Search

Heterocumulenes Se＝C＝NR (R = C6H4OMe-2, C6H4Me-2) undergo facile cycloaddition to [(H-dpp-bian)Na(Et2O)2] (1) (H-dpp-bian = N-protonated 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) resulting in cycloadducts [(H-dpp-bian)Na(SeCNR)(DME)] (2, 3), which are the first cycloadducts derived from a sodium metallacycle reported so far. A comparative reaction of [(dpp-bian)Mg(THF)3] (10) with Se＝C＝NR gives magnesium cycloadducts [(dpp-bian)Mg(SeCNR)(Solv)2] (11, 12), which undergo fast decomposition at room temperature. New compounds are characterized by NMR, EPR, and IR spectroscopy, and elemental and X-ray diffraction analysis. Their electronic structures and reaction pathways were probed using DFT calculations. [ABSTRACT FROM AUTHOR]

[Display omitted] Reactivity of ytterbium and magnesium complexes of gallylenes against carbon dioxide and diphenylketene has been assessed. Ytterbium complex of redox-active gallylene [{(dpp-bian)Ga} 2 Yb(DME) 2 ] (dpp-bian = 1,2-bis[(2,6-diiso-propylphenyl)imino]acenaphthene) on treatment with CO 2 gives complex [(dpp-bian)Ga(DME)Me], while the treatment of magnesium-stabilized gallylene[{(dpp-bian)Ga} 2 Mg(DME) 2 ] with Ph 2 CCO affords cycloadduct [(dpp-bian)(Ph 2 CCO)GaMe]. [ABSTRACT FROM AUTHOR]

The activation of carbon dioxide by metallylene [(dpp-bian)GaNa(DME)2] (dpp-bian = 1,2-bis[(2,6-di-isopropylphenyl)imino]acenaphthene) under mild conditions is described. Furthermore, the reaction of the activation complex [(dpp-bian)Ga(CO2)2Ga(dpp-bian)][Na(DME)2]2 (2) with diphenylketene, cyclohexyl isocyanate, and phenyl isocyanate leads to the elimination of carbon monoxide and the formation of derivatives of oxocarboxylic acid [(dpp-bian)GaOC(O)C(Ph)2C(CPh2)O][Na(DME)2] (6) and carbamate derivatives [(dpp-bian)GaN(Cy)C(O)N(Cy)C(O)O]2[Na(DME)2]2 (7) and [(dpp-bian)GaN(Ph)C(O)O]2[Na(DME)2]2 (8), respectively. Complexes have been characterized by NMR, IR spectroscopy, elemental analysis, and X-ray diffraction analysis. Their electronic structures have been examined by DFT calculations. The possible mechanism of the modification reaction is proposed and supported by the investigation of 13CO2-enriched samples and DFT calculations. [ABSTRACT FROM AUTHOR]

The reductive coupling of carbodiimides RN＝C＝NR (R = 2,6-iPr2C6H3, Cy, iPr) by using [(dpp-bian)GaNa(dme)2] (1); [(dpp-dad)GaNa(thf)3] (2a) and [(dpp-dad)GaK(thf)4Ga(dpp-dad)][K(thf)6] (2b) led to the guanidinate derivatives [(dpp-bian)Ga(NCy)2C＝NCy][Na(thf)2] (3); [LGaN(R)C(RN)N(R)C(RN)][M] L = dpp-bian, M = Na(dme)2, R = iPr, (4a); L = dpp-dad, M = Na(thf)3, R = iPr, (4b); R = Cy, (4c); M = K(thf)4, (4d); L = dpp-bian, M = Na(dme)2, R = Cy, (4e) and [(dpp-dad)Ga(2,6-iPr2C6H3N)2C][Na(thf)2] (5). [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]

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]

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.

A titanium(IV) alkoxido complex, (dpp‐bian)Ti(OBn)2 (2), as well as alkoxido chlorido complexes (dpp‐bian)TiCl(OCH2CH2OMe) (3) and (dpp‐bian)TiCl2OBn (4), were synthesized from the titanium(IV) dichloride precursor [(dpp‐bian)TiCl2]2 (1) by exchange with corresponding sodium salts (comps. 2 and 3) or by the alcoholysis with BnOH (comp. 4). The compounds 2–4 were fully characterized by elemental analysis, NMR or EPR, and IR spectroscopy. Molecular structures of the metal complexes in the solid state have been determined by single‐crystal XRD analysis. Compounds 2–4 were tested as catalysts in the ROP of L‐lactide in a toluene medium. Whereas complexes 2 and 3 produce cyclic PLAs with broad dispersities and unpredictable molecular weights, complex 4 acts as an efficient ROP catalyst which polymerizes the monomer in a highly controllable manner. It produces BnO‐capped PLAs with narrow molecular weight distributions as well as linear dependence of Mns on monomer conversion. [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]

Invited for the cover of this issue is Dr. Alexander Morozov from the G.A. Razuvaev Institute of Organometallic Chemistry of the Russian Academy of Sciences, Nizhny Novgorod, Russian Federation. The cover image shows two basketball players representing the bis(amide) and the radical anionic ligands, with different modes of binding to the Ti metal. [ABSTRACT FROM AUTHOR]

Front Cover: Four- and Five-Coordinate Titanium(IV) Complexes Supported by the dpp-bian Ligand in ROP of L-Lactide (Eur. J. Inorg. B The Front Cover b shows a basketball workout that is like a catalytic ROP of I L i -lactide driven by -diimine-supported titanium coordination compounds. B The Front Cover b shows a basketball workout that is like a catalytic ROP of I L i -lactide driven by -diimine-supported titanium coordination compounds. [Extracted from the article]