A monotopic aluminum telluride with an Al=Te double bond stabilized by N-heterocyclic carbenes

Aluminum chalcogenides are mostly encountered in the form of bulk aluminum oxides that are structurally diverse but typically consist of networks with high lattice energy in which the chalcogen atoms bridge the metal centres. This makes their molecular congeners difficult to synthesize because of a pronounced tendency for oligomerization. Here we describe the isolation of the monotopic aluminum chalcogenide (L(Dip)N)AlTe(L(Et))2 (L(Dip)=1,3-(2,6-diisopropylphenyl)-imidazolin-2-imine, L(Et)=1,3-diethyl-4,5-dimethyl-imidazolin-2-ylidene). Unique features of (L(Dip)N)AlTe(L(Et))2 are the terminal position of the tellurium atom, the shortest aluminum-tellurium distance hitherto reported for a molecular complex and the highest bond order reported for an interaction between these elements, to the best of our knowledge. At elevated temperature (L(Dip)N)AlTe(L(Et))2 equilibrates with dimeric {(L(Dip)N)AlTe(L(Et))}2 in which the chalcogen atoms assume their common role as bridges between the metal centres. These findings demonstrate that (L(Dip)N)AlTe(L(Et))2 comprises the elusive Al=Te double bond in the form of an N-heterocyclic carbene-stabilized species.

Synthesis and structural characterization of aluminum iminophosphonamide complexes

Monoanionic iminophosphonamide ligands have a N-P-N linkage and undergo four-membered ring N,N-ligand formation when treated with aluminum compounds. The reaction of LLi (L = [Ph(2)P(NSiMe(3))(2)]) with equivalent amounts of AlCl(3) and AlMeCl(2) in toluene afforded LAlCl(2) (3) and LAlClMe (4), respectively. L(2)AlH (5), LAlEt(2) (6), and LAl(NMe(2))(2) (7) respectively were prepared by the reaction of LH with AlH(3) x NMe(3), AlEt(3), and Al(NMe(2))(3) in n-hexane. Subsequently compounds 3-7 were characterized by elemental analysis, (1)H, (13)C, and (31)P NMR spectroscopy and X-ray crystallographic studies (for 3, 4, 5, and 7).

Novel dinuclear dimethylamido-3,5-dimethylpyrazolato and tetranuclear dimethylamido-3,5-dimethylpyrazolato-polyoxo zirconium(IV) complexes. Synthesis and structural characterisation

The dinuclear dimethylamido-tris(3,5-dimethylpyrazolato)-zirconium(IV) complex [Zr(3,5-Me2Pz)3(NMe2)]2 1 is prepared by treatment of [Zr(NMe2)4] with 3 equivalents of 3,5-dimethylpyrazole (3,5-Me2PzH) with elimination of dimethylamine. When [Zr(NMe2)4] reacted with 2 equivalents of 3,5-Me2PzH, the bis(dimethylamido)-bis(3,5-dimethylpyrazolato)zirconium(IV) compound [Zr(3,5-Me2Pz)2(NMe2)2]2 2 is obtained. Hydrolysis of [Zr(3,5-Me2Pz)3(NMe2)]2 in wet toluene affords the tetranuclear oxo compound [Zr4(eta2-3,5-Me2Pz)4(NMe2)2(mu3-O)2(mu2-3,5-Me2Pz)4(mu2-NMe2)2] . All synthesised compounds are characterised by NMR spectroscopic and analytical methods. Single crystal X-ray diffraction analysis has established the molecular structures of 1 and 4.

Pyrazoles and pyrazolides-flexible synthons in self-assembly

This Perspective summarises the chemistry of the pyrazole ring, and reviews the metal coordination modes adopted by 1H-pyrazoles and their anions. Pyrazolide anions are probably the most versatile ligands in coordination chemistry, with 20 different terminal or bridging coordination modes having been identified so far. Metal cluster compounds supported by pyrazolido ligation are surveyed, concentrating on those reported during the past ten years. Highlights include the wide structural diversity in apparently simple main group pyrazolides; luminescence and charge-transfer complexes in coinage metal pyrazolide clusters; the use of robust metal pyrazolide clusters to construct liquid crystals, supramolecular materials and metal-organic frameworks; and supramolecular complexes formed by pyrazolide-supported metallacrowns.

Macrocyclic Binucleating β-Diketiminate Ligands and their Lithium, Aluminum, and Zinc Complexes

The incorporation of rigid aromatic linkers into β-diketiminate ligands creates a binucleating scaffold that holds two metals near each other. This paper discloses the synthesis, characterization, and reactivity of mBin(2-), which has a meta-substituted xylylene spacer, and pBin(2-), which has a para-substituted xylylene spacer. Lithium, aluminum, and zinc complexes of each ligand are isolated, and in some cases are characterized by X-ray crystallography. The lithium complexes are coordinated to solvent-derived THF ligands, while the zinc and aluminum complexes have alkyl ligands. Complexes of the mBin(2-) ligand have an anti conformation in which the metals are on opposite sides of the macrocycle, while pBin(2-) complexes prefer a syn conformation. The (1)H NMR spectra of the complexes demonstrate that the conformations rapidly interconvert in the lithium complexes, and less rapidly in the zinc and aluminum complexes.

Reactions of MAlH4 (M = Li, Na) with primary amines — Synthetic and structural studies of alkali metal tetrakis(amido)aluminates and related dinuclear complexes

The reactions of MAlH4 (M = Li, Na) with primary amines NH2R (R = t-Bu, i-Pr, p-tolyl) in a 1:4 molar ratio in THF produce the tetrakis(amido)aluminates, [M(THF)n][Al(NHR)4], in yields of 46%–82% together with secondary products. The extent of solvation of the alkali-metal cation varies from none (n = 0) for M[Al(NH-i-Pr)4] (2b, M = Li; 3b, M = Na) to n = 4 in the complex [Li(THF)4][Al(NH-p-tolyl)4] (2c), which exists as a solvent-separated ion pair. The complexes 2b, 3b, and [Na(THF)][Al(NH-p-tolyl)4]∞ (3c) all exhibit one-dimensional polymeric structures in which the bis-N,N′-chelating tetrakis(amido)aluminate anions are bridged by four- (2b, 3b) and five-coordinate (3c) metal ions, respectively. The structures of two of the secondary products, {[Na(THF)2][(NH-t-Bu)Al(H)(µ-N-t-Bu)]}2 (4) and {[Na(THF)3][(NH-p-tolyl)2Al(µ-N-p-tolyl)]}2 (5), were established by X-ray crystallography. Complex 4 is a dimer of the [HAl(NH-t-Bu)(N-t-Bu)]– anion, which forms a central Al2N2 ring with each monoanion N,N′-chelated to a [Na(THF)2]+ cation. Complex 5 is a dimer of the [Al(NR)(NHR)2]– (R = p-tolyl) anion in which the bridging p-tolyl groups are coordinated in an N-monodentate fashion to the trisolvated [Na(THF)3]+ cations. Key words: aluminohydrides, alkali metals, primary amines, tetrakis(amido)aluminates, structures.

Syntheses, Characterization, and X-ray Crystal Structures of β-Diketiminate Group 13 Hydrides, Chlorides, and Fluorides

A series of organometallic compounds of group 13 metals supported by the sterically encumbered beta-diketiminate ligand containing hydrides, fluorides, chlorides, and bromide have been synthesized and structurally characterized. The synthetic strategy applied utilizes halide metathesis and reduction of metal chlorides to the corresponding hydrides. Thus, the reaction of LLi.OEt2 with MeMCl2 affords LM(Me)Cl (M = Al (1), Ga (2), In (3)) and LGaBr2 (4) with GaBr3. Reduction of LGa(Me)Cl with LiH.BEt3 leads to the formation of LGa(Me)H (10). Synthesis of LGaH(2) (12) has been accomplished by reacting LGaI2 (8) with LiH.BEt3. LAl(Me)Cl (1) and LAlH2 (6) have been converted to LAl(Me)F (5) and LAlF2 (7), respectively. The former was obtained in a reaction of LAl(Me)Cl with Me3SnF while the latter was isolated in a reaction of LAlH2 with BF3.OEt2. Similarly reaction of LGaI2 (8) with Me3SnF affords LGaF2 (9). Compounds reported herein have been characterized by elemental analyses, IR, NMR, EI-MS, and single-crystal X-ray diffraction techniques.

A paradigm change in assembling OH functionalities on metal centers

The synthesis of terminal hydroxide containing Group 13 and 14 metals [LAl(OH)(2)], LAlMeOH, [{LAl(OH)}(2)(mu-O)], LAl(OH)-O-AlLL', LGeOH, and [TsiSn(O)OH](3) [Tsi = (Me(3)Si)(3)C] has been accomplished using innovative synthetic methodologies. All of these compounds have been structurally characterized, both in solution as well as in the solid state. The utility of such metal hydroxides [{LAl(OH)}(2)(mu-O)] and LAlMeOH [L = HC{(CMe)(2,6-i-Pr(2)C(6)H(3)N)}(2)] in the preparation of homo- and heterometallic compounds has been demonstrated. It has also been possible to prepare unusual terminal SH- and SeH-containing compounds LAl(SH)(2), LAl(SeH)(2), and LAl(SeH)-Se-Al(SeH)L using dihydride LAlH(2) as a starting material. The synthesis, structure, and potential utility of these compounds is discussed.

Aluminum Complexes Incorporating Bidentate Amido Phosphine Ligands

A series of aluminum complexes supported by o-phenylene-derived amido phosphine ligands, N-(2-diphenylphosphinophenyl)-2,6-dimethylanilide ([Me-NP]-) and N-(2-diphenylphosphinophenyl)-2,6-diisopropylanilide ([iPr-NP]-), have been prepared. The reactions of trialkylaluminum with H[Me-NP] and H[iPr-NP], respectively, in refluxing toluene produced the corresponding dialkyl complexes [Me-NP]AlR(2) and [iPr-NP]AlR(2) (R = Me, Et). Deprotonation of H[Me-NP] with n-BuLi in THF at -35 degrees C followed by addition of AlCl(3) in toluene at -35 degrees C afforded [Me-NP]AlCl(2), which was subsequently reacted with 2 equiv of trimethylsilylmethyllithium in toluene to give [Me-NP]Al(CH(2)SiMe(3))(2). The aluminum complexes were all characterized by (1)H, (13)C, (31)P, and (27)Al NMR spectroscopy. The solid-state structures of monomeric, four-coordinate [Me-NP]AlEt(2) and [iPr-NP]AlMe(2) and five-coordinate [Me-NP]AlCl(2)(THF) were determined by X-ray crystallography. The (1)H NMR studies of [Me-NP]AlEt(2), [Me-NP]Al(CH(2)SiMe(3))(2), and [iPr-NP]AlEt(2) indicate diastereotopic alpha-hydrogen atoms in these molecules. Heteronuclear COSY and NOE experiments suggest that the phosphorus donor in [Me-NP]Al(CH(2)SiMe(3))(2) and [iPr-NP]AlEt(2) is coupled to only one of the diastereotopic alpha-hydrogen atoms that is virtually antiperiplanar with respect to the phosphorus atom.

Synthesis and Structures of Complexes Demonstrating the Coordinative Versatility of the 2,4-Diimino-3-phosphinopentene Anion (γ-Phosphino-β-diketiminate)

The synthesis and characterization of a 2,4-diimino-3-phosphinopentene anion (gamma-phosphino-beta-diketiminate) is reported and enables diversification of the beta-diketiminate ligand framework, which has been widely employed across the periodic table. Phosphines are observed to adopt the gamma-position of the ligand rather than the N,N' chelate. While aluminum and lithium adopt the familiar N,N' chelate arrangement with the new 2,4-diimino-3-phosphinopentene anion ligand, reactions with AsCl(3) or SbCl(3) result in substitution at the beta-methyl position on the ligand backbone, realizing novel P-->E (E = As or Sb) intramolecular coordination. The chemistry of the 2,4-diimino-3-phosphinopentene anion can be monitored by the (31)P NMR chemical shifts, which are distinctively diagnostic of the coordinative engagement of the ligand.