Bis{μ-N-[(N,N-dimethyl­amino)dimethyl­silyl]-2,6-dimethyl­anilido}lithium(I)

The dimeric lithium amide, [Li₂(C₁₂H₂₁N₂Si)₂], exhibits a four-rung ladder core of Li—N and Si—N bonds.

Key indicators

• Single-crystal X-ray study
• T = 203 K
• Mean [sigma](C-C) = 0.005 Å
• R factor = 0.081
• wR factor = 0.170
• Data-to-parameter ratio = 17.0

checkCIF/PLATON results

No syntax errors found





Alert level B
ABSTM02_ALERT_3_B  The ratio of expected to reported Tmax/Tmin(RR') is < 0.75
            Tmin and Tmax reported:      0.700     0.972
            Tmin(prime) and Tmax expected:      0.957     0.972
            RR(prime) =      0.731
            Please check that your absorption correction is appropriate.
PLAT061_ALERT_3_B Tmax/Tmin Range Test RR' too Large .............       0.73

Alert level C
PLAT042_ALERT_1_C Calc. and Rep. MoietyFormula Strings Differ ....          ?
PLAT125_ALERT_4_C No _symmetry_space_group_name_Hall Given .......          ?
PLAT220_ALERT_2_C Large Non-Solvent    C     Ueq(max)/Ueq(min) ...       2.75 Ratio
PLAT242_ALERT_2_C Check Low       Ueq as Compared to Neighbors for        Si1
PLAT242_ALERT_2_C Check Low       Ueq as Compared to Neighbors for         N2
PLAT340_ALERT_3_C Low Bond Precision on C-C bonds (x 1000) Ang ...          6
PLAT764_ALERT_4_C Overcomplete CIF Bond List Detected (Rep/Expd) .       1.44 Ratio

Alert level G
FORMU01_ALERT_1_G  There is a discrepancy between the atom counts in the
            _chemical_formula_sum and _chemical_formula_moiety. This is
            usually due to the moiety formula being in the wrong format.
            Atom count from _chemical_formula_sum:   C24 H42 Li2 N4 Si2
            Atom count from _chemical_formula_moiety:C12 H21 Li1 N2 Si1

   0 ALERT level A = In general: serious problem
   2 ALERT level B = Potentially serious problem
   7 ALERT level C = Check and explain
   1 ALERT level G = General alerts; check

   2 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   3 ALERT type 2 Indicator that the structure model may be wrong or deficient
   3 ALERT type 3 Indicator that the structure quality may be low
   2 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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Computing details

Data collection: SMART (Bruker, 2000); cell refinement: SAINT (Bruker, 2000); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL/PC (Sheldrick, 1999); software used to prepare material for publication: SHELXTL/PC.

Bis{µ-N-[(N,N-dimethylamino)dimethylsilyl]-2,6-dimethylanilido}lithium(I)

Crystal data

[Li2(C12H21N2Si)2]	Dx = 1.083 Mg m^−3
Mr = 456.68	Melting point = 173–174 K
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
a = 9.7958 (9) Å	Cell parameters from 2419 reflections
b = 10.5049 (11) Å	θ = 2.5–27.6°
c = 14.0597 (14) Å	µ = 0.14 mm^−1
β = 104.499 (2)°	T = 203 K
V = 1400.7 (2) Å^3	Prism, colourless
Z = 2	0.30 × 0.30 × 0.20 mm
F(000) = 496

Data collection

Bruker SMART CCD area-detector diffractometer	2461 independent reflections
Radiation source: fine-focus sealed tube	2305 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.028
ω scans	θmax = 25.0°, θmin = 2.3°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −11→9
Tmin = 0.700, Tmax = 0.972	k = −9→12
5654 measured reflections	l = −16→16

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.081	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.170	H-atom parameters constrained
S = 1.28	w = 1/[σ^2(Fo^2) + (0.0494P)^2 + 1.123P] where P = (Fo^2 + 2Fc^2)/3
2461 reflections	(Δ/σ)max < 0.001
145 parameters	Δρmax = 0.30 e Å^−3
0 restraints	Δρmin = −0.20 e Å^−3

Special details

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 (Ų)

	x	y	z	Uiso*/Ueq
Si1	0.46274 (9)	0.84589 (9)	0.14536 (7)	0.0439 (3)
N1	0.5442 (3)	0.8677 (2)	0.05427 (19)	0.0400 (6)
N2	0.4641 (4)	1.0010 (3)	0.1941 (2)	0.0622 (9)
C1	0.6371 (3)	0.7861 (3)	0.0224 (2)	0.0375 (7)
C2	0.5897 (4)	0.6842 (3)	−0.0418 (2)	0.0474 (8)
C3	0.6840 (5)	0.6123 (4)	−0.0773 (3)	0.0656 (11)
H3A	0.6504	0.5458	−0.1205	0.079*
C4	0.8248 (5)	0.6361 (5)	−0.0507 (3)	0.0755 (13)
H4A	0.8872	0.5856	−0.0741	0.091*
C5	0.8730 (4)	0.7356 (4)	0.0110 (3)	0.0664 (11)
H5A	0.9691	0.7533	0.0284	0.080*
C6	0.7832 (3)	0.8107 (4)	0.0483 (2)	0.0481 (8)
C7	0.4347 (4)	0.6533 (4)	−0.0744 (3)	0.0756 (12)
H7A	0.4215	0.5779	−0.1142	0.113*
H7B	0.3853	0.7230	−0.1119	0.113*
H7C	0.3986	0.6393	−0.0177	0.113*
C8	0.8423 (4)	0.9195 (4)	0.1148 (3)	0.0736 (12)
H8A	0.8011	0.9977	0.0860	0.110*
H8B	0.9427	0.9228	0.1238	0.110*
H8C	0.8211	0.9076	0.1773	0.110*
C9	0.2741 (4)	0.7966 (5)	0.1070 (3)	0.0799 (14)
H9A	0.2221	0.8568	0.0603	0.120*
H9B	0.2358	0.7940	0.1634	0.120*
H9C	0.2673	0.7138	0.0773	0.120*
C10	0.5534 (4)	0.7301 (4)	0.2405 (3)	0.0627 (10)
H10A	0.5491	0.6467	0.2120	0.094*
H10B	0.5077	0.7292	0.2935	0.094*
H10C	0.6502	0.7548	0.2652	0.094*
C11	0.3340 (6)	1.0614 (5)	0.2057 (4)	0.103 (2)
H11A	0.3065	1.0233	0.2601	0.154*
H11B	0.2604	1.0495	0.1468	0.154*
H11C	0.3500	1.1507	0.2177	0.154*
C12	0.5835 (6)	1.0339 (5)	0.2757 (3)	0.0940 (17)
H12A	0.5949	1.1247	0.2790	0.141*
H12B	0.6676	0.9953	0.2657	0.141*
H12C	0.5665	1.0033	0.3360	0.141*
Li1	0.4602 (6)	0.9438 (5)	−0.0761 (4)	0.0491 (14)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Si1	0.0439 (5)	0.0441 (5)	0.0475 (5)	0.0068 (4)	0.0185 (4)	0.0143 (4)
N1	0.0440 (15)	0.0326 (14)	0.0449 (15)	0.0038 (11)	0.0142 (12)	0.0022 (12)
N2	0.094 (2)	0.0501 (18)	0.0548 (19)	0.0175 (17)	0.0428 (18)	0.0100 (15)
C1	0.0415 (17)	0.0403 (17)	0.0310 (15)	0.0047 (14)	0.0098 (13)	0.0095 (13)
C2	0.058 (2)	0.0409 (19)	0.0429 (18)	0.0008 (16)	0.0116 (16)	0.0010 (15)
C3	0.091 (3)	0.053 (2)	0.056 (2)	0.010 (2)	0.023 (2)	−0.0117 (19)
C4	0.081 (3)	0.087 (3)	0.065 (3)	0.038 (3)	0.029 (2)	−0.004 (2)
C5	0.047 (2)	0.095 (3)	0.058 (2)	0.017 (2)	0.0156 (18)	0.005 (2)
C6	0.0397 (18)	0.064 (2)	0.0407 (18)	0.0060 (16)	0.0103 (15)	0.0017 (16)
C7	0.076 (3)	0.070 (3)	0.078 (3)	−0.022 (2)	0.014 (2)	−0.020 (2)
C8	0.051 (2)	0.097 (3)	0.072 (3)	−0.019 (2)	0.014 (2)	−0.020 (3)
C9	0.050 (2)	0.100 (4)	0.098 (3)	0.002 (2)	0.034 (2)	0.028 (3)
C10	0.073 (3)	0.059 (2)	0.057 (2)	0.010 (2)	0.018 (2)	0.0177 (19)
C11	0.163 (5)	0.077 (3)	0.105 (4)	0.057 (3)	0.104 (4)	0.035 (3)
C12	0.160 (5)	0.072 (3)	0.060 (3)	−0.019 (3)	0.046 (3)	−0.016 (2)
Li1	0.063 (4)	0.041 (3)	0.047 (3)	−0.002 (3)	0.019 (3)	0.000 (3)

Geometric parameters (Å, º)

Si1—N1	1.686 (3)	C7—H7B	0.9600
Si1—N2	1.767 (3)	C7—H7C	0.9600
Si1—C10	1.861 (4)	C8—H8A	0.9600
Si1—C9	1.864 (4)	C8—H8B	0.9600
Si1—Li1^i	2.602 (6)	C8—H8C	0.9600
N1—C1	1.402 (4)	C9—H9A	0.9600
N1—Li1	1.980 (6)	C9—H9B	0.9600
N1—Li1^i	2.006 (6)	C9—H9C	0.9600
N2—C12	1.460 (6)	C10—H10A	0.9600
N2—C11	1.469 (5)	C10—H10B	0.9600
N2—Li1^i	2.063 (6)	C10—H10C	0.9600
C1—C2	1.402 (4)	C11—H11A	0.9600
C1—C6	1.410 (4)	C11—H11B	0.9600
C1—Li1	2.542 (6)	C11—H11C	0.9600
C2—C3	1.380 (5)	C12—Li1^i	2.740 (7)
C2—C7	1.507 (5)	C12—H12A	0.9600
C3—C4	1.359 (6)	C12—H12B	0.9600
C3—H3A	0.9300	C12—H12C	0.9600
C4—C5	1.365 (6)	Li1—N1^i	2.006 (6)
C4—H4A	0.9300	Li1—N2^i	2.063 (6)
C5—C6	1.379 (5)	Li1—Li1^i	2.397 (11)
C5—H5A	0.9300	Li1—Si1^i	2.602 (6)
C6—C8	1.498 (5)	Li1—C12^i	2.740 (7)
C7—H7A	0.9600
N1—Si1—N2	102.12 (13)	C6—C8—H8C	109.5
N1—Si1—C10	113.81 (16)	H8A—C8—H8C	109.5
N2—Si1—C10	111.60 (17)	H8B—C8—H8C	109.5
N1—Si1—C9	116.19 (18)	Si1—C9—H9A	109.5
N2—Si1—C9	106.2 (2)	Si1—C9—H9B	109.5
C10—Si1—C9	106.67 (19)	H9A—C9—H9B	109.5
N1—Si1—Li1^i	50.43 (15)	Si1—C9—H9C	109.5
N2—Si1—Li1^i	52.19 (15)	H9A—C9—H9C	109.5
C10—Si1—Li1^i	133.89 (19)	H9B—C9—H9C	109.5
C9—Si1—Li1^i	119.1 (2)	Si1—C10—H10A	109.5
C1—N1—Si1	128.9 (2)	Si1—C10—H10B	109.5
C1—N1—Li1	96.0 (2)	H10A—C10—H10B	109.5
Si1—N1—Li1	126.3 (2)	Si1—C10—H10C	109.5
C1—N1—Li1^i	133.9 (3)	H10A—C10—H10C	109.5
Si1—N1—Li1^i	89.2 (2)	H10B—C10—H10C	109.5
Li1—N1—Li1^i	73.9 (3)	N2—C11—H11A	109.5
C12—N2—C11	111.0 (4)	N2—C11—H11B	109.5
C12—N2—Si1	116.7 (3)	H11A—C11—H11B	109.5
C11—N2—Si1	121.2 (3)	N2—C11—H11C	109.5
C12—N2—Li1^i	100.8 (3)	H11A—C11—H11C	109.5
C11—N2—Li1^i	117.7 (3)	H11B—C11—H11C	109.5
Si1—N2—Li1^i	85.2 (2)	N2—C12—Li1^i	47.7 (2)
N1—C1—C2	122.4 (3)	N2—C12—H12A	109.5
N1—C1—C6	120.2 (3)	Li1^i—C12—H12A	87.2
C2—C1—C6	117.2 (3)	N2—C12—H12B	109.5
N1—C1—Li1	50.77 (18)	Li1^i—C12—H12B	78.8
C2—C1—Li1	94.4 (2)	H12A—C12—H12B	109.5
C6—C1—Li1	122.1 (3)	N2—C12—H12C	109.5
C3—C2—C1	120.5 (3)	Li1^i—C12—H12C	156.4
C3—C2—C7	119.1 (3)	H12A—C12—H12C	109.5
C1—C2—C7	120.4 (3)	H12B—C12—H12C	109.5
C4—C3—C2	121.7 (4)	N1—Li1—N1^i	106.1 (3)
C4—C3—H3A	119.2	N1—Li1—N2^i	135.1 (3)
C2—C3—H3A	119.2	N1^i—Li1—N2^i	82.6 (2)
C3—C4—C5	118.8 (4)	N1—Li1—Li1^i	53.5 (2)
C3—C4—H4A	120.6	N1^i—Li1—Li1^i	52.5 (2)
C5—C4—H4A	120.6	N2^i—Li1—Li1^i	118.5 (4)
C4—C5—C6	121.9 (4)	N1—Li1—C1	33.28 (13)
C4—C5—H5A	119.1	N1^i—Li1—C1	126.7 (3)
C6—C5—H5A	119.1	N2^i—Li1—C1	106.7 (3)
C5—C6—C1	120.0 (3)	Li1^i—Li1—C1	79.0 (3)
C5—C6—C8	119.3 (3)	N1—Li1—Si1^i	126.6 (3)
C1—C6—C8	120.7 (3)	N1^i—Li1—Si1^i	40.39 (13)
C2—C7—H7A	109.5	N2^i—Li1—Si1^i	42.58 (14)
C2—C7—H7B	109.5	Li1^i—Li1—Si1^i	81.7 (3)
H7A—C7—H7B	109.5	C1—Li1—Si1^i	122.4 (2)
C2—C7—H7C	109.5	N1—Li1—C12^i	154.8 (3)
H7A—C7—H7C	109.5	N1^i—Li1—C12^i	93.9 (2)
H7B—C7—H7C	109.5	N2^i—Li1—C12^i	31.56 (17)
C6—C8—H8A	109.5	Li1^i—Li1—C12^i	143.5 (4)
C6—C8—H8B	109.5	C1—Li1—C12^i	121.6 (3)
H8A—C8—H8B	109.5	Si1^i—Li1—C12^i	61.94 (16)

Symmetry code: (i) −x+1, −y+2, −z.