 (5)	C11—C13—H13B	109.5
C9—C8—H8	106.5	H13A—C13—H13B	109.5
C10—C8—H8	106.5	C11—C13—H13C	109.5
C3—C8—H8	106.5	H13A—C13—H13C	109.5
C8—C9—H9C	109.5	H13B—C13—H13C	109.5

C2—N1—C1—C1ⁱ	−179.3 (8)	C5—C6—C7—C11	−178.1 (6)
C1—N1—C2—C7	−90.5 (7)	C3—C2—C7—C6	−3.5 (9)
C1—N1—C2—C3	92.9 (7)	N1—C2—C7—C6	−179.9 (6)
C7—C2—C3—C4	3.3 (8)	C3—C2—C7—C11	174.9 (5)
N1—C2—C3—C4	179.8 (5)	N1—C2—C7—C11	−1.6 (8)
C7—C2—C3—C8	−177.7 (5)	C4—C3—C8—C9	82.5 (8)
N1—C2—C3—C8	−1.2 (8)	C2—C3—C8—C9	−96.4 (8)
C2—C3—C4—C5	0.1 (9)	C4—C3—C8—C10	−45.1 (9)
C8—C3—C4—C5	−178.9 (6)	C2—C3—C8—C10	135.9 (7)
C3—C4—C5—C6	−3.3 (10)	C6—C7—C11—C12	108.2 (9)
C3—C4—C5—Br1	177.6 (5)	C2—C7—C11—C12	−70.1 (9)
C4—C5—C6—C7	3.1 (10)	C6—C7—C11—C13	−18.1 (10)
Br1—C5—C6—C7	−177.8 (5)	C2—C7—C11—C13	163.6 (7)
C5—C6—C7—C2	0.3 (9)

Symmetry code: (i) −x+1, −y+1, −z+1.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C8—H8···N1	0.98	2.40	2.880 (9)	109

Experimental details

Crystal data
Chemical formula	C₂₆H₃₄Br₂N₂
M_r	534.37
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	300
a, b, c (Å)	8.961 (3), 17.848 (7), 8.620 (3)
β (°)	104.260 (11)
V (Å³)	1336.2 (8)
Z	2
Radiation type	Mo Kα
µ (mm⁻¹)	3.05
Crystal size (mm)	0.43 × 0.35 × 0.29

Data collection
Diffractometer	Bruker SMART X2S diffractometer
Absorption correction	Multi-scan (TWINABS; Bruker, 2007)
T_min, T_max	0.103, 0.428
No. of measured, independent and observed [I > 2σ(I)] reflections	2286, 2286, 1585
R_int	0.110
(sin θ/λ)_max (Å⁻¹)	0.590

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.069, 0.199, 1.04
No. of reflections	2286
No. of parameters	142
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.53, −0.60

Computer programs: GIS (Bruker, 2009), SAINT (Bruker, 2007), SHELXTL (Sheldrick, 2008) and OLEX2 (Dolomanov et al., 2009), SHELXTL (Sheldrick, 2008) and OLEX2 (Dolomanov et al., 2009) publCIF (Westrip, 2009) and modiCIFer (Guzei, 2007).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C8—H8···N1	0.98	2.40	2.880 (9)	109

Acknowledgements

We gratefully acknowledge Bruker AXS sponsorship of this publication.

References

Allen, F. H. (2002). Acta Cryst. B58, 380–388. Web of Science CrossRef CAS IUCr Journals Google Scholar
Baker, R. J., Jones, C., Mills, D. P., Pierce, G. A. & Waugh, M. (2008). Inorg. Chim. Acta, 361, 427–435. Web of Science CSD CrossRef CAS Google Scholar
Berger, S., Baumann, F., Scheiring, T. & Kaim, W. (2001). Z. Anorg. Allg. Chem. 627, 620–630. CrossRef CAS Google Scholar
Bruker (2007). TWINABS and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Bruker (2009). GIS. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Dolomanov, O. V., Bourhis, L. J., Gildea, R. J., Howard, J. A. K. & Puschmann, H. (2009). J. Appl. Cryst. 42, 339–341. Web of Science CrossRef CAS IUCr Journals Google Scholar
Guzei, I. A. (2007). modiCIFer. Molecular Structure Laboratory, University of Wisconsin-Madison, Madison, Wisconsin, USA. Google Scholar
Hill, N. J., Moser, D. F., Guzei, I. A. & West, R. (2005). Organometallics, 24, 3346–3349. Web of Science CSD CrossRef CAS Google Scholar
Hill, N. J., Vargas-Baca, I. & Cowley, A. H. (2009). Dalton Trans. pp. 240–253. Web of Science CrossRef Google Scholar
Ittel, S. D., Johnson, L. K. & Brookhart, M. (2000). Chem. Rev. 100, 1169–1203. Web of Science CrossRef PubMed CAS Google Scholar
Jung, I. G., Seo, J., Chung, Y. K., Shin, D. M., Chun, S.-H. & Son, S. U. (2007). J. Polym. Sci. Part A Polym. Chem. 45, 3042–3052. Web of Science CrossRef CAS Google Scholar
Laine, T. V., Klinga, M., Maaninen, A., Aitola, E. & Leskela, M. (1999). Acta Chem. Scand.. 53, 968–973. Web of Science CrossRef CAS Google Scholar
Liu, H.-R., Gomes, P. T., Costa, S. I., Duarte, M. T., Branquinho, R., Fernades, A. C., Chein, J. W., Singh, R. P. & Marques, M. M. (2005). J. Organomet. Chem. 690, 1314–1322. Web of Science CSD CrossRef CAS Google Scholar
Liu, Y., Li, S., Yang, X.-J., Yang, P. & Wu, B. (2009). J. Am. Chem. Soc. 131, 4210–4211. Web of Science CSD CrossRef PubMed CAS Google Scholar
Martin, C. D., Jennings, M. C., Ferguson, M. J. & Ragogna, P. J. (2009). Angew. Chem. Int. Ed. 48, 2210–2213. Web of Science CSD CrossRef CAS Google Scholar
Müller, T., Schrecke, B. & Bolte, M. (2003). Acta Cryst. E59, o1820–o1821. Web of Science CSD CrossRef IUCr Journals Google Scholar
Naka, A., Hill, N. J. & West, R. (2004). Organometallics, 23, 6330–6332. Web of Science CSD CrossRef CAS Google Scholar
Schaub, T. & Radius, U. (2006). Z. Anorg. Allg. Chem. 632, 807–813. Web of Science CSD CrossRef CAS Google Scholar
Segawa, Y., Suzuki, Y., Yamashita, M. & Nozaki, K. (2008). J. Am. Chem. Soc. 130, 16069–16079. Web of Science CSD CrossRef PubMed CAS Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Tomasik, A. C., Hill, N. J. & West, R. (2009). J. Organomet. Chem. 694, 2122–2125. Web of Science CrossRef CAS Google Scholar
Westrip, S. P. (2009). publCIF. In preparation. Google Scholar