FULL PAPER DOI:10.1002/ejic.201500324 Benzoato and Thiobenzoato Ligands in the Synthesis of Dinuclear Palladium(III) and -(II) Compounds: Stability and Catalytic Applications Francisco Estevan, [a] Susana Ibáñez, [a] Albert Ofori, [b] Pipsa Hirva,* [b] Mercedes Sanaú, [a] and M a Angeles Úbeda* [a] Keywords: Homogeneous catalysis / Electrochemistry / Palladium / S ligands / Structure elucidation / Density functional calculations New palladium(III) compounds of formula Pd 2 [(C 6 H 4 )- PPh 2 ] 2 [OXC(C 6 H 5 )] 2 Cl 2 [3a (X = O); 3b (X = S)] were ob- tained by the oxidation of the analogous palladium(II) ones with PhICl 2 and were characterized by 31 P, 1 H, and 13 C NMR spectroscopy at 223 K. Compound 3a was also structurally characterized by single-crystal X-ray diffraction methods, which revealed a Pd–Pd distance of 2.5212(10) Å. DFT calcu- lations were conducted to study the stability of all of these new palladium(III) and -(II) compounds with focus on the in- fluence of the O↔S substitution of the donor atom in the li- Introduction Even though the chemistry of palladium(III) compounds has undergone some major advances in the last ten years, this area is still not well known. [1] Few dinuclear palladium(III) compounds have been well characterized since the first one with a Pd 2 6+ core and a M–M bond was synthesized by Cotton and co-workers. [2] In recent years, our research has focused on the chemistry of this type of palladium(III) compounds, and we reported the first high-yield syntheses of these complexes. [3] Moreover, Ritter and co-workers have characterized not only other discrete dinuclear [4] and 1D wire [5] palladi- um(III) complexes with metal–metal bonds but also a tran- sition-state analogue for the oxidation of a palladium(II) compound to a palladium(III) one. [6] Furthermore, Mirica and co-workers and Bauer and co-workers reported new dinuclear compounds with Pd III –X–Pd III bridges in their structures. [7] We performed a topological charge-density analysis of several ortho-metalated palladium(III) compounds with [a] Departament de Química Inorgànica, Universitat de València, Dr. Moliner 50, 46100 Burjassot, València, Spain E-mail: angeles.ubeda@uv.es http://www.uv.es [b] Department of Chemistry, University of Eastern Finland, Joensuu Campus, P. O. Box 111, 80101 Joensuu, Finland E-mail: pipsa.hirva@uef.fi http://www.uef.fi Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/ejic.201500324. Eur. J. Inorg. Chem. 2015, 2822–2832 © 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 2822 gand. The palladium(II) compounds Pd 2 [(C 6 H 4 )PPh 2 ] 2 - [OXC(C 6 H 5 )] 2 [2a (X = O), 2b (X = S)] were also tested as precatalyst in two reactions: (1) the acetoxylation of 2-phen- ylpyridine and (2) the room-temperature 2-phenylation of indoles. Compound 2b is a better precatalyst than 2a in the first reaction (4 h; isolated yield, 67.5 vs. 50.4 %). In the sec- ond catalytic reaction, isolated yields of 97 (10 h, substrate: 1-methylindole) and 99 % (24 h, substrate: indole) were ob- tained with 2a as the precatalyst, whereas 2b gave low or no conversion. bridging N,S-donor ligands, which had been synthesized and characterized previously. [3e] The results were compared with those obtained with similar compounds with N,O-do- nor ligands. The study showed that the contribution of the sulfur p orbitals to the highest occupied molecular orbital (HOMO) allows a greater stabilization of the dinuclear pal- ladium(III) compounds. In this paper, we present the syn- thesis and characterization of new dinuclear palladium(III) compounds of formula Pd 2 [(C 6 H 4 )PPh 2 ] 2 [OXC(C 6 H 5 )] 2 Cl 2 (X = O or S; Figure 1, A) obtained by the oxidation of compounds of type B (Figure 1, B). The target is the study of their reactivity and stability to obtain information about how these compounds are affected by changes of the O do- nor atom of the bridging ligand to a softer atom such as S. DFT calculations have been performed for all of the palla- dium(III) and -(II) compounds, and the results have been compared with those for other carboxylate compounds. Figure 1. Dinuclear metalated (A) palladium(III) and (B) palla- dium(II) compounds. Palladium compounds are effective catalysts in cross- coupling reactions. The catalytic direct oxidation of arene