Insertion, Rearrangement, and Coupling Processes in the Reactions of the Unsaturated Hydride Complex [W2(η5‑C5H5)2(H)(μ-PCy2)(CO)2] with Isocyanides
dataset
posted on 2013-08-26, 00:00 authored by M. Angeles Alvarez, M. Esther García, Daniel García-Vivó, Miguel A. Ruiz, M. Fernanda VegaThe title complex reacted with stoichiometric
amounts of CNR rapidly
at room temperature or below to give two types of formimidoyl derivatives:
the symmetrically bridged complexes [W2Cp2(μ-C,N:C,N-HCNR)(μ-PCy2)(CO)2] (R = tBu (W–W = 2.8645(5) Å), 4-C6H4OMe), and the asymmetrically bridged [W2Cp2{μ-C:N-HCN(Xyl)}(μ-PCy2)(CO)2] (Cp = η5-C5H5; Xyl = 2,6-C6H3Me2). The latter complex underwent slow isomerization at room temperature
to give the corresponding aminocarbyne derivative [W2Cp2{μ-CNH(Xyl)}(μ-PCy2)(CO)2], which in turn could be decarbonylated through irradiation with
UV–vis light to yield the 30-electron aminocarbyne complex
[W2Cp2{μ-CNH(Xyl)}(μ-PCy2)(μ-CO)] (W–W = 2.4928(4) Å). Density functional
theory calculations revealed that the aminocarbyne complex was the
most stable isomer for the three isocyanides under study, while subtle
steric effects marked the relative stability of the formimidoyl isomers,
which therefore are the kinetic products of these reactions. The reaction
of the title complex with excess CN(4-C6H4OMe)
at room temperature gave in good yield the complex [W2Cp2(μ-C,N:C,C′-HCN(4-C6H4OMe)C{N(4-C6H4OMe)})(μ-PCy2)(CO)2] (W–W = 2.9370(2) Å), having a 5-electron donor aminocarbene-iminoacyl
ligand derived from the N–C coupling of formimidoyl and isocyanide
ligands, whereas the analogous reaction with CNXyl gave the aminocarbyne
complex [W2Cp2{μ-CNH(Xyl)}(μ-PCy2){CN(Xyl)}(CO)] (W–W = 2.677(2) Å) having a terminal
bent isocyanide ligand.
