Premium
Insights into trans ‐Ligand and Spin‐Orbit Effects on Electronic Structure and Ligand NMR Shifts in Transition‐Metal Complexes
Author(s) -
Greif Anja H.,
Hrobárik Peter,
Kaupp Martin
Publication year - 2017
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201700844
Subject(s) - chemistry , ligand (biochemistry) , transition metal , metal , scalar (mathematics) , crystallography , relativistic quantum chemistry , spinor , atomic physics , physics , geometry , quantum mechanics , mathematics , organic chemistry , catalysis , biochemistry , receptor
Abstract Surprisingly general effects of trans ligands L on the ligand NMR shifts in third‐row transition‐metal complexes have been found by quasi‐relativistic computations, encompassing 5d 10 , 5d 8 , and to some extent even 5d 6 situations. Closer analysis, with emphasis on 1 H shieldings in a series of linear HAu I L q complexes, reveals a dominance of spin‐orbit (SO) effects, which can change sign from appreciably shielding for weak trans ligands to appreciably deshielding for ligands with strong trans influence. This may be traced back to increasing destabilization of a σ‐type MO at scalar relativistic level, which translates into very different σ‐/π‐mixing if SO coupling is included. For the strongest trans ligands, the σ‐MO may move above the highest occupied π‐type MOs, thereby dramatically reducing strongly shielding contributions from predominantly π‐type spinors. The effects of SO‐mixing are in turn related to angular momentum admixture from atomic spinors at the metal center. These SO‐induced trends hold for other nuclei and may also be used to qualitatively predict shifts in unknown complexes.