Interligand interaction and the three-dimensional structure of coordination compounds. Monodentate ligands

Revisiting the polytopal rearrangements in penta-coordinate d7-metallocomplexes: modified Berry pseudorotation, octahedral switch, and butterfly isomerization

“…87 )). Classical interligand interaction theory 10 , 18 based on the partitioning of the interligand interactions into 6-exp (one-variable Kitaigorodsky-type) and Coulomb potentials makes it possible to distinguish the contributions of size and polarity of ligand spheres, respectively, to the stabilization of a polyhedral structure. Qualitatively, the increase in the covalent radius of the central metal (assuming fixed valence-shell configuration) results in longer M–L coordination bonds ( i.e.…”

“…Such an increased spacing (which would be expected for the Ru and Os complexes relative to the Fe prototype) will alleviate steric repulsion between the ligands and will thus make coordination polyhedra with smaller baseline ligand separation (such as SP in comparison to EBT) more competitive. 10 …”

“… 2 – 6 , 9 – 11 , 13 – 15 The structural theory of polytopal processes has been developed on a conceptual level using the valence shell electron pair repulsion (VSEPR) theory 16 and related points-on-a-sphere models. 9 , 10 , 17 , 18 A more quantitative, first-principles understanding has been afforded by computational quantum chemistry. 19 – 25 …”

Molecular mechanics calculations of ?-diketonate, aqua, and aqua-?-diketonate complexes of lanthanide ions using Gillespie-Kepert model

“…Technically, the common nonbonded 6-12 or 6-exp potentials with their standard parameters are used. In the molecular mechanics of coordination compounds, this approach may be traced back to the works of Hambley 34 -36 (who, in turn, referred to Dashevskii 37 and Kepert 38 ). Currently, MM-POS is about to become a future de facto standard; there exists a large number of works performed within this paradigm.…”

Full Conformational Analyses of the Ultrafast Isomerization in Penta-coordinated Ru(S2C2(CF3)2)(CO)(PPh3)2: One Compound, Two Crystal Structures, Three CO Frequencies, 24 Stereoisomers, and 48 Transition States

“…The conformational flexibility of penta-coordinated compounds plays a key role in the stereoselectivity and catalytic activity in metallocomplexes. − Although the interconversions between ideal trigonal bipyramidal (TBP) and ideal square pyramidal (SP) structures of penta-coordinated compounds are usually facile and rapid, alternative nonideal coordination geometries − and their fluxional behavior − ,,− present a challenge for simple intramolecular exchange mechanisms. Over the past decades, several mechanistic proposals for different metal–ligand species have been made. − ,,,,,− ,− Berry pseudorotation (BPR) is the most commonly proposed mechanism to describe the interchange of axial and equatorial substituents of penta-coordinated, TBP species. In addition to BPR, other mechanisms include the following: the tetrahedral jump for quasi-tetrahedral HML 4 and H 2 ML 3 complexes; ,, the turnstile rotation, ,− ,, which involves an internal rotation of a trio , with respect to pair of substituents; and the reverse BPR, …”