Reversible dimerization of C₆₀ molecules in the crystal structure of the bis(arene)chromium fulleride [Cr(C₇H₈)]₂C₆₀

Bis(toluene)chromium fulleride, [Cr(C₇H₈)₂]C₆₀, has been synthesized as a black microcrystalline powder from C₆₀ and [Cr(C₇H₈)₂] in toluene. [Cr(C₇H₈)₂]C₆₀ is an ionic compound in which the fullerene is negatively charged and the bis(toluene)chromium molecule positively charged. At T = 250 K a reversible first-order phase transition from a primitive cubic high-temperature phase to a triclinic low-temperature phase occurs. The high-temperature phase [Pmm, a = 9.9840 (1) Å, T = 295 K] is composed of dynamically disordered fulleride anions and bis(toluene)chromium(I) cations in a CsCl-type arrangement. The triclinic low-temperature modification [P, a = 13.6414 (8), b = 13.8338 (7), c = 13.8548 (7) Å, α = 91.830 (3), β = 116.776 (2), γ = 119.333 (2)°, T = 235 K] consists of ordered C₆₀ dimers and two crystallographically distinct bis(toluene)chromium entities.

Computing details

Program(s) used to refine structure: GSAS.

(I)

Crystal data

Triclinic, P1	β = 116.776 (2)°
a = 13.6414 (8) Å	γ = 119.3326 (19)°
b = 13.8338 (7) Å	Synchrotron radiation
c = 13.8548 (7) Å	T = 235 K
α = 91.830 (3)°

Data collection

2θmin = 3.003°, 2θmax = 25.995°, 2θstep = 0.003°

Refinement

Rp = 0.077	15 parameters
Rwp = 0.105	0 restraints
Rexp = 0.122	(Δ/σ)max = 0.06
7665 data points

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

	x	y	z	Uiso*/Ueq
C1	−0.030 (2)	0.0227 (14)	−0.1262 (17)	0.0284 (19)*
C2	0.045 (2)	0.4640 (14)	−0.3896 (17)	0.0284 (19)*
C3	0.1120 (19)	0.1109 (17)	−0.0549 (16)	0.0284 (19)*
C4	−0.0972 (19)	0.3757 (17)	−0.4609 (15)	0.0284 (19)*
C5	0.1922 (18)	0.1324 (18)	−0.0986 (18)	0.0284 (19)*
C6	−0.1774 (18)	0.3543 (18)	−0.4172 (18)	0.0284 (19)*
C7	−0.087 (2)	−0.0403 (10)	−0.2381 (19)	0.0284 (19)*
C8	0.102 (2)	0.5270 (10)	−0.2777 (19)	0.0284 (19)*
C9	−0.003 (2)	−0.0179 (11)	−0.284 (2)	0.0284 (19)*
C10	0.018 (2)	0.5046 (11)	−0.232 (2)	0.0284 (19)*
C11	−0.0970 (19)	0.0654 (16)	−0.1002 (15)	0.0284 (19)*
C12	0.1119 (19)	0.4213 (16)	−0.4156 (16)	0.0284 (19)*
C13	−0.2121 (17)	−0.0634 (7)	−0.3289 (18)	0.0284 (19)*
C14	0.2269 (17)	0.5501 (7)	−0.1869 (18)	0.0284 (19)*
C15	0.133 (2)	0.0666 (16)	−0.215 (2)	0.0284 (19)*
C16	−0.119 (2)	0.4200 (16)	−0.301 (2)	0.0284 (19)*
C17	−0.2172 (16)	0.0433 (15)	−0.1873 (17)	0.0284 (19)*
C18	0.2320 (16)	0.4434 (15)	−0.3285 (17)	0.0284 (19)*
C19	−0.2760 (14)	−0.0225 (11)	−0.3040 (17)	0.0284 (19)*
C20	0.2908 (14)	0.5092 (11)	−0.2118 (18)	0.0284 (19)*
C21	0.3034 (14)	0.2602 (19)	−0.176 (2)	0.0284 (19)*
C22	−0.2886 (14)	0.2265 (19)	−0.3401 (19)	0.0284 (19)*
C23	0.2972 (13)	0.2520 (19)	−0.0741 (17)	0.0284 (19)*
C24	−0.2824 (13)	0.2346 (19)	−0.4417 (17)	0.0284 (19)*
C25	0.3177 (12)	0.3452 (18)	−0.0070 (13)	0.0284 (19)*
C26	−0.3029 (12)	0.1415 (18)	−0.5088 (12)	0.0284 (19)*
C27	0.3298 (11)	0.3612 (17)	−0.2061 (19)	0.0284 (19)*
C28	−0.3150 (11)	0.1255 (17)	−0.3097 (18)	0.0284 (19)*
C29	0.3512 (9)	0.4584 (14)	−0.1361 (17)	0.0284 (19)*
C30	−0.3364 (9)	0.0283 (14)	−0.3797 (16)	0.0284 (19)*
C31	0.2022 (19)	0.1456 (18)	−0.263 (2)	0.0284 (19)*
C32	−0.1874 (19)	0.3411 (18)	−0.253 (2)	0.0284 (19)*
C33	0.2562 (16)	0.3519 (17)	−0.3250 (18)	0.0284 (19)*
C34	−0.2413 (16)	0.1347 (17)	−0.1908 (18)	0.0284 (19)*
C35	0.3453 (10)	0.4506 (15)	−0.0387 (13)	0.0284 (19)*
C36	−0.3305 (10)	0.0361 (15)	−0.4771 (13)	0.0284 (19)*
C37	0.132 (2)	0.1368 (18)	−0.3770 (19)	0.0284 (19)*
C38	−0.117 (2)	0.3499 (17)	−0.1388 (19)	0.0284 (19)*
C39	0.159 (2)	0.2421 (19)	−0.4087 (17)	0.0284 (19)*
C40	−0.144 (2)	0.2446 (18)	−0.1071 (17)	0.0284 (19)*
C41	0.2100 (18)	0.4143 (16)	0.0350 (8)	0.0284 (19)*
C42	−0.1951 (19)	0.0724 (16)	−0.5508 (8)	0.0284 (19)*
C43	0.2341 (17)	0.3228 (18)	0.0385 (8)	0.0284 (19)*
C44	−0.2193 (17)	0.1639 (18)	−0.5543 (8)	0.0284 (19)*
C45	0.1334 (19)	0.2081 (19)	0.0150 (10)	0.0284 (19)*
C46	−0.1186 (19)	0.2786 (19)	−0.5308 (10)	0.0284 (19)*
C47	0.086 (2)	0.3873 (17)	0.0081 (11)	0.0284 (19)*
C48	−0.071 (2)	0.0994 (17)	−0.5239 (12)	0.0284 (19)*
C49	−0.019 (2)	0.2677 (19)	−0.0163 (12)	0.0284 (19)*
C50	0.034 (2)	0.2190 (19)	−0.4995 (13)	0.0284 (19)*
C51	0.2787 (16)	0.4932 (12)	−0.0127 (12)	0.0284 (19)*
C52	−0.2639 (16)	−0.0066 (12)	−0.5031 (12)	0.0284 (19)*
C53	0.026 (2)	0.4381 (15)	−0.0676 (17)	0.0284 (19)*
C54	−0.012 (2)	0.0321 (16)	−0.4643 (18)	0.0284 (19)*
C55	0.004 (2)	0.1800 (18)	−0.0130 (12)	0.0284 (19)*
C56	0.011 (2)	0.3067 (18)	−0.5028 (12)	0.0284 (19)*
C57	0.2208 (18)	0.5420 (8)	−0.0853 (16)	0.0284 (19)*
C58	−0.2059 (18)	−0.0553 (8)	−0.4305 (16)	0.0284 (19)*
C59	0.092 (2)	0.5138 (11)	−0.1133 (18)	0.0284 (19)*
C60	−0.077 (2)	−0.0271 (11)	−0.4025 (18)	0.0284 (19)*
CR61	0.5	0.0	0.0	0.156 (4)*
C62	0.371 (2)	−0.1448 (16)	0.022 (3)	0.156 (4)*
C63	0.495 (3)	−0.074 (3)	0.127 (2)	0.156 (4)*
C64	0.555 (3)	0.049 (3)	0.1681 (8)	0.156 (4)*
C65	0.489 (3)	0.100 (2)	0.104 (3)	0.156 (4)*
C66	0.364 (2)	0.0283 (18)	−0.001 (3)	0.156 (4)*
C67	0.3050 (9)	−0.0939 (16)	−0.042 (2)	0.156 (4)*
H68	0.326 (3)	−0.2374 (15)	−0.010 (5)	0.156 (4)*
H69	0.545 (4)	−0.112 (5)	0.175 (4)	0.156 (4)*
H70	0.649 (3)	0.103 (5)	0.2477 (6)	0.156 (4)*
H71	0.534 (4)	0.192 (2)	0.136 (5)	0.156 (4)*
H72	0.315 (3)	0.067 (3)	−0.049 (5)	0.156 (4)*
C73	0.17349 (12)	−0.169 (3)	−0.153 (3)	0.156 (4)*
CR74	0.5	0.5	0.5	0.156 (4)*
C75	0.3042 (6)	0.4371 (19)	0.3806 (18)	0.156 (4)*
C76	0.3221 (18)	0.437 (3)	0.490 (3)	0.156 (4)*
C77	0.427 (3)	0.539 (4)	0.5865 (19)	0.156 (4)*
C78	0.514 (3)	0.642 (2)	0.5740 (15)	0.156 (4)*
C79	0.497 (2)	0.6428 (11)	0.4647 (18)	0.156 (4)*
C80	0.3915 (16)	0.5402 (16)	0.3681 (11)	0.156 (4)*
H81	0.2246 (14)	0.359 (2)	0.307 (2)	0.156 (4)*
H82	0.256 (2)	0.358 (4)	0.499 (4)	0.156 (4)*
H83	0.441 (5)	0.539 (5)	0.669 (2)	0.156 (4)*
H84	0.594 (5)	0.720 (3)	0.647 (2)	0.156 (4)*
H85	0.563 (3)	0.7210 (13)	0.455 (3)	0.156 (4)*
C86	0.373 (3)	0.541 (3)	0.2530 (14)	0.156 (4)*