C(sp3)–Cl bond activation promoted by a POP-pincer Rhodium(I) complex

The complex [RhCl(κ3P,O,P-{xant(PiPr2)2})] (1; xant(PiPr2)2 = 9,9-dimethyl-4,5-bis(diisopropylphosphino)xanthene) activates C(sp3)–Cl bonds of mono- and dichloroalkanes and catalyzes the dehalogenation of chloroalkanes and the homocoupling of benzyl chloride. Complex 1 reacts with chlorocyclohexane to give [RhHCl2(κ3P,O,P-{xant(PiPr2)2})] (2) and cyclohexene and promotes the dehalogenation of the chlorocycloalkane to cyclohexane using 2-propanol solutions of sodium formate as the reducing agent. The oxidative addition of benzyl chloride to 1 leads to [Rh(CH2Ph)Cl2(κ3P,O,P-{xant(PiPr2)2})] (4). The dehalogenation of this chloroalkane with 2-propanol solutions of sodium formate, in the presence of 1, gives toluene and 1,2-diphenylethane. The latter is selectively formed with KOH instead of sodium formate. Complex 1 also reacts with trans-1,2-dichlorocyclohexane and dichloromethane. The reaction with the former gives [RhCl3(κ3P,O,P-{xant(PiPr2)2})] (5) and cyclohexene, whereas complex 1 undergoes oxidative addition of dichloromethane to afford cis-dichloride-[Rh(CH2Cl)Cl2(κ3P,O,P-{xant(PiPr2)2})] (6a), which evolves into its trans-dichloride isomer 6b. The kinetic study of the overall process suggests that the oxidative addition is cis-concerted and the isomerization an intramolecular reaction which takes place through a σ-C–Cl intermediate with two conformations.Financial support from the MINECO of Spain (Projects CTQ2017-82935-P and Red de Excelencia Consolider CTQ2016-81797-REDC), the Diputacion General de Aragon (Group E06_17R and project LMP148_18), FEDER, and the European Social Fund is acknowledged. L.A.d.l.H. thanks the MECD for her FPU Contract (FPU17/04813).Peer reviewe