Crystal structure of, and solution adduct equilibria involving, tetraphenylarsonium tetrachloro-oxochromate(V)

Abstract

Crystals of the title complex are tetragonal, space group P4/n, with a= 12.590(7), c= 7.840(5)Å, and Z= 2. The crystal structure has been solved by the heavy-atom method and refined by full-matrix least-squares calculations to R 0.059 over 860 statistically signrfrcant reflections from diffractometer measurements (Cu-K_α radiation). The square-pyramidal [CrCl₄O]^– anion has crystallographic 4mm(C_4v) symmetry with Cr–O 1.519(12) and Cr–Cl 2.240(3)Å, and O–Cr–Cl 104.5(1)°. The [AsPh₄]⁺ cation has crystallographic (S₄) symmetry [As–C 1.906(6)Å C–As–C 105.3(3) and 111.5(3)°]. E.s r. spectroscopy has been used to estimate the equilibrium constants for the reaction [CrCl₄O]^–+ L [graphic omitted] [CrCl₄OL]^n– in CH₂Cl₂solution {n= 1 when L = PPh₃O (K= 3 ± 2), P(NMe₂)₃O (K= 463 ± 130), thf (K < 1), or py (K= 160); n= 2 when L = Cl^–(K= 43 ± 10 with [AsPh₄]Cl and 250 ± 33 dm³ mol^–1 with [NEt₄]Cl)}.