Catalytic hydroacetylenation of carbodiimides with homoleptic alkaline earth hexamethyldisilazides

M. Arrowsmith, M.R. Crimmin, M.S. Hill, S.L. Lomas, M.S. Heng, P.B. Hitchcock, G. Kociok-Köhn

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Abstract

The homoleptic alkaline earth hexamethyldisilazides, [M{N(SiMe3)2}2(THF)2] (M = Mg 1a; Ca 1b; Sr 1c), have been shown to act as efficient precatalysts for the hydroacetylenation of organic carbodiimides with alkyl- and arylacetylenes. Catalytic activity was observed to increase with the size of the group 2 metal centre employed and to be strongly influenced by the steric properties of the carbodiimide substrate. The intermediate dimeric calcium and strontium bis(amidinate) complexes, [{PhCCC(NiPr)2}2M]2 (M = Ca 2b, Sr 2c), have been isolated and crystallographically characterised. Kinetic studies using the strontium precursor, 1c, provided a reaction rate law independent of [acetylene] but proportional to [carbodiimide]2 and inversely proportional to the concentration of the amidine product in solution.

Original languageEnglish
Pages (from-to)14249-14256
Number of pages8
JournalDalton Transactions
Volume43
Issue number38
Early online date9 Jan 2014
DOIs
Publication statusPublished - 14 Oct 2014

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