Insertion, Rearrangement, and Coupling Processes in the Reactions of the Unsaturated Hydride Complex [W2(η5‑C5H5)2(H)(μ-PCy2)(CO)2] with Isocyanides

The 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.

标题化合物与等摩尔量的CNR在室温或更低温度下迅速反应，生成两种类型的甲酰脒衍生物：对称桥接的复合物[W2Cp2(μ-C,N:C,N-HCNR)­(μ-PCy2)­(CO)2]（R = tBu，W-W = 2.8645(5) Å，4-C6H4OMe）和不对称桥接的[W2Cp2{μ-C:N-HCN­(Xyl)}­(μ-PCy2)­(CO)2]（Cp = η5-C5H5；Xyl = 2,6-C6H3Me2）。后者在室温下经历缓慢的异构化，生成相应的氨基甲炔衍生物[W2Cp2{μ-CNH­(Xyl)}­(μ-PCy2)­(CO)2]，该衍生物随后可通过紫外线-可见光照射进行脱羰，从而得到30电子的氨基甲炔复合物[W2Cp2{μ-CNH­(Xyl)}­(μ-PCy2)­(μ-CO)]（W-W = 2.4928(4) Å）。密度泛函理论计算表明，对于所研究的三种异氰酸酯，氨基甲炔复合物是最稳定的异构体，而微妙的立体效应标志着甲酰脒异构体的相对稳定性，因此这些异构体是该反应的动力学产物。标题化合物与过量的CN­(4-C6H4OMe)在室温下反应，以良好的产率得到了复合物[W2Cp2(μ-C,N:C,C′-HCN­(4-C6H4OMe)­C­{N­(4-C6H4OMe)})­(μ-PCy2)­(CO)2]（W–W = 2.9370(2) Å），其中含有由甲酰脒配体和异氰酸酯配体的N-C偶联产生的5电子供体氨基甲酰亚胺酰配体，而与CNXyl的类似反应则得到了具有末端弯曲异氰酸酯配体的氨基甲炔复合物[W2Cp2{μ-CNH­(Xyl)}­(μ-PCy2)­{CN­(Xyl)}­(CO)]（W–W = 2.677(2) Å）。