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metal-organic compounds
The title compound, [Li2(C13H22N2Si)2(C4H10O)2], possesses a dinuclear structure featuring four-coordinate Li atoms, each of which shows a further, weak, contact to the central C atom of the NCN linkage of the amidinate ligand. The molecules possess crystallographically imposed inversion symmetry.
Supporting information
 | Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536802017579/bt6195sup1.cif |
 | Structure factor file (CIF format) https://doi.org/10.1107/S1600536802017579/bt6195Isup2.hkl |
CCDC reference: 198321
![[sigma]](https://journals.iucr.org/logos/entities/sigma_rmgif.gif){kind=small}
(C-C) = 0.003 Å
Alert Level C:
Experimental top
The title compound was prepared according to previously described procedures (Boyd et al., 2002). Crystallization of the crude product from a mixture of hexane and Et2O afforded the title compound as air-sensitive colourless blocks.
Refinement top
All H atoms were placed geometrically. Refinement was carried out against 4117 data with I ≥ 0.
Computing details top
Data collection: COLLECT (Nonius, 2000); cell refinement: DENZO; data reduction: DENZO (Otwinowski & Minor, 1997); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: CRYSTALS (Watkin et al., 2001); molecular graphics: CAMERON (Watkin et al., 2001); software used to prepare material for publication: CRYSTALS.
Figures top
![[Figure 1]](https://journals.iucr.org/e/issues/2002/10/00/bt6195/bt6195fig1thm.gif)
| Fig. 1. View of the molecular structure of (I). Displacement parameters are drawn at the 20% probability level and H atoms have been omitted for clarity. Atoms carrying the suffix A are related to their counterparts by the symmetry code (1 − x, 1 − y, 2 − z). |
Bis(µ-N-n-propyl-N-trimethylsilylbenzamidinato)bis[(diethyl ether-O)lithium] top
Crystal data top
| [Li2(C13H22N2Si)2(C4H10O)2] | Z = 1 |
| Mr = 628.94 | F(000) = 344.000 |
| Triclinic, P1 | Dx = 1.078 Mg m−3 |
| a = 8.4111 (17) Å | Mo Kα radiation, λ = 0.71073 Å |
| b = 10.486 (2) Å | Cell parameters from 3991 reflections |
| c = 11.774 (2) Å | θ = 5–27° |
| α = 106.59 (3)° | µ = 0.12 mm−1 |
| β = 96.05 (3)° | T = 150 K |
| γ = 99.38 (3)° | Block, colourless |
| V = 969.2 (4) Å3 | 0.32 × 0.28 × 0.28 mm |
Data collection top
| Enraf-Nonius KappaCCD diffractometer | 2907 reflections with I > 2σ(I) |
| Graphite monochromator | Rint = 0.02 |
| ϕ and ω scans | θmax = 27.5°, θmin = 5.1° |
| Absorption correction: multi-scan DENZO (Otwinowski & Minor, 1997) | h = −10→10 |
| Tmin = 0.97, Tmax = 0.97 | k = −13→13 |
| 7923 measured reflections | l = −14→15 |
| 4372 independent reflections |
Refinement top
| Refinement on F | Primary atom site location: direct methods |
| Least-squares matrix: full | Hydrogen site location: geometric |
| R[F2 > 2σ(F2)] = 0.046 | H-atom parameters constrained |
| wR(F2) = 0.042 | Prince modified Chebychev polynomial (Watkin, 1994), W = [weight][1-(ΔF/6σF)2]2, with -0.679 -2.35 -1.48 -0.984 -0.429 |
| S = 1.05 | (Δ/σ)max = 0.0003 |
| 4117 reflections | Δρmax = 0.39 e Å−3 |
| 199 parameters | Δρmin = −0.47 e Å−3 |
| 0 restraints |
Crystal data top
| [Li2(C13H22N2Si)2(C4H10O)2] | γ = 99.38 (3)° |
| Mr = 628.94 | V = 969.2 (4) Å3 |
| Triclinic, P1 | Z = 1 |
| a = 8.4111 (17) Å | Mo Kα radiation |
| b = 10.486 (2) Å | µ = 0.12 mm−1 |
| c = 11.774 (2) Å | T = 150 K |
| α = 106.59 (3)° | 0.32 × 0.28 × 0.28 mm |
| β = 96.05 (3)° |
Data collection top
| Enraf-Nonius KappaCCD diffractometer | 4372 independent reflections |
| Absorption correction: multi-scan DENZO (Otwinowski & Minor, 1997) | 2907 reflections with I > 2σ(I) |
| Tmin = 0.97, Tmax = 0.97 | Rint = 0.02 |
| 7923 measured reflections |
Refinement top
| R[F2 > 2σ(F2)] = 0.046 | 0 restraints |
| wR(F2) = 0.042 | H-atom parameters constrained |
| S = 1.05 | Δρmax = 0.39 e Å−3 |
| 4117 reflections | Δρmin = −0.47 e Å−3 |
| 199 parameters |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
| x | y | z | Uiso*/Ueq | ||
| Li1 | 0.4338 (4) | 0.5154 (3) | 0.9058 (3) | 0.0291 | |
| N1 | 0.48608 (18) | 0.34673 (15) | 0.79445 (13) | 0.0256 | |
| N2 | 0.38630 (18) | 0.34084 (15) | 0.96694 (13) | 0.0256 | |
| O1 | 0.23336 (16) | 0.58181 (14) | 0.87477 (11) | 0.0332 | |
| Si1 | 0.55364 (6) | 0.29411 (6) | 0.66023 (4) | 0.0284 | |
| C1 | 0.3952 (2) | 0.27907 (17) | 0.85265 (15) | 0.0243 | |
| C2 | 0.2989 (2) | 0.13717 (18) | 0.78689 (15) | 0.0259 | |
| C3 | 0.3693 (2) | 0.02470 (19) | 0.78300 (17) | 0.0319 | |
| C4 | 0.2847 (3) | −0.1046 (2) | 0.71626 (19) | 0.0396 | |
| C5 | 0.1290 (3) | −0.1239 (2) | 0.65442 (18) | 0.0403 | |
| C6 | 0.0573 (2) | −0.0130 (2) | 0.65930 (18) | 0.0385 | |
| C7 | 0.1418 (2) | 0.1168 (2) | 0.72489 (18) | 0.0338 | |
| C8 | 0.2709 (2) | 0.27532 (19) | 1.02876 (16) | 0.0277 | |
| C9 | 0.3518 (2) | 0.2094 (2) | 1.11195 (18) | 0.0350 | |
| C10 | 0.2343 (3) | 0.1571 (2) | 1.18636 (19) | 0.0411 | |
| C11 | 0.7231 (3) | 0.2005 (2) | 0.67087 (18) | 0.0386 | |
| C12 | 0.3989 (3) | 0.1847 (2) | 0.52779 (17) | 0.0450 | |
| C13 | 0.6403 (3) | 0.4523 (2) | 0.62602 (19) | 0.0394 | |
| C14 | 0.1588 (3) | 0.4841 (2) | 0.66233 (19) | 0.0474 | |
| C15 | 0.1012 (3) | 0.5436 (2) | 0.77804 (19) | 0.0419 | |
| C16 | 0.1902 (2) | 0.6552 (2) | 0.98717 (17) | 0.0360 | |
| C17 | 0.1981 (3) | 0.8032 (2) | 0.9993 (2) | 0.0442 | |
| H31 | 0.4813 (2) | 0.03798 (19) | 0.82822 (17) | 0.0394* | |
| H41 | 0.3366 (3) | −0.1845 (2) | 0.71336 (19) | 0.0450* | |
| H51 | 0.0688 (3) | −0.2175 (2) | 0.60636 (18) | 0.0458* | |
| H61 | −0.0552 (2) | −0.0263 (2) | 0.61487 (18) | 0.0425* | |
| H71 | 0.0895 (2) | 0.1967 (2) | 0.72875 (18) | 0.0406* | |
| H81 | 0.2168 (2) | 0.34545 (19) | 1.07744 (16) | 0.0366* | |
| H82 | 0.1867 (2) | 0.20385 (19) | 0.96695 (16) | 0.0366* | |
| H91 | 0.4450 (2) | 0.2780 (2) | 1.16757 (18) | 0.0476* | |
| H92 | 0.3939 (2) | 0.1313 (2) | 1.06246 (18) | 0.0476* | |
| H101 | 0.2916 (3) | 0.1143 (2) | 1.24002 (19) | 0.0557* | |
| H102 | 0.1922 (3) | 0.2349 (2) | 1.23622 (19) | 0.0557* | |
| H103 | 0.1410 (3) | 0.0882 (2) | 1.13112 (19) | 0.0557* | |
| H111 | 0.7597 (3) | 0.1714 (2) | 0.59101 (18) | 0.0493* | |
| H112 | 0.8166 (3) | 0.2618 (2) | 0.73191 (18) | 0.0493* | |
| H113 | 0.6840 (3) | 0.1187 (2) | 0.69559 (18) | 0.0493* | |
| H121 | 0.4527 (3) | 0.1606 (2) | 0.45493 (17) | 0.0512* | |
| H122 | 0.3495 (3) | 0.0998 (2) | 0.54444 (17) | 0.0512* | |
| H123 | 0.3115 (3) | 0.2352 (2) | 0.51359 (17) | 0.0512* | |
| H131 | 0.6822 (3) | 0.4276 (2) | 0.54789 (19) | 0.0499* | |
| H132 | 0.7317 (3) | 0.5085 (2) | 0.69142 (19) | 0.0499* | |
| H133 | 0.5530 (3) | 0.5056 (2) | 0.62041 (19) | 0.0499* | |
| H141 | 0.0663 (3) | 0.4568 (2) | 0.59397 (19) | 0.0569* | |
| H142 | 0.2463 (3) | 0.5537 (2) | 0.65028 (19) | 0.0569* | |
| H143 | 0.2041 (3) | 0.4025 (2) | 0.66583 (19) | 0.0569* | |
| H151 | 0.0562 (3) | 0.6253 (2) | 0.77504 (19) | 0.0481* | |
| H152 | 0.0139 (3) | 0.4742 (2) | 0.79059 (19) | 0.0481* | |
| H161 | 0.2681 (2) | 0.6485 (2) | 1.05450 (17) | 0.0455* | |
| H162 | 0.0767 (2) | 0.6132 (2) | 0.99236 (17) | 0.0455* | |
| H171 | 0.1680 (3) | 0.8508 (2) | 1.0781 (2) | 0.0539* | |
| H172 | 0.3115 (3) | 0.8460 (2) | 0.9946 (2) | 0.0539* | |
| H173 | 0.1201 (3) | 0.8107 (2) | 0.9324 (2) | 0.0539* |
Atomic displacement parameters (Å2) top
| U11 | U22 | U33 | U12 | U13 | U23 | |
| Li1 | 0.0318 (16) | 0.0257 (15) | 0.0263 (15) | 0.0074 (12) | 0.0018 (12) | 0.0027 (12) |
| N1 | 0.0269 (7) | 0.0246 (7) | 0.0234 (7) | 0.0037 (6) | 0.0050 (6) | 0.0047 (6) |
| N2 | 0.0272 (8) | 0.0259 (8) | 0.0232 (7) | 0.0051 (6) | 0.0048 (6) | 0.0068 (6) |
| O1 | 0.0288 (7) | 0.0401 (8) | 0.0286 (7) | 0.0116 (6) | 0.0003 (5) | 0.0060 (6) |
| Si1 | 0.0266 (3) | 0.0322 (3) | 0.0225 (2) | 0.0036 (2) | 0.00445 (19) | 0.0035 (2) |
| C1 | 0.0219 (8) | 0.0244 (8) | 0.0254 (8) | 0.0062 (6) | 0.0020 (6) | 0.0056 (7) |
| C2 | 0.0260 (9) | 0.0267 (9) | 0.0236 (8) | 0.0033 (7) | 0.0050 (7) | 0.0063 (7) |
| C3 | 0.032 (1) | 0.029 (1) | 0.032 (1) | 0.0058 (8) | 0.0035 (8) | 0.0071 (8) |
| C4 | 0.0461 (12) | 0.026 (1) | 0.0429 (12) | 0.0047 (9) | 0.0096 (9) | 0.0051 (8) |
| C5 | 0.0448 (12) | 0.031 (1) | 0.0350 (11) | −0.0053 (9) | 0.0076 (9) | 0.0009 (8) |
| C6 | 0.030 (1) | 0.0431 (12) | 0.032 (1) | −0.0061 (8) | −0.0015 (8) | 0.0064 (9) |
| C7 | 0.0278 (9) | 0.034 (1) | 0.037 (1) | 0.0041 (8) | 0.0023 (8) | 0.0081 (8) |
| C8 | 0.0260 (9) | 0.0297 (9) | 0.0275 (9) | 0.0061 (7) | 0.0070 (7) | 0.0080 (7) |
| C9 | 0.035 (1) | 0.0382 (11) | 0.036 (1) | 0.0084 (8) | 0.0086 (8) | 0.0156 (9) |
| C10 | 0.0487 (13) | 0.0405 (12) | 0.0418 (12) | 0.009 (1) | 0.017 (1) | 0.021 (1) |
| C11 | 0.0389 (11) | 0.0413 (12) | 0.0375 (11) | 0.0150 (9) | 0.0132 (9) | 0.0089 (9) |
| C12 | 0.0405 (12) | 0.0562 (14) | 0.024 (1) | 0.000 (1) | 0.0030 (8) | −0.0034 (9) |
| C13 | 0.0411 (12) | 0.0440 (12) | 0.0356 (11) | 0.0056 (9) | 0.0101 (9) | 0.0167 (9) |
| C14 | 0.0529 (14) | 0.0522 (14) | 0.0319 (11) | 0.0142 (11) | −0.0040 (9) | 0.007 (1) |
| C15 | 0.031 (1) | 0.0489 (13) | 0.0376 (11) | 0.0054 (9) | −0.0055 (8) | 0.0063 (9) |
| C16 | 0.033 (1) | 0.0443 (12) | 0.031 (1) | 0.0116 (9) | 0.0052 (8) | 0.0083 (9) |
| C17 | 0.0421 (12) | 0.0394 (12) | 0.0444 (12) | 0.0089 (9) | 0.0045 (9) | 0.003 (1) |
Geometric parameters (Å, º) top
| Li1—N1 | 2.023 (3) | C8—H82 | 1.000 |
| Li1—N2 | 2.145 (3) | C9—C10 | 1.525 (3) |
| Li1—N2i | 2.073 (3) | C9—H91 | 1.000 |
| Li1—O1 | 1.965 (3) | C9—H92 | 1.000 |
| Li1—C1 | 2.334 (3) | C10—H101 | 1.000 |
| N1—Si1 | 1.7083 (15) | C10—H102 | 1.000 |
| N1—C1 | 1.330 (2) | C10—H103 | 1.000 |
| N2—C1 | 1.332 (2) | C11—H111 | 1.000 |
| N2—C8 | 1.470 (2) | C11—H112 | 1.000 |
| O1—C15 | 1.421 (2) | C11—H113 | 1.000 |
| O1—C16 | 1.444 (2) | C12—H121 | 1.000 |
| Si1—C11 | 1.871 (2) | C12—H122 | 1.000 |
| Si1—C12 | 1.872 (2) | C12—H123 | 1.000 |
| Si1—C13 | 1.870 (2) | C13—H131 | 1.000 |
| C1—C2 | 1.512 (2) | C13—H132 | 1.000 |
| C2—C3 | 1.395 (3) | C13—H133 | 1.000 |
| C2—C7 | 1.393 (3) | C14—C15 | 1.494 (3) |
| C3—C4 | 1.386 (3) | C14—H141 | 1.000 |
| C3—H31 | 1.000 | C14—H142 | 1.000 |
| C4—C5 | 1.384 (3) | C14—H143 | 1.000 |
| C4—H41 | 1.000 | C15—H151 | 1.000 |
| C5—C6 | 1.384 (3) | C15—H152 | 1.000 |
| C5—H51 | 1.000 | C16—C17 | 1.507 (3) |
| C6—C7 | 1.387 (3) | C16—H161 | 1.000 |
| C6—H61 | 1.000 | C16—H162 | 1.000 |
| C7—H71 | 1.000 | C17—H171 | 1.000 |
| C8—C9 | 1.516 (3) | C17—H172 | 1.000 |
| C8—H81 | 1.000 | C17—H173 | 1.000 |
| N1—Li1—N2 | 66.61 (11) | C10—C9—H91 | 108.79 |
| N1—Li1—N2i | 121.29 (16) | C8—C9—H92 | 108.7 |
| N2—Li1—N2i | 107.22 (14) | C10—C9—H92 | 108.80 |
| N1—Li1—O1 | 123.08 (16) | H91—C9—H92 | 109.467 |
| N2—Li1—O1 | 111.49 (16) | C9—C10—H101 | 110.21 |
| N2i—Li1—O1 | 113.47 (15) | C9—C10—H102 | 109.10 |
| Li1—N1—Si1 | 140.05 (12) | H101—C10—H102 | 109.476 |
| Li1—N1—C1 | 85.59 (14) | C9—C10—H103 | 109.09 |
| Si1—N1—C1 | 131.63 (13) | H101—C10—H103 | 109.476 |
| Li1—N2—Li1i | 72.78 (14) | H102—C10—H103 | 109.476 |
| Li1—N2—C1 | 80.64 (13) | Si1—C11—H111 | 109.54 |
| Li1i—N2—C1 | 127.44 (15) | Si1—C11—H112 | 109.21 |
| Li1—N2—C8 | 141.30 (14) | H111—C11—H112 | 109.476 |
| Li1i—N2—C8 | 108.94 (14) | Si1—C11—H113 | 109.65 |
| C1—N2—C8 | 119.81 (15) | H111—C11—H113 | 109.476 |
| Li1—O1—C15 | 134.78 (15) | H112—C11—H113 | 109.476 |
| Li1—O1—C16 | 109.67 (14) | Si1—C12—H121 | 109.76 |
| C15—O1—C16 | 112.43 (15) | Si1—C12—H122 | 109.22 |
| N1—Si1—C11 | 111.66 (9) | H121—C12—H122 | 109.476 |
| N1—Si1—C12 | 117.17 (9) | Si1—C12—H123 | 109.42 |
| C11—Si1—C12 | 106.78 (11) | H121—C12—H123 | 109.476 |
| N1—Si1—C13 | 105.94 (9) | H122—C12—H123 | 109.476 |
| C11—Si1—C13 | 107.1 (1) | Si1—C13—H131 | 109.50 |
| C12—Si1—C13 | 107.7 (1) | Si1—C13—H132 | 109.55 |
| N1—C1—N2 | 118.71 (16) | H131—C13—H132 | 109.475 |
| N1—C1—C2 | 119.68 (15) | Si1—C13—H133 | 109.36 |
| N2—C1—C2 | 121.55 (15) | H131—C13—H133 | 109.476 |
| C1—C2—C3 | 120.25 (16) | H132—C13—H133 | 109.476 |
| C1—C2—C7 | 120.77 (16) | C15—C14—H141 | 110.17 |
| C3—C2—C7 | 118.91 (17) | C15—C14—H142 | 108.86 |
| C2—C3—C4 | 120.14 (19) | H141—C14—H142 | 109.476 |
| C2—C3—H31 | 119.62 | C15—C14—H143 | 109.37 |
| C4—C3—H31 | 120.24 | H141—C14—H143 | 109.476 |
| C3—C4—C5 | 120.6 (2) | H142—C14—H143 | 109.476 |
| C3—C4—H41 | 119.56 | O1—C15—C14 | 109.84 (17) |
| C5—C4—H41 | 119.88 | O1—C15—H151 | 109.45 |
| C4—C5—C6 | 119.64 (18) | C14—C15—H151 | 109.64 |
| C4—C5—H51 | 120.05 | O1—C15—H152 | 109.28 |
| C6—C5—H51 | 120.31 | C14—C15—H152 | 109.14 |
| C5—C6—C7 | 120.16 (19) | H151—C15—H152 | 109.467 |
| C5—C6—H61 | 120.02 | O1—C16—C17 | 112.18 (17) |
| C7—C6—H61 | 119.82 | O1—C16—H161 | 108.7 |
| C2—C7—C6 | 120.58 (9) | C17—C16—H161 | 108.63 |
| C2—C7—H71 | 119.36 | O1—C16—H162 | 109.0 |
| C6—C7—H71 | 120.06 | C17—C16—H162 | 108.87 |
| N2—C8—C9 | 113.22 (15) | H161—C16—H162 | 109.467 |
| N2—C8—H81 | 108.73 | C16—C17—H171 | 109.97 |
| C9—C8—H81 | 108.3 | C16—C17—H172 | 109.33 |
| N2—C8—H82 | 108.55 | H171—C17—H172 | 109.476 |
| C9—C8—H82 | 108.5 | C16—C17—H173 | 109.09 |
| H81—C8—H82 | 109.467 | H171—C17—H173 | 109.476 |
| C8—C9—C10 | 112.37 (17) | H172—C17—H173 | 109.476 |
| C8—C9—H91 | 108.7 |
| Symmetry code: (i) −x+1, −y+1, −z+2. |
Experimental details
| Crystal data | |
| Chemical formula | [Li2(C13H22N2Si)2(C4H10O)2] |
| Mr | 628.94 |
| Crystal system, space group | Triclinic, P1 |
| Temperature (K) | 150 |
| a, b, c (Å) | 8.4111 (17), 10.486 (2), 11.774 (2) |
| α, β, γ (°) | 106.59 (3), 96.05 (3), 99.38 (3) |
| V (Å3) | 969.2 (4) |
| Z | 1 |
| Radiation type | Mo Kα |
| µ (mm−1) | 0.12 |
| Crystal size (mm) | 0.32 × 0.28 × 0.28 |
| Data collection | |
| Diffractometer | Enraf-Nonius KappaCCD diffractometer |
| Absorption correction | Multi-scan DENZO (Otwinowski & Minor, 1997) |
| Tmin, Tmax | 0.97, 0.97 |
| No. of measured, independent and observed [I > 2σ(I)] reflections | 7923, 4372, 2907 |
| Rint | 0.02 |
| (sin θ/λ)max (Å−1) | 0.650 |
| Refinement | |
| R[F2 > 2σ(F2)], wR(F2), S | 0.046, 0.042, 1.05 |
| No. of reflections | 4117 |
| No. of parameters | 199 |
| H-atom treatment | H-atom parameters constrained |
| Δρmax, Δρmin (e Å−3) | 0.39, −0.47 |
Computer programs: COLLECT (Nonius, 2000), DENZO (Otwinowski & Minor, 1997), SIR97 (Altomare et al., 1999), CRYSTALS (Watkin et al., 2001), CAMERON (Watkin et al., 2001), CRYSTALS.
Selected geometric parameters (Å, º) top
| Li1—N1 | 2.023 (3) | N1—Si1 | 1.7083 (15) |
| Li1—N2 | 2.145 (3) | N1—C1 | 1.330 (2) |
| Li1—N2i | 2.073 (3) | N2—C1 | 1.332 (2) |
| Li1—O1 | 1.965 (3) | N2—C8 | 1.470 (2) |
| Li1—C1 | 2.334 (3) | C1—C2 | 1.512 (2) |
| N1—Li1—N2 | 66.61 (11) | Li1i—N2—C1 | 127.44 (15) |
| N1—Li1—N2i | 121.29 (16) | Li1—N2—C8 | 141.30 (14) |
| N2—Li1—N2i | 107.22 (14) | Li1i—N2—C8 | 108.94 (14) |
| N1—Li1—O1 | 123.08 (16) | C1—N2—C8 | 119.81 (15) |
| N2—Li1—O1 | 111.49 (16) | Li1—O1—C15 | 134.78 (15) |
| N2i—Li1—O1 | 113.47 (15) | Li1—O1—C16 | 109.67 (14) |
| Li1—N1—Si1 | 140.05 (12) | C15—O1—C16 | 112.43 (15) |
| Li1—N1—C1 | 85.59 (14) | N1—C1—N2 | 118.71 (16) |
| Si1—N1—C1 | 131.63 (13) | N1—C1—C2 | 119.68 (15) |
| Li1—N2—Li1i | 72.78 (14) | N2—C1—C2 | 121.55 (15) |
| Li1—N2—C1 | 80.64 (13) |
| Symmetry code: (i) −x+1, −y+1, −z+2. |
In recent years, there has been much interest in N-silylated benzamidinates (Edelmann, 1994). New types of amidinate ligands with pendant amine or pyridine functionalities have recently been reported (Brandsma et al., 1998; Doyle et al., 2000; Kincaid et al., 1999). We have been interested in developing the chemistry of pendant-arm-functionalized amidinates as supporting ligands for group 4 imido chemistry (Boyd et al., 2002). As part of these studies, we were interested in using an N-propyl-substituted benzamidinate ligand, namely Me3SiNC(Ph)NCH2CH2CH3, for comparison with the pendant alkylamine-substituted amidinates Me3SiNC(Ph)NCH2CH2NMe2 and Me3SiNC(Ph)NCH2CH2CH2NMe2 (Brandsma et al., 1998; Doyle et al., 2000). We describe here the structure of the diethyl ether adduct of the lithium salt of this ligand, (I).
Molecules of (I) adopt a dinuclear structure in the solid state, possessing crystallographically imposed Ci molecular symmetry. Each Li atom, and each propyl-substituted benzamidinate N atom, is four-coordinated, with Li deviating the most from an ideal tetrahedral geometry due to the restricted bite angle of the amidinate group. The central motif of the structure is a four-membered ring of alternating Li and N atoms, which is planar by symmetry. To either end of this ring is fused another, slightly-puckered, four-membered ring. This puckering sees atoms C1 and Li lying out of the Li1/N1/C1/N2 least-squares plane of the ring by ca 0.19 and 0.07 Å, respectively. This creates a close Li1···C1 contact of 2.334 (3) Å which is possibly electrostatic in nature. This distance is at the lower end of Li···CN2 distances observed for other lithiated amidinates, which are in the range ca 2.30–2.42 Å (Fletcher et al., 1996). The Li—N distances and N—Li—N angles in (I) span the typical ranges reported for lithiated amides (Fletcher et al., 1996; Allen & Kennard, 1993).
The structural motif in (I) is closely related to that of the Li salt of the pendant N-propylamine-substituted ligand, namely Li2{Me3SiNC(Ph)NCH2CH2CH2NMe2}2, synthesized by Lappert and co-workers (Doyle et al., 2000). In this case, there is no Et2O coordinated to Li and the remaining site is occupied by the chelating pendant amine N-donor.