Stereochemistry of some organic derivatives of Group VB elements. Part VII. Crystal and molecular structure of triphenyl-(2-acetyl-3,4,5-triphenylcyclopenta-2,4-dienyl)arsonium perchlorate

Abstract

The crystal structure of the title compound has been determined by three-dimensional X-ray methods. It is formed by protonation of the parent arsonium cyclopentadienylide at the 1-position of the cyclopentadienyl ring. There is thus no delocalisation between the arsonium moiety and the cyclopentadiene system. The environment at arsenic is slightly distorted tetrahedral [As⁺⋯ O(Ac) 3.100(11)Å]; As⁺–C(sp³) is 1.963 ± 0.013 Å, and mean As⁺C(Ph) 1.908 ± 0.007 Å.

The perchlorate ion is held in the crystal by a C–H ⋯ O hydrogen bond (H ⋯ O 2.2 Å) between a perchlorate oxygen and the acidic five-membered ring proton. Crystals are monoclinic, space group P2₁/c with Z= 4 in a cell of dimensions a= 11.939(1). b= 18.337(2), c= 17.570(2)Å, β= 105.85(2)°. The structure was solved from diffractometer data by the heavy-atom method and refined by least-squares calculations to R 0.066 for 1558 observed reflexions.