The Fluoro Analogue of Wilkinson's Catalyst and Unexpected Ph−Cl Activation

Abstract

The fluoro analogue of Wilkinson's catalyst, [(Ph3P)3RhF] (1), was synthesized and fully characterized. Both solution behavior and solid-state geometry parameters of 1 were found to be surprisingly similar to those of Wilkinson's catalyst. Unlike Wilkinson's catalyst however, 1 exhibited most unusual reactivity toward the notoriously inert C-Cl bond of nonactivated chloroarenes. The novel Ph-Cl activation with 1 includes fluorine transfer from the metal to a phosphine ligand and evidently phenyl transfer from the phosphine to Rh to produce an electron-rich sigma-phenylrhodium intermediate.

Transition metal bifluorides

“…These species were typically prepared by Cl/F exchange using AgF [17], or by C-F activation/hydrogenolysis of fluorinated alkenes [61]. Nowadays, the use of NEt 3 ·3HF is considered a more practical approach for metal fluoride synthesis [26,62]. However, since this reagent is also an excellent bifluoride promoter, various reports of Rh-FHF complexes have started to appear in the literature.…”

“…This type of complexes has shown a remarkable ability to promote various transformations [16-Page 4 of 44 A c c e p t e d M a n u s c r i p t 26]. Furthermore, it is now known that the reactivity of these compounds can be further influenced by interactions of the M-F bond with hydrogen bond donors, such as -OH, -NH or -CH groups [27,28].…”

“To Bend or not To Bend?” Both! The Planar and Bent Structures of[(Ph3P)4Rh2(μ‐F)2]

“…In this communication, we report the first example of such a complex, [(Ph 3 P) 4 Rh 2 (µ-F) 2 ]. Some of us recently reported [10,11] that the fluoro congener of Wilkinson's catalyst, [(Ph 3 P) 3 RhF], exhibits intriguing reactivity patterns. For instance, heating of [(Ph 3 P) 3 RhF] in benzene (at 80°C for 2.5 h) leads to F transfer to one of the P atoms, as shown in Equation (1).…”

“…For instance, heating of [(Ph 3 P) 3 RhF] in benzene (at 80°C for 2.5 h) leads to F transfer to one of the P atoms, as shown in Equation (1). [10] (1)…”

Synthesis of fluorinated oxygen- and sulfur-containing heteroaromatics

“…A series of mechanistic studies by Grushin et al had previously highlighted the challenges associated with formation of Ar-F bonds via reductive elimination [77][78][79][80][81][82]. The tBuBrettPhos ligand is crucial to the success of this methodology, as its large size both promotes reductive elimination of the Ar-F bond and also prevents the formation of unwanted dimeric [LPdAr(F)] 2 complexes.…”