Thermodynamic control in the reactions of gas phase anions

The gas phase ion molecule reactions of a number of anions, Xsup(-), with diborane, Bsub(2)Hsub(6), have been investigated using ion cyclotron resonance spectroscopy. Two distinct reaction channels are observed in addition to simple proton transfer. The first of these is production of BHsub(4)sup(-) and BHsub(2)X while the second is formation of BHsub(3)Xsup(-) and BHsub(3). In order to determine the importance of thermodynamic factors in the course of reaction ab initio calculations have been carried out on the species involved to obtain the relative stabilities of the two possible pairs of products. The 4-31 + G basis set incorporating additional flat s and p functions has been used since this basis set has been demonstrated to give the most accurate description of anions to date. The results obtained indicate that the thermochemical factors are instrumental in determining the reaction pathway