In the title compound, dibromobis(tetrahydrofuran-
O)chromium(II), [CrBr
2(C
4H
8O)
2], CrBr
2 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
CCDC reference: 159712
Key indicators
- Single-crystal X-ray study
- T = 203 K
- Mean (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
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
(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.
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.
dibromobis(tetrahydrofuran-O)chromium(II)
top
Crystal data top
[CrBr2(C4H8O)2] | Z = 1 |
Mr = 356.03 | F(000) = 174 |
Triclinic, P1 | Dx = 2.126 Mg m−3 |
a = 4.1043 (7) Å | Mo Kα radiation, λ = 0.71073 Å |
b = 7.4530 (13) Å | Cell parameters from 839 reflections |
c = 9.2875 (16) Å | θ = 2.2–27.4° |
α = 87.777 (3)° | µ = 8.18 mm−1 |
β = 78.619 (3)° | T = 203 K |
γ = 87.281 (3)° | Plate, pale yellow |
V = 278.07 (8) Å3 | 0.25 × 0.20 × 0.15 mm |
Data collection top
Siemens SMART 1000 diffractometer | 962 independent reflections |
Radiation source: normal-focus sealed tube | 897 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.029 |
Detector resolution: 8.3 pixels mm-1 | θmax = 25.0°, θmin = 2.2° |
ω scans | h = −4→4 |
Absorption correction: empirical (using intensity measurements) (SADABS; Sheldrick, 1999) | k = −8→8 |
Tmin = 0.184, Tmax = 0.293 | l = −11→11 |
2917 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)] = 0.027 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.071 | H-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 parameters | Δρmax = 0.58 e Å−3 |
0 restraints | Δρmin = −0.70 e Å−3 |
Crystal data top
[CrBr2(C4H8O)2] | γ = 87.281 (3)° |
Mr = 356.03 | V = 278.07 (8) Å3 |
Triclinic, P1 | Z = 1 |
a = 4.1043 (7) Å | Mo Kα radiation |
b = 7.4530 (13) Å | µ = 8.18 mm−1 |
c = 9.2875 (16) Å | T = 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 = 0.293 | Rint = 0.029 |
2917 measured reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.027 | 0 restraints |
wR(F2) = 0.071 | H-atom parameters constrained |
S = 1.08 | Δρmax = 0.58 e Å−3 |
962 reflections | Δρmin = −0.70 e Å−3 |
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 | x | y | z | Uiso*/Ueq | |
Br1 | 0.10559 (9) | 0.70378 (5) | 0.37413 (4) | 0.02022 (17) | |
Cr1 | 0.5000 | 0.5000 | 0.5000 | 0.0180 (2) | |
O1 | 0.4032 (7) | 0.6622 (3) | 0.6810 (3) | 0.0245 (6) | |
C1 | 0.2743 (10) | 0.5980 (5) | 0.8298 (4) | 0.0242 (9) | |
H1A | 0.3974 | 0.4886 | 0.8536 | 0.029* | |
H1B | 0.0382 | 0.5724 | 0.8425 | 0.029* | |
C3 | 0.2812 (11) | 0.9167 (5) | 0.8283 (4) | 0.0244 (9) | |
H3A | 0.0454 | 0.9507 | 0.8342 | 0.029* | |
H3B | 0.3948 | 1.0190 | 0.8558 | 0.029* | |
C2 | 0.3237 (10) | 0.7515 (5) | 0.9266 (4) | 0.0240 (9) | |
H2A | 0.5459 | 0.7433 | 0.9508 | 0.029* | |
H2B | 0.1558 | 0.7528 | 1.0177 | 0.029* | |
C4 | 0.4399 (10) | 0.8560 (5) | 0.6761 (4) | 0.0232 (9) | |
H4A | 0.3266 | 0.9144 | 0.6022 | 0.028* | |
H4B | 0.6753 | 0.8848 | 0.6524 | 0.028* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Br1 | 0.0210 (2) | 0.0198 (2) | 0.0199 (3) | 0.00074 (15) | −0.00461 (16) | 0.00071 (15) |
Cr1 | 0.0230 (5) | 0.0167 (4) | 0.0144 (5) | 0.0034 (3) | −0.0046 (4) | −0.0026 (3) |
O1 | 0.0390 (16) | 0.0173 (13) | 0.0152 (14) | −0.0007 (12) | −0.0004 (12) | −0.0019 (11) |
C1 | 0.029 (2) | 0.022 (2) | 0.018 (2) | 0.0006 (16) | 0.0015 (17) | −0.0007 (16) |
C3 | 0.027 (2) | 0.024 (2) | 0.021 (2) | 0.0004 (16) | −0.0020 (17) | −0.0058 (16) |
C2 | 0.028 (2) | 0.027 (2) | 0.017 (2) | 0.0021 (17) | −0.0026 (17) | −0.0052 (17) |
C4 | 0.032 (2) | 0.0162 (19) | 0.021 (2) | −0.0041 (16) | −0.0036 (17) | −0.0010 (15) |
Geometric parameters (Å, º) top
Br1—Cr1 | 2.5825 (5) | O1—C4 | 1.458 (4) |
Cr1—O1i | 2.072 (3) | C1—C2 | 1.527 (6) |
Cr1—O1 | 2.072 (3) | C3—C4 | 1.512 (5) |
Cr1—Br1i | 2.5825 (5) | C3—C2 | 1.528 (6) |
O1—C1 | 1.450 (5) | | |
| | | |
O1i—Cr1—O1 | 180.00 (9) | C1—O1—Cr1 | 124.1 (2) |
O1i—Cr1—Br1i | 90.09 (8) | C4—O1—Cr1 | 125.1 (2) |
O1—Cr1—Br1i | 89.91 (8) | O1—C1—C2 | 104.7 (3) |
O1i—Cr1—Br1 | 89.91 (8) | C4—C3—C2 | 103.6 (3) |
O1—Cr1—Br1 | 90.09 (8) | C1—C2—C3 | 102.1 (3) |
Br1i—Cr1—Br1 | 180.0 | O1—C4—C3 | 105.2 (3) |
C1—O1—C4 | 110.7 (3) | | |
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 |
C4—H4A···Br1 | 0.98 | 2.99 | 3.599 (4) | 122 |
C1—H1A···Br1i | 0.98 | 2.99 | 3.607 (4) | 122 |
Symmetry code: (i) −x+1, −y+1, −z+1. |
Experimental details
Crystal data |
Chemical formula | [CrBr2(C4H8O)2] |
Mr | 356.03 |
Crystal system, space group | Triclinic, 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) |
V (Å3) | 278.07 (8) |
Z | 1 |
Radiation type | Mo Kα |
µ (mm−1) | 8.18 |
Crystal size (mm) | 0.25 × 0.20 × 0.15 |
|
Data collection |
Diffractometer | Siemens SMART 1000 diffractometer |
Absorption correction | Empirical (using intensity measurements) (SADABS; Sheldrick, 1999) |
Tmin, Tmax | 0.184, 0.293 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 2917, 962, 897 |
Rint | 0.029 |
(sin θ/λ)max (Å−1) | 0.595 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.027, 0.071, 1.08 |
No. of reflections | 962 |
No. of parameters | 61 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.58, −0.70 |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
C4—H4A···Br1 | 0.98 | 2.99 | 3.599 (4) | 121.6 |
C1—H1A···Br1i | 0.98 | 2.99 | 3.607 (4) | 121.9 |
Symmetry code: (i) −x+1, −y+1, −z+1. |
(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.