On the origin of the trans‐influence in square planar d 8 ‐complexes: A theoretical study

The trans influence of ligands T in trans‐[Ni(Cl) 2 NH 3 T] n complexes with T − B(Me)   2 − , H − , CP − , CH 2 CH   3 − , CN − , HCC − , Cl − , F − for n = −1 and TPF 3 , PH 3 , P(CH 3 ) 3 , CO for n = 0 has been analyzed with the help of the extended transition state (ETS) energy decomposition scheme as well as the natural orbitals for chemical valence (NOCV) method. The TCl 2 NiNH 3 bond is made up of the bonding interaction between the empty σ Ni acceptor orbital on the [TCl 2 Ni] n fragment and the σ NH3 donor orbital. The σ Ni orbital is in turn an out‐of‐phase combination between d   z   2on the metal and an occupied σ T orbital: σ Ni = d   z   2− C 1 × σ T . It is shown that the trans influence is related to the contribution ( C 1 ) to σ Ni from σ T . Thus, the smaller the contribution C 1 to σ Ni the larger the <σ Ni |σ NH3 > overlap and the stronger the TCl 2 NiNH 3 bond. The contribution C 1 is in turn related to the orbital energy ε(σ T ) of T. Thus the lower ε(σ T ) is, the smaller is C 1 . There is thus an inverse relation between the trans influence of a ligand T and its electronegativity. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009