| Research Abstract |
The reactions of transition metal complexes having M-Si a-bond were investigated both from experimental and theoretical views. Pt(SiHPh_2)_2(Pme_3)_2 undergoes thermal elimination of diphenylsilane to produce a new trinuclear Pt complex, [Pt(ヲフ-SiPh_2)(Pme_3)]_3. The molecular orbital calculation revealed that it is the first example of trinuclear complexes composed of Pt(0) centers and electron-releasing ligands. The reaction of dimethyl acetylenedicarboxylate (DMAD) with [Pt(ヲフ-SiPh_2)(Pme_3)]_3 leads to transformation of the framework to linear triplatinum clusters. Sila-3-platinacyclobutene was isolated from the reaction of Pt(SiHPh_2)_2(Pme_3)_2 with DMAD and characterized by X-ray crystallography. The formation pathway was found to involve ヲテ-Si-H bond activation of the 3-sila-1-propenylplatinum intermediate that is formed by the insertion of a DMAD into a Pt-Si bond of Pt(SiHPh_2)_2(Pme_3)_2. The results provided a new mechanism for the general reaction of alkyne with organosilane catalyzed by Pt ; the cylcization pathway with a low energy intermediate is more plausible than the classic mechanism that involves silylenoid intermediate with an extremely high energy.
Rh and Ir complexes having halogeno (Cl, I) ligands and organosilyl ligands undergo coupling of these ligands to release the corresponding halosilanes. Dependence of the reaction rate on the structure of the complexes and on kind of the halogeno and silyl ligands revealed that the reaction involves intramolecular reductive elimination via concerted mechanism.
In summary, the present study involving experimenetal and theoretical approach has revealed various aspects of reactions of organotransition metal complexes and elucidated the mechanism of several synthetic organic reactions that involve transmetalation as a crucial step.
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