Abstract
Exploiting bimetallic cooperation alkali-metal manganate (II) complexes can efficiently promote oxidative homocoupling of terminal alkynes furnishing an array of conjugated 1,3-diynes. The influence of the alkali-metal on these C−C bond forming processes has been studied by preparing and structurally characterizing the alkali-metal tetra(alkyl) manganates [(TMEDA)2Na2Mn(CH2SiMe3)4] and [(PMDETA)2K2Mn(CH2SiMe3)4]. Reactivity studies using phenylacetylene as a model substrate have revealed that for the homocoupling to take place initial metalation of the alkyne is required. In this regard, the lack of basicity of neutral Mn(CH2SiMe3)2 precludes the formation of the diyne. Contrastingly, the tetra(alkyl) alkali-metal manganates behave as polybasic reagents, being able to easily deprotonate phenylacetylene yielding [{(THF)4Na2Mn(C≡CPh)4}∞] and [(THF)4Li2Mn(C≡CPh)4]. Controlled exposure of [{(THF)4Na2Mn(C≡CPh)4}∞] and [(THF)4Li2Mn(C≡CPh)4] to dry air confirmed their intermediary in formation of 1,4-diphenyl-1,3-butadiyne in excellent yields. While the Na/Mn(II) partnership proved to be the most efficient in stoichiometric transformations, under catalytic regimes, the combination of MC≡CAr (M= Li, Na) and MnCl2 (6 mol %) only works for lithium, most likely due to the degradation of alkynylsodiums under the aerobic reaction conditions.
Original language | English |
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Article number | e202300593 |
Number of pages | 8 |
Journal | Chemistry - A European Journal |
Volume | 29 |
Issue number | 33 |
Early online date | 27 Apr 2023 |
DOIs | |
Publication status | Published - 13 Jun 2023 |
Data Availability Statement
The data that support the findings of this study are available in the supplementary material of this article.Funding
We thank the X‐ray crystal structure service unit at the University of Bern for measuring, solving, refining, and summarizing the structure of compounds and . Swiss National Science Foundation (SNF) (projects numbers 206021_177033 and 188573) and Royal Society (University Research Fellowship to M. U.) are acknowledged for the funding of this research. Our thanks are extended to Dr Marco De Tullio (I) for obtaining preliminary data on homocoupling of phenylacetylene with lithium manganate. 5 6
Keywords
- 1,3-diynes
- alkali-metal effect
- homocoupling
- manganates
- metal - metal cooperativity
ASJC Scopus subject areas
- Catalysis
- Organic Chemistry