researchD

Jäkle Group
Research in Organometallic & Polymer Chemistry

Research


Project D. Supramolecular Assembly of Organocopper Compounds

IPentafluorophenylcopper, which was first described by Sheppard and Cairncross and has been further explored in our laboratory, display a tetrameric structure as confirmed by X-ray crystallography.[1] The copper centers in [C6F5Cu]4 act as Lewis acids towards sigma- or pi-donors.[2] We found that binding of nucleophiles can have a profound influence on the degree of association. Thus novel supramolecular aggregates form, for example, in the presence of pyridine or 4,4’-bipyridine (Figure 1). In both structures the copper centers are aligned in one-dimensional chains as shown by X-ray crystallography.[3] However, while cuprophilic interactions dominate the assembly of the blue-luminescent complex [C6F5Cu](py) (Cu-Cu = 2.8924(3) Å) (Figure 1a), a total of eight (!) pi-stacking interactions per molecule force the copper centers in [C6F5Cu]2(4,4'-bipy) to longer distances of ca. 3.639 Å, typical of strong pi-stacking interactions (Figure 1b). In collaboration with the Piotrowiak group we are currently further investigating a possible link between the luminescent properties of [C6F5Cu](py) and the alignment of the copper atoms in one-dimensional chains.
Figure 1. Supramolecular aggregates of pentafluorophenylcopper pyridine complexes. a) Structure and luminescence spectra of [C6F5Cu](py). b) Structure of [C6F5Cu]2(4,4'-bipy). X-ray structures courtesy of Prof. Rheingold.

Pentafluorophenylcopper also serves as a versatile reagent in organometallic chemistry.[1] For instance, in the synthesis of our perfluorinated organoborane Lewis acids we often take advantage of pentafluorophenylcopper as a mild reagent for transfer of the pentafluorophenyl moiety.[4] Rather unusual reactivity patterns are also sometimes observed: pentafluorophenylcopper reacts with aryltin reagents with highly selective transfer of copper to the aryl group. This can be exploited for the preparation of arylcopper species that are otherwise difficult to prepare. An interesting example is the formation of an organocopper cluster from reaction of 1,2-fc(SnMe3)2 with pentafluorophenylcopper.[5]

References:

(1) Details are provided in a recent review: F. Jäkle, Dalton Trans. (Invited Perspective) 2007, 2851-2858; "Pentafluorophenyl Copper: Aggregation and Complexation Phenomena, Photoluminescence Properties, and Applications as Reagent in Organometallic Synthesis".

(2) A. Sundararaman, R. Lalancette, L. N. Zakharov, A. L. Rheingold, F. Jäkle, Organometallics 2003, 22, 3526-3532; "Structural Diversity of Pentafluorophenylcopper Complexes. First Evidence of pi-Coordination of Unsupported Arenes to Organocopper Aggregates".

(3) A. Sundararaman, L. N. Zakharov, A. L. Rheingold, F. Jäkle, Chem. Commun. 2005, 1708-1710; "Cuprophilic and pi-Stacking Interactions in the Formation of Supramolecular Stacks from Dicoordinate Organocopper Complexes".

(4) A. Sundararaman and F. Jäkle, J. Organomet. Chem. 2003, 681, 134-142; "A Comparative Study of Base-Free Arylcopper Reagents for the Transfer of Aryl Groups to Boron Halides".

(5) K . Venkatasubbaiah, A. G. DiPasquale, A. L. Rheingold, M. Bolte, F. Jäkle, Angew. Chem. Int. Ed. 2006, 45, 6838-6841; "Mono- and Dimetalated Ferrocenylcopper Complexes via Tin-Copper Exchange".

Research

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Project B

Project C