X-ray Structural Characterization of [Cr(CNPh)6][CF3SO3], [Cr(CNPh)6][PF6]2, and [Cr(CNPh)6][SbCl6]3.CH2Cl2. Completion of a Unique Series of Complexes in Which the Metal Attains Four Different Oxidation States While Maintaining Identical Ligation

David A. Bohling, Kent R. Mann

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Abstract

The crystal structures of [Cr(CNC6H5)6] [CF3SO3] (A), [Cr(CNC6H5)][PF6]2 (B), and [Cr(CNC6H5)6][SbCl6]3-CH2Cl2 (C) have been determined by single-crystal X-ray diffraction techniques. Compound A crystallizes in the P21/n (No. 14) space group with Z = 2, V = 2061 (2) Å3, a = 10.757 (3) Å, b = 19.994 (6) Å, c = 10.242 (3) Å, and β = 110.69 (20)°. Full-matrix least-squares refinement (264 variables, 3679 reflections) converged to give R and Rw values of 0.042 and 0.061, respectively. The structure of A consists of discrete [Cr(CNC6H5)6]+ cations and disordered [CF3SO3]- anions. A minor Jahn-Teller distortion is observed in the Cr-C bond lengths, which average 1.975 Å. Compound B crystallizes in the P21/n (No. 14) space group with Z = 4, V= 4365 (5) Å3, a = 13.888 (4) Å, b = 19.638 (4) Å, c = 16.009 (11) Å, and β = 91.20 (4)°. Least-squares refinement (329 variables, 2335 reflections) gave R = 0.060 and Rw = 0.070. The Cr site is a general position in the unit cell. The ligands show a pronounced angular distortion with the C-Cr-C bond angles ranging from 83.7 to 97.0°. The Cr-C bonds average 2.014 A. Compound C crystallizes in the Cccm (No. 66) space group with Z = 4, V = 6483 (6) Å3, a = 14.818 (6) Å, b = 18.450 (5) Å, c = 23.714 (7) Å, and β = 90.0°. Full-matrix least-squares refinement (180 variables, 1445 reflections) converged to give R = 0.058 and Rw = 0.059. The CH2Cl2 of crystallization was disordered. The four crystallographically related equatorial ligands exhibit Cr-C bonds of 2.049 (10) Å relative to the long Cr-C axial bonds of 2.091 (14) Å. Changes in the Cr-C and C≡N bond lengths are discussed in relation to the d-electron configuration of the central metal. The origin of the large positive value previously obtained for the Cr(CNPh)63+/Cr(CNPh)62+ reduction potential is discussed in relation to the large negative value reported for the Cr(CN)63-Cr(CN)64- couple.

Original languageEnglish (US)
Pages (from-to)1426-1432
Number of pages7
JournalInorganic chemistry
Volume23
Issue number10
DOIs
StatePublished - Jan 1984

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