New supramolecular assemblies in heterobimetallic chemistry : synthesis of a homologous series of unsolvated alkali-metal zincates

Armstrong, David R. and Emerson, Helena S. and Hernán-Gómez, Alberto and Kennedy, Alan R. and Hevia, Eva (2014) New supramolecular assemblies in heterobimetallic chemistry : synthesis of a homologous series of unsolvated alkali-metal zincates. Dalton Transactions, 43 (38). pp. 14229-14238. ISSN 1477-9226 (https://doi.org/10.1039/c4dt01131g)

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Abstract

Using an interlocking co-complexation approach, a homologous series of unsolvated alkali-metal zincates [MZn(CH2SiMe3)3] (M = Li 1, Na 2, K 3) was prepared by reacting equimolar amounts of Zn(CH2SiMe3)2with the relevant alkali-metal alkyl M(CH2SiMe3) employing non-coordinating hexane as a solvent. X-ray crystallographic studies reveal that these heterobimetallic compounds exhibit unprecedented supramolecular assemblies made up exclusively of a three-fold combination of M-CH2, Zn-CH2and M⋯Me interactions. Revealing an important alkali-metal effect, 1 displays a linear chain structure; whereas 2 and 3 form much more intricate 3D and 2D coordination networks respectively. Shedding new light into the formation of these solvent-free zincates, DFT calculations indicate that the infinite degree of aggregation observed in 1-3 plays a major role in thermodynamically driving the co-complexation reactions of their homometallic precursors. NMR spectroscopic studies suggest that in C6D6solution 1-3 exist as discrete contacted ion-pair species, where the alkali-metal is partially solvated by molecules of deuterated solvent. The supramolecular assemblies of 1-3 can be easily deaggregated by adding the polydentate N-donors PMDETA (N,N,N′,N′′,N′′-pentamethyldiethylenetriamine) or TMEDA (N,N,N′,N′-tetramethylethylenediamine), affording monomeric [(PMDETA)LiZn(CH2SiMe3)3] (4) and [(TMEDA)2NaZn(CH2SiMe3)3] (5).

ORCID iDs

Armstrong, David R., Emerson, Helena S., Hernán-Gómez, Alberto ORCID logoORCID: https://orcid.org/0000-0001-8150-7249, Kennedy, Alan R. ORCID logoORCID: https://orcid.org/0000-0003-3652-6015 and Hevia, Eva ORCID logoORCID: https://orcid.org/0000-0002-3998-7506;
CORE (COnnecting REpositories)