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Acta Cryst. (2012). E68, m1474    [ doi:10.1107/S160053681204576X ]

Bis[[mu]-N-(tert-butyldimethylsilyl)quinolin-8-aminato-1:2[kappa]2N1,N8:N8](N,N,N',N'-tetramethylethane-1,2-diamine-1[kappa]2N,N')lithiumsodium

J. Chen and L. Yuan

Abstract top

In the heterometallic title bulky amido complex, [LiNa(C15H21N2Si)2(C6H16N2)], both alkali metal ions are four-coordinated with distorted tetrahedral geometries. The Li+ ion is N,N'-chelated by the N-silylated amido ligand, with Li-N = 2.015 (5) and 2.074 (5) Å. The two amido ligands are arranged cis to each other. The molecule exhibits a twofold rotational symmetry operation along the Li-Na axis. The Na+ ion is coordinated by two N atoms from the tetramethylethylenediamine ligand [Na-N = 2.553 (4) Å] and shares two amido N atoms from the N-silylated amido ligands with the Li+ ion. Although the crystal structure contains voids with an approximate volume of 50 Å3 there is no inclusion of solvent molecules.

Comment top

8–aminoquinoline is a good chelate amido ligand precursor. It could yield a tetranuclear lithium complex after reacting with n–LiBu in Et2O. The product has a centrosymmetric dimeric structure with a Li4N4 step–ladder arrangement (Jones et al., 2000). The silylated aminoquinoline, HN(8–C9H6N)(SiMe3), is a bulky ligand and it has proven to be suitable to coordinate to Li, Mg, Zn and Al ions (Engelhardt et al., 1988; 1990; 1991). The corresponding lithium complexes exist in either monomeric or dimeric form. The silyl–bridged aminoquinoline turn into a tetradentate ligand and its lithium derivative is tetranuclear (Jones et al., 2000).

The research involving mixed organo–alkali metal amides is vivid as they could serve as superbase reagents and have interesting structures (Forbes et al., 2003; Mulvey, 2006; Wei et al., 2008). Based on the above work, we employed the bulky more demanding aminoquinoline analogue [HN(8–C9H6N)(SiButMe2)] to prepare a Li/Na hetero alkali metal amide. Its crystal structure is described here.

The title compound was prepared by metallation of the amine with half an equivalent of n–butyl lithium and half an equivalent of butyl sodium. Neutral donor TMEDA was added into the mixture and the red crystalline product was grown from hexane.

In the molecule of title compound, the lithium ion is fixed by two equivalents of the chelating quinolyl amido ligand, the corresponding bite angle Namido–Li–Nquinolyl being 84.77 (12)°. The observed Li–Namido bond distance of 2.074 (5)Å is marginally different from reported values in literature and slightly longer than the Li–Nquinolyl bond (2.015 (5)Å). It results a distorted tetrahedral configuration around the lithium ion. The sodium atom is connected by the amido nitrogen atoms and it is bound to the neutral donor TMEDA simultaneously, which also leads to a distorted tetrahedral geometry. The molecule exhibits a C2 rotational symmetrical operation along the axis crossing Li and Na atoms. It makes the [Li–Namido–Na–Namido] cyclic ring to be planar. The two metal atoms are separated by the distance of 2.951 (7)Å.

Related literature top

For related metal complexes with N-silylated quinolyl amido ligands, see: Engelhardt et al. (1988, 1990, 1991). For silyl-bridged aminoquinoline derivatives, see: Jones et al. (2000). For mixed alkali metal systems as superbase reagents, see: Forbes et al. (2003); Mulvey (2006); Wei et al. (2008).

Experimental top

A solution of 8–tert–butyldimethylsilylaminoquinoline (0.71 g, 2.73 mmol) in Et2O (ca 20 ml) was added into the mixture of n–LiBu (1.6 M, 0.86 ml, 1.37 mmol) and n–NaBu (0.11 g, 1.37 mmol) in Et2O (ca 20 ml) at 195 K. Then TMEDA (0.16 g, 1.37 mmol) was added and the resulting mixture was kept stirring overnight. The red solution was concentrated and the residue was recrystallized with hexane to give the title compound as red crystals (yield 0.35 g, 39%). 1H NMR (300 MHz, C6D6): δ = 8.588 - 6.735 (m, 12H; quinoline ring), 1.906, 1.840 (d, 16H; TMEDA), 1.326, 1.028 (d, 18H; t–butyl), 0.497, 0.277 (d, 12H; methyls on silyl); 13C NMR (75 MHz, C6D6): δ = 147.452, 137.652, 136.399, 121.771, 115.578, 110.415 (CH of quinoline ring), 57.652, 46.140 TMEDA, 29.237, 26.889 (methyl of t–butyl), 18.664, 15.921 (ipso–C of t–butyl), -0.242, -4.122 (methyls on silyl). Anal. Calc. for C36H58LiN6NaSi2: C, 65.42; H, 8.84; N, 12.71%. Found: C, 65.10; H, 8.81; N, 12.69%.

Refinement top

The methyl H atoms were constrained to an ideal geometry, with C—H distances of 0.96Å and Uiso(H) = 1.5Ueq(C), but each group was allowed to rotate freely about its C—C, C—N and C—Si bonds. The methylene H atoms were constrained with C—H distances of 0.97Å and Uiso(H) = 1.2Ueq(C). The quinolyl H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms, with C—H distances in the range 0.93Å and Uiso(H) = 1.2Ueq(C).

The crystal structure contains four voids (V = 48Å3) with coordinates: 0.000, 0.373, 0.250; 0.000, 0.627, 0.750; 0.500, 0.873, 0.250; 0.500, 0.127, 0.750. Inclusion of solvent molecules into the voids was not supported by diffraction experiment.

Computing details top

Data collection: SMART (Bruker, 2000); cell refinement: 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 (Sheldrick, 2008); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. The molecular structure, showing the atom–numbering scheme. Displacement ellipsoids are drawn at the 30% probability level. H atoms are presented as a small spheres of arbitrary radius. Symmetry code: (i) -x+2, y, -z+1/2.
Bis[µ-N-(tert-butyldimethylsilyl)quinolin-8-aminato- 1:2κ2N1,N8:N8](N,N,N', N'-tetramethylethane-1,2-diamine-1κ2N,N')lithiumsodium top
Crystal data top
[LiNa(C15H21N2Si)2(C6H16N2)]F(000) = 1432
Mr = 660.99Dx = 1.080 Mg m−3
Monoclinic, C2/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2ycCell parameters from 3078 reflections
a = 12.653 (2) Åθ = 2.2–25.5°
b = 18.542 (3) ŵ = 0.13 mm−1
c = 18.296 (3) ÅT = 295 K
β = 108.794 (3)°Block, red
V = 4063.6 (11) Å30.30 × 0.25 × 0.20 mm
Z = 4
Data collection top
Bruker SMART CCD
diffractometer		4001 independent reflections
Radiation source: fine-focus sealed tube2128 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.071
φ and ω scansθmax = 26.0°, θmin = 2.0°
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)		h = −8→15
Tmin = 0.962, Tmax = 0.975k = −22→22
11843 measured reflectionsl = −22→22
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)] = 0.062Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.195H-atom parameters constrained
S = 0.97 w = 1/[σ2(Fo2) + (0.1027P)2]
where P = (Fo2 + 2Fc2)/3
4001 reflections(Δ/σ)max = 0.011
209 parametersΔρmax = 0.32 e Å−3
1 restraintΔρmin = −0.26 e Å−3
Crystal data top
[LiNa(C15H21N2Si)2(C6H16N2)]V = 4063.6 (11) Å3
Mr = 660.99Z = 4
Monoclinic, C2/cMo Kα radiation
a = 12.653 (2) ŵ = 0.13 mm−1
b = 18.542 (3) ÅT = 295 K
c = 18.296 (3) Å0.30 × 0.25 × 0.20 mm
β = 108.794 (3)°
Data collection top
Bruker SMART CCD
diffractometer		4001 independent reflections
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)		2128 reflections with I > 2σ(I)
Tmin = 0.962, Tmax = 0.975Rint = 0.071
11843 measured reflectionsθmax = 26.0°
Refinement top
R[F2 > 2σ(F2)] = 0.062H-atom parameters constrained
wR(F2) = 0.195Δρmax = 0.32 e Å−3
S = 0.97Δρmin = −0.26 e Å−3
4001 reflectionsAbsolute structure: ?
209 parametersFlack parameter: ?
1 restraintRogers parameter: ?
Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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
Si10.79825 (8)0.03304 (5)0.11244 (5)0.0488 (3)
Na11.0000−0.04676 (9)0.25000.0575 (5)
Li11.00000.1121 (4)0.25000.0521 (19)
N10.9134 (3)0.16649 (16)0.30734 (17)0.0624 (8)
N20.8563 (2)0.05043 (13)0.20820 (14)0.0464 (7)
N31.0507 (4)−0.15746 (18)0.1852 (2)0.0823 (11)
C10.9395 (4)0.2245 (2)0.3513 (2)0.0823 (13)
H1A0.99850.25300.34830.099*
C20.8829 (5)0.2453 (3)0.4023 (3)0.110 (2)
H2A0.90420.28620.43290.132*
C30.7970 (5)0.2042 (4)0.4057 (3)0.108 (2)
H3A0.75910.21700.43970.130*
C40.7628 (4)0.1428 (3)0.3595 (2)0.0729 (12)
C50.6742 (4)0.1006 (4)0.3607 (3)0.1021 (18)
H50.63370.11170.39360.122*
C60.6462 (4)0.0414 (3)0.3125 (3)0.0976 (17)
H60.58670.01240.31340.117*
C70.7050 (3)0.0245 (2)0.2627 (2)0.0748 (12)
H70.6828−0.01580.23110.090*
C80.7963 (3)0.06445 (18)0.25710 (18)0.0504 (8)
C90.8254 (3)0.1260 (2)0.30898 (18)0.0545 (9)
C100.9163 (3)0.0301 (2)0.0717 (2)0.0705 (11)
H10A0.89320.05170.02140.106*
H10B0.9374−0.01920.06790.106*
H10C0.97890.05610.10500.106*
C110.7207 (4)−0.05573 (19)0.0867 (2)0.0783 (13)
H11A0.6527−0.04830.04470.117*
H11B0.7035−0.07380.13070.117*
H11C0.7666−0.09000.07150.117*
C120.6967 (3)0.10601 (18)0.05847 (19)0.0565 (9)
C130.7530 (4)0.1797 (2)0.0801 (3)0.0890 (14)
H13A0.70260.21700.05340.134*
H13B0.81950.18140.06570.134*
H13C0.77210.18690.13480.134*
C140.5904 (3)0.1066 (2)0.0806 (2)0.0827 (13)
H14A0.54160.14390.05250.124*
H14B0.60910.11540.13500.124*
H14C0.55370.06070.06830.124*
C150.6644 (4)0.0951 (3)−0.0291 (2)0.0963 (16)
H15A0.61320.1323−0.05510.144*
H15B0.62950.0489−0.04260.144*
H15C0.73010.0974−0.04430.144*
C161.1708 (6)−0.1574 (4)0.2048 (4)0.154 (3)
H16A1.1936−0.19830.18140.231*
H16B1.2042−0.16010.25980.231*
H16C1.1942−0.11390.18610.231*
C171.0020 (6)−0.1651 (3)0.1025 (3)0.142 (3)
H17A1.0289−0.20870.08620.213*
H17B1.0226−0.12460.07740.213*
H17C0.9222−0.16730.08890.213*
C181.0183 (8)−0.2176 (3)0.2183 (4)0.168 (3)
H18A0.9594−0.24040.17710.201*
H18B1.0813−0.25040.23100.201*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Si10.0479 (6)0.0477 (5)0.0494 (5)0.0042 (4)0.0139 (4)−0.0013 (4)
Na10.0601 (12)0.0466 (10)0.0622 (11)0.0000.0148 (10)0.000
Li10.046 (5)0.046 (4)0.067 (5)0.0000.022 (4)0.000
N10.057 (2)0.0589 (18)0.0668 (19)0.0077 (16)0.0129 (16)−0.0110 (15)
N20.0419 (15)0.0502 (15)0.0484 (15)0.0008 (12)0.0166 (13)−0.0002 (12)
N30.104 (3)0.056 (2)0.085 (3)0.005 (2)0.028 (2)−0.0130 (17)
C10.078 (3)0.071 (3)0.088 (3)0.015 (2)0.011 (3)−0.025 (2)
C20.102 (4)0.113 (4)0.090 (4)0.046 (4)−0.004 (4)−0.044 (3)
C30.092 (4)0.171 (6)0.051 (3)0.068 (4)0.008 (3)−0.022 (3)
C40.055 (3)0.123 (4)0.039 (2)0.033 (3)0.0122 (19)0.005 (2)
C50.069 (3)0.193 (6)0.049 (3)0.034 (4)0.027 (3)0.023 (3)
C60.052 (3)0.178 (5)0.067 (3)0.001 (3)0.025 (2)0.046 (3)
C70.057 (2)0.106 (3)0.058 (2)−0.011 (2)0.015 (2)0.017 (2)
C80.0383 (19)0.065 (2)0.0451 (18)0.0073 (16)0.0099 (16)0.0119 (16)
C90.044 (2)0.073 (2)0.0430 (18)0.0215 (18)0.0091 (17)0.0048 (16)
C100.065 (3)0.086 (3)0.062 (2)0.014 (2)0.024 (2)−0.0095 (19)
C110.092 (3)0.061 (2)0.069 (2)−0.003 (2)0.008 (2)−0.0072 (19)
C120.057 (2)0.061 (2)0.051 (2)0.0083 (18)0.0166 (18)0.0067 (16)
C130.093 (3)0.059 (2)0.113 (3)0.014 (2)0.030 (3)0.020 (2)
C140.061 (3)0.101 (3)0.083 (3)0.023 (2)0.019 (2)0.021 (2)
C150.105 (4)0.119 (4)0.054 (2)0.037 (3)0.012 (3)0.014 (2)
C160.114 (5)0.159 (6)0.172 (6)0.003 (5)0.023 (5)−0.084 (5)
C170.183 (7)0.135 (5)0.087 (4)0.072 (5)0.015 (4)−0.026 (3)
C180.278 (10)0.063 (3)0.199 (8)0.010 (5)0.127 (7)−0.021 (4)
Geometric parameters (Å, º) top
Si1—N21.698 (3)C5—H50.9300
Si1—C101.873 (4)C6—C71.386 (6)
Si1—C111.896 (4)C6—H60.9300
Si1—C121.908 (3)C7—C81.403 (5)
Si1—Na13.3014 (12)C7—H70.9300
Na1—N2i2.498 (3)C8—C91.454 (5)
Na1—N22.498 (3)C10—H10A0.9600
Na1—N32.553 (4)C10—H10B0.9600
Na1—N3i2.553 (4)C10—H10C0.9600
Na1—Li12.946 (7)C11—H11A0.9600
Na1—Si1i3.3014 (12)C11—H11B0.9600
Li1—N1i2.015 (5)C11—H11C0.9600
Li1—N12.015 (5)C12—C141.524 (5)
Li1—N22.074 (5)C12—C151.533 (5)
Li1—N2i2.074 (5)C12—C131.533 (5)
Li1—C9i2.765 (4)C13—H13A0.9600
Li1—C92.765 (4)C13—H13B0.9600
Li1—C82.768 (4)C13—H13C0.9600
Li1—C8i2.768 (4)C14—H14A0.9600
N1—C11.321 (4)C14—H14B0.9600
N1—C91.351 (5)C14—H14C0.9600
N2—C81.373 (4)C15—H15A0.9600
N3—C181.392 (6)C15—H15B0.9600
N3—C161.444 (7)C15—H15C0.9600
N3—C171.446 (5)C16—H16A0.9600
C1—C21.400 (7)C16—H16B0.9600
C1—H1A0.9300C16—H16C0.9600
C2—C31.345 (8)C17—H17A0.9600
C2—H2A0.9300C17—H17B0.9600
C3—C41.401 (7)C17—H17C0.9600
C3—H3A0.9300C18—C18i1.379 (10)
C4—C51.373 (7)C18—H18A0.9700
C4—C91.432 (5)C18—H18B0.9700
C5—C61.381 (7)
N2—Si1—C10106.28 (15)C3—C2—C1118.0 (5)
N2—Si1—C11116.03 (15)C3—C2—H2A121.0
C10—Si1—C11106.90 (18)C1—C2—H2A121.0
N2—Si1—C12113.25 (14)C2—C3—C4121.9 (5)
C10—Si1—C12107.79 (17)C2—C3—H3A119.0
C11—Si1—C12106.18 (17)C4—C3—H3A119.0
N2—Si1—Na147.72 (9)C5—C4—C3123.3 (5)
C10—Si1—Na176.71 (12)C5—C4—C9120.7 (4)
C11—Si1—Na190.67 (12)C3—C4—C9116.0 (5)
C12—Si1—Na1159.86 (11)C4—C5—C6119.0 (4)
N2i—Na1—N287.66 (13)C4—C5—H5120.5
N2i—Na1—N3117.08 (11)C6—C5—H5120.5
N2—Na1—N3134.80 (10)C5—C6—C7121.3 (5)
N2i—Na1—N3i134.80 (10)C5—C6—H6119.4
N2—Na1—N3i117.08 (11)C7—C6—H6119.4
N3—Na1—N3i72.99 (19)C6—C7—C8123.8 (4)
N2i—Na1—Li143.83 (6)C6—C7—H7118.1
N2—Na1—Li143.83 (6)C8—C7—H7118.1
N3—Na1—Li1143.51 (9)N2—C8—C7126.1 (3)
N3i—Na1—Li1143.51 (9)N2—C8—C9119.8 (3)
N2i—Na1—Si1i30.20 (6)C7—C8—C9114.1 (3)
N2—Na1—Si1i102.57 (8)N2—C8—Li146.37 (17)
N3—Na1—Si1i117.78 (10)C7—C8—Li1166.6 (3)
N3i—Na1—Si1i104.74 (9)C9—C8—Li174.7 (2)
Li1—Na1—Si1i63.38 (3)N1—C9—C4121.6 (4)
N2i—Na1—Si1102.57 (8)N1—C9—C8117.3 (3)
N2—Na1—Si130.20 (6)C4—C9—C8121.0 (4)
N3—Na1—Si1104.74 (9)N1—C9—Li143.6 (2)
N3i—Na1—Si1117.78 (10)C4—C9—Li1161.7 (3)
Li1—Na1—Si163.38 (3)C8—C9—Li174.8 (2)
Si1i—Na1—Si1126.75 (6)Si1—C10—H10A109.5
N1i—Li1—N1119.9 (4)Si1—C10—H10B109.5
N1i—Li1—N2130.03 (11)H10A—C10—H10B109.5
N1—Li1—N284.77 (12)Si1—C10—H10C109.5
N1i—Li1—N2i84.77 (12)H10A—C10—H10C109.5
N1—Li1—N2i130.03 (11)H10B—C10—H10C109.5
N2—Li1—N2i113.1 (4)Si1—C11—H11A109.5
N1i—Li1—C9i27.53 (11)Si1—C11—H11B109.5
N1—Li1—C9i142.5 (3)H11A—C11—H11B109.5
N2—Li1—C9i128.53 (19)Si1—C11—H11C109.5
N2i—Li1—C9i58.66 (11)H11A—C11—H11C109.5
N1i—Li1—C9142.5 (3)H11B—C11—H11C109.5
N1—Li1—C927.53 (11)C14—C12—C15108.5 (3)
N2—Li1—C958.66 (11)C14—C12—C13107.5 (3)
N2i—Li1—C9128.53 (19)C15—C12—C13109.4 (3)
C9i—Li1—C9169.3 (3)C14—C12—Si1111.8 (2)
N1i—Li1—C8148.81 (15)C15—C12—Si1110.8 (3)
N1—Li1—C857.60 (12)C13—C12—Si1108.6 (3)
N2—Li1—C828.62 (10)C12—C13—H13A109.5
N2i—Li1—C8121.7 (3)C12—C13—H13B109.5
C9i—Li1—C8157.1 (2)H13A—C13—H13B109.5
C9—Li1—C830.47 (10)C12—C13—H13C109.5
N1i—Li1—C8i57.60 (12)H13A—C13—H13C109.5
N1—Li1—C8i148.81 (15)H13B—C13—H13C109.5
N2—Li1—C8i121.7 (3)C12—C14—H14A109.5
N2i—Li1—C8i28.62 (10)C12—C14—H14B109.5
C9i—Li1—C8i30.47 (10)H14A—C14—H14B109.5
C9—Li1—C8i157.1 (2)C12—C14—H14C109.5
C8—Li1—C8i142.7 (3)H14A—C14—H14C109.5
N1i—Li1—Na1120.0 (2)H14B—C14—H14C109.5
N1—Li1—Na1120.0 (2)C12—C15—H15A109.5
N2—Li1—Na156.53 (18)C12—C15—H15B109.5
N2i—Li1—Na156.53 (18)H15A—C15—H15B109.5
C9i—Li1—Na195.34 (17)C12—C15—H15C109.5
C9—Li1—Na195.34 (17)H15A—C15—H15C109.5
C8—Li1—Na171.37 (16)H15B—C15—H15C109.5
C8i—Li1—Na171.37 (16)N3—C16—H16A109.5
C1—N1—C9119.0 (4)N3—C16—H16B109.5
C1—N1—Li1130.8 (3)H16A—C16—H16B109.5
C9—N1—Li1108.9 (3)N3—C16—H16C109.5
C8—N2—Si1124.2 (2)H16A—C16—H16C109.5
C8—N2—Li1105.0 (2)H16B—C16—H16C109.5
Si1—N2—Li1121.45 (14)N3—C17—H17A109.5
C8—N2—Na1115.99 (18)N3—C17—H17B109.5
Si1—N2—Na1102.07 (12)H17A—C17—H17B109.5
Li1—N2—Na179.64 (19)N3—C17—H17C109.5
C18—N3—C16109.0 (6)H17A—C17—H17C109.5
C18—N3—C17106.9 (5)H17B—C17—H17C109.5
C16—N3—C17108.6 (5)C18i—C18—N3126.3 (3)
C18—N3—Na1106.8 (3)C18i—C18—H18A105.8
C16—N3—Na1106.6 (3)N3—C18—H18A105.8
C17—N3—Na1118.6 (3)C18i—C18—H18B105.8
N1—C1—C2123.3 (5)N3—C18—H18B105.8
N1—C1—H1A118.4H18A—C18—H18B106.2
C2—C1—H1A118.4
Symmetry code: (i) −x+2, y, −z+1/2.
Acknowledgements top

This work was supported by grants from the Natural Science Foundation of China (20702029) and the Natural Science Foundation of Shanxi Province (2008011024).

references
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