Synthesis and Characterization of Bulky 1,3-Diamidopropane Complexes of Group 2 Metals (Be-Sr).

Reaction of lithium 1,3-diamidopropane Li(NCN) (NCN=[{(Trip)NCH}CH], Trip=2,4,6-triisopropylphenyl) with BeBr(OEt) gave the diamido beryllium complex, [(NCN)Be(OEt)]. Deprotonation reactions between the bulkier 1,3-diaminopropane (NCN)H (NCN=[{(TCHP)NCH}CH], TCHP=2,4,6-tricyclohexylphenyl) and magnesium alkyls afforded the adduct complexes [(NCN)Mg(OEt)] and [(NCN)Mg(THF)], depending on the reaction conditions employed. Treating [(NCN)Mg(THF)] with the N-heterocyclic carbene :C{(MeNCMe)} (TMC) gave [(NCN)Mg(TMC)] via substitution of the THF ligands. Reactions of (NCN)H (Ar=Trip or TCHP) with Mg{CH(SiMe)}, in the absence of Lewis bases, yielded the N-bridged dimers [{(NCN)Mg}]. Salt metathesis reactions between alkali metal salts M(NCN) (M=Li or K) and CaI or SrI led to the THF adduct compounds [(NCN)Ca(THF)] and [(NCN)Sr(THF)], the differing number of THF ligands in which is a result of the different sizes of the metals involved. The described complexes hold potential as precursors to kinetically protected, low oxidation state group 2 metal species.