THE VIBRATIONAL-SPECTRA OF NATURAL AND PERDEUTERATED MONOCHLOROGALLANE, H2GA(MU-CL)(2)GAH2 AND AN EMPIRICAL HARMONIC POTENTIAL FUNCTION

MONOCHLOROGALLANE has been synthesized recently by the reaction betwee n powdered gallium(III) chloride and an excess of trimethylsilane [1]. Despite proving to be unusually air- and moisture-sensitive the compo und has been characterized by chemical analysis, by its infrared, Rama n, and H-1 NMR spectra, and by the products of its reaction with trime thylamine [1]. A preliminary electron-diffraction study confirmed that the predominant form of the compound in the vapour phase is the dimer . H2Ga(mu-Cl)(2)GaH2, conforming to D-2h symmetry [1]. In addition, mo nochlorogallane has proved to be an important precursor in the synthes is of other uncoordinated gallium hydrides, namely H-2 Ga(mu-H)(2)GaH2 [2], H2Ga(mu-H)(2)BH2 [3] and H2GaB3H8 [4]. An analysis of the vibrat ional spectra of monochlorogallane is therefore important for the foll owing reasons: (i) monochlorogallane represents the first uncoordinate d gallium hydride for which a detailed analysis of the vibrational spe ctra has been undertaken, and hence provides a reference point for fut ure analyses of the vibrational spectra of the related molecules H2Ga( mu-H)(2)GaH2 [2] and H2Ga(mu-H)(2)BH2 [3], (ii) it allows a comparison to be made between the experimental spectra and the results of recent theoretical calculations of the vibrational properties associated wit h monochlorogallane [5], and (iii) it enables the calculation of vibra tional corrections for use in analysing the electron-diffraction patte rn of monochlorogallane vapour thereby providing a means of obtaining an r(alpha) structure.