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The title compound, [CrZn2(CH3)2Cl4(C4H8O)4], contains a central distorted octa­hedral Cr atom, located at an inversion center, bound to two tetra­hydro­furan ligands and four chloro ligands that bridge to two symmetry-related tetra­hedral Zn atoms. The coordination around zinc is completed by methyl and tetra­hydro­furan ligands. This structure is compared with a previously reported complex of vanadium, and their differences in metric parameters are explained.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270106041783/gz3045sup1.cif
Contains datablocks I, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270106041783/gz3045Isup2.hkl
Contains datablock I

CCDC reference: 632911

Comment top

We have recently been investigating the organometallic chemistry of chromium supported by a bis-(N-heterocyclic) carbene ligand (L) (Kreisel et al., 2006). In the hope of synthesizing a stable methyl complex of chromium(II), we reacted ZnMe2 with the chromium dichloride precursor LCrCl2(THF), (I) (THF is tetrahydrofuran). However, isolation of the product gave the title complex, (II), as colorless crystals from THF at 263 K in good yield.

Complex (II) is trinuclear, containing an octahedral Cr atom located at an inversion center. The Cr atom is ligated by four bridging, equatorial chloro ligands and two axial THF ligands. Furthermore, each pair of bridging Cl atoms is coordinated to a tetrahedral Zn atom, which has methyl and THF ligands. The complex is a congener of a previously reported vanadium complex, V(THF)2[(µ2-Cl)2ZnCl(PPh3)]2, (III), making it the second known complex with a Zn—(X)2M—(X)2—Zn motif (Cotton et al., 1985), where M is any metal and X is any halide.

The Cr1—Cl2 bond length in (II) is 2.4576 (5) Å; however, the Cr1—Cl1 bond length is considerably longer at 2.7149 (6) Å. In the vanadium analog, these bond distances are more similar to each other [2.501 (1) and 2.526 (1) Å]. We propose that the significant lengthening of the Cr1—Cl1 bond is caused by a Jahn–Teller distortion, which is due to an unpaired electron that occupies either of the degenerate dz2 or dx2-y2 orbitals of an octahedral complex. Complex (III) does not show this distortion because there are no electrons in these degenerate orbitals. The asymmetry in the bridging chlorine distances to the Zn atoms [2.3105 (5) and 2.3954 (6) Å] may be due to the increased basicity of Cl1, which is involved in the Jahn–Teller distortion. A longer Cr1—Cl1 distance indicates less orbital overlap of the lone pair electrons of the chloro ligand with the Cr atom, suggesting more localization of the electrons in the Zn1—Cl1 bond. In addition, the acute Cl1—Cr1—Cl2 bond angle of 84.33 (2)° reflects the large Cr···Zn interatomic separation of 3.481 (6) Å.

Alternatively, one can think of the asymmetric binding of the bridging Cl atoms as a weak ZnMeCl(THF) adduct of square-planar CrCl2(THF)2. Similar cases of apparent distorted octahedral coordination geometries of high-spin CrII metal centers have been interpreted as square-pyramidal coordination with a weakly coordinated ligand occupying a sixth site (Robertson et al., 2003). In either interpretation of the coordination geometry, the electronic structure should remain the same.

Experimental top

Complex (I) (0.210 g; 0.316 mmol) in 20 ml of THF was cooled to 243 K. To the slurry was added ZnMe2 (0.058 g) and the solution was allowed to warm to room temperature. After stirring overnight, the reaction mixture was filtered, concentrated and cooled to 243 K overnight to yield colorless crystals of complex (II) in 62% yield.

Refinement top

The molecule is located at an inversion center. The heavy-atom bond framework shows significant differences in the component anisotropic displacement parameters along the bonding directions, perhaps because of insufficient absorption corrections. Numerical corrections were unsatisfactory because of indeterminate crystal faces. The results presented represent the best of several attempts at multi-scan absorption corrections. H atoms were assigned calculated positions (C—H = 0.98 and 0.98 Å) with constrained Uiso(H) values of 1.2–1.5 times Ueq(C).

Computing details top

Data collection: SMART (Bruker, 2002); cell refinement: SAINT (Bruker, 2002); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Sheldrick, 2001); software used to prepare material for publication: SHELXTL.

Figures top
[Figure 1] Fig. 1. The molecular structure of (II), with ellipsoids depicted at 50% probability. H atoms have been omitted for clarity. [Symmetry code: (i) −x, 2 − y, −z.]
Tetra-µ-chloro-1:2κ4Cl;1:3κ4Cl-dimethyl-2κC,3κC- tetrakis(tetrahydrofuran)-1κ2O,2κO,3κO-chromium(II)dizinc(II) top
Crystal data top
[CrZn2(CH3)2Cl4(C4H8O)4]Z = 1
Mr = 643.02F(000) = 330
Triclinic, P1Dx = 1.616 Mg m3
Hall symbol: -P 1Mo Kα radiation, λ = 0.71073 Å
a = 7.8530 (14) ÅCell parameters from 980 reflections
b = 8.8695 (16) Åθ = 2.8–28.0°
c = 10.7901 (19) ŵ = 2.63 mm1
α = 68.759 (2)°T = 120 K
β = 71.741 (2)°Block, colourless
γ = 77.434 (2)°0.10 × 0.06 × 0.04 mm
V = 660.6 (2) Å3
Data collection top
Bruker APEX
diffractometer
2938 independent reflections
Radiation source: fine-focus sealed tube2794 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.016
Detector resolution: 836.6 pixels mm-1θmax = 28.2°, θmin = 2.1°
ω scansh = 109
Absorption correction: multi-scan
(SADABS; Sheldrick, 2003)
k = 1111
Tmin = 0.779, Tmax = 0.902l = 1414
7317 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)] = 0.023Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.059H-atom parameters constrained
S = 1.03 w = 1/[σ2(Fo2) + (0.0337P)2 + 0.2798P]
where P = (Fo2 + 2Fc2)/3
2938 reflections(Δ/σ)max = 0.001
134 parametersΔρmax = 0.36 e Å3
1 restraintΔρmin = 0.22 e Å3
Crystal data top
[CrZn2(CH3)2Cl4(C4H8O)4]γ = 77.434 (2)°
Mr = 643.02V = 660.6 (2) Å3
Triclinic, P1Z = 1
a = 7.8530 (14) ÅMo Kα radiation
b = 8.8695 (16) ŵ = 2.63 mm1
c = 10.7901 (19) ÅT = 120 K
α = 68.759 (2)°0.10 × 0.06 × 0.04 mm
β = 71.741 (2)°
Data collection top
Bruker APEX
diffractometer
2938 independent reflections
Absorption correction: multi-scan
(SADABS; Sheldrick, 2003)
2794 reflections with I > 2σ(I)
Tmin = 0.779, Tmax = 0.902Rint = 0.016
7317 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0231 restraint
wR(F2) = 0.059H-atom parameters constrained
S = 1.03Δρmax = 0.36 e Å3
2938 reflectionsΔρmin = 0.22 e Å3
134 parameters
Special details top

Experimental. Data collection is performed with four batch runs at ϕ = 0.00 ° (600 frames), at ϕ = 90.00 ° (600 frames), at ϕ = 180 ° (600 frames) and at ϕ = 270 ° (600 frames). Frame width = 0.30 \& in ω. Data is merged, corrected for decay, and treated with multi-scan absorption corrections.

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.

The highest unassigned peak is located 0.71 (1) Å from atom C3. The deepest electron density hole is located 0.26 (1) Å from atom H2B. All structure factors are from the SHELXTL program libary (Sheldrick, 2001).

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Zn10.12951 (3)0.91456 (2)0.301086 (19)0.01957 (7)
Cr10.00001.00000.00000.01439 (9)
Cl10.10738 (5)1.09447 (5)0.22835 (4)0.01946 (9)
Cl20.26459 (5)0.85785 (5)0.08810 (4)0.01968 (9)
O10.13570 (15)1.20042 (14)0.11310 (12)0.0195 (2)
O20.29183 (18)1.08799 (15)0.27424 (13)0.0241 (3)
C10.1294 (3)0.7330 (2)0.47226 (19)0.0300 (4)
H1A0.05410.76820.55070.045*
H1B0.25310.69850.48190.045*
H1C0.08080.64170.46970.045*
C20.3185 (2)1.1955 (2)0.2030 (2)0.0273 (4)
H2A0.32681.14170.27100.033*
H2B0.40671.13460.14850.033*
C30.3558 (3)1.3703 (2)0.2748 (2)0.0294 (4)
H3A0.33911.40920.36900.035*
H3B0.48041.38270.28010.035*
C40.2177 (2)1.4634 (2)0.18521 (19)0.0241 (4)
H4A0.26191.46210.10830.029*
H4B0.18791.57770.23980.029*
C50.0571 (2)1.3689 (2)0.1332 (2)0.0234 (4)
H5A0.02131.38360.04550.028*
H5B0.01511.40450.20150.028*
C60.3039 (3)1.2418 (2)0.16305 (19)0.0255 (4)
H6A0.18321.30510.16440.031*
H6B0.35571.22320.07280.031*
C70.4267 (3)1.3306 (2)0.1891 (2)0.0281 (4)
H7A0.39701.45020.15310.034*
H7B0.55511.30050.14670.034*
C80.3863 (3)1.2716 (2)0.3456 (2)0.0306 (4)
H8A0.48891.28080.37640.037*
H8B0.27621.33410.38670.037*
C90.3588 (3)1.0954 (2)0.38312 (19)0.0246 (4)
H9A0.47401.02390.38780.030*
H9B0.27001.06060.47340.030*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Zn10.02186 (12)0.02004 (11)0.01819 (11)0.00295 (8)0.00913 (8)0.00399 (8)
Cr10.01368 (17)0.01423 (17)0.01660 (18)0.00112 (13)0.00625 (13)0.00473 (14)
Cl10.01863 (19)0.02114 (19)0.0218 (2)0.00005 (15)0.00807 (15)0.00949 (15)
Cl20.01718 (18)0.0235 (2)0.0208 (2)0.00153 (15)0.00830 (15)0.00916 (16)
O20.0307 (7)0.0248 (6)0.0221 (6)0.0082 (5)0.0147 (5)0.0039 (5)
O10.0160 (6)0.0160 (5)0.0247 (6)0.0005 (4)0.0028 (5)0.0073 (5)
C10.0348 (10)0.0267 (9)0.0218 (9)0.0001 (8)0.0082 (8)0.0013 (7)
C20.0175 (8)0.0255 (9)0.0379 (11)0.0050 (7)0.0021 (7)0.0153 (8)
C30.0270 (9)0.0243 (9)0.0282 (10)0.0037 (7)0.0013 (8)0.0031 (8)
C40.0273 (9)0.0166 (8)0.0267 (9)0.0049 (7)0.0075 (7)0.0031 (7)
C50.0219 (8)0.0156 (8)0.0310 (9)0.0010 (7)0.0061 (7)0.0079 (7)
C60.0274 (9)0.0249 (9)0.0244 (9)0.0056 (7)0.0112 (7)0.0027 (7)
C70.0262 (9)0.0273 (9)0.0334 (10)0.0069 (7)0.0085 (8)0.0097 (8)
C80.0322 (10)0.0363 (10)0.0329 (10)0.0076 (8)0.0097 (8)0.0188 (9)
C90.0254 (9)0.0335 (10)0.0206 (8)0.0029 (7)0.0109 (7)0.0113 (7)
Geometric parameters (Å, º) top
Zn1—C11.9618 (18)C3—C41.524 (3)
Zn1—O22.0913 (13)C3—H3A0.9900
Zn1—Cl12.3105 (5)C3—H3B0.9900
Zn1—Cl22.3954 (6)C4—C51.511 (2)
Cr1—O1i2.0548 (12)C4—H4A0.9900
Cr1—O12.0548 (12)C4—H4B0.9900
Cr1—Cl22.4576 (5)C5—H5A0.9900
Cr1—Cl2i2.4576 (5)C5—H5B0.9900
Cr1—Cl12.7149 (6)C6—C71.514 (3)
Cr1—Cl1i2.7149 (6)C6—H6A0.9900
O2—C61.452 (2)C6—H6B0.9900
O2—C91.455 (2)C7—C81.524 (3)
O1—C51.4523 (19)C7—H7A0.9900
O1—C21.461 (2)C7—H7B0.9900
C1—H1A0.9800C8—C91.513 (3)
C1—H1B0.9800C8—H8A0.9900
C1—H1C0.9800C8—H8B0.9900
C2—C31.508 (3)C9—H9A0.9900
C2—H2A0.9900C9—H9B0.9900
C2—H2B0.9900
C1—Zn1—O2111.80 (7)C2—C3—H3A110.9
C1—Zn1—Cl1130.04 (6)C4—C3—H3A110.9
O2—Zn1—Cl197.36 (4)C2—C3—H3B110.9
C1—Zn1—Cl2117.76 (6)C4—C3—H3B110.9
O2—Zn1—Cl298.98 (4)H3A—C3—H3B108.9
Cl1—Zn1—Cl295.261 (17)C5—C4—C3102.30 (14)
O1i—Cr1—O1180.000 (1)C5—C4—H4A111.3
O1i—Cr1—Cl290.19 (4)C3—C4—H4A111.3
O1—Cr1—Cl289.81 (4)C5—C4—H4B111.3
O1i—Cr1—Cl2i89.81 (4)C3—C4—H4B111.3
O1—Cr1—Cl2i90.19 (4)H4A—C4—H4B109.2
Cl2—Cr1—Cl2i180.0O1—C5—C4104.41 (13)
O1i—Cr1—Cl188.09 (4)O1—C5—H5A110.9
O1—Cr1—Cl191.91 (4)C4—C5—H5A110.9
Cl2—Cr1—Cl184.326 (15)O1—C5—H5B110.9
Cl2i—Cr1—Cl195.674 (15)C4—C5—H5B110.9
O1i—Cr1—Cl1i91.91 (4)H5A—C5—H5B108.9
O1—Cr1—Cl1i88.09 (4)O2—C6—C7105.12 (14)
Cl2—Cr1—Cl1i95.674 (15)O2—C6—H6A110.7
Cl2i—Cr1—Cl1i84.326 (15)C7—C6—H6A110.7
Cl1—Cr1—Cl1i180.0O2—C6—H6B110.7
Zn1—Cl1—Cr187.281 (16)C7—C6—H6B110.7
Zn1—Cl2—Cr191.639 (17)H6A—C6—H6B108.8
C6—O2—C9110.02 (13)C6—C7—C8102.64 (15)
C6—O2—Zn1123.52 (10)C6—C7—H7A111.2
C9—O2—Zn1123.81 (11)C8—C7—H7A111.2
C5—O1—C2109.26 (12)C6—C7—H7B111.2
C5—O1—Cr1125.54 (10)C8—C7—H7B111.2
C2—O1—Cr1124.56 (10)H7A—C7—H7B109.2
Zn1—C1—H1A109.5C9—C8—C7102.88 (15)
Zn1—C1—H1B109.5C9—C8—H8A111.2
H1A—C1—H1B109.5C7—C8—H8A111.2
Zn1—C1—H1C109.5C9—C8—H8B111.2
H1A—C1—H1C109.5C7—C8—H8B111.2
H1B—C1—H1C109.5H8A—C8—H8B109.1
O1—C2—C3106.21 (14)O2—C9—C8105.60 (14)
O1—C2—H2A110.5O2—C9—H9A110.6
C3—C2—H2A110.5C8—C9—H9A110.6
O1—C2—H2B110.5O2—C9—H9B110.6
C3—C2—H2B110.5C8—C9—H9B110.6
H2A—C2—H2B108.7H9A—C9—H9B108.8
C2—C3—C4104.22 (15)
C1—Zn1—Cl1—Cr1124.30 (8)Cl2i—Cr1—O1—C539.34 (13)
O2—Zn1—Cl1—Cr1108.99 (4)Cl1—Cr1—O1—C556.34 (13)
Cl2—Zn1—Cl1—Cr19.204 (14)Cl1i—Cr1—O1—C5123.66 (13)
O1i—Cr1—Cl1—Zn181.41 (4)Cl2—Cr1—O1—C249.54 (13)
O1—Cr1—Cl1—Zn198.59 (4)Cl2i—Cr1—O1—C2130.46 (13)
Cl2—Cr1—Cl1—Zn18.975 (14)Cl1—Cr1—O1—C2133.85 (13)
Cl2i—Cr1—Cl1—Zn1171.025 (14)Cl1i—Cr1—O1—C246.15 (13)
C1—Zn1—Cl2—Cr1130.96 (7)C5—O1—C2—C33.4 (2)
O2—Zn1—Cl2—Cr1108.50 (4)Cr1—O1—C2—C3174.67 (12)
Cl1—Zn1—Cl2—Cr110.170 (15)O1—C2—C3—C419.4 (2)
O1i—Cr1—Cl2—Zn179.41 (4)C2—C3—C4—C533.82 (19)
O1—Cr1—Cl2—Zn1100.59 (4)C2—O1—C5—C425.10 (18)
Cl1—Cr1—Cl2—Zn18.648 (13)Cr1—O1—C5—C4163.78 (11)
Cl1i—Cr1—Cl2—Zn1171.352 (13)C3—C4—C5—O136.09 (18)
C1—Zn1—O2—C6174.25 (14)C9—O2—C6—C714.67 (19)
Cl1—Zn1—O2—C635.63 (13)Zn1—O2—C6—C7176.82 (11)
Cl2—Zn1—O2—C660.92 (13)O2—C6—C7—C831.90 (19)
C1—Zn1—O2—C914.53 (15)C6—C7—C8—C936.79 (19)
Cl1—Zn1—O2—C9124.09 (13)C6—O2—C9—C88.89 (19)
Cl2—Zn1—O2—C9139.37 (13)Zn1—O2—C9—C8153.20 (12)
Cl2—Cr1—O1—C5140.66 (13)C7—C8—C9—O228.48 (19)
Symmetry code: (i) x, y+2, z.

Experimental details

Crystal data
Chemical formula[CrZn2(CH3)2Cl4(C4H8O)4]
Mr643.02
Crystal system, space groupTriclinic, P1
Temperature (K)120
a, b, c (Å)7.8530 (14), 8.8695 (16), 10.7901 (19)
α, β, γ (°)68.759 (2), 71.741 (2), 77.434 (2)
V3)660.6 (2)
Z1
Radiation typeMo Kα
µ (mm1)2.63
Crystal size (mm)0.10 × 0.06 × 0.04
Data collection
DiffractometerBruker APEX
diffractometer
Absorption correctionMulti-scan
(SADABS; Sheldrick, 2003)
Tmin, Tmax0.779, 0.902
No. of measured, independent and
observed [I > 2σ(I)] reflections
7317, 2938, 2794
Rint0.016
(sin θ/λ)max1)0.664
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.023, 0.059, 1.03
No. of reflections2938
No. of parameters134
No. of restraints1
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.36, 0.22

Computer programs: SMART (Bruker, 2002), SAINT (Bruker, 2002), SAINT, SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), SHELXTL (Sheldrick, 2001), SHELXTL.

 

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