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.

We report on the structures of three unprecedented heteroleptic Sb-centered radicals [L(Cl)Ga](R)SbC (2-R,R= B[N(Dip)CH] 2 2-B,2 ,6-Mes 2 C 6 H 3 2-C,N (SiMe 3 )Dip 2-N) stabilized by one electropositive metal fragment [L(Cl)Ga] (L = HC[C(Me)N(Dip)] 2 ,Dip = 2,6-i-Pr 2 C 6 H 3 )and one bulky B-(2-B), C-(2-C), or N-based (2-N)substituent. Compounds 2-R are predominantly metal-centered radicals.T heir electronic properties are largely influenced by the electronic nature of the ligands R, and significant delocalization of unpairedspin density onto the ligands was observed in 2-B and 2-N. Cyclic voltammetry (CV) studies showed that 2-B undergoes aq uasi-reversible one-electron reduction, whichw as confirmed by the synthesis of [K([2.2.2]crypt)][L(Cl)GaSbB[N-(Dip)CH] 2 ]( [K([2.2.2]crypt)][2-B]) containing the stibanyl anion [2-B] À ,w hich was shown to possess significant SbÀB multiple-bonding character.

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.

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The syntheses and properties of long‐lived arsenic, antimony, and bismuth‐centered radicals are reviewed. In contrast to the rich phosphorus‐based radical chemistry, that of the heavier congeners is far less advanced, which can be attributed to the increased instability of coordinatively and electronically unsaturated heavy main‐group element centers. However, the development of new synthetic strategies and stabilization methods particularly in the last decade enabled the isolation and characterization of several unpaired electron‐containing heavy group 15 element species featuring various structural motifs and electronic properties. The long‐lived character of these radicals allowed for the elucidation of their electronic structures and bonding properties, as well as the exploration of their unique reactivity.