A COMPARATIVE-STUDY OF STRUCTURES AND BINDING-ENERGIES FOR AH3EH3 ADDUCTS (A=B, AL, GA, IN E=N, P, AS)

We report an ab initio study of twelve adducts of the type AH3EH3 (A = B, Al, Ga, In; E=N, P, As) containing acceptor atoms from Group 13 an d donors from Group 15. Pseudopotentials were used on the A and E atom s, supplemented with double-zeta plus polarization bases for the valen ce space. A double-zeta basis was used for H atoms. Structures have be en optimized at the SCF and MP2 levels of theory. Correlation effects shorten all A-E bonds and strengthen them, sometimes markedly. Trends in the binding energies, ''structural reorganization'' energies and ch arge transfer from donor to acceptor are analysed. Electronic bond ene rgies at the MP2 level range from 141 (AlH3NH3) to 37 (InH3AsH3) kJ/mo l, though these values are reduced to 120 and 31 kJ/mol after correcti on for BSSE. In general, bond energies decrease with the size of both donor and acceptor atoms, but the changes from row to row of the Perio dic Table are irregular. NH3 does not behave in the same way as the ot her donors, and forms a slightly stronger bond to AlH3 than to BH3.