Organoelement Compounds Possessing AlAl, GaGa, InIn, and TlTl Single Bonds

NHC-Stabilized Dialanes(4) of Al2 Mes4

The synthesis and characterization of novel N-heterocyclic carbene (NHC) stabilized dialanes Al2 Mes4 as well as first investigations concerning the reactivity of these compounds are reported. The synthesis of these compounds proceeds via the mesityl-substituted alanes (NHC)⋅AlHMes2 (NHC=IMeMe {=1,3,4,5-tetramethyl-imidazolin-2-ylidene}, IiPrMe {=1,3-di-iso-propyl-4,5-dimethylimidazolin-2-ylidene}) and iodo-alanes (NHC)⋅AlIMes2 (NHC=IMeMe , IiPrMe ). Metallic reduction of (NHC)⋅AlIMes2 afforded the new NHC-stabilized dialanes (NHC)2 ⋅Al2 Mes4 (NHC=IMeMe , IiPrMe ). The NHC-ligated dialanes are thermally robust and storable synthons for the dialane Al2 Mes4 . First reactivity studies on (IMeMe )2 ⋅Al2 Mes4 towards small molecules confirm this, as this compound shows controlled and selective reactions with several substrates. Reaction with CuCl leads to oxidation of the dialane and formation of (IMeMe )⋅AlClMes2 , reactions with pyridine N-oxide and t Bu-N=C=S, respectively, gave the chalcogenide-bridged dimers {(IMeMe )⋅AlMes2 }2 -μ-E (E=O, S), and reaction with acetylene afforded the dimetallaacetylide {(IMeMe )⋅AlMes2 }2 -μ-(C≡C).

Reactions of Iso(thio)cyanates with Dialanes: Cycloaddition, Reductive Coupling, or Cleavage of the C═S or C═O Bond

The dialanes [(dpp-Bian)Al-Al(dpp-Bian)] (1) and [(dpp-dad)Al(THF)-(THF)Al(dpp-dad)] (2) (dpp-Bian = 1,2-[(2,6-iPr₂C₆H₃)NC]₂C₁₂H₆, dpp-dad = [(2,6-iPr₂C₆H₃)NC(CH₃)]₂) react with some isothiocyanates, isocyanates, and diphenylketene via [2 + 4] cycloaddition of the C═O or C═S bond across the C═C-N-Al fragment to afford complexes [L(X═C-Y)Al-Al(X═C-Y)L] with an intact Al-Al single bond (3, L = dpp-Bian, X = PhN, Y = O; 4, L = dpp-Bian, X = Ph₂C, Y = O; 6, L = dpp-dad, X = BnN, Y = S; 7, L = dpp-dad, X = tBuN, Y = O; 8, L = dpp-dad, X = iPrN, Y = S; and 9, L = dpp-dad, X = CyN, Y = S). A mixed C═N and C═O mode cycloadduct, [(dpp-Bian)(TosN═C-O)Al-Al(TosN-C═O)(dpp-Bian)] 5, was obtained in the reaction of 1 with tosylisocyanate. Heating the solution of 3 resulted in a thermal transformation and a change of the cycloaddition mode from C═O to C═N to give the product [(dpp-Bian)(PhN-C═O)Al(O)Al(PhN-C═O)(dpp-Bian)] 10. The reduction of 7 and 8 with Na yielded the products [Na(THF)_n]₂[(dpp-dad^-H)(X═C-Y)Al]₂ (12, X = iPrN, Y = S, n = 2 and 13, X = tBuN, Y = O, n = 3) in which one of the methyl groups of the backbone of the initial dpp-dad ligand was dehydrogenated. When 2 was reacted with the bulky adamantyl isocyanate AdNCO, the C-C coupling of two substrates occurred to form 14 [(dpp-dad)Al(O═C-NAd)₂Al(dpp-dad)] in which the coupled dianionic oxamide ligand bridged two Al atoms in a μ,η⁴-N,O/N,O mode. Moreover, in the presence of 2.0 equiv of Na metal, precursor 2 reacts with tBuNCS, p-TolylNCS, or Me₃SiNCO, possibly through the reduced Al^I intermediate, to yield the sulfur- or oxygen-bridged dimer [Na(solv)_n]₂[(dpp-dad)Al(μ-E)]₂ (15, E = S, solv = THF, n = 3 and 16, E = O, solv = DME, n = 2) upon C═S or C═O bond cleavage. Dialane 1 reacts with dimethylsulfone to give a Lewis adduct [(dpp-Bian)(Me₂SO₂)Al]₂ (17), which releases dimethylsulfone upon heating. The diamagnetic compounds 3-10 and 12-17 were characterized by NMR and IR spectroscopy. The molecular structures of 3-17 were established by single-crystal X-ray diffraction analysis. Electronic structures of the compounds and possible isomers have been examined by DFT calculations.

Activation and modification of carbon dioxide by redox-active low-valent gallium species

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.

In-Depth Investigation of a Donor-Acceptor Interaction on the Heavy-Group-14@Group-13-Diyls in Transition-Metal Tetrylone Complexes: Structure, Bonding, and Property

Stabilization for tetrylone complexes, which carry ylidone(0) ligands [(CO)₅W-X (YCp*)₂] (X = Ge, Sn, Pb; Y = B-Tl), has become an active theoretical research because of their promising application. Structure, bonding, and quantum properties of the transition-metal donor-acceptor complexes were theoretically investigated at the level of theory BP86 with several types of basis sets including SVP, TZVPP, and TZ2P+. The optimized structures reveal that all ligands X (YCp*)₂ are strongly bonded in tilted modes to the metal fragment W(CO)₅, and Cp* rings are mainly η₅-bonded to atom X. DFT-based bonding analysis results in an implication that the stability of W-X bond strength primarily stems from the donation (CO)₅W ← X(YCp*)₂ formed by both σ- and π-bondings and the electrostatic interaction ΔE _elstat. The W-X bond possesses a considerable polarizability toward atom X, and analysis on its hybridization is either sp²-characteristic or mainly p-characteristic. EDA-NOCV-based results further imply that the ligands XY perform as significant σ-donors but minor π-donors. The visual simulations of NOCV pairs and the deformation densities assemble a comprehensive summary on different components of the chemical bond via σ- and π-types in the complexes. This work contributes to the literature as an in-depth overview on predicted molecular structures and quantum parameters of the complexes [(CO)₅W-X(YCp*)₂] (X = Ge, Sn, Pb; Y = B-Tl), conducive to either further theoretical reference or extending experimental research.

On-Surface Atom-by-Atom-Assembled Aluminum Binuclear Tetrabenzophenazine Organometallic Magnetic Complex

The Kondo effect results from the interactions of the conduction electrons in a metal bulk with localized magnetic impurities. While adsorbed atop a metallic surface, the on-surface nanoscale version of this effect is observed when a single magnetic atom or a single magnetic molecule (SMM) is interacting with the conduction electrons. SMMs are commonly organometallic complexes incorporating transition-metal atoms in different oxidation states. We demonstrate how a single nonmagnetic neutral tetrabenzo[a,c,j,h]phenazine molecule can be on-surface-coordinated with exactly two aluminum metal atoms (between Al(I) and Al(II) oxidation state on the Au(111) surface) by low-temperature scanning tunneling microscope (LT-STM) single-atom manipulation. It results in a Kondo measurable localized molecular magnetic moment. This opens a new way to design SMM complexes without the need for heavy transition-metal atoms and complex ligands to stabilize the molecular coordination sphere.

Understanding the reactivity of carbene-analogous phosphane complexes with group 13 elements as a central atom: a theoretical investigation

The reactions of carbenic cations (PtBu₃)₂M⁺ (M = B, Al, Ga, In, and Tl) with methane and ethene are studied using density functional theory.

Monomeric Cp3tAl(i): synthesis, reactivity, and the concept of valence isomerism

With the isolation of Cp3tAl (1), the first monomeric Cp-based Al(i) species could be realized in a pure form via a three-step reaction sequence (salt elimination/adduct formation/adduct cleavage) starting from readily available AlBr3. Due to its monomeric structure, reactions involving 1 were found to proceed more selectively, faster, and under milder conditions than for tetrameric (Cp*Al)4. Thus, 1 readily formed simple Lewis acid-base adducts with tBuAlCl2 (6) and AlBr3 (7), reactions that before have always been interfered with by the presence of aluminum halide bonds. In addition, the 2 : 1 reaction of 1 with AlBr3 enabled the realization of the very rare trialuminum adduct species 8. 1 also reacted rapidly with N2O and PhN3 at room temperature to afford Al3O3 and Al2N2 heterocycles 9 and 10, respectively. With the structural characterization of products 4 and 5, the reaction of monovalent 1 with Cp3tAlBr2 (2) provided the first experimental evidence for the concept of valence isomerism between dialanes and their Al(i)/Al(iii) Lewis adducts.

Reduction vs. Addition: The Reaction of an Aluminyl Anion with 1,3,5,7-Cyclooctatetraene

The potassium aluminyl complex K[Al(NON^Ar )] (NON=NON^Ar =[O(SiMe₂ NAr)₂ ]^2- , Ar=2,6-iPr₂ C₆ H₃ ) reacts with 1,3,5,7-cyclooctatetraene (COT) to give K[Al(NON^Ar )(COT)]. The COT-ligand is present in the asymmetric unit as a planar μ₂ -η² :η⁸ -bridge between Al and K, with additional K⋅⋅⋅π-aryl interactions to neighboring molecules that generate a helical chain. DFT calculations indicate significant aromatic character, consistent with reduction to [COT]^2- . Addition of 18-crown-6 causes a rearrangement of the C₈ -carbocycle to form the isomeric 9-aluminabicyclo[4.2.1]nona-2,4,7-triene anion.

A Stable Neutral Compound with an Aluminum-Aluminum Double Bond

Homodinuclear multiple-bonded neutral Al compounds, aluminum analogues of alkenes, have been a notoriously difficult synthetic target over the past several decades. Herein, we report the isolation of a stable neutral compound featuring an Al═Al double bond stabilized by N-heterocyclic carbenes. X-ray crystallographic and spectroscopic analyses demonstrate that the dialuminum entity possesses trans-planar geometry and an Al-Al bond length of 2.3943(16) Å, which is the shortest distance reported for a molecular dialuminum species. This new species reacts with ethylene and phenyl acetylene to give the [2+2] cycloaddition products. The structure and bonding were also investigated by detailed density functional theory calculations. These results clearly demonstrate the presence of an Al═Al double bond in this molecule.

Synthesis and structural characterization of tris(2-pyridonyl)methyl complexes of zinc and thallium: a new class of metallacarbatranes and a monovalent thallium alkyl compound

Tris(2-pyridonyl)methanes may be synthesized via the reactions of the respective 2-pyridone with CHX3 (X = Cl, Br) and K2CO3 in the presence of [Bu(n)4N]Br, followed by acid-catalyzed isomerization with camphorsulfonic acid. These compounds provide access to a new class of alkyl ligands that feature oxygen donors and are capable of forming metallacarbatranes and a monovalent thallium alkyl compound.

An organogallium subfluoride and subhydroxide: three Ga-Ga bonds in single molecules

Treatment of the digallium compound R2Ga-GaR2 1 [R = CH(SiMe3)2] with hydrogen fluoride or water in the presence of 2-aminonicotinic acid afforded the corresponding fluoride or hydroxide, R(X)Ga-Ga(X)R (X = F, OH), by substituent exchange and retainment of the Ga-Ga bonds. Both compounds form trimeric formula units in which three Ga-Ga bonds in a parallel orientation are bridged by six fluoro or hydroxo ligands.

[(dpp-bian)GaGa(dpp-bian)] and [(dpp-bian)ZnGa(dpp-bian)]: Synthesis, Molecular Structures, and DFT Studies of These Novel Bimetallic Molecular Compounds

1,2-Bis[(2,6-diisopropylphenyl)imino]acenaphthene) (dpp-bian) stabilizes gallium-gallium and zinc-gallium bonds (compounds 1-3). The compound [(dpp-bian)Ga-Ga(dpp-bian)] (2) was prepared by the reaction of GaCl3 with K3[dpp-bian] and the heterometallic [(dpp-bian)Zn-Ga(dpp-bian)] (3) was prepared by a simple one-pot reaction of [{(dpp-bian)ZnI}(2)] with GaCl3 and K4[dpp-bian]. In contrast to [(dpp-bian)Zn-Zn(dpp-bian)] (1) and 3, compound 2 is ESR silent, thus proving the dianionic character of both dpp-bian ligands. The solution ESR spectrum of 3 reveals the coupling of an unpaired electron with the gallium nuclei (69)Ga and (71)Ga (A((69)Ga)=0.97, A((71)Ga)=1.23 mT), thus confirming the presence of Zn-Ga bonds in solution. According to the results of the X-ray crystal structure analyses the metal-metal bond lengths in 2 (2.3598(3) A) and 3 (2.3531(8) A) are close to that found in 1 (2.3321(2) A). The electronic structures of compounds 2 and 3 were studied by DFT (B3 LYP/6-31G* level). The metal-metal pi bond in 2 is mainly formed by overlap of the p orbitals of Ga in the HOMO and HOMO-1, the latter showing a stronger interaction. The s and p orbitals of Ga overlap in the deeper located HOMO-17 producing a Ga-Ga sigma bond. In contrast to the Zn-Zn bond in 1, which has 95 % s character, the NBO (natural bond order) analysis of 2 reveals 67.8 % s, 32.0 % p, and 0.2 % d character for the Ga-Ga bond. Compound 3 has a doublet electronic ground state. The unpaired electron occupies the alpha HOMO-1 localized at the Zn-containing fragment. The Ga-Zn bond is mainly formed by overlap of the metal orbitals in the alpha HOMO-6 and beta HOMO-5. According to the results of the NBO analysis, the Zn wave functions are responsible for 28.7 % of the Zn-Ga bond, with 96.7 % s, 1.0 % p, and 2.3 % d character.

A Linear Homocatenated Compound Containing Six Indium Centers

In contrast to carbon and its heavier congeners, group 13 elements are rarely observed to catenate into linear chains. Here, we find that treatment of indium(I) iodide with a protonated N-xylyl beta-diketiminate and a strong potassium base in tetrahydrofuran yields a hexa-indium chain. X-ray crystallography revealed one beta-diketiminate ligand bound to each indium center with no bridging ligands supporting the five indium-indium single bonds. The terminal indium centers were capped with iodine. Electronic spectroscopy and computations on a model compound offer preliminary support for sigma delocalization along the chain.