ELECTROCHEMICAL SYNTHESIS AND CRYSTALLIZATION OF A NOVEL TETRAARYLAURATE ANION - SYNTHESIS, STRUCTURE, AND PHYSICAL-PROPERTIES OF (BEDT-TTF)AU(C6CL5)(4)

The homoleptic tetraarylaurate anion, Au(C6Cl5)(4)(-), which has never been prepared via traditional chemical methods, has been synthesized by use of an electrochemical technique and crystallized in situ with t he bis(ethylenedithio)tetrathiafulvalene tetrathiafulvalene (BEDT-TTF, or ET) electron-donor molecule. This salt, (C10H8S8)Au(C6Cl5)(4), cry stallizes having the monoclinic space group P2(1)/c, with a = 14.7835( 9) Angstrom, b = 20.2270(12) Angstrom, c = 16.7303(10) Angstrom, beta = 101.396(1)degrees, Z = 4. The crystal structure of this (ET)Au(C6Cl5 )(4) salt contains the Au(C6Cl5)(4)(-) anion in an essentially square- planar coordination with the pentachlorophenyl groups arranged in a pr opeller-like D-4 symmetry, consistent with the formal oxidation state +3 of the central metal atom. The ET+ cations are completely surrounde d by the pentachlorophenyl rings of the anions, thereby precluding the formation of a S...S network with concomitant conducting properties. Analysis of the Raman spectrum of (ET)Au(C6Cl5)(4) confirms that the E T molecule in this salt is in the fl oxidation state. The variable tem perature spin susceptibility data obtained from ESR spectroscopy indic ate a weak ferromagnetic coupling between the radical ET+ cations. Thi s salt provides the unique opportunity to investigate the properties o f a highly isolated ET+ cation in the solid state.