Investigations of Intramolecular and Intermolecular Noncovalent Interactions in Alkaline Earth Metal Complexes of – OC(Ph)(CF ₃ ) ₂

High Resolution Image Download MS PowerPoint Slide Alkaline earth metals are relatively abundant, inexpensive and desirable as metal–organic complexes for applications in electronics and catalysis. Synthetic challenges arise from their high reactivity and the tendency of their compounds to form aggregates. Previous work demonstrated that certain fluorinated alkoxide ligands improved the volatility of alkaline earth metal and mixed-metal complexes, in part due to the presence of noncovalent secondary M···F interactions. This work further explores the impact of secondary interactions on their structure. The fluorinated alkoxide 2,2,2,2′,2′,2′-hexafluorocumyl alkoxide, – OC(Ph)(CF 3 ) 2 (“L”), introduces the possibility of both M···F and M···π stabilizing interactions. Synthetic methods including alkane elimination (Mg), direct metalation (Ca, Sr, Ba), and protonolysis (Ba) with complexation to L in the controlled presence and/or absence of neutral donors afforded [MgL 2 (thf) 2 ] ( 1 ), [ trans -CaL 2 (thf) 4 ] ( 2 ), [ cis -SrL 2 (thf) 4 ] ( 3 ), [Sr 2 (μ 2 -L) 3 L(thf) 3 ] ( 4 ), [Sr 3 (μ 2 -L) 4 L 2 (OEt 2 ) 2 ] ( 5 ), [Ba(μ 2 -L) 2 ] n · 1 4 (OEt 2 ) ( 6 ), and [Ba(μ 2 -L) 2 ] n ( 7 ). Structural characterization shows the number of secondary interactions increase for the heavier metals and decreasing presence of the neutral donor, coinciding with increased nuclearity. Computational studies predict notable differences between preferred configurations that might exist in the gas-phase and those observed in the solid state.