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

Reaction of lithium 1,3‐diamidopropane Li2(TripNCN) (TripNCN=[{(Trip)NCH2}2CH2]2−, Trip=2,4,6‐triisopropylphenyl) with BeBr2(OEt2)2 gave the diamido beryllium complex, [(TripNCN)Be(OEt2)]. Deprotonation reactions between the bulkier 1,3‐diaminopropane (TCHPNCN)H2 (TCHPNCN=[{(TCHP)NCH2}2CH2]2−, TCHP=2,4,6‐tricyclohexylphenyl) and magnesium alkyls afforded the adduct complexes [(TCHPNCN)Mg(OEt2)] and [(TCHPNCN)Mg(THF)2], depending on the reaction conditions employed. Treating [(TCHPNCN)Mg(THF)2] with the N‐heterocyclic carbene :C{(MeNCMe)2} (TMC) gave [(TCHPNCN)Mg(TMC)2] via substitution of the THF ligands. Reactions of (ArNCN)H2 (Ar=Trip or TCHP) with Mg{CH2(SiMe3)}2, in the absence of Lewis bases, yielded the N‐bridged dimers [{(ArNCN)Mg}2]. Salt metathesis reactions between alkali metal salts M2(TCHPNCN) (M=Li or K) and CaI2 or SrI2 led to the THF adduct compounds [(TCHPNCN)Ca(THF)3] and [(TCHPNCN)Sr(THF)4], 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. Two bulky 1,3‐diamidopropane ligands have been used to prepare a series of complexes with the group 2 metals Be, Mg, Ca and Sr. In these, the metal centers are coordinated with, or are free of, auxillary Lewis bases. The described complexes hold potential as precursors to kinetically protected low oxidation state group 2 metal species.