Ligand “Brackets” for Ga–Ga Bond

Chen

Zhao

et al. 2019

Self Cite

Digallane [L 1 GaÀGaL 1 ]( 1,L 1 = dpp-bian = 1,2-[(2,6-iPr 2 C 6 H 3 )NC] 2 C 12 H 6 )r eacts with RN=C=O( R = Ph or To s) by [2+ +4] cycloaddition of the isocyanate C=Nb onds across both of its C=CÀNÀGa fragments to afford [L 1 (O=CÀNR)GaÀ Ga(RNÀC=O)L 1 ]( R = Ph, 3;R = Tos, 4). The reactions with both isocyanates result in new CÀCa nd NÀGa single bonds.In the case of allyl isocyanate, the [2+ +4] cycloaddition across one C=CÀNÀGa fragment of 1 is accompanied by insertion of as econd allyl isocyanate molecule into the GaÀNb ond of the same fragment to afford compound [L 1 GaÀGa(AllNÀ C=O) 2 L 1 ]( 5)( All = allyl). In the presence of Na metal, the related digallane [L 2 GaÀGaL 2 ]( 2;L 2 = dpp-dad = [(2,6-iPr 2 C 6 H 3 )NC(CH 3 )] 2 )i sc onverted into the gallium(

Section: Resultsmentioning

confidence: 99%

Gallium “Shears” for C=N and C=O Bonds of Isocyanates

Chen

Zhao

et al. 2019

Self Cite

“…[7d, 21] The reactivity of GaÀGa-bonded compounds towards isothiocyanates has not been reported so far,a lthought he cleavage of SÀS, BiÀC, SbÀN, BiÀBi, and TeÀC single bonds andN ÀNd ouble bonds( 99.9 kcal mol À1 )w ith Ga compounds is known. [17,18,22] We demonstrate that digallanes 1 and 2 are able to cleave the very stable C=Sb ond (137 kcal mol À1 )o fi sothiocyanates. The C=Sb ond can also undergo [2+ +4] cycloaddition reactions to the GaN 2 C 2 ring to yield metallacycles.…”

Section: Introductionmentioning

confidence: 97%

“…α‐Diimine ligands proved to be successful in stabilizing a variety of low‐valent metal complexes, including group 13 metal–metal‐bonded compounds such as digallanes and dialumanes –. These complexes have shown promising reactivity towards various small molecules, such as alkynes, alkenes, disulfides, azobenzenes, phenazine, sulfur dioxide, and ketone derivatives . Further, the α‐diimines are redox‐active ligands that can be easily oxidized or reduced, can serve as electron reservoirs, and allow significant extension of the reactivity of metal complexes.…”

Section: Introductionmentioning

confidence: 99%

“…The interactions between organometallic complexes and heterocumulene reagents have only been explored to a minor degree . The reactivity of Ga−Ga‐bonded compounds towards isothiocyanates has not been reported so far, although the cleavage of S−S, Bi−C, Sb−N, Bi−Bi, and Te−C single bonds and N−N double bonds (99.9 kcal mol −1 ) with Ga compounds is known …”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Cycloaddition versus Cleavage of the C=S Bond of Isothiocyanates Promoted by Digallane Compounds with Noninnocent α‐Diimine Ligands

Zhang

Chen

et al. 2018

Self Cite

Whereas the chemistry of single-bond activation by compounds of the main group elements has undergone some development in recent years, the cleavage of multiple bonds remains underexplored. Herein, the reactions of two digallanes bearing α-diimine ligands, namely, [L Ga-GaL ] (1, L =dpp-dad=[(2,6-iPr C H )NC(CH )] ) and [L Ga-GaL ] (2, L =dpp-bian=1,2-[(2,6-iPr C H )NC] C H ), with isothiocyanates are reported. Reactions of 1 or 2 with isothiocyanates in 1:2 molar ratio proceeded with [2+4] cycloaddition of the C=S bond across the C N Ga metallacycle with formation of C-C and S-Ga single bonds to afford [L (RN=C-S)Ga-Ga(S-C=NR)L ] (3, R=Me; 4, R=Ph) and [L (RN=C-S)Ga-Ga(S-C=NR)L ] (8, R=allyl; 9, R=Ph). In the cases of 8 and 9, this cycloaddition is reversible. The digallanes reacted with 2 equiv of PhNCS in the presence of Na metal or at high temperatures through a unique reductive cleavage of the C=S bond to yield the disulfide-bridged digallium species [Na(THF) ] [L Ga(μ-S) GaL ] (5), [L Ga(μ-S) GaL ] (10), and [Na(DME) ][L Ga(μ-S) GaL ] (11). Moreover, products 4 and 5 can further react with an excess of isothiocyanate, through cleavage of the C=S bond or cycloaddition, to give the bis- or mono-S-bridged complexes [Na(THF) ] [L (PhN=C-S)Ga(μ-S) Ga(S-C=NPh)L ] (6) and [L (PhN=C-S)Ga(μ-S)Ga(S-C=NPh)L ] (7). All the newly prepared compounds were characterized by elemental analysis, single-crystal X-ray diffraction, IR spectroscopy, NMR (3-9) or ESR spectroscopy (11), and DFT calculations.

“…In contrast, compound 2 reacts with different alkynes to form cycloadducts that liberate “coordinated” alkyne upon heating . When combined with oxidizing reagents, compound 2 revealed an electron transfer dualism: depending on the substrate, oxidation may occur first on the ligands or involve the metal–metal bond . The substrates for oxidative addition reactions to complex 2 were limited to iodine and disulfides.…”

Section: Introductionmentioning

confidence: 99%

Redox‐Active Ligand‐Assisted Two‐Electron Oxidative Addition to Gallium(II)

Fedushkin

Skatova

et al. 2018

Self Cite

The reaction of digallane (dpp-bian)Ga-Ga(dpp-bian) (2) (dpp-bian=1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) with allyl chloride (AllCl) proceeded by a two-electron oxidative addition to afford paramagnetic complexes (dpp-bian)Ga(η -All)Cl (3) and (dpp-bian)(Cl)Ga-Ga(Cl)(dpp-bian) (4). Treatment of complex 4 with pyridine induced an intramolecular redox process, which resulted in the diamagnetic complex (dpp-bian)Ga(Py)Cl (5). In reaction with allyl bromide, complex 2 gave metal- and ligand-centered addition products (dpp-bian)Ga(η -All)Br (6) and (dpp-bian-All)(Br)Ga-Ga(Br)(dpp-bian-All) (7). The reaction of digallane 2 with Ph SnNCO afforded (dpp-bian)Ga(SnPh ) (8) and (dpp-bian)(NCO)Ga-Ga(NCO)(dpp-bian) (9). Treatment of GaCl with (dpp-bian)Na in diethyl ether resulted in the formation of (dpp-bian)GaCl (10). Diorganylgallium derivatives (dpp-bian)GaR (R=Ph, 11; tBu, 14; Me, 15; Bn, 16) and (dpp-bian)Ga(η -All)R (R=nBu, 12; Cp, 13) were synthesized from complexes 3, 10, Bn GaCl, or tBu GaCl by salt metathesis. The salt elimination reaction between (dpp-bian)GaI (17) and tBuLi was accompanied by reduction of both the metal and the dpp-bian ligand, which resulted in digallane 2 as the final product. Similarly, the reaction of complex 10 with MentMgCl (Ment=menthyl) proceeded with reduction of the dpp-bian ligand to give the diamagnetic complex [(dpp-bian)GaCl ][Mg Cl (THF) ] (18). Compounds 11, 12, 13, 15, and 16 were thermally robust, whereas compound 14 decomposed when heated at reflux in toluene to give complex (dpp-bian-tBu)GatBu (19). Both complexes 7 and 19 contain R-substituted dpp-bian ligand: in the former compound the allyl group was attached to the imino-carbon atom, whereas in complex 19, the tBu group was situated on the naphthalene ring. Crystal structures of complexes 3, 8, 9, 10, 13, 14, 18, and 19 were determined by single-crystal X-ray analysis. The presence of dpp-bian radical anions in 3, 6, 8, and 10-16 was determined by ESR spectroscopy.