Theoretical calculations for Hj and hydride

Qualitative ideas of catalytic Hj activation on metals were devised in the late 1950s in connection with the formation of transition states or intermediates prior to OA of H2 to hydride complexes (see Chapter 2). Surprisingly, there was no molecular orbital analysis of this intriguing theoretical problem until Dedieu carried one out in 1979. Both extended Huckel and ab initio Hartree-Fock calculations were carried out on H2 addition to square-planar 4 RhCl(PH3)3, a model for the well-known Wilkinson catalyst in which the phosphine is PPhj. In this 16e complex, the approaches the filled d i metal orbital. Calculations indicate that at the beginning of the reaction, end-on (i/ ) proach of H-H is preferred over side-on (ri ) proach (Eq. 4.1). 

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