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.

M Angeles Alvarez, M Esther García, Rocío González, Miguel A Ruiz

Index: Dalton Trans. 41(48) , 14498-513, (2012)

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Abstract

The title complexes reacted readily with the methylating agents MeI and CF(3)SO(3)Me, chalcogens (O(2), S(8)) and borane adducts BH(3)·L (L = THF, N(t)Bu(3), PPh(3)) to initially give the corresponding neutral or cationic derivatives of the type [Fe(2)Cp(2){μ-P(E)R}(μ-CO)(CO)(2)](n) (Cp = η(5)-C(5)H(5); n = 0, E = O, S, BH(3); n = +1, E = Me), which could be further functionalized through additional reactions. Thus, the oxophosphinidene complex [Fe(2)Cp(2){μ-P(O)Cy}(μ-CO)(CO)(2)] could be protonated or alkylated with HBF(4)·OEt(2) or CF(3)SO(3)Me, to give the complexes [Fe(2)Cp(2){μ-P(OR')Cy}(μ-CO)(CO)(2)](+) (R' = H, Me) respectively, while the photochemical treatment of compounds [Fe(2)Cp(2){μ-P(BH(3))R}(μ-CO)(CO)(2)] gave the dicarbonyl derivatives [Fe(2)Cp(2){μ-κ(1):κ(1),η(2)-P(BH(3))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 [Fe(2)Cp(2)(μ-CO)(2)(CO){P(O(2)C(6)H(2)(t)Bu(2))R}], while the second reaction yielded initially the corresponding 1 : 1 adducts [Fe(2)Cp(2){μ-P(N(3)CH(2)Ph)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 [Fe(2)Cp(2){μ-P(NCH(2)Ph)Cy}(μ-CO)(CO)(2)], which in turn could be protonated selectively with [NH(4)]PF(6) at the P-bound nitrogen atom, to yield the aminophosphide derivative [Fe(2)Cp(2){μ-P(NHCH(2)Ph)Cy}(μ-CO)(CO)(2)]PF(6) (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 [Fe(3)Cp(3)(μ(3)-PCy){μ-κ(1):κ(1)-C(O)(NHCH(2)Ph)}(μ-CO)(2)], having phosphinidene and C:O-bound aminoacyl ligands bridging the metal atoms.