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Theoretical investigation into the mechanism of reductive elimination from bimetallic palladium complexes

Citation

Ariafard, A and Hyland, CJT and Canty, AJ and Sharma, M and Yates, BF, Theoretical investigation into the mechanism of reductive elimination from bimetallic palladium complexes, Inorganic Chemistry, 50, (14) pp. 6449-6457. ISSN 0020-1669 (2011) [Refereed Article]


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Copyright Statement

Copyright 2011 American Chemical Society

DOI: doi:10.1021/ic102323s

Abstract

Reductive elimination of C-Cl and C-C bonds from binuclear organopalladium complexes containing Pd-Pd bonds with overall formal oxidation state +III are explored by density functional theory for dichloromethane and acetonitrile solvent environments. An X-ray crystallographically authenticated neutral complex, [(L-C,N)ClPd(μ-O2CMe)]2 (L = benzo[h]quinolinyl) (I), is examined for C-Cl coupling, and the proposed cation, [(L-C,N)PhPd1(mu-O2CMe)2Pd2 (L-C, N)]+ (II), examined for C-C coupling together with (L-C, N)PhPd1(μ-O2CMe)2Pd2Cl(L-C,N) (III) as a neutral analogue of II. In both polar and nonpolar solvents, reaction from III via chloride dissociation from Pd2 to form II is predicted to be favored. Cation II undergoes Ph-C coupling at Pd1 with concomitant Pd1-Pd2 lengthening and shortening of the Pd1-O bond trans to the carbon atom of L; natural bond orbital analysis indicates that reductive coupling from II involves depopulation of the dx2-y2 orbital of Pd1 and population of the dz2 orbitals of Pd1 and Pd2 as the Pd-Pd bond lengthens. Calculations for the symmetrical dichloro complex I indicate that a similar dissociative pathway for C-Cl coupling is competitive with a direct (nondissociative) pathway in acetonitrile, but the direct pathway is favored in dichloromethane. In contrast to the dissociative mechanism, direct coupling for I involves population of the dx2-y2 orbital of Pd1 with Pd1-O1 lengthening, significantly less population occurs for the dz2 orbital of Pd1 than for the dissociative pathway, and dz2 at Pd2 is only marginally populated resulting in an intermediate that is formally a Pd1(I)-Pd2(III) species, (L-CI-N,Cl)Pd1(μ-O2CMe)Pd2Cl(O2CMe)(L-C,N) that releases chloride from Pd2 with loss of Pd(I)-Pd(III) bonding to form a Pd (II) species. A similar process is formulated for the less competitive direct pathway for C-C coupling from III, in this case involving decreased population of the dz2 orbital of Pd2 and strengthening of the Pd(I)-Pd(III) interaction in the analogous intermediate with η2-coordination at Pd1 by L-Ph-N, C1-C2.

Item Details

Item Type:Refereed Article
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
Author:Ariafard, A (Associate Professor Alireza Ariafard)
Author:Hyland, CJT (Dr Chris Hyland)
Author:Canty, AJ (Professor Allan Canty)
Author:Sharma, M (Dr Manab Sharma)
Author:Yates, BF (Professor Brian Yates)
ID Code:72717
Year Published:2011
Web of Science® Times Cited:35
Deposited By:Chemistry
Deposited On:2011-08-31
Last Modified:2017-10-25
Downloads:0

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