Halogenation and Nucleophilic Quenching: Two Routes to E−X Bond Formation in Cobalt Triple‐Decker Complexes (E=As, P; X=F, Cl, Br, I)

The oxidation of [(Cp’’’Co)(2)(μ,η(2) : η(2)‐E(2))(2)] (E=As (1), P (2); Cp’’’=1,2,4‐tri(tert‐butyl)cyclopentadienyl) with halogens or halogen sources (I(2), PBr(5), PCl(5)) was investigated. For the arsenic derivative, the ionic compounds [(Cp’’’Co)(2)(μ,η(4) : η(4)−As(4)X)][Y] (X=I, Y=[As(6)I(8)](0.5) (3 a), Y=[Co(2)Cl(6‐n )I( n )](0.5) (n=0, 2, 4; 3 b); X=Br, Y=[Co(2)Br(6)](0.5) (4); X=Cl, Y=[Co(2)Cl(6)](0.5) (5)) were isolated. The oxidation of the phosphorus analogue 2 with bromine and chlorine sources yielded the ionic complexes [(Cp’’’Co)(2)(μ‐PBr(2))(2)(μ‐Br)][Co(2)Br(6)](0.5) (6 a), [(Cp’’’Co)(2)(μ‐PCl(2))(2)(μ‐Cl)][Co(2)Cl(6)](0.5) (6 b) and the neutral species [(Cp’’’Co)(2)(μ‐PCl(2))(μ‐PCl)(μ,η(1) : η(1)‐P(2)Cl(3)] (7), respectively. As an alternative approach, quenching of the dications [(Cp’’’Co)(2)(μ,η(4) : η(4)‐E(4))][TEF](2) (TEF=[Al{OC(CF(3))(3)}(4)](−), E=As (8), P (9)) with KI yielded [(Cp’’’Co)(2)(μ,η(4) : η(4)‐As(4)I)][I] (10), representing the homologue of 3, and the neutral complex [(Cp’’’Co)(Cp’’’CoI(2))(μ,η(4) : η(1)‐P(4))] (11), respectively. The use of [(CH(3))(4)N]F instead of KI leads to the formation of [(Cp’’’Co)(2)(μ‐PF(2))(μ,η(2) : η(1) : η(1)‐P(3)F(2))] (12) and 2, thereby revealing synthetic access to polyphosphorus compounds bearing P−F groups and avoiding the use of very strong fluorinating reagents, such as XeF(2), that are difficult to control.