Alvarez Belén, Alvarez M Angeles, García M Esther, García-Vivó Daniel, Ruiz Miguel A
Departamento de Química Orgánica e Inorgánica/IUQOEM, Universidad de Oviedo, 33071, Oviedo, Spain.
Chemistry. 2017 Oct 9;23(56):14027-14038. doi: 10.1002/chem.201702998. Epub 2017 Sep 8.
Reaction of [Mo Cp (μ-κ :κ ,η -PMes*)(CO) ] with S or Se followed by protonation with H(OEt ) gave the cationic derivatives Mo Cp {μ-κ :κ ,η -EP(C H tBu )}(CNR)(CO) (E=S; R=tBu, iPr, Ph, 4-C H OMe, Xyl; or E=Se; R=tBu; Ar'=3,5-C H (CF ) ). Reaction of the latter with K[BHsBu ] yielded the aldimine complexes [Mo Cp {μ-κ :κ ,η -SP(C H tBu (CHNR))}(CO) ] and their aminocarbene isomers [Mo Cp {μ-κ :κ ,η -SP(C H tBu (NRCH))}(CO) ] (R ≠ Xyl), following C-C and C-N couplings, respectively. Monitoring of these reactions revealed that the initial H attack takes place at a Cp ligand to give cyclopentadiene intermediates [Mo Cp{μ-κ :κ ,η -SP(C H tBu )}(η -C H )(CNR)(CO) ], which then undergo C-H oxidative addition to give the hydride isomers [Mo Cp {μ-κ :κ ,η -SP(C H tBu )}(H)(CNR)(CO) ]. In turn, the latter rearrange to give the aldimine and aminocarbene complexes. DFT calculations revealed that the hydride intermediates first undergo migratory insertion of the isocyanide ligand into the Mo-H bond to give unobservable formimidoyl intermediates, which then evolve either by nucleophilic attack of the N atom on the C ring (C-N coupling) or by migratory insertion of the formimidoyl ligand into the C ring (C-C coupling). Our data suggest that increasing the size of the substituent R at the isocyanide ligand destabilizes the aldimine isomer to a greater extent, thus favoring formation of the aminocarbene complex.
[Mo Cp (μ-κ :κ,η -PMes*)(CO) ]与S或Se反应，随后用H(OEt ) 进行质子化，得到阳离子衍生物Mo Cp {μ-κ :κ,η -EP(C H tBu )}(CNR)(CO) （E = S；R = tBu、iPr、Ph、4-C H OMe、Xyl；或E = Se；R = tBu；Ar' = 3,5-C H (CF ) ）。后者与K[BHsBu ]反应，分别经过C-C和C-N偶联后，生成醛亚胺配合物[Mo Cp {μ-κ :κ,η -SP(C H tBu (CHNR))}(CO) ]及其氨基卡宾异构体[Mo Cp {μ-κ :κ,η -SP(C H tBu (NRCH))}(CO) ]（R ≠ Xyl）。对这些反应的监测表明，最初的H进攻发生在一个Cp配体上，生成环戊二烯中间体[Mo Cp{μ-κ :κ,η -SP(C H tBu )}(η -C H )(CNR)(CO) ]，然后该中间体进行C-H氧化加成，生成氢化物异构体[Mo Cp {μ-κ :κ,η -SP(C H tBu )}(H)(CNR)(CO) ]。相应地，后者重排生成醛亚胺和氨基卡宾配合物。密度泛函理论计算表明，氢化物中间体首先经历异氰化物配体向Mo-H键的迁移插入，生成不可观测的甲脒基中间体，然后该中间体通过N原子对C环的亲核进攻（C-N偶联）或甲脒基配体向C环的迁移插入（C-C偶联）而演化。我们的数据表明，异氰化物配体上取代基R尺寸的增加会使醛亚胺异构体更不稳定，从而有利于氨基卡宾配合物的形成。
