Neutral stibinyl and bismuthinyl radicals are typically short-lived, reactive species. Here we show the synthesis and solid-state structures of two stable stibinyl [L(Cl)Ga]2Sb· 1 and bismuthinyl radicals [L(I)Ga]2Bi· 4, which are stabilized by electropositive metal centers. Their description as predominantly metal-centered radicals is consistent with the results of NMR, EPR, SQUID, and DFT studies. The Lewis-acidic character of the Ga ligands allow for significant electron delocalization of the Sb- and Bi- unpaired radical onto the ligand. Single-electron reduction of [L(Cl)Ga]2Sb· gave LGaSbGa(Cl)L 5, the first compound containing a Ga=Sb double bond. The π-bonding contribution is estimated to 9.56 kcal mol−1 by NMR spectroscopy. The bonding situation and electronic structure is analyzed by quantum mechanical computations, revealing significant π backdonation from the Sb to the Ga atom. The formation of 5 illustrates the high-synthetic potential of 1 for the formation of new compounds with unusual electronic structures.

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 Cp Ar AsCl2 (Cp Ar = C5(4-t-BuC6H4)5) with formation of the arsenic-centered radical [L(Cl)Ga]2As• 1. In contrast, the analogous reaction with TerSbCl2 (Ter = 2,6-Mes2C6H3; Mes = 2,4,6-Me3C6H2) yields the gallastibene LGa=SbTer 2 containing a Ga-Sb double bond, whereas reactions of DipSbCl2 with one and two equivalents of LGa give the monoinsertion and bisinsertion products L(Cl)GaSb(ClDip 3 and [L(Cl]Ga]2SbDip 4, respectively. 1 -4 were structurally characterized by single crystal X-ray diffraction. The description of 1 as arsenic-centered radical is consistent with results of EPR and DFT studies. The π-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 π-bonding interaction between Sb and Ga. ASSOCIATED CONTENTThe Supporting Information is available free of charge via the Internet at http://pubs.acs.org. Experimental procedures, 1 H, 13 C NMR, IR and EPR spectra, crystallographic details, bond lengths and angles of 1 -4 and results from quantum chemical calculations (pdf).

Two equivalents of LGa (L=HC[C(Me)N(2,6-iPr C H )] ) reacted with PX (X=Cl, Br) with insertion into two P-X bonds and formation of [L(X)Ga] PX (X=Cl 1, Br 2), whereas the analogous reaction with AsCl occurred with twofold insertion and subsequent elimination of LGaCl and formation of the Ga-substituted diarsene [L(Cl)Ga] As (3). Analogous findings were observed in the reactions with Me NAsCl , yielding the unsymmetrically-substituted diarsene [L(Cl)Ga]As=As[Ga(NMe )L] (4). The reaction of As(NMe ) with LGa gave [L(Me N)Ga] As (5) after heating at 165 °C for five days, whereas the reaction with LAl gave [L(Me N)Al] As (6) after heating at only 80 °C for one day. Finally, two equivalents of LGa reacted with Bi(NEt ) to give [L(Et N)Ga] Bi (7). Complexes 1-7 were characterized by NMR spectroscopy ( H, C, P), elemental analysis, and single-crystal X-ray diffraction (except for 1 and 5). The bonding situations in 4, 6, and 7 were analyzed by quantum chemical calculations.

CNMR spectroscopy,e lemental analysis,a nd single crystal X-ray diffraction. In addition, their bonding situation was analyzed by quantum chemical calculations.

Cp*AsCl (Cp* = CMe) reacts with one equivalent of LGa (L = HC[C(Me)N(2,6- i-PrCH)]) with formation of L(Cl)GaAs(Cl)Cp* 1, whereas the reaction with two equivalents of LGa yielded gallaarsene LGaAsCp* 2 containing a Ga═As double bond and (η-Ga(Cp*)L(η-GaL)(μ-As) 3. Compounds 2 and 3 were structurally characterized by single crystal X-ray diffraction, and the π-bonding contribution in 2 was analyzed by temperature-dependent H NMR spectroscopy (9.65 kcal mol) and by quantum mechanical computation.