Nonastannide(4-) anion Sn/sub 9//sup 4 -/, a novel capped antiprismatic configuration (C/sub 4/. nu. )
Reaction of alloy compositions near NaSn/sub 2.25/ with 2,2,2-crypt (4,7,13,16,21,24-hexaoxa-1,10-diazobicyclo(8.8.8)-hexacosane) in ethylenediamine yields dark red to black rods which have been shown to be (crypt-Na/sup +/)/sub 4/Sn/sub 9//sup 4 -/ by x-ray crystallography. The compound crystallizes in the P1 space group with Z = 2 and a = 16.655 (3) A, b = 21.207 (10) A, c = 15.370 (7) A, ..cap alpha.. = 107.98 (5)/sup 0/, ..beta.. = 103.43 (6)/sup 0/, and ..gamma.. = 81.70 (9)/sup 0/ at 5/sup 0/C. The 117 independent (nonhydrogen) atoms in the structure yielded, with anisotropic thermal parameters for tin and sodium, R = 0.121 and R/sub w/ = 0.143 for 4803 independent observed reflections with 0 < 20 < 45/sup 0/. One of the four cations exhibits the first example of six rather than eight coordination by 2,2,2-crypt with two opposite oxygen atoms displaced from the coordination sphere (3.12 and 3.30 A from sodium). The novel anion Sn/sub 9//sup 4 -/ represents the first example of a unicapped antiprismatic (C/sub 4v/) configuration, the distinguishing dihedral angles being: square base (vicinal), delta = 2.6 (2)/sup 0/, opposed (parallel to fourfold, delta = 157.7 (1)/sup 0/, 158.3 (1)/sup 0/. The contrast between the C/sub 4v/ symmetry of Sn/sub 9//sup 4 -/ and the D/sub 3h/ symmetry known for the isoelectronic Bi/sub 9//sup 5 +/ (in the HfCl/sub 6//sup 2 -/ salt) is considered in terms of a potential stereochemical nonrigidity. The distorted Bi/sub 9//sup 5 +/ found in the ''monochloride'' salt Bi/sub 12/Cl/sub 14/ exhibits dihedral angles which indicate a 25% distortion from D/sub 3h/ toward C/sub 4v/ symmetry. Semiempirical SCF-CNDO-MO calculations suggest there is a negligible barrier along the geometric path between these two limits.
- Research Organization:
- Iowa State Univ., Ames
- OSTI ID:
- 7220864
- Journal Information:
- J. Am. Chem. Soc.; (United States), Vol. 99:10
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
TIN COMPOUNDS
STRUCTURAL CHEMICAL ANALYSIS
SYNTHESIS
ANIONS
BOND ANGLE
BOND LENGTHS
CRYSTALLOGRAPHY
DIAZO COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
SODIUM COMPOUNDS
X-RAY DIFFRACTION
ALKALI METAL COMPOUNDS
CHARGED PARTICLES
COHERENT SCATTERING
DIFFRACTION
IONS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
SCATTERING
400201* - Chemical & Physicochemical Properties
400301 - Organic Chemistry- Chemical & Physicochemical Properties- (-1987)