title: Two alternative approaches to access mixed hydride-amido zinc complexes: synthetic, structural and solution implications.
abstract: Using bis(amide) Zn(HMDS)2 (HMDS = 1,1,1,3,3,3-hexamethyldisilazide) as a precursor, this study explores the synthesis of N-heterocyclic carbene stabilized mixed amido-hydride zinc complexes using two alternative hydride sources, namely dimethylamine borane (DMAB) and phenylsilane PhSiH3. Hydride-rich zinc cluster Zn4(HMDS)2H6·2IPr () (IPr = 1,3-bis(2,6-di-isopropylphenyl)imidazol-2-ylidene), which can be envisaged as a co-complex of IPr·ZnH2 and (HMDS)ZnH, is obtained when DMAB is employed, with the concomitant formation of heteroleptic bis(amido)borane [HB(NMe2)(HMDS)] and H2 evolution. NMR studies in d8-THF show that although the bulky carbene IPr does not bind to the zinc bis(amide), its presence in the reaction media is required in order to stabilise . Reactions using the slightly less sterically demanding NHC IXy (IXy = 1,3-bis-(2,6-dimethylphenyl)imidazol-2-ylidene) led to the isolation and structural elucidation of the carbene adduct Zn(HMDS)2·IXy (). Contrastingly, mixtures of equimolar amounts of PhSiH3 and the zinc bis(amide) (60 °C, 3 h, hexane) afforded monomeric heteroleptic hydride (HMDS)ZnH·IPr (). NMR studies, including DOSY experiments, revealed that while the integrity of is retained in polar d8-THF solutions, in lower polarity C6D6 it displays a much more complex solution behaviour, being in equilibrium with the homoleptic species ZnH2·IPr, Zn(HMDS)2 and IPr.
authors.affiliation: WestCHEM, Department of Pure and Applied Chemistry, University of Strathclyde, Glasgow, G1 1XL, UK. eva.hevia@strath.ac.uk stuart.d.robertson@strath.ac.uk.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Roberts
authors.forename: William
authors.initials: W
authors.lastname: Clegg
authors.forename: Alan R
authors.initials: AR
authors.lastname: Kennedy
authors.forename: Michael R
authors.initials: MR
authors.lastname: Probert
authors.forename: Stuart D
authors.initials: SD
authors.lastname: Robertson
authors.forename: Eva
authors.initials: E
authors.lastname: Hevia