Structure of compounds E(SnMe₃)₄ (E = Si, Ge) as seen by high-resolution X-ray powder diffraction and solid-state NMR

The compounds tetrakis(trimethylstannyl)germane, Ge(SnMe₃)₄ (1), and tetrakis(trimethylstannyl)silane, Si(SnMe₃)₄ (2), have crystal structures with the quasispherical molecules in a closed-packed stacking. At room temperature both structures have the space group P (Z = 2) with a = 9.94457 (5), b = 14.52927 (8), c = 9.16021 (5) Å, α = 90.53390 (30), β = 111.73080 (30), γ = 90.0049 (4)°, and V = 1229.414 (12) ų for (1) and a = 9.92009 (7), b = 14.51029 (11), c = 9.13585 (7) Å, α = 90.4769 (4), β = 111.6724 (4), γ = 89.9877 (6)°, and V = 1222.037 (16) ų for (2). The molecules are found to be ordered as a result of steric interactions between neighboring molecules, as shown by analyzing the distances between the atoms. Upon heating, both compounds undergo a first-order phase transition at temperatures T_c = 348 ± 5 K, as characterized by a relative jump of the lattice parameter of ∼16%. At 353 K, both structures have the space group P (Z = 4), with a = 14.2037 (2) Å, and V = 2865.52 (7) ų for (1) and a = 14.1346 (2) Å, and V = 2823.90 (7) ų for (2). Rietveld refinements were performed for the low-temperature phases measured at T = 295 K [R_wp = 0.0844 for (1), R_wp = 0.0940 for (2)] and for the high-temperature phases measured at T = 353 K [R_wp = 0.0891 for (1), R_wp = 0.0542 for (2)]. The combination of high-resolution X-ray powder diffraction measurements and variable-temperature magic-angle-spinning ¹³C, ²⁹Si and ¹¹⁹Sn NMR experiments demonstrates low crystallographic and molecular (C₁) symmetries for the low-temperature phases of (1) and (2) at temperatures T < 348 ± 5 K and high crystallographic symmetry due to rotational disorder for the high-temperature phases at temperatures T > 348 ± 5 K.

Computing details

For both compounds, cell refinement: GSAS; program(s) used to solve structure: DASH; program(s) used to refine structure: GSAS.

(sisnme)

Crystal data

SiSn4C12H36	γ = 89.9877 (6)°
Mr = 683.3	V = 1222.04 (2) Å^3
Triclinic, P1	Z = 2
a = 9.92009 (7) Å	Synchrotron radiation, λ = 0.491213(2) Å
b = 14.5103 (1) Å	µ = 8.09 mm^−1
c = 9.13585 (7) Å	T = 295 K
α = 90.4769 (4)°	white
β = 111.6724 (4)°	cylinder, 0.7 × 0.7 mm

Data collection

ESRF BBM16 diffractometer	Data collection mode: transmission
Radiation source: synchrotron, bending magnet	Scan method: continuous
Si(111) double monochromator	2θmin = 1.003°, 2θmax = 31.981°, 2θstep = 0.003°
Specimen mounting: lithiumborate glass capillary 0.7 mm diameter

Refinement

Refinement on Inet	46 restraints
Rp = 0.065	0 constraints
Rwp = 0.094	H-atom parameters not defined
R(F^2) = 0.1618	(Δ/σ)max = 0.04
Profile function: pseudo-Voigt	Background function: manual
55 parameters

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Si1	0.7645 (5)	0.2509 (4)	0.2435 (6)	0.004 (4)
Sn2	1.0211 (2)	0.2495 (2)	0.2364 (3)	0.0601 (4)
Sn3	0.7004 (3)	0.0925 (2)	0.3256 (3)	0.0601 (4)
Sn4	0.7435 (3)	0.3693 (2)	0.4387 (4)	0.0601 (4)
Sn5	0.5807 (3)	0.2896 (2)	−0.0300 (3)	0.0601 (4)
C6	0.789 (2)	0.5060 (7)	0.370 (2)	0.132 (3)
C7	0.900 (1)	0.3400 (9)	0.671 (1)	0.132 (3)
C8	0.518 (1)	0.366 (1)	0.439 (2)	0.132 (3)
C9	0.850 (1)	0.0617 (8)	0.563 (1)	0.132 (3)
C10	0.474 (1)	0.0970 (8)	0.321 (2)	0.132 (3)
C11	0.720 (2)	−0.0128 (8)	0.164 (2)	0.132 (3)
C12	0.589 (2)	0.1849 (9)	−0.200 (1)	0.132 (3)
C13	0.360 (1)	0.294 (1)	−0.022 (2)	0.132 (3)
C14	0.635 (2)	0.4221 (8)	−0.103 (1)	0.132 (3)
C15	1.181 (1)	0.225 (1)	0.460 (1)	0.132 (3)
C16	1.036 (1)	0.1456 (9)	0.079 (2)	0.132 (3)
C17	1.066 (1)	0.3783 (8)	0.153 (2)	0.132 (3)

Geometric parameters (Å, º)

Si1—Sn2	2.570 (5)	Sn3—C10	2.24 (1)
Si1—Sn3	2.575 (5)	Sn3—C11	2.18 (1)
Si1—Sn4	2.529 (5)	Sn4—C6	2.18 (1)
Si1—Sn5	2.557 (5)	Sn4—C7	2.16 (1)
Sn2—C15	2.11 (1)	Sn4—C8	2.24 (1)
Sn2—C16	2.12 (1)	Sn5—C12	2.18 (1)
Sn2—C17	2.13 (1)	Sn5—C13	2.22 (1)
Sn3—C9	2.18 (1)	Sn5—C14	2.17 (1)
Sn2—Si1—Sn3	110.7 (2)	C9—Sn3—C10	109.5 (3)
Sn2—Si1—Sn4	111.3 (2)	C9—Sn3—C11	109.2 (3)
Sn2—Si1—Sn5	109.4 (2)	C10—Sn3—C11	110.4 (7)
Sn3—Si1—Sn4	107.7 (2)	Si1—Sn4—C6	109.3 (3)
Sn3—Si1—Sn5	108.9 (2)	Si1—Sn4—C7	109.7 (3)
Sn4—Si1—Sn5	108.7 (2)	Si1—Sn4—C8	109.1 (3)
Si1—Sn2—C15	112.0 (3)	C6—Sn4—C7	108.5 (3)
Si1—Sn2—C16	109.9 (3)	C6—Sn4—C8	109.4 (7)
Si1—Sn2—C17	109.9 (3)	C7—Sn4—C8	110.7 (3)
C15—Sn2—C16	108.7 (3)	Si1—Sn5—C12	109.7 (3)
C15—Sn2—C17	108.6 (3)	Si1—Sn5—C13	109.3 (3)
C16—Sn2—C17	107.6 (3)	Si1—Sn5—C14	109.4 (3)
Si1—Sn3—C9	109.3 (3)	C12—Sn5—C13	109.8 (7)
Si1—Sn3—C10	108.9 (3)	C12—Sn5—C14	108.5 (3)
Si1—Sn3—C11	109.3 (3)	C13—Sn5—C14	110.3 (3)

(gesnme)

Crystal data

GeSn4C12H36	V = 1229.41 (1) Å^3
Mr = 727.9	Z = 2
Triclinic, P1	Synchrotron radiation, λ = 0.491213(2) Å
a = 9.94457 (5) Å	µ = 10.5 mm^−1
b = 14.52927 (8) Å	T = 295 K
c = 9.16021 (5) Å	white
α = 90.5339 (3)°	cylinder, 0.7 × 0.7 mm
β = 111.7308 (3)°	Specimen preparation: Prepared at 248 K
γ = 90.0049 (4)°

Data collection

ESRF BBM16 diffractometer	Data collection mode: transmission
Radiation source: synchrotron, bending magnet	Scan method: continuous
Si(111) double monochromator	2θmin = 1.003°, 2θmax = 29.995°, 2θstep = 0.003°
Specimen mounting: lithiumborate glass capillary 0.7 mm diameter

Refinement

Refinement on Inet	46 restraints
Rp = 0.067	0 constraints
Rwp = 0.084	H-atom parameters not defined
R(F^2) = 0.1378	(Δ/σ)max = 0.03
Profile function: pseudo-Voigt	Background function: manual
55 parameters

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Ge1	0.7615 (3)	0.2490 (2)	0.2412 (3)	0.016 (1)
Sn2	1.0232 (2)	0.2487 (2)	0.2356 (3)	0.0641 (5)
Sn3	0.7019 (3)	0.0891 (2)	0.3246 (3)	0.0641 (5)
Sn4	0.7440 (3)	0.3700 (2)	0.4415 (3)	0.0641 (5)
Sn5	0.5792 (2)	0.2897 (2)	−0.0346 (3)	0.0641 (5)
C6	0.798 (1)	0.5050 (4)	0.379 (1)	0.136 (3)
C7	0.893 (1)	0.3349 (7)	0.6751 (8)	0.136 (3)
C8	0.5239 (9)	0.3709 (7)	0.438 (2)	0.136 (3)
C9	0.849 (1)	0.0601 (6)	0.5614 (9)	0.136 (3)
C10	0.4815 (9)	0.0890 (5)	0.317 (2)	0.136 (3)
C11	0.724 (1)	−0.0152 (5)	0.165 (1)	0.136 (3)
C12	0.588 (2)	0.1867 (6)	−0.2035 (7)	0.136 (3)
C13	0.3621 (8)	0.294 (1)	−0.032 (1)	0.136 (3)
C14	0.634 (1)	0.4236 (6)	−0.1001 (9)	0.136 (3)
C15	1.1783 (6)	0.2159 (9)	0.4661 (9)	0.136 (3)
C16	1.0353 (7)	0.1470 (8)	0.067 (1)	0.136 (3)
C17	1.0715 (7)	0.3837 (6)	0.168 (2)	0.136 (3)

Geometric parameters (Å, º)

Ge1—Sn2	2.622 (3)	Sn3—C10	2.169 (6)
Ge1—Sn3	2.588 (3)	Sn3—C11	2.163 (6)
Ge1—Sn4	2.582 (3)	Sn4—C6	2.170 (6)
Ge1—Sn5	2.580 (3)	Sn4—C7	2.170 (6)
Sn2—C15	2.161 (6)	Sn4—C8	2.176 (6)
Sn2—C16	2.161 (6)	Sn5—C12	2.168 (6)
Sn2—C17	2.170 (6)	Sn5—C13	2.170 (6)
Sn3—C9	2.166 (6)	Sn5—C14	2.170 (6)
Sn2—Ge1—Sn3	110.0 (1)	C9—Sn3—C10	109.4 (5)
Sn2—Ge1—Sn4	110.1 (1)	C9—Sn3—C11	109.6 (2)
Sn2—Ge1—Sn5	108.9 (1)	C10—Sn3—C11	109.4 (2)
Sn3—Ge1—Sn4	108.3 (1)	Ge1—Sn4—C6	109.6 (2)
Sn3—Ge1—Sn5	110.4 (1)	Ge1—Sn4—C7	109.5 (2)
Sn4—Ge1—Sn5	109.09 (9)	Ge1—Sn4—C8	108.9 (2)
Ge1—Sn2—C15	109.6 (2)	C6—Sn4—C7	109.6 (2)
Ge1—Sn2—C16	109.4 (2)	C6—Sn4—C8	109.5 (2)
Ge1—Sn2—C17	109.4 (2)	C7—Sn4—C8	109.4 (5)
C15—Sn2—C16	109.4 (2)	Ge1—Sn5—C12	109.6 (2)
C15—Sn2—C17	109.5 (5)	Ge1—Sn5—C13	109.6 (2)
C16—Sn2—C17	109.5 (5)	Ge1—Sn5—C14	109.1 (2)
Ge1—Sn3—C9	109.6 (2)	C12—Sn5—C13	109.3 (6)
Ge1—Sn3—C10	109.4 (2)	C12—Sn5—C14	109.7 (2)
Ge1—Sn3—C11	109.5 (2)	C13—Sn5—C14	109.3 (5)