Reactions of the phosphinidene-bridged complexes [Fe2(η5-C5H5)2(μ-PR)(μ-CO)(CO)2] (R = Cy, Ph) with electrophiles based on p-block elements

Abstract

The title complexes reacted readily with the methylating agents MeI and CF₃SO₃Me, chalcogens (O₂, S₈) and borane adducts BH₃·L (L = THF, N^tBu₃, PPh₃) to initially give the corresponding neutral or cationic derivatives of the type [Fe₂Cp₂{μ-P(E)R}(μ-CO)(CO)₂]ⁿ (Cp = η⁵-C₅H₅; n = 0, E = O, S, BH₃; n = +1, E = Me), which could be further functionalized through additional reactions. Thus, the oxophosphinidene complex [Fe₂Cp₂{μ-P(O)Cy}(μ-CO)(CO)₂] could be protonated or alkylated with HBF₄·OEt₂ or CF₃SO₃Me, to give the complexes [Fe₂Cp₂{μ-P(OR′)Cy}(μ-CO)(CO)₂]⁺ (R′ = H, Me) respectively, while the photochemical treatment of compounds [Fe₂Cp₂{μ-P(BH₃)R}(μ-CO)(CO)₂] gave the dicarbonyl derivatives [Fe₂Cp₂{μ-κ¹:κ¹,η²-P(BH₃)R}(μ-CO)(CO)], with a phosphinidene–borane ligand displaying coordination of a B–H bond to one of the iron atoms in a side-on fashion (Fe–H = 1.78(4) Å, Fe–B = 2.351(5) Å for the PCy compound). The title complexes also reacted readily with 3,5-di-tert-butyl-o-benzoquinone or benzyl azide. The first reaction gave the phosphonite complex [Fe₂Cp₂(μ-CO)₂(CO){P(O₂C₆H₂^tBu₂)R}], while the second reaction yielded initially the corresponding 1 : 1 adducts [Fe₂Cp₂{μ-P(N₃CH₂Ph)R}(μ-CO)(CO)₂], with a P:P-bound phosphatriazadiene ligand. The PCy compound underwent clean denitrogenation in toluene at 368 K to give the iminophosphinidene complex [Fe₂Cp₂{μ-P(NCH₂Ph)Cy}(μ-CO)(CO)₂], which in turn could be protonated selectively with [NH₄]PF₆ at the P-bound nitrogen atom, to yield the aminophosphide derivative [Fe₂Cp₂{μ-P(NHCH₂Ph)Cy}(μ-CO)(CO)₂]PF₆ (Fe–Fe = 2.6362(8) Å). Denitrogenation could be also induced photochemically on the phosphatriazadiene complex, but this also caused fragmentation and recombination of different bonds to give the trinuclear compound [Fe₃Cp₃(μ₃-PCy){μ-κ¹:κ¹-C(O)(NHCH₂Ph)}(μ-CO)₂], having phosphinidene and C:O-bound aminoacyl ligands bridging the metal atoms.