Computational study of the cyclopalladation mechanism of azobenzene with PdCl2 in N,N-dimethylformamide

Babić, Darko; Ćurić, Manda; Smith, David M. (2011) Computational study of the cyclopalladation mechanism of azobenzene with PdCl2 in N,N-dimethylformamide. Journal of Organometallic Chemistry, 696 (3). pp. 661-669. ISSN 0022-328X

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Abstract

The mechanism of cyclopalladation of azobenzene (L) with PdCl2 in N,N-dimethylformamide (dmf) was studied computationally, using DFT (B3LYP) methods supplemented with a continuum solvation model. Since the exact nature of the reacting complex is unknown, several candidates were considered. These were: (1) a mononuclear adduct with two ligand molecules, L-PdCl2-L, (2) a mononuclear adduct with one ligand and one solvent molecule, L-PdCl2-dmf, (3) a dinuclear adduct with a double chloride bridge, [L-PdCl-(mu-Cl)]2, and (4) a coordinatively unsaturated complex with an agostic interaction, L-PdCl2. The reaction profile initiating from L-PdCl2-dmf, which displays an agostic intermediate produced after displacement of the dmf molecule by the activating C-H bond, has the lowest barrier (20.4 kcal/mol in the step with the proton transfer to the O(dmf) atom). In all other reaction pathways, the proton migration is to a chlorine atom and is associated with remarkably high barriers. The results are related to previous experimental and other computational findings. While none of the reaction profiles includes explicit dissociation of the ligand, the proton transfer was found to occur only after the ligand is almost completely displaced from the coordinating shell. It was concluded that the transition state corresponds to 14-electron coordination of Pd and that ease of a ligand dissociation is an important, but not necessarily decisive, factor for cyclopalladation.

Item Type:	Article
Uncontrolled Keywords:	azobenzene; palladium chloride; agostic complex; N,N-Dimethyl formamide; C-H activation
Subjects:	NATURAL SCIENCES > Chemistry > Physical Chemistry NATURAL SCIENCES > Chemistry > Inorganic Chemistry NATURAL SCIENCES > Chemistry > Organic Chemistry
Divisions:	Division of Organic Chemistry and Biochemistry Division of Physical Chemistry
Projects:	Project title Project leader Project code Project type Dizajn, sinteza i svojstva organskih liganada i njihovih metalnih kompleksa [124246] Ćurić, Manda 098-0982915-2950 MZOS Računalno proučavanje strukture i funkcije proteina [260506] Smith, David Matthew 098-0982933-2937 MZOS
Depositing User:	Darko Babić
Date Deposited:	23 Oct 2012 14:11
URI:	http://fulir.irb.hr/id/eprint/435
DOI:	10.1016/j.jorganchem.2010.09.038

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