[Benzyldi­methyl­(di­methyl­amino)­silyl-κ²C,N](N,N,N,N-tetra­methyl­enedi­amine-κ²N,N)­lithium(I)

The molecule of the title compound, [Li(C₁₁H₁₈NSi)(C₆H₁₆N₂)] contains a four-membered heterocycle with a folded conformation. The coordination around the Li, N, C and Si atoms in this ring is distorted tetrahedral.

Key indicators

• Single-crystal X-ray study
• T = 183 K
• Mean [sigma](C-C) = 0.008 Å
• R factor = 0.076
• wR factor = 0.104
• Data-to-parameter ratio = 16.7

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


 Alert Level C:



RINTA_01  Alert C The value of Rint is greater than 0.10
          Rint given   0.122

STRVAL_01
         From the CIF: _refine_ls_abs_structure_Flack   -0.300
         From the CIF: _refine_ls_abs_structure_Flack_su    0.300
           Alert C Flack parameter is too small

PLAT_213  Alert C Atom C17     has ADP max/min Ratio ...........       3.30 prolate

PLAT_320  Alert C Check Hybridisation of  C(14)  in Main Residue          ?

PLAT_320  Alert C Check Hybridisation of  C(15)  in Main Residue          ?

General Notes



REFLT_03
         From the CIF: _diffrn_reflns_theta_max           25.00
         From the CIF: _reflns_number_total               3588
         Count of symmetry unique reflns         2061
         Completeness (_total/calc)            174.09%
         TEST3: Check Friedels for noncentro structure
         Estimate of Friedel pairs measured      1527
         Fraction of Friedel pairs measured     0.741
         Are heavy atom types Z>Si present          yes
          Please check that the estimate of the number of Friedel pairs is
          correct. If it is not, please give the correct count in the
          _publ_section_exptl_refinement section of the submitted CIF.


 0 Alert Level A = Potentially serious problem

 0 Alert Level B = Potential problem

 5 Alert Level C = Please check

---

S1. Comment

Organolithium compounds are intriguing from a number of points of view, viz. structural, bond theoretical and practical. The N atom is found in a large number of saturated and unsaturated organolithium compounds, in segments such as N—Li—C, N—Li—N, Si—N—C, Si—N—Li, etc. Recently, we have synthesized the title compound, (I), containing the C—Si—N—Li ring. The title compound has unusual features and possesses important potential properties for the synthesis of other novel organometallic compounds. This compound has been characterized by single-crystal X-ray diffraction analysis. The geometric parameters of the heterocyclic moieties of (I) are listed in Table 1 and the molecular structure is illustrated in Fig 1.

The four-membered heterocyclic ring adopts a folded conformation. The angle between the C1—Li1—N1 and C1—Si1—N1 planes is 20.8°. The N atom is bonded to the Li atom and the ring contains a four-coordinate Li centre. As a consequence of the coordination of the N atom to the Li atom, the Si1—N1 bond [1.787 (4) Å] is longer than the N3—Si4 bond [1.748 (22) Å] involving three-coordinated nitrogen and four-coordinated silicon (Allen et al., 1987), as nitrogen is four-coordinated being bound to lithium. The bond angles Si1—C1—Li1, C1—Li1—N1, Li1—N1—Si1 and N1—Si1—C1 indicate that the C1, Li1, N1 and Si atoms are sp³-hybridized and coordination around each is distorted tetrahedral. The two Li1—N2 and Li1—N3 bond distances of the pentaatomic ring (see Table 1 and Fig. 1) are not significantly different and are a little shorter than the Li1—N1 bond of the tetraatomic ring. The Si1—N1 and Si1—C1 bond lengths are equal and a little shorter than the two Si1—C8 and Si1—C9 exocyclic bonds. The longest bond in the tetraatomic ring is Li1—C1 that is a little longer than the Csp²—Li(three-coordinated) bond [2.141 (4) Å] quoted in the literature (Hill & Hitchcock, 2002).

S2. Experimental

n-Butyllithium (molar ratio 1:1:1) was added dropwise to a solution of toluene and TMEDA (N,N,N',N'-tetramethylethylenediamine) in hexane at 273 K and the temperature was allowed to rise to room temperature. The mixture was stirred for more than 24 h and then N,N-dimethyldimethylchlorosilane [please check, no nitrogen in this compound] (molar ratio 1:1) was added at 273 K and the temperature was allowed to rise to room temperature. The mixture was stirred for a further 15 h, to yield a white precipitate (LiCl). The mixture was filtered and N,N-dimethyldimethylbenzylsilylamine was isolated by vacuum distillation as a colourless liquid. A solution of LiⁿBu in hexane was slowly added to N,N-dimethyldimethylbenzylsilylamine and TMEDA in pentane (molar ratio 1:1) at ambient temperature. The mixture was stirred for 18 h. The title compound was obtained, The precipitate of title compound which was dissolved in Et₂O. The solution was concentrated yielded a yellow crystal of the title compound carefully under vacuum. Crystals suitable for a single-crystal X-ray diffraction study were grown from a concentrated Et₂O solution at 253 K. All reactions were performed under argon using standard Schlenk techniques. The hexane was dried by distilling with a sodium–potassium alloy. Et₂O was distilled from an drying agent with sodium.

S3. Refinement

All H atoms were initially located in a difference Fourier map. The methyl H atoms were then constrained to an ideal geometry, with C—H distances of 0.98 Å and U_iso(H) = 1.5U_eq(C), but each group was allowed to rotate freely about the C—N bond, All other H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms, with C—H distances in the range 0.95–1.00 Å and U_iso(H) = 1.2U_eq(C).

Computing details

Data collection: SMART (Siemens, 1996); cell refinement: SAINT (Siemens, 1996); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: SHELXL97.

Figures

	Fig. 1. The molecular structure of (I), showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level. H atoms are represented by small spheres of arbitrary radii.
	Fig. 2. A packing diagram of the title molecule, viewed along the a axis. For clarity, all H atoms have been omitted.

[Dimethyl(dimethylamino)silicyl]benzyl-κ²C,N](N,N,N,N-tetramethylenediamine- κ²N,N)lithium(I)

Crystal data

[Li(C11H18NSi)(C6H16N2)]	Dx = 1.025 Mg m^−3
Mr = 315.50	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, P212121	Cell parameters from 436 reflections
a = 8.533 (4) Å	θ = 2.7–13.6°
b = 14.753 (6) Å	µ = 0.12 mm^−1
c = 16.241 (7) Å	T = 183 K
V = 2044.6 (15) Å^3	Block, yellow
Z = 4	0.2 × 0.2 × 0.2 mm
F(000) = 696

Data collection

Siemens SMART CCD area-detector diffractometer	3588 independent reflections
Radiation source: oil sealed	1645 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.122
ω scans	θmax = 25.0°, θmin = 1.9°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −8→10
Tmin = 0.977, Tmax = 0.977	k = −17→15
8455 measured reflections	l = −19→15

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.077	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.104	w = 1/[σ^2(Fo^2)]
S = 0.83	(Δ/σ)max = 0.002
3588 reflections	Δρmax = 0.24 e Å^−3
215 parameters	Δρmin = −0.24 e Å^−3
0 restraints	Absolute structure: (Flack, 1983)
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: −0.3 (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
Li1	0.8745 (10)	0.0886 (6)	0.7972 (6)	0.032 (2)
N1	1.1108 (4)	0.1042 (3)	0.8417 (3)	0.0344 (12)
N2	0.7606 (6)	0.1976 (3)	0.7418 (3)	0.0373 (14)
N3	0.7939 (6)	0.0058 (3)	0.7002 (3)	0.0401 (14)
Si1	1.02525 (16)	0.10344 (10)	0.94211 (11)	0.0328 (4)
C1	0.8315 (5)	0.0596 (3)	0.9304 (3)	0.0246 (14)
H1	0.7561	0.1037	0.9521	0.029*
C2	0.7662 (6)	−0.0292 (3)	0.9362 (3)	0.0259 (13)
C3	0.6033 (6)	−0.0446 (4)	0.9414 (4)	0.0321 (14)
H3	0.5371	0.0055	0.9414	0.039*
C4	0.5368 (7)	−0.1295 (4)	0.9463 (4)	0.0418 (16)
H4	0.4286	−0.1354	0.9506	0.050*
C5	0.6314 (7)	−0.2065 (4)	0.9450 (4)	0.0460 (18)
H5	0.5879	−0.2643	0.9475	0.055*
C6	0.7916 (7)	−0.1947 (4)	0.9399 (4)	0.0439 (17)
H6	0.8569	−0.2452	0.9395	0.053*
C7	0.8560 (5)	−0.1098 (4)	0.9355 (3)	0.0315 (13)
H7	0.9645	−0.1049	0.9318	0.038*
C8	1.0144 (6)	0.2246 (3)	0.9743 (3)	0.0463 (18)
H8A	1.1183	0.2471	0.9845	0.069*
H8B	0.9532	0.2295	1.0237	0.069*
H8C	0.9663	0.2597	0.9314	0.069*
C9	1.1636 (6)	0.0445 (4)	1.0145 (4)	0.0543 (19)
H9A	1.1672	−0.0189	1.0015	0.081*
H9B	1.1277	0.0523	1.0701	0.081*
H9C	1.2665	0.0701	1.0090	0.081*
C10	1.2285 (6)	0.1734 (4)	0.8225 (4)	0.065 (2)
H10A	1.3267	0.1569	0.8472	0.098*
H10B	1.1948	0.2308	0.8439	0.098*
H10C	1.2410	0.1777	0.7639	0.098*
C11	1.1737 (6)	0.0154 (4)	0.8153 (4)	0.055 (2)
H11A	1.1904	0.0158	0.7568	0.083*
H11B	1.1002	−0.0315	0.8291	0.083*
H11C	1.2713	0.0041	0.8428	0.083*
C12	0.6756 (8)	0.2604 (5)	0.7947 (4)	0.098 (3)
H12A	0.6296	0.3074	0.7617	0.147*
H12B	0.7466	0.2868	0.8338	0.147*
H12C	0.5945	0.2283	0.8235	0.147*
C13	0.8727 (7)	0.2514 (4)	0.6950 (4)	0.087 (3)
H13A	0.9400	0.2119	0.6642	0.131*
H13B	0.9345	0.2873	0.7321	0.131*
H13C	0.8173	0.2906	0.6578	0.131*
C16	0.9085 (7)	−0.0416 (4)	0.6498 (4)	0.071 (2)
H16A	0.9611	−0.0865	0.6825	0.107*
H16B	0.9838	0.0010	0.6290	0.107*
H16C	0.8562	−0.0706	0.6046	0.107*
C17	0.6813 (8)	−0.0602 (4)	0.7316 (4)	0.094 (3)
H17A	0.6321	−0.0908	0.6863	0.142*
H17B	0.6032	−0.0296	0.7638	0.142*
H17C	0.7348	−0.1037	0.7655	0.142*
C14	0.7091 (8)	0.0706 (4)	0.6469 (4)	0.056 (2)
H14A	0.6251	0.0387	0.6189	0.067*
H14B	0.7806	0.0932	0.6053	0.067*
C15	0.6414 (9)	0.1492 (5)	0.6927 (5)	0.073 (3)
H15A	0.765 (5)	0.147 (3)	0.643 (3)	0.030 (15)*
H15B	0.586 (7)	0.210 (4)	0.671 (4)	0.15 (3)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Li1	0.040 (6)	0.035 (6)	0.021 (6)	0.012 (5)	−0.004 (5)	0.001 (5)
N1	0.036 (3)	0.026 (3)	0.042 (3)	−0.002 (3)	0.009 (2)	−0.002 (3)
N2	0.041 (3)	0.033 (3)	0.038 (4)	0.005 (3)	0.003 (3)	0.001 (3)
N3	0.046 (4)	0.043 (3)	0.031 (3)	0.008 (3)	0.001 (3)	0.004 (3)
Si1	0.0321 (9)	0.0344 (9)	0.0319 (10)	0.0008 (9)	−0.0022 (9)	−0.0021 (9)
C1	0.017 (3)	0.022 (3)	0.034 (4)	0.002 (3)	0.012 (3)	−0.004 (3)
C2	0.030 (3)	0.037 (4)	0.011 (3)	0.001 (3)	−0.005 (3)	−0.002 (3)
C3	0.037 (4)	0.035 (4)	0.025 (4)	−0.003 (3)	−0.010 (4)	0.006 (3)
C4	0.045 (4)	0.049 (4)	0.031 (4)	−0.008 (4)	−0.008 (4)	0.008 (3)
C5	0.068 (5)	0.027 (4)	0.043 (5)	−0.029 (4)	−0.008 (4)	0.000 (3)
C6	0.054 (5)	0.032 (4)	0.046 (5)	−0.005 (3)	−0.014 (4)	0.006 (4)
C7	0.036 (3)	0.034 (3)	0.025 (4)	0.002 (3)	−0.006 (3)	−0.008 (3)
C8	0.046 (4)	0.042 (4)	0.051 (5)	−0.017 (4)	−0.002 (3)	−0.008 (3)
C9	0.044 (4)	0.066 (5)	0.053 (5)	0.002 (4)	−0.017 (4)	0.006 (4)
C10	0.061 (5)	0.070 (5)	0.064 (6)	−0.021 (4)	0.025 (4)	0.006 (4)
C11	0.041 (4)	0.074 (5)	0.051 (5)	−0.008 (4)	−0.003 (4)	−0.009 (4)
C12	0.103 (6)	0.118 (7)	0.073 (7)	0.070 (6)	0.003 (5)	−0.001 (5)
C13	0.076 (6)	0.073 (6)	0.113 (8)	0.004 (5)	0.015 (6)	0.051 (5)
C16	0.091 (6)	0.060 (5)	0.063 (6)	0.041 (4)	−0.007 (5)	−0.019 (4)
C17	0.148 (7)	0.111 (7)	0.025 (5)	−0.076 (6)	−0.024 (5)	0.019 (4)
C14	0.056 (5)	0.058 (5)	0.053 (6)	0.002 (4)	−0.015 (4)	−0.003 (4)
C15	0.083 (6)	0.060 (6)	0.076 (7)	0.034 (5)	−0.028 (5)	−0.027 (5)

Geometric parameters (Å, º)

Li1—N2	2.083 (9)	N3—C14	1.479 (7)
Li1—N3	2.108 (10)	Si1—C1	1.785 (4)
Li1—N1	2.155 (9)	Si1—C8	1.865 (5)
Li1—C1	2.235 (10)	Si1—C9	1.879 (5)
N1—C10	1.465 (6)	C1—C2	1.428 (6)
N1—C11	1.479 (6)	C2—C3	1.411 (6)
N1—Si1	1.787 (4)	C2—C7	1.415 (6)
N2—C12	1.457 (7)	C3—C4	1.377 (6)
N2—C13	1.457 (6)	C4—C5	1.395 (7)
N2—C15	1.477 (8)	C5—C6	1.381 (6)
N3—C16	1.455 (6)	C6—C7	1.369 (6)
N3—C17	1.460 (7)	C14—C15	1.495 (8)
N2—Li1—N3	88.4 (4)	C17—N3—Li1	109.9 (5)
N2—Li1—N1	119.9 (5)	C14—N3—Li1	102.8 (4)
N3—Li1—N1	128.1 (5)	C1—Si1—N1	106.5 (2)
N2—Li1—C1	119.3 (4)	C1—Si1—C8	109.3 (2)
N3—Li1—C1	123.9 (5)	N1—Si1—C8	105.7 (2)
N1—Li1—C1	81.4 (3)	C1—Si1—C9	118.8 (2)
C10—N1—C11	107.9 (4)	N1—Si1—C9	108.5 (2)
C10—N1—Si1	118.5 (4)	C8—Si1—C9	107.4 (3)
C11—N1—Si1	114.0 (4)	C2—C1—Si1	133.4 (4)
C10—N1—Li1	130.1 (4)	C2—C1—Li1	107.7 (4)
C11—N1—Li1	98.5 (4)	Si1—C1—Li1	83.2 (3)
Si1—N1—Li1	85.6 (3)	C3—C2—C7	113.5 (5)
C12—N2—C13	106.8 (5)	C3—C2—C1	122.4 (5)
C12—N2—C15	106.4 (5)	C7—C2—C1	124.0 (5)
C13—N2—C15	115.7 (6)	C4—C3—C2	123.7 (5)
C12—N2—Li1	117.9 (5)	C3—C4—C5	120.1 (5)
C13—N2—Li1	109.9 (4)	C6—C5—C4	118.1 (5)
C15—N2—Li1	100.4 (5)	C7—C6—C5	121.1 (5)
C16—N3—C17	108.5 (5)	C6—C7—C2	123.4 (5)
C16—N3—C14	108.0 (5)	N3—C14—C15	113.6 (6)
C17—N3—C14	108.3 (5)	N2—C15—C14	112.2 (6)
C16—N3—Li1	118.7 (4)