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Abstract:
A convenient synthetic route to Ga-stabilized pnictogen-centered radicals and gallapnictenes by manipulation of pnictogen-carbon bond strengths is presented. Two equivalents of LGa (L = HC[C(Me)N(Dip)](2), Dip = 2,6-i-Pr2C6H3) react with (CpAsCl2)-As-Ar(Cp-Ar = C-5(4-t-BuC6H4)(5)) with formation of the arsenic-centered radical [L(Cl)Ga](2)As. 1. In contrast, the analogous reaction with TerSbCl(2). (Ter = 2,6-Mes(2)C(6)H(3); Mes = 2,4,6-Me3C6H2) yields the gallastibene LGa=SbTer (2) containing a Ga-Sb double bond, whereas reactions of DipSbCl(2) with one and two equivalents of LGa give the monoinsertion and bisinsertion products L(Cl)GaSb(ClDip) (3) and [L(Cl]Ga](2)SbDip (4), respectively. 1-4 were structurally characterized by single crystal X-ray diffraction. The description of 1 as an arsenic-centered radical is consistent with results of electron paramagnetic resonance and density functional theory (DFT) studies. The pi-bonding in LGa=SbTer (2) is estimated to 10.68 kcal mol(-1) by variable-temperature (VT) NMR spectroscopy, and DFT studies reveal a significant pi-bonding interaction between Sb and Ga.
