A DFT study of alkyl halide exchange from Pd(IV) to Pd(II) centers supports proposals for an S_N2 process in which nucleophilic Pd(II) square-planar complexes attack the axial alkyl group in electrophilic squarepyramidal Pd(IV) centers, leading to transfer of R⁺ from Pd(IV) to Pd(II) involving a transition structure of the form [R₂(bpy)··R··PdR₂ (bpy)]⁺ (bpy = 2,20’ -bipyridine). Computation accounts for the selectivity in benzyl (Bn) over methyl transfer from PhMeBnPd^IV(bpy)Br to Me₂Pd^II(bpy), giving PhMePd^II(bpy) and BnMe₂Pd^IV(bpy). Transition structures are formed by the interaction of a d_z2-like HOMO at the Pd(II) nucleophile and the Pd-C σ* LUMO at the cationic Pd(IV) electrophile. Isomerization of octahedral palladium(IV) complexes via halide loss followed by involvement of trigonal-bipyramidal transition structures to facilitate isomerization is also examined. A lower barrier for Bn⁺ than Me⁺ transfer is attributed to stabilisation of the transition structure by delocalisation of positive charge within the benzyl group, reflected in a higher total charge density for the benzyl group than found for the methyl group.

Item Type:	Refereed Article
Keywords:	organopalladium, palladium(IV), DFT, exchange reactions, redox transmetallation, octahedral isomerism, isomerization
Research Division:	Chemical Sciences
Research Group:	Other Chemical Sciences
Research Field:	Organometallic Chemistry
Objective Division:	Expanding Knowledge
Objective Group:	Expanding Knowledge
Objective Field:	Expanding Knowledge in the Chemical Sciences
UTAS Author:	Canty, AJ (Professor Allan Canty)
UTAS Author:	Ariafard, A (Associate Professor Alireza Ariafard)
ID Code:	128212
Year Published:	2018
Deposited By:	Chemistry
Deposited On:	2018-09-10
Last Modified:	2019-03-07
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