Solid-state structures of triarylantimony dihalides; the isolation of some mixed-halide species and crystal structures of Ph3SbI2 and [Ph4Sb]I3

Abstract

Fifteen compounds of stoichiometry R3SbX2(R = Ph or substituted aryl; X2= Br2, I2 or IBr) were synthesised and studied by Raman spectroscopy. The crystal structure of Ph3SbI2 has been determined, which shows it to be a distorted trigonal-bipyramidal molecule. The distortion from regular trigonal-bipyramidal geometry may be explained by a pseudorotation process towards a rectangular pyramid. Moreover, there are two independent molecules within the unit cell and its distorted structure is in direct contrast to the known Ph3SbX2(X = Cl or Br) which both adopt regular trigonal-bipyramidal geometry. The interhalogen compounds R3SbIBr also have trigonal-bipyramidal geometry. In direct contrast to the molecules Ph3EI2(E = P or As), which ionise in solution to form [Ph3EI]I, Ph3SbI2 is chemically changed in acetonitrile solution and forms the ionic [Ph4Sb]I3, there being no evidence for [Ph3SbI]I. The crystal structure of [Ph4Sb]I3 has also been determined.