title: Catalytic hydroacetylenation of carbodiimides with homoleptic alkaline earth hexamethyldisilazides.
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, [{PhC≡CC(N(i)Pr)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.
authors.affiliation: Department of Chemistry, University of Bath, Claverton Down, Bath, BA2 7AY, UK. msh27@bath.ac.uk.
authors.forename: Merle
authors.initials: M
authors.lastname: Arrowsmith
authors.forename: Mark R
authors.initials: MR
authors.lastname: Crimmin
authors.forename: Michael S
authors.initials: MS
authors.lastname: Hill
authors.forename: Sarah L
authors.initials: SL
authors.lastname: Lomas
authors.forename: Myra Sae
authors.initials: MS
authors.lastname: Heng
authors.forename: Peter B
authors.initials: PB
authors.lastname: Hitchcock
authors.forename: Gabriele
authors.initials: G
authors.lastname: Kociok-Köhn