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- Title
C−C and C−N Couplings Following Hydride Addition on Isocyanide Cyclopolyenyl Dimolybdenum Complexes to Give Tethered Aldimine and Aminocarbene Derivatives.
- Authors
Alvarez, Belén; Alvarez, M. Angeles; García, M. Esther; García ‐ Vivó, Daniel; Ruiz, Miguel A.
- Abstract
Reaction of [Mo2Cp2(μ-κ1:κ1,η6-PMes*)(CO)2] with S or Se followed by protonation with [H(OEt2)2](BAr′4) gave the cationic derivatives [Mo2Cp2{μ-κ2P,E:κ1P,η5-EP(C6H3 tBu3)}(CNR)(CO)2](BAr′4) (E=S; R= tBu, iPr, Ph, 4-C6H4OMe, Xyl; or E=Se; R= tBu; Ar′=3,5-C6H3(CF3)2). Reaction of the latter with K[BH sBu3] yielded the aldimine complexes [Mo2Cp2{μ-κ2P,E:κ2P,N,η4-SP(C6H3 tBu3(CHNR))}(CO)2] and their aminocarbene isomers [Mo2Cp2{μ-κ2P,E:κ2P,C,η4-SP(C6H3 tBu3(NRCH))}(CO)2] (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 [Mo2Cp{μ-κ2P,S:κ1P,η5-SP(C6H3 tBu3)}(η4-C5H6)(CNR)(CO)2], which then undergo C−H oxidative addition to give the hydride isomers [Mo2Cp2{μ-κ2P,S:κ1P,η3-SP(C6H3 tBu3)}(H)(CNR)(CO)2]. 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 C6 ring (C−N coupling) or by migratory insertion of the formimidoyl ligand into the C6 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.
- Subjects
HYDRIDE transfer reactions; ISOCYANIDES; MOLYBDENUM compounds; CATALYTIC activity; ALDIMINES; CARBENE derivatives
- Publication
Chemistry - A European Journal, 2017, Vol 23, Issue 56, p14027
- ISSN
0947-6539
- Publication type
Article
- DOI
10.1002/chem.201702998