METALLABORANES WITH GROUP-8 AND GROUP-9 TRANSITION-METALS - IS ACCURATE AB-INITIO MOLECULAR-ORBITAL CALCULATION OF STRUCTURE, STABILITY, AND NMR CHEMICAL-SHIFTS POSSIBLE

Ab initio MO study of structure, stability and rearrangements of nido- metallaboranes with Ir, Co, and Fe transition metals has been performe d at HF and correlated MP2 levels. Reasonable agreement with experimen t has been found for RHF optimized geometry of [(IrB5H8)(CO)(PH3)2] ir idaborane, and the MP2 optimization improves the agreement to the maxi mum error of 0.035 angstrom. Two geometric isomers, 2- with basal Ir a nd 1- with apical Ir are close in energy for [(IrB5H8)(CO)(PH3)2]. NMR B-11 and H-1 chemical shifts calculated by the IGLO method qualitativ ely reproduce experimental spectra. Methods more sophisticated than MP 2 would be necessary for accurate calculations of metallaboranes with first row transition metals.