TY - JOUR
T1 - Structural and synthetic insights on oxidative homocouplings of alkynes mediated by alkali-metal manganates
AU - Mastropierro, Pasquale
AU - Platten, Andrew W.J.
AU - Kennedy, Alan R.
AU - Hevia, Eva
AU - Uzelac, Marina
N1 - Funding Information:
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
Data access statement:
The data that support the findings of this study are available in the supplementary material of this article.
PY - 2023/4/27
Y1 - 2023/4/27
N2 - 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.
AB - 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.
KW - 1,3-diynes
KW - alkali-metal effect
KW - homocoupling
KW - manganates
KW - metal - metal cooperativity
UR - http://www.scopus.com/inward/record.url?scp=85153761317&partnerID=8YFLogxK
U2 - 10.1002/chem.202300593
DO - 10.1002/chem.202300593
M3 - Article
AN - SCOPUS:85153761317
SN - 0947-6539
JO - Chemistry - A European Journal
JF - Chemistry - A European Journal
M1 - e202300593
ER -