Synthesis and reactivity of [M(η3-allyl)(η2-amidinato)(CO)2(phosphonium ylide)] (M = Mo, W): Investigation of the ligand properties of phosphonium ylides

• Published in: Inorganica Chimica Acta 2018-02, Vol.471, p.310-315
• Main Authors: Takaki, Daichi, Ogata, Kenichi, Kurihara, Youji, Ueda, Kazuyoshi, Hashimoto, Toru, Yamaguchi, Yoshitaka
• Format: Article
• Language: English
• Subjects: Bond strength; Bonding strength; Coordination compounds; DFT calculations; Diffraction; Electron donating ability; Electrons; Ligands; Molecules; Phosphonium ylide; Salt; Spectrum analysis; Substitution reactions; X-ray diffraction
• ISSN: 0020-1693; 1873-3255
• DOI: 10.1016/j.ica.2017.11.019

Phosphonium ylide complexes of Mo and W were prepared. The electron donating ability of phosphonium ylide and the robustness of the M-C(phosphonium ylide) bond were investigated. [Display omitted] •Phosphonium ylide complexes of Mo and W were prepared and characterized spectroscopically, as well as by X-ray diffraction.•The electron donating ability of phosphonium ylide as a ligand was estimated by experimental and theoretical studies.•The robustness of the M-C(phosphonium ylide) bond was investigated by reaction with two-electron donors. Phosphonium ylide complexes of Mo and W formulated as [M(η3-allyl){η2-(NPh)2CH}(CO)2(CH2PR3)] (M = Mo, R = Me: 2a-Mo; M = Mo, R = Ph: 2b-Mo, and M = W, R = Me: 2a-W) were prepared by the reaction of amidinato(pyridine) complex, [M(η3-allyl){η2-(NPh)2CH}(CO)2(NC5H5)] (M = Mo: 1-Mo and M = W: 1-W), with a phosphonium ylide, CH2PR3 (R = Me, Ph), which was generated in situ by the reaction of the corresponding phosphonium salt with nBuLi. These complexes were characterized spectroscopically, as well as by the X-ray diffraction. The phosphonium ylide ligand shows stronger electron donating ability toward the metal than N-heterocyclic carbene or phosphine ligands. This trend is supported by the comparison of the spectroscopic data and the DFT calculations. We also investigated the reactivity of the phosphonium ylide complexes 2-Mo with two-electron donors such as PEt3 and NHC. In the case of the PPh3 ylide complex (2b-Mo), the substitution reaction of the ylide ligand for the two-electron donors took place cleanly to yield the corresponding complexes. On the other hand, in the PMe3 ylide complex (2a-Mo), the substituted complexes formed but the unreacted ylide complex 2a-Mo was also present in the reaction mixture. These results show that the bond strength of the M-C(phosphonium ylide) bond is affected by the substituents on the phosphorus atom.