Synthesis, Characterization and Real Molecule DFT Calculations for Neutral Organogallium(I) Aryl Dimers and Monomers: Weakness of GalliumGallium Bonds in Digallenes and Digallynes

Move closer : The galliumgallium bond strength in terphenyl gallium(I) dimers [ArGaGaAr] (see figure) is similar to those in other molecules with closed shell interactions, implying that the GaGa bond in doubly reduced Na 2 [ArGaGaAr] is much closer to a single than a triple one.A series of stable aryl gallium(I) terphenyl derivatives was synthesized and characterized spectroscopically, structurally and by density functional calculations. Dimeric structures with trans ‐bent planar CGaGaC core arrangements were observed for [(GaAr*‐4‐ t Bu) 2 ] ( 7 , Ar*‐4‐ t Bu=C 6 H 2 ‐2,6(C 6 H 2 ‐2,4,6‐ i Pr 3 ) 2 ‐4‐ t Bu) and [(GaAr*‐4‐CF 3 ) 2 ] ( 8 , Ar*‐4‐CF 3 =C 6 H 2 ‐2,6(C 6 H 2 ‐2,4,6‐ i Pr 3 ) 2 ‐4‐CF 3 ), whereas monomeric structures featuring one coordinate gallium were observed for the more crowded complexes [:GaAr*‐3,5‐ i Pr 2 ] ( 10 , Ar*‐3,5‐ i Pr 2 =C 6 H‐2,6(C 6 H 2 ‐2,4‐6‐ i Pr 3 ) 2 ‐3,5‐ i Pr 2 ) and [GaAr′‐3,5‐ i Pr 2 ] ( 11 , Ar′‐3,5‐ i Pr 2 =C 6 H‐2,6(C 6 H 3 ‐2,6‐ i Pr 2 ) 2 ‐3,5‐ i Pr 2 ). Complexes 7 and 8 dissociate to monomers in hydrocarbon solution and their electronic spectra closely resemble those of 10 and 11 as well as those of [Ar′GaGaAr′] (Ar′=C 6 H 3 ‐2,6(C 6 H 3 ‐2,6‐ i Pr 3 ) 2 ) and [(GaAr*) n ] (Ar*=C 6 H 3 ‐2,6(C 6 H 2 ‐2,4,6‐ i Pr 3 ) 2 ). The calculations showed that the binding energies of the compounds are weak, resemble closed‐shell interactions and average ≈5 kcal mol −1 , as in [Ar*GaGaAr*] with a lowest value of ≈−2 kcal mol −1 for monomeric 10 and a highest value ≈9 kcal mol −1 for the least crowded species [Ar′GaGaAr′]. The weak bonding in the complexes supports the view that the GaGa bonding in the previously published doubly reduced Na 2 [Ar*GaGaAr*] and Na 2 [Ar′GaGaAr′] is also weak and is consistent with approximate single bonding.