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

ABSTRACT: The oxidation of [(Cp'''Co)₂ (μ,η²  : η² -E₂ )₂ ] (E=As (1), P (2); Cp'''=1,2,4-tri(tert-butyl)cyclopentadienyl) with halogens or halogen sources (I₂ , PBr₅ , PCl₅ ) was investigated. For the arsenic derivative, the ionic compounds [(Cp'''Co)₂ (μ,η⁴  : η⁴ -As₄ X)][Y] (X=I, Y=[As₆ I₈ ]_0.5 (3 a), Y=[Co₂ Cl_6-n I_n ]_0.5 (n=0, 2, 4; 3 b); X=Br, Y=[Co₂ Br₆ ]_0.5 (4); X=Cl, Y=[Co₂ Cl₆ ]_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-PBr₂ )₂ (μ-Br)][Co₂ Br₆ ]_0.5 (6 a), [(Cp'''Co)₂ (μ-PCl₂ )₂ (μ-Cl)][Co₂ Cl₆ ]_0.5 (6 b) and the neutral species [(Cp'''Co)₂ (μ-PCl₂ )(μ-PCl)(μ,η¹  : η¹ -P₂ Cl₃ ] (7), respectively. As an alternative approach, quenching of the dications [(Cp'''Co)₂ (μ,η⁴  : η⁴ -E₄ )][TEF]₂ (TEF=[Al{OC(CF₃ )₃ }₄ ]^- , E=As (8), P (9)) with KI yielded [(Cp'''Co)₂ (μ,η⁴  : η⁴ -As₄ I)][I] (10), representing the homologue of 3, and the neutral complex [(Cp'''Co)(Cp'''CoI₂ )(μ,η⁴  : η¹ -P₄ )] (11), respectively. The use of [(CH₃ )₄ N]F instead of KI leads to the formation of [(Cp'''Co)₂ (μ-PF₂ )(μ,η²  : η¹  : η¹ -P₃ F₂ )] (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 XeF₂ , that are difficult to control.

SUBMITTER: Garbagnati A 

PROVIDER: S-EPMC9400891 | biostudies-literature | 2022 Aug

REPOSITORIES: biostudies-literature