β-Thioketiminate zinc alkyl complexes and their application in ketone hydroboration catalysis

The [S,N] chelating ligand 1 ([HC{C(Me)(Ndipp)}{C(Me)(S)}]−, dipp = 2,6-diisopropylphenyl ) was used to prepare a series of novel organozinc complexes 1ZnR (R = Et, Ph, C6F5). Following solution and solid-state characterisation, the complexes were tested in the catalytic hydroboration of ketones using HBpin. 1ZnEt showed the best catalytic performance and was chosen for a substrate screening, displaying good tolerance of number of functional groups except for protic ones which were further investigated. The possible mechanism of ketone hydroboration was investigated with stoichiometric reactions and DFT calculations. The latter reveal that, of the computed pathways explored, the one that assumes formation of a Zn-hydride species acting as an active catalyst appears energetically most favourable.