STABILITIES AND ENERGETICS OF INORGANIC BENZENE ISOMERS - PRISMANES

Ab initio calculations of inorganic prismanes, with the formula (XH-YH)(3), where X = B, Al, and Ga and Y = N, P, and As, as well as X or Y = C, Si, and Ge, were carried out. Energetics of these species are compared with those of the planar benzene analog and chair/boat conformers. The prismane and planar structures containing first period elements (B, C, and N) are all stable (i.e. minima on the potential energy surfaces). Chair and boat conformers are potential energy minima only in compounds containing second or third period elements. For those species with a first period element in the 1, 3, 5 positions, the planar benzene-like structure is the global minumum; otherwise, the planar structure is not a minimum. The lowest minimum found is the prismane arrangement for Si6H6 and Ge6H6 and the chair structure for Si3Ge3H6. Other molecules have distorted minima.