Palladium motion in cyclomeric compounds: a theoretical study.

Area of Science:

• Organometallic Chemistry
• Computational Chemistry
• Supramolecular Chemistry

Background:

• Intramolecular palladium shifts in cyclomeric complexes are explored.
• The potential for continuous motion of palladium moieties within organic structures is investigated.

Purpose of the Study:

• To computationally study successive intramolecular 1,n palladium shifts (n=3-5) in palladium complexes of organic cyclomers.
• To determine the feasibility of endless motion for palladium moieties in different cyclomeric systems.

Main Methods:

• Density Functional Theory (DFT) with the B3LYP functional was employed.
• Calculations focused on palladium shifts (PdBr(phosphine) moiety) and hydrogen atom exchange within cyclomers.

Main Results:

• [1,1,1,1]paracyclophane exhibits high energy barriers for 1,2 Pd/H exchange, restricting motion to a pendulum-like movement.
• THF-based systems (16-crown-4 and cyclic dimer) show more accessible endo-face pathways.
• An endless motion involving successive 1,2 and 1,5 shifts was identified in the 16-crown-4 system with barriers under 30 kcal mol(-1).

Conclusions:

• The [1,1,1,1]paracyclophane is unsuitable for circular palladium motion due to high energy barriers.
• THF-based cyclomers, particularly the 16-crown-4 structure, demonstrate potential for sustained intramolecular palladium movement.
• Computational insights guide the design of molecular systems for controlled dynamic processes.