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)(mu,eta(2) : eta(2)-E-2)(2)] (E = As (1), P (2); Cp''' = 1,2,4-tri(tert-butyl)cyclopentadienyl) with halogens or halogen sources (I-2, PBr5, PCl5) was investigated. For the arsenic derivative, the ionic compounds [(Cp'''Co)(2)(mu,eta(4) : eta(4)-As4X)][Y] (X = I, Y = [As(6)I8](0.5) (3 a), Y = [Co2Cl6-nIn](0.5 )(n = 0, 2, 4; 3 b); X = Br, Y = [Co2Br6](0.5) (4); X = Cl, Y = [Co2Cl6](0.5) (5)) were isolated. The oxidation of the phosphorus analogue 2 with bromine and chlorine sources yielded the ionic complexes [(Cp'''Co)(2)(mu-PBr2)(2)(mu-Br)][Co2Br6](0.5) (6a), [(Cp'''Co)(2)(mu-PCl2)(2)(mu-Cl)][Co2Cl6](0.5) (6b) and the neutral species [(Cp'''Co)(2)(mu-PCl2)(mu-PCl)(mu,eta(1) : eta(1)-P2Cl3] (7), respectively. As an alternative approach, quenching of the dications [(Cp'''Co)(2)(mu,eta(4) : eta(4)-E-4)][TEF](2) (TEF = [Al{OC(CF3)(3)}(4)](-), E = As (8), P (9)) with KI yielded [(Cp'''Co)(2)(mu,eta(4) : eta(4)-As4I)][I] (10), representing the homologue of 3, and the neutral complex [(Cp'''Co)(Cp'''CoI2)(mu,eta(4) : eta(1)-P-4)] (11), respectively. The use of [(CH3)(4)N]F instead of KI leads to the formation of [(Cp'''Co)(2)(mu-PF2)(mu,eta(2) : eta(1) : eta(1)-P3F2)] (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.

Automated summary

This study investigated the oxidation of [(Cp'''Co)(2)(mu,eta(2) : eta(2)-E-2)(2)] (E = As (1), P (2); Cp''' = 1,2,4-tri(tert-butyl)cyclopentadienyl) with halogens or halogen sources. Various ionic compounds and neutral species were obtained and characterized, providing a new method for the synthesis of polyphosphorus compounds.