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Oxidation of [(ArBIG-bian)2−Yb2+(dme)] (1) (ArBIG-bian = 1,2-bis[(2,6-dibenzhydryl-4-methylphenyl)imino]acenaphthene; dme = 1,2-dimethoxyethane) by 0.5 equivalent of Me2NC(S)S–S(S)CNMe2 in dme at ambient temperature affords a mixture of two products, [(ArBIG-bian)2−Yb3+{SC(S)NMe2}1−(dme)] and [(ArBIG-bian)1−Yb2+{SC(S)NMe2}1−(dme)], which represent two redox-isomers (2a and 2b, respectively). Their ratio in solution depends on the solvent as well as on the temperature. In the solid state, a decrease of temperature (350 → 100 K) caused an electron transfer from the Yb2+ ion to the ArBIG-bian radical-anion in isomer 2b to afford isomer 2a. Accordingly, the ratio of isomers 2a and 2b changes from 1 : 1 (350 K) to 3 : 1 (100 K). In contrast, in the dimer [(dme)(dpp-bian)1−Yb2+(μ-Cl)2Yb3+(dpp-bian)2−(dme)] (dpp-bian = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene), which is the sole example of a lanthanide complex that reveals solid-state redox-isomerism (valence tautomerism) reported so far, the electron transfer from the Yb2+ ion to the dpp-bian radical-anion takes place at around 150 K and is completed within a temperature interval of ca. 7 K. [ABSTRACT FROM AUTHOR]

The reactions of oxide [(dpp-bian)Al(μ2-O)2Al(dpp-bian)] (1) (dpp-bian = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) with phenyl- or cyclohexylisocyanates result in the formation of carbonimidate derivatives [(dpp-bian)Al(μ-O)(μ-RNCO2)Al(dpp-bian)] (R = Ph, 2; Cy, 3). Addition of N,N′-dicyclohexylcarbodiimide to compound 1 leads to the formation of ureate complex [(dpp-bian)Al(μ-O)(μ-(CyN)2CO)Al(dpp-bian)] (4). The reactions of the oxide 1 with pinacolborane and catecholborane afford oxo-bridged hydride [{(dpp-bian)Al(H)}(μ-O){Al(OBpin)(dpp-bian)}] (5) and compound [{(dpp-bian)Al(OBCat)}2(μ-O)] (7), respectively. Insertion of cyclohexylisocyanate into the Al–H bond of compound 5 gives C＝O insertion product [{(dpp-bian)Al(OC(H)NCy)}(μ-O){Al(OBpin)(dpp-bian)}] (6). New compounds have been characterized by ESR and IR spectroscopy; their molecular structures have been established by single-crystal X-ray analysis. The oxide 1 serves as a catalyst for the hydroboration of heteroallenes (isocyanates, carbodiimides) with pinacolborane. [ABSTRACT FROM AUTHOR]

Reduction of 1,2-bis[(2,6-dibenzhydryl-4-methylphenyl)imino] acenaphthene (ArBIG-bian) with an excess of magnesium in tetrahydrofuran (thf) or with an excess of calcium in 1,2-dimethoxyethane (dme) and crystallization of the crude products from the reaction mixtures affords monomeric complexes [(ArBIG-bian)Mg(thf)2] (1) or [(ArBIG-bian)Ca(dme)2] (2), respectively. Hydrolysis of complex 1 affords metal-free diamine [ArBIGbianH2(thf)] (3). Complexes 1 and 2 readily react with CO2 to form the corresponding carbamates [(ArBIG-bian)(CO2)2Mg(thf)2] (4) and [(ArBIG-bian)(CO2)2Ca(dme)2] (5). Compounds 1-5 have been characterized by NMR and IR spectroscopy as well as elemental analysis. The molecular structures of 1, 2, 3, and 5 have been determined by the single crystal X-ray analysis. [ABSTRACT FROM AUTHOR]

The reaction of dialane [LAl‐AlL] (1; L=dianion of 1,2‐bis[(2,6‐diisopropylphenyl)imino]acenaphthene, dpp‐bian) with carbon dioxide results in two different products depending on solvent. In toluene at temperatures of about 0 °C, the reaction gives cycloadduct [L(CO2)Al‐Al(O2C)L] (2), whereas in diethyl ether, the reaction affords oxo‐bridged carbamato derivative [L(CO2)(Et2O)Al(μ‐O)AlL] (3). The DFT and QTAIM calculations provide reasonable explanations for the reversible formation of complex 2 in the course of two subsequent (2+4) cycloaddition reactions. Consecutive transition states with low activation barriers were revealed. Also, the DFT study demonstrated a crucial effect of diethyl ether coordination to aluminium on the reaction of dialane 1 with CO2. The optimized structures of key intermediates were obtained for the reactions in the presence of Et2O; calculated thermodynamic parameters unambiguously testify the irreversible formation of the product 3. [ABSTRACT FROM AUTHOR]

Reduction of ArBIG‐bian (1, 1,2‐bis[(2,6‐dibenzhydryl‐4‐methylphenyl)imino]acenaphthene) with one molar equivalent of Li, Na or K in tetrahydrofuran (THF) affords corresponding radical‐anionic salts (ArBIG‐bian)M(THF) (M=Li, 2; Na, 3; K, 4). Compounds 2–4 were isolated in good yields and characterized by the elemental analysis, IR and ESR spectroscopy as well as the single‐crystal X‐Ray analysis. Bulky Ph2(H)C groups in ArBIG‐bian ligand prevent dimerization of complexes 2–4 and limit a number of coordinated THF molecules to one. In all three products a saturation of the alkali metal coordination sphere is achieved through an interaction with Ph rings of Ph2(H)C substituents. [ABSTRACT FROM AUTHOR]

Reduction of ArBIG-bian (1, 1,2-bis[(2,6-dibenzhydryl-4-methylphenyl)imino]acenaphthene) with an excess of samarium in tetrahydrofuran (thf) and crystallization of the crude product from a thf/toluene mixture affords [(ArBIG-bian)Sm]·C7H8 (2a), which is free of the coordinating solvent. The use of 1,2-dimethoxyethane (dme) as the reaction medium resulted in the same product, [(ArBIG-bian)Sm]·C4H10O2 (2b), which differs from 2a only in the crystal lattice solvent. Reduction of 1 with an excess of ytterbium in dme gives compound [(ArBIG-bian)Yb(dme)]·2.5C7H8 (3), containing a coordinated dme molecule. All three products consist of dianionic ArBIG-bian ligands whose bulky 2,6-(Ph2CH)2-4-Me–C6H2 groups shield effectively the metal atoms. The newly prepared compounds 2a, 2b and 3 were characterized by 1H NMR and IR spectroscopy. The molecular structures of complexes 2a, 2b and 3 have been established by single crystal X-ray analysis. The intramolecular interactions were analysed on the basis of DFT calculations. The temperature dependence of the magnetic susceptibility of 2b and 3 in the region of 2–300 K was studied. The magnetic moments of complex 2b correspond to divalent samarium. [ABSTRACT FROM AUTHOR]

The reduction of [(dpp-bian)BBr] (1, dpp-bian = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) with dilithium naphthalenide in Et2O gives [{(dpp-bian)BBr}Li2(Et2O)2]2 (3). The treatment of [(dpp-bian)BONa] (5) and [(dpp-bian)Ge:] (7) with sodium is accompanied by protonation of the acenaphthylene fragment and affords [{(H-dpp-bian)BONa(dme)2}Na(dme)3] (6) and [(H-dpp-bian)Ge:][Na(dme)3] (8), respectively. Compounds 3, 6 and 8 have been characterized by 1H NMR and IR spectroscopy. The molecular structures of 3, [(dpp-bian)BOK] (4) and 8 have been established by single crystal X-ray analysis. [ABSTRACT FROM AUTHOR]

Digallane [L1Ga−GaL1] (1, L1=dpp‐bian=1,2‐[(2,6‐iPr2C6H3)NC]2C12H6) reacts with RN=C=O (R=Ph or Tos) by [2+4] cycloaddition of the isocyanate C=N bonds across both of its C=C−N−Ga fragments to afford [L1(O=C−NR)Ga−Ga(RN−C=O)L1] (R=Ph, 3; R=Tos, 4). The reactions with both isocyanates result in new C−C and N−Ga single bonds. In the case of allyl isocyanate, the [2+4] cycloaddition across one C=C−N−Ga fragment of 1 is accompanied by insertion of a second allyl isocyanate molecule into the Ga−N bond of the same fragment to afford compound [L1Ga−Ga(AllN− C=O)2L1] (5) (All=allyl). In the presence of Na metal, the related digallane [L2Ga−GaL2] (2; L2=dpp‐dad=[(2,6‐iPr2C6H3)NC(CH3)]2) is converted into the gallium(I) carbene analogue [L2Ga:]− (2 A), which undergoes a variety of reactions with isocyanate substrates. These include the cycloaddition of ethyl isocyanate to 2 A affording [Na2(THF)5]{L2Ga[EtN−C(O)]2GaL2} (6), cleavage of the N=C bond with release of 1 equiv. of CO to give [Na(THF)2]2[L2Ga(p‐MeC6H4)(N−C(O))2−N(p‐MeC6H4)]2 (7), cleavage of the C=O bond to yield the di‐O‐bridged digallium compound [Na(THF)3]2[L2Ga‐(μ‐O)2‐GaL2] (8), and generation of the further addition product [Na2(THF)5][L2Ga(CyNCO2)]2 (9). Complexes 3–9 have been characterized by NMR (1H, 13C), IR spectroscopy, elemental analysis, and X‐ray diffraction analysis. Their electronic structures have been examined by DFT calculations. [ABSTRACT FROM AUTHOR]

Reduction of [(dpp-bian)2−M2+(thf)4] (M = Ca, 1; Yb, 6; dpp-bian = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) by alkali metals results in heterometallic, [(dpp-bian)3−M2+K+(thf)2]2 (M = Ca, 2; Yb, 7), [(dpp-bian)4−Ca2+A2+(thf)4]2 (A = Na, 3; Li, 4; K, 5), [(dpp-bian)4−Yb2+K2+(thf)4]2 (8) and [(dpp-bian)24−Yb32+K2+(thf)8] (9). The reduction of [(dpp-bian)TmBr(thf)n] (in situ) affords [(dpp-bian)4−Tm3+Na+(thf)]2 (10). [ABSTRACT FROM AUTHOR]

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, [L1Ga−GaL1] (1, L1=dpp‐dad=[(2,6‐iPr2C6H3)NC(CH3)]2) and [L2Ga−GaL2] (2, L2=dpp‐bian=1,2‐[(2,6‐iPr2C6H3)NC]2C10H6), 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 C2N2Ga metallacycle with formation of C−C and S−Ga single bonds to afford [L1(RN=C−S)Ga−Ga(S−C=NR)L1] (3, R=Me; 4, R=Ph) and [L2(RN=C−S)Ga−Ga(S−C=NR)L2] (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)3]2[L1Ga(μ‐S)2GaL1] (5), [L2Ga(μ‐S)2GaL2] (10), and [Na(DME)3][L2Ga(μ‐S)2GaL2] (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)2]2[L1(PhN=C−S)Ga(μ‐S)2Ga(S−C=NPh)L1] (6) and [L1(PhN=C−S)Ga(μ‐S)Ga(S−C=NPh)L1] (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. Three reaction types: Reactions of digallanes [LGa−GaL] (L=dianionic α‐diimine ligand) with isothiocyanates were investigated. Three types of reaction were observed (see scheme): 1) [2+4] cycloaddition with retention of the Ga−Ga bond, 2) complete cleavage of the C=S bond to yield bis‐sulfide‐bridged digallium species, and 3) both cycloaddition and reductive cleavage of the C=S bond to give the [2+4] cycloaddition and mono‐ or bis‐S‐bridged complexes. [ABSTRACT FROM AUTHOR]

Abstract: 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(η1‐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(η1‐All)Br (6) and (dpp‐bian‐All)(Br)Ga−Ga(Br)(dpp‐bian‐All) (7). The reaction of digallane 2 with Ph3SnNCO afforded (dpp‐bian)Ga(SnPh3)2 (8) and (dpp‐bian)(NCO)Ga−Ga(NCO)(dpp‐bian) (9). Treatment of GaCl3 with (dpp‐bian)Na in diethyl ether resulted in the formation of (dpp‐bian)GaCl2 (10). Diorganylgallium derivatives (dpp‐bian)GaR2 (R=Ph, 11; tBu, 14; Me, 15; Bn, 16) and (dpp‐bian)Ga(η1‐All)R (R=nBu, 12; Cp, 13) were synthesized from complexes 3, 10, Bn2GaCl, or tBu2GaCl by salt metathesis. The salt elimination reaction between (dpp‐bian)GaI2 (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)GaCl2][Mg2Cl3(THF)6] (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)GatBu2 (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. [ABSTRACT FROM AUTHOR]

The reactivity of digallane (dpp-Bian)Ga-Ga(dpp-Bian) (1), which consists of redox-active ligand 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphfhene (dpp-Bian), has been studied. The reaction of 1 with I2 proceeds via one-electron oxidation of each of two dpp-Bian ligands to a radical-anionic state and affords complex (dpp-Bian)IGa -- Gal(dpp-Bian) (2). Dissolution of complex 2 in pyridine (Py) gives monomeric compound (dpp-Bian)Gal(Py) (3) as a result of a solvent-induced intramolecular electron transfer from the metal-metal bond to the dpp-Bian ligands. Treatment of compound 3 with B(C6F5)3 leads to removal of pyridine and restores compound 2. The reaction of compound 1 with 3,6-di-tert-butyl-ortho-benzoquinone (3,6-Q) proceeds with oxidation of all the redox-active centers in 1 (the Ga-Ga bond and two dpp-Bian dianions) and results in mononuclear catecholate (dpp-Bian)Ga(Cat) (4) (Cat = [3,6-Q]2-). Treatment of 4 with AgBF4 gives a mixture of [(dpp-Bian)2Ag][BF4] (5) and (dpp-Bian)GaF(Cat) (6), which both consist of neutral dpp-Bian ligands. The reduction of benzylideneacetone (BA) with 1 generates the BA radical-anions, which dimerize, affording (dpp-Bian)Ga-(BA-BA)-Ga(dpp-Bian) (7). In this case the Ga-Ga bond remains unchanged. Within 10 min at 95 °C in solution compound 7 undergoes transformation to paramagnetic complex (dpp-Bian)Ga(BA-BA) (8) and metal-free compound C36H40N2 (9). The latter is a product of intramolecular addition of the C-H bond of one of the iPr groups to the C=N bond in dpp-Bian. Diamagnetic compounds 3, 5, 6, and 9 have been characterized by NMR spectroscopy, and paramagnetic complexes 2, 4, 7, and 8 by ESR spectroscopy. Molecular structures of 2-7 and 9 have been established by single-crystal X-ray analysis. [ABSTRACT FROM AUTHOR]

Molybdenum hexacarbonyl reacts with 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (1, dpp-BIAN) and 1,2-bis[(trimethylsilyl)imino]acenaphthene (2, tms-BIAN) in toluene to produce (dpp-BIAN)Mo(CO)4(3) and (tms-BIAN)Mo(CO)4(4), respectively. The reaction of [CpNi(CO)]2with 1yields (dpp-BIAN)NiCp (5). Metathesis between Li2(tms-BIAN) and NiCl2(dppe) affords the Ni(0) complex (tms-BIAN)Ni(dppe) (6). The diamagnetic compounds 3, 4and 6have been characterized by 1H, 29Si and 31P NMR spectroscopy, IR spectroscopy and elemental analysis. The ESR spectrum of the paramagnetic compound 5indicates the presence of Ni(i) coordinated by Cp and a neutral dpp-BIAN ligand. The molecular structures of 3–6have been determined by single-crystal X-ray analysis. [ABSTRACT FROM AUTHOR]

Highlights from the article: Keywords: cleavage of multiple bonds; cycloaddition; digallane; isocyanates; main group elements; non-innocent -diimine ligands B 1,3,2-Diazagalols reveal a high reactivity b towards carbon-heteroatom double bonds of isocyanates. Cleavage of multiple bonds, cycloaddition, digallane, isocyanates, main group elements, non-innocent -diimine ligands.

The interaction of aluminum hydrides [(dpp-bian)AlH 2 ] (1) and [(Ar BIG -bian)AlH 2 (THF)] (2) (dpp-bian = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene; Ar BIG -bian = 1,2-bis[(2,6-dibenzhydryl-4-methylphenyl)imino]acenaphthene) with isocyanates RNCO (R = Ph, Cy, 3,5-Cl 2 Ph) proceeds via insertion of two molecules of isocyanates into each Al-H bond with the formation of unique Al carboxamides [(Ar-bian)Al{OC(H)N(R)C(NR)O} 2 ] (Ar = dpp, R = Ph, 3; Ar = Ar BIG , R = Ph, 4; Ar = Ar BIG , R = Cy, 5; Ar = Ar BIG , R = 3,5-Cl 2 C 6 H 3 , 6). In contrast, the reactions of 1 and 2 with an excess of tert -butylisocyanate afford formimidate derivatives [(Ar-bian)Al{OC(H)N( t Bu)} 2 ] (Ar = dpp, 7; Ar = Ar BIG , 8). The reactions of N , N '-dicyclohexylcarbodiimide with 1 and 2 give [(dpp-bian)Al{(NCy) 2 CH} 2 ] (9) and [(Ar BIG -bian)Al(H){(NCy) 2 CH}] (10), correspondingly. New compounds 3-10 have been characterized by ESR spectroscopy; their molecular structures have been established by single-crystal X-ray analysis.

The reactions of H 2 AlCl with [(dpp-Bian)Na(Et 2 O) n ] and [(Ar BIG -Bian)Na(THF)] produce respective aluminum hydrides supported by radical-anionic 1,2-bis(arylimino)acenaphthene ligands, [(dpp-Bian)AlH 2 ] ( 1) and [(Ar BIG -Bian)AlH 2 (THF)] ( 2 ) (dpp-Bian = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene); Ar BIG -Bian = 1,2-bis[(2,6-dibenzhydryl-4-methylphenyl)imino]acenaphthene). The reaction of 1 with CO 2 proceeds with reduction of both C═O bonds and results in diolate [{(dpp-Bian)Al(μ-O 2 CH 2 )} 2 ] ( 3 ). Complex 2 reacts with CO 2 to carbonate [{(Ar BIG -Bian)Al(μ-OCH 2 OCO 2 )} 2 ] ( 4 ) that is a result of the insertion of CO 2 into the Al-O bond in diolate species formed initially. Aluminum monohydrides [(dpp-Bian)AlH(X)] (X = Cl, 5 ; Me, 6 ) react with CO 2 to form respective alumoxanes [{(dpp-Bian)AlX} 2 (μ-O)] (X = Cl, 7 and X = Me, 8 ). Compounds 1 - 4 , 7 , and 8 have been characterized by ESR and IR spectroscopy, and their molecular structures have been determined by single-crystal X-ray analysis.

The reaction of dialane [LAl-AlL] (1; L=dianion of 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene, dpp-bian) with carbon dioxide results in two different products depending on solvent. In toluene at temperatures of about 0 °C, the reaction gives cycloadduct [L(CO 2 )Al-Al(O 2 C)L] (2), whereas in diethyl ether, the reaction affords oxo-bridged carbamato derivative [L(CO 2 )(Et 2 O)Al(μ-O)AlL] (3). The DFT and QTAIM calculations provide reasonable explanations for the reversible formation of complex 2 in the course of two subsequent (2+4) cycloaddition reactions. Consecutive transition states with low activation barriers were revealed. Also, the DFT study demonstrated a crucial effect of diethyl ether coordination to aluminium on the reaction of dialane 1 with CO 2 . The optimized structures of key intermediates were obtained for the reactions in the presence of Et 2 O; calculated thermodynamic parameters unambiguously testify the irreversible formation of the product 3., (© 2021 Wiley-VCH GmbH.)

Reduction of ArBIG-bian (1, 1,2-bis[(2,6-dibenzhydryl-4-methylphenyl)imino]acenaphthene) with an excess of samarium in tetrahydrofuran (thf) and crystallization of the crude product from a thf/toluene mixture affords [(ArBIG-bian)Sm]·C7H8 (2a), which is free of the coordinating solvent. The use of 1,2-dimethoxyethane (dme) as the reaction medium resulted in the same product, [(ArBIG-bian)Sm]·C4H10O2 (2b), which differs from 2a only in the crystal lattice solvent. Reduction of 1 with an excess of ytterbium in dme gives compound [(ArBIG-bian)Yb(dme)]·2.5C7H8 (3), containing a coordinated dme molecule. All three products consist of dianionic ArBIG-bian ligands whose bulky 2,6-(Ph2CH)2-4-Me-C6H2 groups shield effectively the metal atoms. The newly prepared compounds 2a, 2b and 3 were characterized by 1H NMR and IR spectroscopy. The molecular structures of complexes 2a, 2b and 3 have been established by single crystal X-ray analysis. The intramolecular interactions were analysed on the basis of DFT calculations. The temperature dependence of the magnetic susceptibility of 2b and 3 in the region of 2-300 K was studied. The magnetic moments of complex 2b correspond to divalent samarium.

Digallane [L 1 Ga-GaL 1 ] (1, L 1 =dpp-bian=1,2-[(2,6-iPr 2 C 6 H 3 )NC] 2 C 12 H 6 ) reacts with RN=C=O (R=Ph or Tos) by [2+4] cycloaddition of the isocyanate C=N bonds across both of its C=C-N-Ga fragments to afford [L 1 (O=C-NR)Ga-Ga(RN-C=O)L 1 ] (R=Ph, 3; R=Tos, 4). The reactions with both isocyanates result in new C-C and N-Ga single bonds. In the case of allyl isocyanate, the [2+4] cycloaddition across one C=C-N-Ga fragment of 1 is accompanied by insertion of a second allyl isocyanate molecule into the Ga-N bond of the same fragment to afford compound [L 1 Ga-Ga(AllN- C=O) 2 L 1 ] (5) (All=allyl). In the presence of Na metal, the related digallane [L 2 Ga-GaL 2 ] (2; L 2 =dpp-dad=[(2,6-iPr 2 C 6 H 3 )NC(CH 3 )] 2 ) is converted into the gallium(I) carbene analogue [L 2 Ga:] - (2 A), which undergoes a variety of reactions with isocyanate substrates. These include the cycloaddition of ethyl isocyanate to 2 A affording [Na 2 (THF) 5 ]{L 2 Ga[EtN-C(O)] 2 GaL 2 } (6), cleavage of the N=C bond with release of 1 equiv. of CO to give [Na(THF) 2 ] 2 [L 2 Ga(p-MeC 6 H 4 )(N-C(O)) 2 -N(p-MeC 6 H 4 )] 2 (7), cleavage of the C=O bond to yield the di-O-bridged digallium compound [Na(THF) 3 ] 2 [L 2 Ga-(μ-O) 2 -GaL 2 ] (8), and generation of the further addition product [Na 2 (THF) 5 ][L 2 Ga(CyNCO 2 )] 2 (9). Complexes 3-9 have been characterized by NMR ( 1 H, 13 C), IR spectroscopy, elemental analysis, and X-ray diffraction analysis. Their electronic structures have been examined by DFT calculations., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

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 1 Ga-GaL 1 ] (1, L 1 =dpp-dad=[(2,6-iPr 2 C 6 H 3 )NC(CH 3 )] 2 ) and [L 2 Ga-GaL 2 ] (2, L 2 =dpp-bian=1,2-[(2,6-iPr 2 C 6 H 3 )NC] 2 C 10 H 6 ), 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 2 N 2 Ga metallacycle with formation of C-C and S-Ga single bonds to afford [L 1 (RN=C-S)Ga-Ga(S-C=NR)L 1 ] (3, R=Me; 4, R=Ph) and [L 2 (RN=C-S)Ga-Ga(S-C=NR)L 2 ] (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) 3 ] 2 [L 1 Ga(μ-S) 2 GaL 1 ] (5), [L 2 Ga(μ-S) 2 GaL 2 ] (10), and [Na(DME) 3 ][L 2 Ga(μ-S) 2 GaL 2 ] (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) 2 ] 2 [L 1 (PhN=C-S)Ga(μ-S) 2 Ga(S-C=NPh)L 1 ] (6) and [L 1 (PhN=C-S)Ga(μ-S)Ga(S-C=NPh)L 1 ] (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., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

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 1 -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 1 -All)Br (6) and (dpp-bian-All)(Br)Ga-Ga(Br)(dpp-bian-All) (7). The reaction of digallane 2 with Ph 3 SnNCO afforded (dpp-bian)Ga(SnPh 3 ) 2 (8) and (dpp-bian)(NCO)Ga-Ga(NCO)(dpp-bian) (9). Treatment of GaCl 3 with (dpp-bian)Na in diethyl ether resulted in the formation of (dpp-bian)GaCl 2 (10). Diorganylgallium derivatives (dpp-bian)GaR 2 (R=Ph, 11; tBu, 14; Me, 15; Bn, 16) and (dpp-bian)Ga(η 1 -All)R (R=nBu, 12; Cp, 13) were synthesized from complexes 3, 10, Bn 2 GaCl, or tBu 2 GaCl by salt metathesis. The salt elimination reaction between (dpp-bian)GaI 2 (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 2 ][Mg 2 Cl 3 (THF) 6 ] (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 2 (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., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Acetylene, phenylacetylene, and alkylbutynoates add reversibly to (dpp-bian)Ga-Ga(dpp-bian) (dpp-bian=1,2-bis[(2,6-diisopropylphenyl)-imino]acenaphthene) to give addition products [dpp-bian(R(1)C=CR(2))]Ga-Ga[(R(2)C=CR(1))dpp-bian]. The alkyne adds across the Ga-N-C section, which results in new carbon-carbon and carbon-gallium bonds. The adducts were characterized by electron absorption, IR, and (1)H NMR spectroscopy and their molecular structures have been determined by single-crystal X-ray analysis. According to the X-ray data, a change in the coordination number of gallium from three [in (dpp-bian)Ga-Ga(dpp-bian)] to four (in the adducts) results in elongation of the metal-metal bond by approximately 0.13 Å. The adducts undergo a facile alkynes elimination at elevated temperatures. The equilibrium between [dpp-bian(PhC=CH)]Ga-Ga[(HC=CPh)dpp-bian] and [(dpp-bian)Ga-Ga(dpp-bian) + 2 PhC≡CH] in toluene solution was studied by (1)H NMR spectroscopy. The equilibrium constants at various temperatures (298≤T≤323 K) were determined, from which the thermodynamic parameters for the phenylacetylene elimination were calculated (ΔG°=2.4 kJ mol(-1), ΔH°=46.0 kJ mol(-1), ΔS°=146.0 J K(-1) mol(-1)). The reactivity of (dpp-bian)Ga-Ga(dpp-bian) towards alkynes permits use as a catalyst for carbon-nitrogen and carbon-carbon bond-forming reactions. The bisgallium complex was found to be a highly effective catalyst for the hydroamination of phenylacetylene with anilines. For instance, with [(dpp-bian)Ga-Ga(dpp-bian)] (2 mol%) in benzene more than 99% conversion of PhNH(2) and PhC≡CH into PhN=C(Ph)CH(3) was achieved in 16 h at 90 °C. Under similar conditions, the reaction of 1-aminoanthracene with PhC≡CH catalyzed by (dpp-bian)Ga-Ga(dpp-bian) formed a carbon-carbon bond to afford 1-amino-2-(1-phenylvinyl)anthracene in 99% yield., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The reduction of benzophenone with the magnesium complex [(2,6-iPr(2)C(6)H(3)-bian)Mg(thf)(3)] (1), containing the 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene dianion, affords the pinacolato complex [(2,6-iPr(2)C(6)H(3)-bian)Mg(thf)](2)[micro-O(2)C(2)Ph(4)].(C(6)H(6))(4) (2). The reaction of 1 with 9(10H)-anthracenone yields the 9-anthracenolato complex [(2,6-iPr(2)C(6)H(3)-bian)Mg(OC(14)H(9))(thf)(2)] (3). Complexes 2 and 3 were characterized by elemental analyses, UV/Vis, IR, and ESR spectroscopy, as well as by single crystal X-ray diffraction. Complex 2 dissociates in solution with splitting of the bridging pinacolato unit, forming the biradical diimino/ketyl complex [(2,6-iPr(2)C(6)H(3)-bian)Mg(thf)(OCPh(2))].