Experimental and calculated molecular structures and high symmetry conformations of [Sb 2F 11] − (D 4h) and 1,4-C 4H 4N 2·2SbF 5 (D 2h)

Abstract

Antimony(V) fluoride, SbF 5, forms a molecular adduct with pyrazine (1,4-diazine) of the composition 1,4-C 4H 4N 2·2SbF 5. Its molecular structure is obtained by single crystal X-ray diffraction. Crystal data of pyrazine·2SbF 5: orthorhombic, spacegroup Pbca (# 61); a=8.8052(8) Å; b=9.948(1) Å; c=12.297(2) Å; V=1077.1(2) Å 3; Z=4; T=173(1) K; R 1( I>3 σ( I))=0.031; wR 2=0.083. The Sb–F 4(eq) planes are eclipsed and the planar C 4H 4N 2 ring is at a 45° angle to give D 2h symmetry for pyrazine·2SbF 5. A very similar high symmetry conformation of pointgroup D 4h is found for the [Sb 2F 11] − anion in the metal carbonyl salts [Rh(CO) 4][Sb 2F 11], [Au(CO) 2][Sb 2F 11] and in [H 3F 2][Sb 2F 11]. Structural data for pyrazine·2SbF 5 and [Sb 2F 11] − from [H 3F 2][Sb 2F 11], as well as vibrational data for [Sb 2F 11] − (D 4h) are compared to calculated (DFT-B3LYP) data. According to the DFT calculations, the conformation for the [Sb 2F 11] − anion (D 4h) and pyrazine·2SbF 5 (D 2h) are both eclipsed with respect to the SbF 5-groups and eclipsed with respect to the pyrazine plane in pyrazine·2SbF 5 in their respective ground states.