Disordered crystal structure of pentamethylcyclopentadienylsodium as seen by high-resolution X-ray powder diffraction

The crystal structure of pentamethylcyclopentadienylsodium, [NaC₁₀H₁₅] (NaCp*), has been determined from high-resolution X-ray powder diffraction. The compound crystallizes in space group Cmcm with lattice parameters a = 4.61030 (3), b = 16.4621 (3), c = 14.6751 (2) Å, V = 1113.77 (4) Å³ (Z = 4). NaCp* forms polymeric multidecker chains along the a axis. The Rietveld refinement (R_p = 0.050 and R_F = 0.163) shows that the Cp* moieties occupy, with disorder, two different orientations rotated away from the eclipsed conformation by ±13.8°.

Computing details

Cell refinement: GSAS; program(s) used to refine structure: GSAS.

Figures

pentamethylcyclopentadienylsodium

Crystal data

NaC10H15	Z = 4
Mr = 158.22	? radiation, λ = 0.491213(2) Å
Orthorhombic, Cmcm	T = 298 K
a = 4.61030 (3) Å	white
b = 16.4621 (3) Å	cylinder, ? × ? × ? mm
c = 14.6751 (2) Å	Specimen preparation: Prepared at 298 K K and ambient kPa
V = 1113.77 (4) Å^3

Data collection

Beamline BM16 at the European Synchrotron Radiation Facility, Grenoble, France diffractometer	Data collection mode: transmission
Radiation source: synchrotron, ESRF beamlime BM16	Scan method: continuous
Si 111 monochromator	2θmin = 2.003°, 2θmax = 25.994°, 2θstep = 0.003°
Specimen mounting: 0.7 mm quartz capillary

Refinement

Least-squares matrix: full	? data points
Rp = 0.050	Profile function: Pseudo-voigt function (Thompson, Cox & Hastings, 1987) with an additional symmetry correction according to Finger, Cox & Jephcoat (1994). Anisotropic strain-broadening effects were modeled following the method by Stephens (1999).
Rwp = 0.066	9 parameters
Rexp = ?
R(F^2) = 0.136	Background function: visually estimated fixed background
χ^2 = 0.168

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

	x	y	z	Uiso*/Ueq	Occ. (<1)
NA1	0.5	0.1422 (2)	0.25	0.10021
C1	0.0	0.07422 (10)	0.23026 (12)	0.0428 (12)*	.5
C2	0.0	0.10664 (14)	0.31979 (7)	0.0428 (12)*	.5
C3	0.0	0.19256 (14)	0.31287 (8)	0.0428 (12)*	.5
C4	0.0	0.21325 (11)	0.21907 (12)	0.0428 (12)*	.5
C5	0.0	0.14011 (15)	0.168011 (9)	0.0428 (12)*	.5
C6	0.0	−0.01446 (12)	0.2057 (3)	0.1775 (16)*	.75
C7	0.0	0.0584 (2)	0.40680 (15)	0.1775 (16)*	.75
C8	0.0	0.2514 (2)	0.39126 (18)	0.1775 (16)*	.75
C9	0.0	0.29789 (14)	0.1805 (3)	0.1775 (16)*	.75
C10	0.0	0.1336 (3)	0.065787 (20	0.1775 (16)*	.75

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
NA1	0.0184 (19)	0.0	0.0	0.168 (4)	0.114 (4)	0.0