The rhodium and iridium fluorido bifluorido complexes trans‐[Rh(4‐C5F4N)(F)(FHF)(CNtBu)(PEt3)2] (1) and trans‐[Ir(4‐C5F4N)(F)(FHF)(CNtBu)(PiPr3)2] (2) have been synthesized by protonation of the peroxido complexes trans‐[M(4‐C5F4N)(O2)(CNtBu)(PR3)2] with an HF source (M = Rh, R = Et; M = Ir, R = iPr). Abstraction of the coordinated HF resulted in the formation of the difluorido compounds trans‐[M(4‐C5F4N)(F)2(CNtBu)(PR3)2] (4: M = Rh, R = Et; 5: M = Ir, R = iPr).

Rh and Ir peroxido complexes have been studied in the metal-mediated hydrogenation of O2. Dissimilar reaction pathways have been found on using the Lewis-acid B(C6F5)3 or the Brønsted-acid [H(OEt2)2][B{3,5-(CF3)2C6H3}4] to give H2O·B(C6F5)3 or H2O2.

Treatment of the iridium(I) complex trans‐[Ir(4‐C5F4N)(CNtBu)(PiPr3)2] (2) with O2 or H2O2 gave the iridium(III) peroxido complex trans‐[Ir(4‐C5F4N)(O2)(CNtBu)(PiPr3)2] (3a). The peroxido complex 3a reacts with Brønsted acids to give the iridium(III) complexes cis‐[Ir(4‐C5F4N)(X)2(CNtBu)(L)(PiPr3)] (4: X = Cl, L = PiPr3, 5: X = CF3COO, L = H2O) and hydrogen peroxide. In the presence of formic acid, 3a yields the carbonato complex trans‐[Ir{κ2‐OC(O)O}(4‐C5F4N)(CNtBu)(PiPr3)2] (6) as the main product. Reactions between formic acid or dihydrogen and the iridium(I) complex 2 give the isomeric dihydrido complexes trans,trans‐[Ir(4‐C5F4N)(H)2(CNtBu)(PiPr3)2] (7a) and cis,trans‐[Ir(4‐C5F4N)(H)2(CNtBu)(PiPr3)2] (9a), respectively.

Invited for the cover of this issue is the group of Thomas Braun at Humboldt-Universität zu Berlin, Germany. The cover image shows the reaction pathways to the bifluorido and difluorido complexes mentioned in the paper.

The cover picture shows a part of the train and subway map of Berlin as well as the Oberbaum Bridge across the Spree River with a subway train in the background. The train lines symbolize the reaction pathways to convert one compound into another, and the construction sign indicates that the bifluorido complexes are not accessible from the metal (I) precursors, but there is a pathway starting from the peroxido complexes. The difluorido compounds are accessible by HF abstraction with a base. Details are discussed in the article by T. Braun et al. on http://onlinelibrary.wiley.com/doi/10.1002/ejic.201600682/abstract. For more on the story behind the cover research, see the http://onlinelibrary.wiley.com/doi/10.1002/ejic.201601152/full.