metal-organic compounds
catena-Poly[[(N,N-dimethylcyanamide-κN)lithium]-μ3-bromido]
aInstitute of Applied Chemistry, Shanxi University, Taiyuan 030006, People's Republic of China
*Correspondence e-mail: mszhou@sxu.edu.cn
The title complex, [LiBr(C3H6N2)]n, is the unexpected product of a reaction beteween (Dipp)N(Li)SiMe3 (Dipp = 2,6-diisopropylphenyl), Me2NCN and CuBr. The compound is a one-dimensional polymer with a step structure derived from the association of inversion dimers, formed by bromido ligands bridging two Li+ cations, each of which carries a dimethylcyanamide ligand. The planar (LiBr)2 unit of the polymer core has a regular rhombic shape [Li—Br—Li 77.55 (16)° and Br—Li—Br 102.45 (16)°]. These (LiBr·NCNMe2)2 dimers represent the repeat unit of a polymer system propagated by additional Br—Li and Li—Br bonds generating an infinite step structure along the a-axis direction.
CCDC reference: 982978
Related literature
For examples of lithium halides solvated by Lewis bases, see: Snaith & Wright (1995); Mulvey (1991); Raston, Skelton et al. (1988), Raston, Whitaker & White (1988, 1989a,b); Edwards et al. (1993); Neumann et al. (1995); Gregory et al. (1991). For related crystal structures, see: Edwards et al. (1993); Raston, Skelton et al. (1988). A 1,3,5,7-tetraazaheptatrienyl–lithium salt was reported by Boesveld et al. (2009)
Experimental
Crystal data
|
Data collection: SMART (Bruker, 2000); cell SAINT (Bruker, 2000); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL/PC (Sheldrick, 2008); software used to prepare material for publication: SHELXL97.
Supporting information
CCDC reference: 982978
10.1107/S1600536814001652/sj5383sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536814001652/sj5383Isup2.hkl
Me2NCN (0.76 mL, 9.38 mmol) was added to a solution of (Dipp)N(Li)SiMe3 (0.60 g, 2.35 mmol) in Et2O (30 mL) at -78°C. The resulting mixture was warmed to ca. 25°C and stirred for overnight. The resulting mixture was added dropwise into a suspension of CuBr (0.34 g, 2.35 mmol) in Et2O (10 mL) at -78°C. The resulting mixture was warmed to ca. 25°C and stirred for 24 h, then filtered. The filtrate was concentrated in vacuo and stored at 20°C for ten days, yielding colorless crystals of the title compound (0.503 g, 68%) .
Anal. calcd. for C6H12Br2Li2N4(%): C, 22.96; H, 3.85; N, 17.85. Found: C, 22.93; H, 3.89; N, 17.87. All manipulations were performed under argon using standard Schlenk and vacuum line techniques. Et2O was dried and distilled over Na under argon prior to use. Elemental analysis is completely in agreement with the structure of the compound.
Crystal data, data collection and structure
details are summarized in Table 1. The methyl H atoms were constrained to an ideal geometry, with C—H distances of 0.98 Å and Uiso(H) = 1.5Ueq(C).Lithium halidies solvated by Lewis bases have been studied extensively in the past and the various crystal structures exhibit remarkable structural diversity (Snaith et al., 1995; Mulvey, 1991, Gregory et al., 1991). Monomers, dimers, tetramers, larger oligomers and polymers are known (Raston, Whitaker & White 1988, 1989a,b; Raston, Skelton et al. 1988; Edwards et al.,1993). Pyridines, chelating ∞, was isolated from the reaction mixture. Here we present the synthesis and of the complex (I).
and Lewis bases containing oxygen usually serve as ligands (Neumann et al., 1995). A 1,3,5,7-tetraazaheptatrienyl-lithium salt was reported by W. Marco Boesveld (Boesveld et al., 2009) and we were attempting to synthesize a 1,3,5,7-tetraazaheptatrienylcopper complex by the reaction of (Dipp)N(Li)SiMe3 (Dipp = 2,6-diisopropylphenyl), Me2NCN and CuBr. No copper complex was obtained but instead the title polymeric lithium complex (I), (C6H12Br2Li2N4)A low-temperature X-ray crystallographic study shows the basic unit (Fig. 1) of the step structure of complex (I) is centrosymmetric, and to have a polymeric structure (Fig. 2) in the solid state. In the unit, atoms Li1, Br1, Li1A and Br1A are exactly co-planar and constitute a regular rhombic shape [Li—Br—Li 77.55 (16)° and Br—Li—Br 102.45 (16)° ]. The Li1—Br1 and Li1—N1 bond lengths are 2.543 (5) (av.) and 1.999 (5) Å. The bond angles N1—Li1—Br1, N1—Li1—Br1A are 113.1 (2) and 119.6 (2)°, respectively.
Lithium halidies solvated by Lewis bases have been studied extensively in the past and the various crystal structures exhibit remarkable structural diversity (Snaith et al., 1995; Mulvey, 1991, Gregory et al., 1991). Monomers, dimers, tetramers, larger oligomers and polymers are known (Raston, Whitaker & White 1988, 1989a,b; Raston, Skelton et al. 1988; Edwards et al.,1993). Pyridines, chelating ∞, was isolated from the reaction mixture. Here we present the synthesis and of the complex (I).
and Lewis bases containing oxygen usually serve as ligands (Neumann et al., 1995). A 1,3,5,7-tetraazaheptatrienyl-lithium salt was reported by W. Marco Boesveld (Boesveld et al., 2009) and we were attempting to synthesize a 1,3,5,7-tetraazaheptatrienylcopper complex by the reaction of (Dipp)N(Li)SiMe3 (Dipp = 2,6-diisopropylphenyl), Me2NCN and CuBr. No copper complex was obtained but instead the title polymeric lithium complex (I), (C6H12Br2Li2N4)A low-temperature X-ray crystallographic study shows the basic unit (Fig. 1) of the step structure of complex (I) is centrosymmetric, and to have a polymeric structure (Fig. 2) in the solid state. In the unit, atoms Li1, Br1, Li1A and Br1A are exactly co-planar and constitute a regular rhombic shape [Li—Br—Li 77.55 (16)° and Br—Li—Br 102.45 (16)° ]. The Li1—Br1 and Li1—N1 bond lengths are 2.543 (5) (av.) and 1.999 (5) Å. The bond angles N1—Li1—Br1, N1—Li1—Br1A are 113.1 (2) and 119.6 (2)°, respectively.
For examples of lithium halides solvated by Lewis bases, see: Snaith & Wright (1995); Mulvey (1991); Raston, Skelton et al. (1988), Raston, Whitaker & White (1988, 1989a,b); Edwards et al. (1993); Neumann et al. (1995); Gregory et al. (1991). For related crystal structures, see: Edwards et al. (1993); Raston, Skelton et al. (1988). A 1,3,5,7-tetraazaheptatrienyl–lithium salt was reported by Boesveld et al. (2009).
Me2NCN (0.76 mL, 9.38 mmol) was added to a solution of (Dipp)N(Li)SiMe3 (0.60 g, 2.35 mmol) in Et2O (30 mL) at -78°C. The resulting mixture was warmed to ca. 25°C and stirred for overnight. The resulting mixture was added dropwise into a suspension of CuBr (0.34 g, 2.35 mmol) in Et2O (10 mL) at -78°C. The resulting mixture was warmed to ca. 25°C and stirred for 24 h, then filtered. The filtrate was concentrated in vacuo and stored at 20°C for ten days, yielding colorless crystals of the title compound (0.503 g, 68%) .
Anal. calcd. for C6H12Br2Li2N4(%): C, 22.96; H, 3.85; N, 17.85. Found: C, 22.93; H, 3.89; N, 17.87. All manipulations were performed under argon using standard Schlenk and vacuum line techniques. Et2O was dried and distilled over Na under argon prior to use. Elemental analysis is completely in agreement with the structure of the compound.
detailsCrystal data, data collection and structure
details are summarized in Table 1. The methyl H atoms were constrained to an ideal geometry, with C—H distances of 0.98 Å and Uiso(H) = 1.5Ueq(C).Data collection: SMART (Bruker, 2000); cell
SAINT (Bruker, 2000); data reduction: SAINT (Bruker, 2000); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL/PC (Sheldrick, 2008); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).[LiBr(C3H6N2)] | F(000) = 304 |
Mr = 156.85 | Dx = 1.607 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
a = 4.2680 (8) Å | Cell parameters from 1538 reflections |
b = 17.214 (3) Å | θ = 2.4–26.5° |
c = 8.9685 (17) Å | µ = 6.22 mm−1 |
β = 100.089 (3)° | T = 200 K |
V = 648.7 (2) Å3 | Block, colourless |
Z = 4 | 0.35 × 0.33 × 0.32 mm |
Bruker SMART APEX CCD diffractometer | 1140 independent reflections |
Radiation source: fine-focus sealed tube | 965 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.032 |
ω scans | θmax = 25.1°, θmin = 2.4° |
Absorption correction: multi-scan (SADABS; Bruker, 2000) | h = −5→3 |
Tmin = 0.220, Tmax = 0.241 | k = −20→18 |
3498 measured reflections | l = −10→10 |
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)] = 0.025 | H-atom parameters constrained |
wR(F2) = 0.061 | w = 1/[σ2(Fo2) + (0.0285P)2 + 0.3312P] where P = (Fo2 + 2Fc2)/3 |
S = 1.03 | (Δ/σ)max = 0.001 |
1140 reflections | Δρmax = 0.57 e Å−3 |
67 parameters | Δρmin = −0.38 e Å−3 |
0 restraints | Extinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0053 (16) |
[LiBr(C3H6N2)] | V = 648.7 (2) Å3 |
Mr = 156.85 | Z = 4 |
Monoclinic, P21/c | Mo Kα radiation |
a = 4.2680 (8) Å | µ = 6.22 mm−1 |
b = 17.214 (3) Å | T = 200 K |
c = 8.9685 (17) Å | 0.35 × 0.33 × 0.32 mm |
β = 100.089 (3)° |
Bruker SMART APEX CCD diffractometer | 1140 independent reflections |
Absorption correction: multi-scan (SADABS; Bruker, 2000) | 965 reflections with I > 2σ(I) |
Tmin = 0.220, Tmax = 0.241 | Rint = 0.032 |
3498 measured reflections |
R[F2 > 2σ(F2)] = 0.025 | 0 restraints |
wR(F2) = 0.061 | H-atom parameters constrained |
S = 1.03 | Δρmax = 0.57 e Å−3 |
1140 reflections | Δρmin = −0.38 e Å−3 |
67 parameters |
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. |
x | y | z | Uiso*/Ueq | ||
Li1 | 0.2655 (11) | 0.4372 (3) | 0.0594 (6) | 0.0289 (11) | |
Br1 | 0.81425 (7) | 0.485193 (18) | 0.18525 (3) | 0.03230 (16) | |
N1 | 0.2914 (7) | 0.32132 (16) | 0.0517 (3) | 0.0475 (8) | |
N2 | 0.5102 (8) | 0.18972 (16) | 0.0853 (3) | 0.0509 (8) | |
C1 | 0.3896 (8) | 0.25987 (19) | 0.0667 (4) | 0.0352 (8) | |
C2 | 0.3986 (11) | 0.1281 (2) | −0.0201 (5) | 0.0672 (12) | |
H2A | 0.2384 | 0.1487 | −0.1023 | 0.101* | |
H2B | 0.3037 | 0.0868 | 0.0327 | 0.101* | |
H2C | 0.5779 | 0.1070 | −0.0621 | 0.101* | |
C3 | 0.7254 (9) | 0.1720 (2) | 0.2260 (5) | 0.0581 (11) | |
H3A | 0.7997 | 0.2206 | 0.2775 | 0.087* | |
H3B | 0.9081 | 0.1426 | 0.2035 | 0.087* | |
H3C | 0.6130 | 0.1410 | 0.2916 | 0.087* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Li1 | 0.025 (3) | 0.022 (3) | 0.038 (3) | 0.0034 (19) | 0.001 (2) | 0.004 (2) |
Br1 | 0.0248 (2) | 0.0371 (2) | 0.0339 (2) | 0.00073 (13) | 0.00223 (13) | 0.00497 (14) |
N1 | 0.052 (2) | 0.0287 (17) | 0.057 (2) | 0.0056 (14) | −0.0034 (15) | 0.0025 (14) |
N2 | 0.068 (2) | 0.0252 (16) | 0.053 (2) | 0.0129 (14) | −0.0071 (16) | −0.0022 (14) |
C1 | 0.035 (2) | 0.032 (2) | 0.0363 (19) | −0.0027 (15) | −0.0003 (14) | −0.0015 (14) |
C2 | 0.108 (4) | 0.036 (2) | 0.062 (3) | −0.003 (2) | 0.027 (2) | −0.0161 (19) |
C3 | 0.050 (2) | 0.058 (3) | 0.065 (3) | 0.0178 (19) | 0.003 (2) | 0.019 (2) |
Li1—N1 | 1.999 (5) | N2—C1 | 1.312 (4) |
Li1—Br1i | 2.535 (5) | N2—C2 | 1.445 (5) |
Li1—Br1ii | 2.541 (5) | N2—C3 | 1.457 (5) |
Li1—Br1 | 2.553 (5) | C2—H2A | 0.9800 |
Li1—Li1iii | 3.179 (9) | C2—H2B | 0.9800 |
Li1—Li1ii | 3.251 (10) | C2—H2C | 0.9800 |
Br1—Li1iv | 2.535 (5) | C3—H3A | 0.9800 |
Br1—Li1ii | 2.541 (5) | C3—H3B | 0.9800 |
N1—C1 | 1.137 (4) | C3—H3C | 0.9800 |
N1—Li1—Br1i | 113.1 (2) | C1—N1—Li1 | 161.0 (3) |
N1—Li1—Br1ii | 119.6 (2) | C1—N2—C2 | 121.0 (3) |
Br1i—Li1—Br1ii | 102.45 (16) | C1—N2—C3 | 118.4 (3) |
N1—Li1—Br1 | 106.6 (2) | C2—N2—C3 | 119.9 (3) |
Br1i—Li1—Br1 | 114.03 (19) | N1—C1—N2 | 178.5 (4) |
Br1ii—Li1—Br1 | 100.67 (17) | N2—C2—H2A | 109.5 |
N1—Li1—Li1iii | 135.1 (3) | N2—C2—H2B | 109.5 |
Br1i—Li1—Li1iii | 51.30 (14) | H2A—C2—H2B | 109.5 |
Br1ii—Li1—Li1iii | 51.15 (14) | N2—C2—H2C | 109.5 |
Br1—Li1—Li1iii | 118.2 (2) | H2A—C2—H2C | 109.5 |
N1—Li1—Li1ii | 127.7 (3) | H2B—C2—H2C | 109.5 |
Br1i—Li1—Li1ii | 119.2 (2) | N2—C3—H3A | 109.5 |
Br1ii—Li1—Li1ii | 50.50 (13) | N2—C3—H3B | 109.5 |
Br1—Li1—Li1ii | 50.17 (13) | H3A—C3—H3B | 109.5 |
Li1iii—Li1—Li1ii | 83.2 (2) | N2—C3—H3C | 109.5 |
Li1iv—Br1—Li1ii | 77.55 (16) | H3A—C3—H3C | 109.5 |
Li1iv—Br1—Li1 | 114.03 (19) | H3B—C3—H3C | 109.5 |
Li1ii—Br1—Li1 | 79.33 (17) |
Symmetry codes: (i) x−1, y, z; (ii) −x+1, −y+1, −z; (iii) −x, −y+1, −z; (iv) x+1, y, z. |
Experimental details
Crystal data | |
Chemical formula | [LiBr(C3H6N2)] |
Mr | 156.85 |
Crystal system, space group | Monoclinic, P21/c |
Temperature (K) | 200 |
a, b, c (Å) | 4.2680 (8), 17.214 (3), 8.9685 (17) |
β (°) | 100.089 (3) |
V (Å3) | 648.7 (2) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 6.22 |
Crystal size (mm) | 0.35 × 0.33 × 0.32 |
Data collection | |
Diffractometer | Bruker SMART APEX CCD |
Absorption correction | Multi-scan (SADABS; Bruker, 2000) |
Tmin, Tmax | 0.220, 0.241 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 3498, 1140, 965 |
Rint | 0.032 |
(sin θ/λ)max (Å−1) | 0.596 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.025, 0.061, 1.03 |
No. of reflections | 1140 |
No. of parameters | 67 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.57, −0.38 |
Computer programs: SMART (Bruker, 2000), SAINT (Bruker, 2000), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL/PC (Sheldrick, 2008).
Acknowledgements
The authors acknowledge the financial support of the Natural Science Foundation of China (No. 21371111) and Shanxi Scholarship Council of China (No. 2013–025).
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