The copper compound [Cu(C6Cl2F3)(tht)]4 (1) (tht: tetrahydrothiophene) is an excellent catalyst for the trans-to cis-isomerization of complexes [PdAr2(tht)2](Ar: fluoroaryl) and also for the exchange of aryls between those palladium complexes. Herein, we also communicate the synthesis and characterization of 1, and some of its derivatives. The x-ray structure of 1 shows a linear chain of copper atoms, supported by fluoroaryl rings. The NMR 19 F-DOSY study indicates that this structure is preserved in solution although in equilibrium with other species. ASSOCIATED CONTENT Supporting Information. The supporting information contains: Experimental and computational methods (11 pages). This material is available free of charge via the Internet at http://pubs.acs.org AUTHOR INFORMATION

[Cu(bipy)(C 6 F 5 )] reacts with most aryl iodides to form heterobiphenyls by cross-coupling, but when Rf–I is used (Rf = 3,5-dicholoro-2,4,6-trifluorophenyl), homocoupling products are also formed. Kinetic studies suggest that, for the homocoupling reaction, a mechanism based on transmetalation from [Cu(bipy)(C 6 F 5 )] to Cu(III) intermediates formed in the oxidative addition step is at work. Density functional theory calculations show that the interaction between these Cu(III) species and the starting Cu(I) complex involves a Cu(I)–Cu(III) electron transfer concerted with the formation of an iodine bridge between the metals and that a fast transmetalation takes place in a dimer in a triplet state between two Cu(II) units.