Polarised single-crystal electronic absorption spectra of tetraphenylarsonium tetrahalogenonitrido-osmate(VI) compounds and the crystal and molecular structures of tetraphenylarsonium tetrabromonitrido-osmate(VI)

Abstract

The single-crystal polarised electronic absorption spectra of [AsPh4][OsNX4](X = Cl, Br, or I) at room temperature and 5 K are reported in the range 10 000–40 000 cm–1. The spectra have been interpreted using the observed polarisation and vibrational fine-structure data in conjunction with a parameterised ligand-field model. The single-crystal structure of [AsPh4][OsNBr4] has been determined by X-ray crystallography. The compound crystallises in the tetragonal space group P4/n, a=b= 12.774(3), c= 8.008(3)A, Z= 2. The [OsNBr4]– ion has 4mm(C4v) symmetry with Os–N 1.583(15), Os–Br 2.457(1)A, N–Os–Br 104.29(3)°. The [AsPh4]+ cation has crystallographic (S4) symmetry with As–C 1.891 (8)A, C–As–C 105.12(48) and 116.69(25)°.