Zinc Ammonio-dodecaborates: Synthesis, Lewis Acid Strength, and Reactivity.

Two series of zinc salts, [EtZn][A] and Zn[A], with weakly coordinating anions [A] as counterions have been prepared, and their activities as catalysts for hydrosilylation reactions of 1-hexene, benzophenone, and acetophenone have been investigated. The counterions and per- and partially chlorinated 1-ammonio--dodecaborate anions [MeNBCl] [], [PrNBHCl] [], [BuNBHCl] [], and [HexNBHCl] [] were chosen as potential and more readily available alternatives to carborate anions such as [CHBCl] and [HexCBCl]. The basicity of anion [] was determined as being close to that of the triflimide anion [N(SOCF)], and the fluoride ion affinities (FIAs) of compounds [EtZn][] and Zn[] are lower than those of the Lewis acids B(CF) and Zn[HexCBCl].

Towards Naked Zinc(II) in the Condensed Phase: A Highly Lewis Acidic Zn Dication Stabilized by Weakly Coordinating Carborate Anions.

The employment of the hexyl-substituted anion [HexCB Cl ] allowed the synthesis of a Zn species, Zn[HexCB Cl ] , 3, in which the Zn cation is only weakly coordinated to two carborate counterions and that is soluble in low polarity organic solvents such as bromobenzene. DOSY NMR studies show the facile displacement of at least one of the counterions, and this near nakedness of the cation results in high catalytic activity in the hydrosilylation of 1-hexene and 1-methyl-1cyclohexene. Fluoride ion affinity (FIA) calculations reveal a solution Lewis acidity of 3 (FIA=262.

Convenient Access to Gallium(I) Cations through Hydrogen Elimination from Cationic Gallium(III) Hydrides.

Although gallium hydrides GaH ( = monoanionic substituent) are usually stable compounds, cationic arene-solvated species [HGa(arene)] spontaneously eliminate dihydrogen at room temperature to afford the arene-solvated gallium(I) compounds [Ga(PhF)][CHBCl] () and [Ga(PhCH)][B(CF)] (). A key requirement appears to be the presence of a weakly coordinating anion. Use of the more basic triflimide anion, [NTf], reverses the stability, i.

Chlorination of 1-Carba-closo-dodecaborate and 1-Ammonio-closo-dodecaborate Anions.

Fully chlorinated carborate and dodecaborate cages such as [CHBCl] and [MeNBCl] are prominent examples of valuable and chemically rather inert weakly coordinating anions. While both anions can be obtained by chlorination of the precursors [CHB] and [HNBH] with SOCl followed by methylation for the synthesis of [MeNBCl], best results were found using photochemical chlorination with SOCl for [CHB] and thermal chlorination with SOCl for [HNBH]. The hexachlorinated anion [n-PrNBHCl] was formed readily within 30 min by chlorination of [n-PrNBH], but attempts to synthesize isopropyl-substituted ammonio-dodecaborates with a higher chlorination number resulted in the formation of mixtures and partial decomposition.

Synthesis and reactivity of indium(I) 1-carba-closo-undecachlorododecaborate.

The arene-solvated indium(I) species [In(C7H8)3][CHB11Cl11] (1) and [In(C6H5Br)1.5][CHB11Cl11] (2) were obtained by a redox reaction involving the silver salt Ag[CHB11Cl11] and indium powder at 80 °C in a toluene or bromobenzene solution. These thermally stable compounds react with triphenylphosphine and the N-heterocyclic carbene 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene under reduction of indium(I) to indium metal and oxidation of the ligands to phosphonium and imidazolium cations contrary to the more commonly observed disproportionation reactions.

A direct stereoselective preparation of a fish pheromone and application of the zinc porphyrin tweezer chiroptical protocol in its stereochemical assignment.

A two-step stereoselective preparation of a goldfish pheromone, 17α,20β-dihydroxy-4-pregnen-3-one, is reported from the readily available cortexolone in 64% overall yield. The (20S)-epimer was also synthesized in three steps from cortexolone with an overall yield of 47%. A microscale chiroptical technique based on a host/guest complexation mechanism between the substrate and a dimeric metalloporphyrin host (tweezer) was used to confirm the stereochemical assignment, while Density Functional Theory (DFT) calculations were employed to explain the high stereoselectivity induced by the 17α-hydroxyl and C18-methyl groups.

Deoxygenative reduction of carbon dioxide to methane, toluene, and diphenylmethane with [Et2Al]+ as catalyst.

The strong Lewis acid [Et(2)Al](+) catalyzes the reduction of carbon dioxide with hydrosilanes under mild conditions to methane. In benzene solution, the side products toluene and diphenylmethane are also obtained through Lewis acid catalyzed benzene alkylation by reaction intermediates.

Cationic ethylzinc compound: a benzene complex with catalytic activity in hydroamination and hydrosilylation reactions.

The tight ion pair [EtZn(η(3)-C(6)H(6))][CHB(11)Cl(11)]·C(6)H(6) (1·C(6)H(6)) was obtained through β-hydrogen abstraction and concomitant ethene elimination from Et(2)Zn with the trityl salt [Ph(3)C][CHB(11)Cl(11)]. This ionlike species shows catalytic activity in hydrosilylation and intramolecular hydroamination reactions. The amine adduct {CH(2)CHCH(2)C(Ph(2))CH(2)NH(2)}(3)ZnCB(11)Cl(11) (3), which features a rare transition metal-carborane σ bond, was isolated from a hydroamination experiment.

Synthesis of aryloxyaluminium hydrides and their conversion into aryloxyalumoxanes (ArOAlO)n.

The reaction of bulky phenols with H(3)Al x NMe(3) afforded the new primary phenoxyalanes Mes*OAlH(2) x NMe(3), 2 (Mes* = 2,4,6-(t)Bu(3)-C(6)H(2)-), 2,6-Dipp(2)C(6)H(3)OAlH(2) x NMe(3), 3 (Dipp = 2,6-(i)Pr(2)C(6)H(3)-), and 2,6-Trip(2)C(6)H(3)OAlH(2) x NMe(3), 4 (Trip = 2,4,6-(i)Pr(3)C(6)H(2)-) as colorless crystalline solids. Subsequent reactions of 2,6-(t)Bu(2)-4-MeC(6)H(2)OAlH(2) x NMe(3), 1, and 2 with oxygen sources such as (Me(2)HSi)(2)O or Me(2)SO gave the disiloxyalane 2,6-(t)Bu(2)-4-Me-C(6)H(2)OAl(OSiHMe(2))(2) x NMe(3), 5, and the alumoxane (Mes*OAlO.OSMe(2))(4), 6.

Facile synthesis of monoazidotitanium isopropoxides.

The monoazidotitanium trisisopropoxide {(N(3))Ti(OiPr)(3)}(4) (2) was obtained by the reaction of (N(3))(2)Ti(OiPr)(2) (1) with Ti(OiPr)(4). Colorless 2 possesses an interesting tetrameric structure featuring bridging azide and isoproxide ligands and five- and six-coordinate titanium centers. It can be sublimed in vacuo at ca.

Size matters: room temperature P-C bond formation through C-H activation in m-terphenyldiiodophosphines.

m-Terphenyl- and biphenyl-2-diiodophosphines, TerphPI 2 and BiphPI 2, have been obtained by halide exchange from the chloro derivatives TerphPCl 2 and BiphPCl 2 and excess LiI in a benzene solution at room temperature. Whereas BiphPI 2 compounds are stable, the TerphPI 2 species undergo intramolecular C-H activation at room temperature and cyclize to form unsymmetrical 9-iodo-9-phosphafluorenes 1-(3,5-dimethylphenyl)-6,8-dimethyl-9-iodo-9-phosphafluorene, 4; 1-(4-t-butylphenyl)-7-t-butyl-9-iodo-9-phosphafluorene, 5; and 1-(2-methylphenyl)-5-methyl-9-iodo-9-phosphafluorene, 6, albeit the latter reaction is rather slow due to unfavorable steric interactions. Cyclization of the alkyl-substituted 4,4'-di- tert-butyl-biphenyl-2-diiodophosphine, 11, is slow in refluxing benzene solution, but faster than that for the parent biphenyl-2-diiodophosphine.

Aluminumoxyhydride: improved synthesis and application as a selective reducing agent.

Aluminumoxyhydride (HAlO) has been obtained by the reaction of aluminum hydride with the siloxane (Me2HSi)2O or the stannoxane (Bu3Sn)2O as an amorphous colorless insoluble powder. The highest-purity product resulted from the reaction of H3Al.NMe3 with (Me2HSi)2O.

Facile synthesis of unsymmetrical 9-phospha- and 9-arsafluorenes.

Unsymmetrical 9-chloro-9-phosphafluorenes (dibenzophospholes) and 9-chloro-9-arsafluorenes (dibenzoarsoles) have been obtained by simple thermolysis of m-terphenyldichlorophosphines and -arsines in close to quantitative yields. The reaction temperatures are about 200 degrees C for the phosphines and 140 degrees C for the arsine, and the reactions are complete within 5 min. Alternatively, these compounds can be synthesized through an AlCl3-catalyzed Friedel-Crafts type ring-closure reaction at low temperatures, but this method suffers from difficult workup procedures.

[2,6-Mes(2)C(6)H(3)](2)Ga(+)Li[Al(OCH(CF(3))(2))(4)](2)(-) (Mes = 2,4,6-Me(3)C(6)H(2)): A compound containing a linear unsolvated two-coordinate gallium cation.

The title compound [2,6-Mes(2)C(2)H(3)](2)Ga(+)Li[Al(OCH(CF(3))(2))(4)](2)(-), 1, containing a linear two-coordinate gallium cation, has been obtained by metathesis reaction of [2,6-Mes(2)C(2)H(3)](2)GaCl with 2 equiv of Li[Al(OCH(CF(3))(2))(4)] in C(6)H(5)Cl solution at room temperature. Compound 1 has been characterized by (1)H, (13)C((1)H), (19)F, and (27)Al NMR spectroscopy and X-ray crystallography. Compound 1 consists of isolated [2,6-Mes(2)C(6)H(3)](2)Ga(+) cations and Li[Al(OCH(CF(3))(2))(4)](2)(-) anions.

Reaction of the Primary Alane (2,4,6-t-Bu(3)H(2)C(6)AlH(2))(2) with Nitriles, Isonitriles, and Primary Amines.

The reactions of the sterically encumbered primary alane (MesAlH(2))(2) (Mes = C(6)H(2)-2,4,6-t-Bu(3)) with the nitriles t-BuCN, MesCN (Mes = C(6)H(2)-2,4,6-Me(3)) or MeCN lead eventually to dimeric amido alane products in which one of the ortho t-Bu groups of the Mes ligand is metalated and the nitrile is reduced to the amide ligand N(H)CH(2)R (R = t-Bu, Mes, or Me). The compounds (R = t-Bu, 2 (cis), 3 (trans); Mes, 4 (cis), 5 (trans); Me, 6 (cis)) have been isolated and characterized spectroscopically and also by X-ray crystallography in the cases of 4 and 5. The intermediate, dimeric iminato complex [MesAl(H){&mgr;(2)-NC(H)t-Bu}](2) (1), can also be isolated under carefully controlled, mild conditions.

Monomeric Alanes: Synthesis, Structure, and Thermolysis of MesAl(H)N(SiMe(3))(2) and a One-Pot Synthetic Route to Mes(2)AlH (Mes = -C(6)H(2)-2,4,6-t-Bu(3)).

The reaction of (MesAlH(2))(2) (Mes = -C(6)H(2)-2,4,6-t-Bu(3)) with HN(SiMe(3))(2) affords the monomeric amidoarylalane MesAl(H)N(SiMe(3))(2), 1. This product can also be synthesized by the reaction of [MesAlH(2)](2) with LiN(SiMe(3))(2), which, in addition, yields the byproducts LiAlH(2){N(SiMe(3))(2)}(2), 3, and MesH. Thermolysis of 1 at 175-180 degrees C affords three different the related and the imide [MesAlN(SiMe(3))](n)(), 5.

Multiple Ga-Ga Bonding Character in Na [Ga(GaTrip ) ], and a Comparison with Neutral Ga(GaTrip ) (Trip=2,4,6-iPr C H ).

Delocalized over the Ga framework, the two electrons are lost in the oxidation of Na [Ga(GaTrip ) ] to Ga(GaTrip ) . This leads to a lengthening of the Ga-Ga bond by about 0.08 Å.

Synthesis and Characterization of Sterically Encumbered Derivatives of Aluminum Hydrides and Halides: Assessment of Steric Properties of Bulky Terphenyl Ligands.

The synthesis and characterization of several sterically encumbered monoterphenyl derivatives of aluminum halides and aluminum hydrides are described. These compounds are [2,6-Mes(2)C(6)H(3)AlH(3)LiOEt(2)](n)() (1), (Mes = 2,4,6-Me(3)C(6)H(2)-), 2,6-Mes(2)C(6)H(3)AlH(2)OEt(2) (2), [2,6-Mes(2)C(6)H(3)AlH(2)](2) (3), 2,6-Mes(2)C(6)H(3)AlCl(2)OEt(2) (4), [2,6-Mes(2)C(6)H(3)AlCl(3)LiOEt(2)](n)() (5), [2,6-Mes(2)C(6)H(3)AlCl(2)](2) (6), TriphAlBr(2)OEt(2) (7), (Triph = 2,4,6-Ph(3)C(6)H(2)-), [2,6-Trip(2)C(6)H(3)AlH(3)LiOEt(2)](2) (8) (Trip = 2,4,6-i-Pr(3)C(6)H(2)-), 2,6-Trip(2)C(6)H(3)AlH(2)OEt(2) (9), [2,6-Trip(2)C(6)H(3)AlH(2)](2) (10), 2,6-Trip(2)C(6)H(3)AlCl(2)OEt(2) (11), and the partially hydrolyzed derivative [2,6-Trip(2)C(6)H(3)Al(Cl)(0.68)(H)(0.

New Routes to Synthetically Useful, Sterically Encumbered Arylaluminum Halides and Hydride Halides.

The synthesis and structural characterization of the compounds MesAlCl(2)(THF) (1), MesAlCl(2) (2), MesAl(H)Cl(THF) (3a), MesAl(H)Cl (4a), and (MesAlH(2))(2) (5) (Mes = 2,4,6-t-Bu(3)C(6)H(2)(-)) are described as well as those for two compounds 3b and 4b that are analogs of 3a and 4a but have H:Cl ratios that are less than 1:1. All compounds were characterized by (1)H, (13)C NMR, and IR spectroscopy, and 1, 2, 3a, and 4b were additionally characterized by X-ray crystallography. Compound 1 is best synthesized by the reaction of [(THF)(2)LiH(3)AlMes](2) (6) with 6 equiv of Me(3)SiCl.