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In the title compound, di­bromo­bis­(tetra­hydro­furan-O)chromium(II), [CrBr2(C4H8O)2], CrBr2 is solvated by two tetra­hydro­furan (thf) mol­ecules, with a Cr—O distance of 2.072 (3) Å and a Cr—Br distance of 2.5825 (5) Å. The Cr atom lies on the center of inversion. The Cr atom is octahedrally coordinated, with the thf Cr—O bond orthogonal to the Cr—Br bond, and the vacant sites are occupied with a Cr...Br intermolecular interaction of 2.9874 (5) Å. The latter interaction is almost orthogonal to the Cr—O vector. This extends the system into a linear chain along the [100] direction.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536801001660/na6034sup1.cif
Contains datablocks global, bt172

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S1600536801001660/na6034Isup2.hkl
Contains datablock I

CCDC reference: 159712

Key indicators

  • Single-crystal X-ray study
  • T = 203 K
  • Mean [sigma](C-C) = 0.005 Å
  • R factor = 0.027
  • wR factor = 0.071
  • Data-to-parameter ratio = 15.8

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry
Yellow Alert Alert Level C:
ABSTM_02 Alert C The ratio of expected to reported Tmax/Tmin(RR) is > 1.10 Tmin and Tmax reported: 0.184 0.293 Tmin and Tmax expected: 0.154 0.293 RR = 1.195 Please check that your absorption correction is appropriate.
0 Alert Level A = Potentially serious problem
0 Alert Level B = Potential problem
1 Alert Level C = Please check

Comment top

(THF)2CrBr2, (I), bears a close resemblance to the parent compound CrBr2 (Tracy et al., 1962). Both show slightly distorted octahedral coordination and both have similar in-plane Cr—Br bond distances, 2.5825 (5) Å in (I) and 2.545 (1) Å in CrBr2. The solvent molecule, THF in this case, occupies an in-plane coordination site with a Cr—O distance of 2.072 (3) Å. The solvent molecule is coordinated orthogonally to the Cr—Br vector with an angle of 90.009 (8)°. The THF molecule is in a half-chair conformation with a total puckering amplitude of QT = 0.363 Å (Cremer & Pople, 1975). The orientation of the THF molecule is influenced by the intramolecular interactions C4—H4a···Br1 and C1—H1a···Br1i (see Table 1) which tilt the ring towards each Br atom. The out-of-plane coordination site is occupied with an intermolecular Cr1···Br1ii interaction of 2.9874 (5) Å [symmetry code: (ii) 1 + x, y, z]. The corresponding interaction in CrBr2 has a Cr···Br distance of 2.998 (1) Å. The distortion from ideal octahedral geometry is also reflected in the Br1—Cr1—Br1ii angle of 94.65 (2)°. With the THF molecules occupying the other coordination sites, (I) can only form a staggered chain instead of the planar sheets found in CrBr2. In this case, the direction of propagation is along [100] (Fig. 1). Other solvent coordinated CrIIBr2 species that are octahedrally coordinated show a wide range of Cr—Br distances. The complex CrBr2(CH3CN)2 (Halepoto et al., 1990), which also forms linear chains, has an in-plane Cr—Br distance of 2.545 Å and an out-of-plane distance of 2.976 (1) Å. However, the molecular species trans-CrBr2(pyridine)4 (Holah et al., 1998) has a Cr—Br bond distance of 2.998 (1) Å which indicates a very weakly associated Br atom.

Experimental top

(THF)2CrBr2 was synthesized as a side product during the attempted synthesis of a chromocene bromide. Tetramethylethylenediyl(η5-biscyclopentadienyl)chromoceneII carbonyl (331 mg, 1.1 mmol) was reacted with 1-bromo-2-methylpropane (155 mg, 1.1 mmol) in THF for 20 h at 378 K, with no color change. Dibromomethane (excess) was then added to increase the bromide concentration. Excess solvent and reagents were removed under reduced pressure and the green residue redissolved in THF (20 ml) and filtered. The resulting solution was concentrated to promote crystallization and cooled in a 278 K refrigerator overnight. The supernatant was decanted yielding a green crystalline product. The supernatant was concentrated under reduced pressure to yield a fine pale green powder. Combined yield 68 mg, 19.1%, m.p. > 573 K.

Computing details top

Data collection: SMART (Bruker, 1997); cell refinement: SMART; data reduction: SAINT-Plus (Bruker, 1999); program(s) used to solve structure: SHELXTL (Sheldrick, 1998); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Figures top
[Figure 1] Fig. 1. Packing diagram of (I) showing the staggered propagation along the [100] direction. H atoms have been omitted for clarity.
dibromobis(tetrahydrofuran-O)chromium(II) top
Crystal data top
[CrBr2(C4H8O)2]Z = 1
Mr = 356.03F(000) = 174
Triclinic, P1Dx = 2.126 Mg m3
a = 4.1043 (7) ÅMo Kα radiation, λ = 0.71073 Å
b = 7.4530 (13) ÅCell parameters from 839 reflections
c = 9.2875 (16) Åθ = 2.2–27.4°
α = 87.777 (3)°µ = 8.18 mm1
β = 78.619 (3)°T = 203 K
γ = 87.281 (3)°Plate, pale yellow
V = 278.07 (8) Å30.25 × 0.20 × 0.15 mm
Data collection top
Siemens SMART 1000
diffractometer
962 independent reflections
Radiation source: normal-focus sealed tube897 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.029
Detector resolution: 8.3 pixels mm-1θmax = 25.0°, θmin = 2.2°
ω scansh = 44
Absorption correction: empirical (using intensity measurements)
(SADABS; Sheldrick, 1999)
k = 88
Tmin = 0.184, Tmax = 0.293l = 1111
2917 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)] = 0.027Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.071H-atom parameters constrained
S = 1.08 w = 1/[σ2(Fo2) + (0.0436P)2 + 0.1523P]
where P = (Fo2 + 2Fc2)/3
962 reflections(Δ/σ)max = 0.001
61 parametersΔρmax = 0.58 e Å3
0 restraintsΔρmin = 0.70 e Å3
Crystal data top
[CrBr2(C4H8O)2]γ = 87.281 (3)°
Mr = 356.03V = 278.07 (8) Å3
Triclinic, P1Z = 1
a = 4.1043 (7) ÅMo Kα radiation
b = 7.4530 (13) ŵ = 8.18 mm1
c = 9.2875 (16) ÅT = 203 K
α = 87.777 (3)°0.25 × 0.20 × 0.15 mm
β = 78.619 (3)°
Data collection top
Siemens SMART 1000
diffractometer
962 independent reflections
Absorption correction: empirical (using intensity measurements)
(SADABS; Sheldrick, 1999)
897 reflections with I > 2σ(I)
Tmin = 0.184, Tmax = 0.293Rint = 0.029
2917 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0270 restraints
wR(F2) = 0.071H-atom parameters constrained
S = 1.08Δρmax = 0.58 e Å3
962 reflectionsΔρmin = 0.70 e Å3
61 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
xyzUiso*/Ueq
Br10.10559 (9)0.70378 (5)0.37413 (4)0.02022 (17)
Cr10.50000.50000.50000.0180 (2)
O10.4032 (7)0.6622 (3)0.6810 (3)0.0245 (6)
C10.2743 (10)0.5980 (5)0.8298 (4)0.0242 (9)
H1A0.39740.48860.85360.029*
H1B0.03820.57240.84250.029*
C30.2812 (11)0.9167 (5)0.8283 (4)0.0244 (9)
H3A0.04540.95070.83420.029*
H3B0.39481.01900.85580.029*
C20.3237 (10)0.7515 (5)0.9266 (4)0.0240 (9)
H2A0.54590.74330.95080.029*
H2B0.15580.75281.01770.029*
C40.4399 (10)0.8560 (5)0.6761 (4)0.0232 (9)
H4A0.32660.91440.60220.028*
H4B0.67530.88480.65240.028*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Br10.0210 (2)0.0198 (2)0.0199 (3)0.00074 (15)0.00461 (16)0.00071 (15)
Cr10.0230 (5)0.0167 (4)0.0144 (5)0.0034 (3)0.0046 (4)0.0026 (3)
O10.0390 (16)0.0173 (13)0.0152 (14)0.0007 (12)0.0004 (12)0.0019 (11)
C10.029 (2)0.022 (2)0.018 (2)0.0006 (16)0.0015 (17)0.0007 (16)
C30.027 (2)0.024 (2)0.021 (2)0.0004 (16)0.0020 (17)0.0058 (16)
C20.028 (2)0.027 (2)0.017 (2)0.0021 (17)0.0026 (17)0.0052 (17)
C40.032 (2)0.0162 (19)0.021 (2)0.0041 (16)0.0036 (17)0.0010 (15)
Geometric parameters (Å, º) top
Br1—Cr12.5825 (5)O1—C41.458 (4)
Cr1—O1i2.072 (3)C1—C21.527 (6)
Cr1—O12.072 (3)C3—C41.512 (5)
Cr1—Br1i2.5825 (5)C3—C21.528 (6)
O1—C11.450 (5)
O1i—Cr1—O1180.00 (9)C1—O1—Cr1124.1 (2)
O1i—Cr1—Br1i90.09 (8)C4—O1—Cr1125.1 (2)
O1—Cr1—Br1i89.91 (8)O1—C1—C2104.7 (3)
O1i—Cr1—Br189.91 (8)C4—C3—C2103.6 (3)
O1—Cr1—Br190.09 (8)C1—C2—C3102.1 (3)
Br1i—Cr1—Br1180.0O1—C4—C3105.2 (3)
C1—O1—C4110.7 (3)
Symmetry code: (i) x+1, y+1, z+1.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C4—H4A···Br10.982.993.599 (4)122
C1—H1A···Br1i0.982.993.607 (4)122
Symmetry code: (i) x+1, y+1, z+1.

Experimental details

Crystal data
Chemical formula[CrBr2(C4H8O)2]
Mr356.03
Crystal system, space groupTriclinic, P1
Temperature (K)203
a, b, c (Å)4.1043 (7), 7.4530 (13), 9.2875 (16)
α, β, γ (°)87.777 (3), 78.619 (3), 87.281 (3)
V3)278.07 (8)
Z1
Radiation typeMo Kα
µ (mm1)8.18
Crystal size (mm)0.25 × 0.20 × 0.15
Data collection
DiffractometerSiemens SMART 1000
diffractometer
Absorption correctionEmpirical (using intensity measurements)
(SADABS; Sheldrick, 1999)
Tmin, Tmax0.184, 0.293
No. of measured, independent and
observed [I > 2σ(I)] reflections
2917, 962, 897
Rint0.029
(sin θ/λ)max1)0.595
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.027, 0.071, 1.08
No. of reflections962
No. of parameters61
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.58, 0.70

Computer programs: SMART (Bruker, 1997), SMART, SAINT-Plus (Bruker, 1999), SHELXTL (Sheldrick, 1998), SHELXTL.

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C4—H4A···Br10.982.993.599 (4)121.6
C1—H1A···Br1i0.982.993.607 (4)121.9
Symmetry code: (i) x+1, y+1, z+1.
 

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