Describing Polytopal Rearrangements of Fluxional Molecules with Curvilinear Coordinates Derived from Normal Vibrational Modes: A Conceptual Extension of Cremer–Pople Puckering Coordinates

Abstract

In this work a new curvilinear coordinate system is presented for the comprehensive description of polytopal rearrangements of N-coordinate compounds (N = 4–7) and systems containing an N-coordinate subunit. It is based on normal vibrational modes and a natural extension of the Cremer–Pople puckering coordinates (J. Am. Chem. Soc.1975971354) together with the Zou–Izotov–Cremer deformation coordinates (J. Phys. Chem. A20111158731) for ring structures to N-coordinate systems. We demonstrate that the new curvilinear coordinates are ideal reaction coordinates describing fluxional rearrangement pathways by revisiting the Berry pseudorotation and the lever mechanism in sulfur tetrafluoride, the Berry pseudorotation and two Muetterties’ mechanisms in pentavalent compounds, the chimeric pseudorotation in iodine pentafluoride, Bailar and Ray-Dutt twists in hexacoordinate tris-chelates as well as the Bartell mechanism in iodine heptafluoride. The results of our study reveal that this dedicated curvilinear coordinate system can be applied to most coordination compounds opening new ways for the systematic modeling of fluxional processes.

Describing Polytopal Rearrangement Processes of Octacoordinate Structures. I. Renewed Insights into Fluxionality of the Rhenium Polyhydride Complex ReH5(PPh3)2(Pyridine)

“…As a part of our enduring interest in describing the polytopal rearrangement mechanisms with theoretical chemistry, we chose the octacoordinate rhenium polyhydride complexes ReH 5 (PPh 3 ) 2 L (L = pyridine and 2-(acetylamino)­pyridine) as the subject to be investigated in this work. We chose rhenium polyhydrides as the first target in this series of investigations over other octacoordinate compounds − because fluxionality in rhenium polyhydrides is a current topic of interest in the experimental organometallic community. − …”

Interplay of Rotational and Pseudorotational Motions in Flexible Cyclic Molecules

“…From another point of view, this work is an initial assessment of usefulness and advantages of CPCs for the formulation of the NSE. The usefulness of CPCs and RDCs for the construction of n D-PESs (or to perform conformational studies) is well-known, ,− and new contributions concerning these coordinate systems and their generalization appeared in the literature in the last two years; , therefore, in the opinion of the authors the development and the assessment of computational tools aiming at the employment of these coordinates in a quantum mechanical description of the nuclear motions is worthwhile.…”

Theoretical Study on Epoxide Ring-opening in CO2/Epoxide Copolymerization Catalyzed by Bifunctional Salen-Type Cobalt(III) Complexes: Influence of Stereoelectronic Factors

“…Therefore, for the model system 1, we consider the SS-δ-trans and SS-δ-Λ-cis-β stereoisomers of the catalyst in the complexes with (R)-and (S)-enantiomers of propylene oxide (denoted in the following as RPO and SPO). It should be emphasized here that in the present work we focus on the relative stability of the alternative isomers, without considering the possible interconversion reactions between these complexes, such as e.g., nondissociative ligand exchange processes [63][64][65][66][67]. Our previous results for simple Co(III)-salcy complexes [51] indicated that trans ↔ cis-β interconversions can be characterized by relatively low barriers (13-15 kcal/mol), but they involve disfavored pentacoordinated trans species.…”