Trifluoroacetate as a bridging ligand for antimony(V): crystal and molecular structures of µ-fluro-µ-trifluoroacetato-bis[tetrafluoroantimony(V)](1) and of µ-oxo-di-µ-trifluoroacetato-bis[trifluoroantimony(V)](2)

Abstract

Crystals of title compound (1), Sb₂(O₂CCF₃)F₉, are monoclinic. Space group P2₁/c with a= 9.386(6), b= 15.119(8), c= 16.250(7)Å, β= 110.52(11)°, and Z= 8. The asymmetric unit contains two equivalent but crystallographically independent binuclear complexes in which the Sb atoms are bridged by a F atom (F_b) and by a trifluoroacetato-group. The distorted octahedral co-ordination at each Sb centre is completed by four terminal F atoms (F_t). The mean bond distances are : Sb–F_b 2.025(21), Sb–O 2.026(23), and Sb–F_t 1.836(24)Å. The heavy atoms have been located directly and full-matrix least-squares refinement with anisotropic thermal parameters for the Sb atoms has given R= 0.090 with 1 791 independent observed reflections. Title compound (2), Sb₂O(O₂CCF₃)₂F₆, crystallizes in the monoclinic space group Cc with a= 12.322(6), b= 13.867(8), c= 9.443(5)Å, β= 122.75(5)°, and Z= 4. The two Sb atoms are bridged by an oxygen atom (O_b) and by two trifluoroacetato-groups with the octahedral co-ordination at Sb completed by terminal fluorines (F_t). The binuclear complex has approximate C_2v symmetry and exhibits the following mean bond distances: Sb–O_b 1.893(21), Sb–O 2.064(16), and Sb–F_t 1.840(17)Å. The analysis is based on 1 760 independent observed reflections and refined by weighted full-matrix least-squares analysis to R= 0.043.