Equiv Of n-BuLi Research Articles

Interaction of germanium analogue of organic isonitrile with Cu(I) imide in side-on mode.

[NHC → GeN(Ar)Cu2NAr]2, the formal adduct of germanium analogue of organic isonitrile [GeNAr] with Cu(I) imide [(Cu2NAr)2] (Ar = 2,6-iPr2C6H3) was prepared from the N-heterocyclic carbene (NHC) stabilized acyclic germylene Ge[N(H)Ar]2 by reacting with two equivalents of nBuLi and CuCl(PPh3)3. As elucidated by X-ray crystal structural characterization, the two separated [GeNAr] moieties interacted with [(Cu2NAr)2] core in the side-on mode.

Bidentate and tridentate coordination modes of bis(3-methylindolyl)-2-(1-methylimidazolyl)methane in complexes of aluminum and gallium

Bis(3-methylindolyl)-2-(1-methylimidazolyl)methane (1) was synthesized by acid-catalyzed condensation of methyl-2-formylimidazole and two equivalents of 3-methylindole, followed by deprotonation of the imidazole moiety of the protonated compound, [(1-CH3C3H2N2H)HC(3-CH3C8H4NH)2][HSO4] ([1•H][HSO4 ]). Reactions of a trialkylaluminum or tri‑tert-butylgallium with 1 produced complexes (1-CH3C3H2N2)HC(3-CH3C8H4N)(3-CH3C8H4NH)MR2 (M = Al, R = Me (2a), Et (2b), iBu (2c), tBu (2d); M = Ga, R = tBu (3)) in which mono-deprotonated 1 adopts a bidentate coordination mode. Thermolysis of 2a-2d or 3 in refluxing toluene did not result in further alkane elimination. Deprotonation of 1 with two equivalents of nBuLi followed by reaction with an alkylaluminum dichloride yielded monomeric, tripodal complexes (1-CH3C3H2N)HC(3-CH3C8H4N)2MR (M = Al, R = Me (4a), Et (4b), iBu (4c), tBu (4d)) in which bis-deprotonated 1 adopts a tridentate coordination mode. Reaction of 1 with two equivalents of trimethylaluminum or triethylaluminum yields dialuminum complexes (1-CH3C3H2N)HC(3-CH3C8H4N)2Al2R4 (R = Me (5a), Et (5b). In addition to NMR (1H, 13C) spectroscopy, compounds 1, 2d, 3, and 4b were further characterized by X-ray crystallography as CH2Cl2 or toluene solvates.

Dilithium complex incorporating phenyl bridged neutral pyrrolyl-arylamide ligand: Synthesis, characterization, reaction, and catalytic activity

The phenyl bridged neutral pyrrolyl-arylamide ligand with the formula 2-(2, 5-Me2C4H2N)C6H4NHSiMe3 (HL) was synthesized and characterized. Treatment of the ligand HL with equivalent of nBuLi or LiCH2SiMe3 afforded the lithiated complex [η5:(μ-η1:η1)-2-(2,5-Me2C4H2N)C6H4NSiMe3Li]2 (1) smoothly in good yield. The reaction of complex 1 with two equivalents of ErCl3(thf)3.5 and LiCH2SiMe3 produced novel trinuclear erbium-lithium cluster [η5:η1:(μ-η1:η1)-2-(2,5-Me2C4H2N)C6H4NSiMe2CH2ErCl]2LiCl(thf)2 (2) through sp3 C-H bond activation of methyl group and the resulting methylene group bonding two erbium centers in a rare μ2-η1:η1 mode. In addition, the dilithium complex 1 exhibited a high catalytic activity toward ring-opening polymerization of ε-caprolactone.

Synthesis and Structure of Bismuth-Nitrogen Cage Compounds and Heterocubanes: [Cl-Bi(μ3-N-TMP)]4: A Dimer of a 1,3-Dichloro-cyclo-dibismadiazane.

The reaction of TMP-NH2 [TMP = m,m-(CF3)2-C6H3] with 2 equiv of n-BuLi led to the in situ formation of Li2[N-TMP], which, after the addition of BiCl3, formed a [Cl-Bi(μ3-N-TMP)]4-type heterocubane in up to 30% yield. Transmetalation reactions, thought of as alternatives, starting from the analogous tin-nitrogen heterocubane [Sn(μ3-N-TMP)]4 and BiCl3 resulted in the isolation of a complex reaction mixture from which different Bi-N and Bi-Sn-N cage compounds could be isolated. The structures of all cage compounds that contain bismuth are discussed, and the thermodynamics of the formation of [Cl-Bi(μ3-N-TMP)]4 are highlighted. In an attempt to isolate Li2[N-TMP], generated in situ from TMP-NH2 and 2 equiv of n-BuLi, it was possible to isolate a lithium salt with a negatively charged lithium cluster of the type [Li9(N-TMP)5F]2- with an unusual Li9N5F skeleton.

Unexpected Activation of Ethers and Polysiloxanes by a Phosphine-Borane-Stabilized 1,3-Dicarbanion/Butyllithium Couple

The reaction between the tertiary phosphine-borane PhP(BH3)(CH2Ph)2 (6) and 1 equiv of nBuLi, PhCH2Na, or PhCH2K gives the monodeprotonation products [PhP(BH3)(CHPh)(CH2Ph)]MLn (MLn = Li(OEt2)0.25 (7), Na(THF)0.5 (8), K(OEt2)0.5 (9)). Similarly, the reaction between 6 and 2 equiv of either PhCH2Na or PhCH2K gives the 1,3-dicarbanion complexes [PhP(BH3)(CHPh)2][MLn]2 (MLn = Na(THF) (10), K(THF)0.25 (11)). However, the reaction between 6 and 2 equiv of nBuLi in Et2O, THF, or nBu2O gives a mixture of mono- and dimetalated products. Unexpectedly, the reaction between 6 and 3 equiv of nBuLi in diethyl ether in the presence of silicone grease gives the trinuclear cluster [PhP(BH3)(CHPh)2]Li3(OSiMe2CH2CH2CH2CH3)(OEt2)3 (12); this compound may be isolated in essentially quantitative yield from the reaction between 6, hexamethyltrisiloxane, and nBuLi in a 3:1:9 ratio. Similar tri-lithium complexes are isolated from the reaction between 6 and 3 equiv of nBuLi in Et2O or tBuOMe, which yields [PhP(BH3)(CHPh)2]Li3(OEt)(OEt2)3 (13) and [PhP(BH3)(CHPh)2]Li3(OMe)(OtBuMe)3 (14), respectively. The reaction between 6, 2 equiv of nBuLi, and 1 equiv of in situ generated LiOEt or LiOiPr gave the tri-lithium clusters 13 and [PhP(BH3)(CHPh)2]Li3(OiPr)(OEt2)3 (16), respectively.

Influence of Chain Length on the Structures and Dynamic Behavior of Alkyl-Tethered α,ω-Diphosphide Complexes of Lithium and Their Use in the Synthesis of P-Heterocyclic Stannylenes.

The alkyl-tethered α,ω-diphosphines (Dipp)PH(CH2) nPH(Dipp) ( n = 1 (3H), 2 (4H), 3 (5H), 4 (6H), and 5 (7H)) were prepared in good yield and characterized by multinuclear NMR spectroscopy [Dipp = 2,6- iPr2C6H3]. Treatment of 3H with 2 equiv of nBuLi and 2 equiv of TMEDA gives the diphosphide complex [CH2{P(Dipp)}2]Li2(TMEDA)2 (3Lia), which crystallizes as discrete monomers which do not exhibit temperature-dependent NMR behavior. Treatment of 4H-7H with 2 equiv of nBuLi in THF gives the diphosphides [[CH2{P(Dipp)}]2]2Li4(THF)2(OEt2)2 (4Li), [CH2{CH2P(Dipp)}2]Li2(THF)4 (5Li), [{CH2CH2P(Dipp)}2]Li2(THF)6 (6Li), and [CH2{CH2CH2P(Dipp)}2]2Li4(THF)6·PhMe (7Li) after crystallization. Compounds 4Li-7Li adopt either monomeric or dimeric structures in the solid state, depending on the length of the alkyl tether of the diphosphide ligand. In solution, compounds 4Li-7Li exhibit dynamic behavior: variable-temperature 31P{1H} and 7Li NMR spectroscopic studies indicate that this involves equilibria between monomeric and dimeric or higher oligomeric species with the nature of the equilibrium again depending on the length of the alkyl tether of the diphosphide ligand. The reactions between 3Li, 6Li, or 7Li and SnCl2 in THF give mixtures of products which could not be separated. In contrast, the reactions between 4Li or 5Li and 1 equiv of SnCl2 give the dimeric P-heterocyclic stannylenes [{CH2P(Dipp)}2Sn]2 (4Sn) and [CH2{CH2P(Dipp)}2Sn]2.1/2THF (5Sn), respectively. While compound 5Sn is isolated exclusively as the cis isomer, 4Sn is isolated as a mixture of cis and trans isomers in an approximate 5:1 ratio. The solid-state structures of trans-4Sn and cis-5Sn were obtained, and multinuclear NMR spectroscopy indicates that the dimeric structures of these compounds are maintained in solution. Compounds 4Sn and 5Sn represent the first P-heterocyclic stannylene dimers to be structurally characterized.

H2-release from alcohols, diols, and compounds with amino functionality promoted by titanium(II) sandwich complex, [Cp2Ti]: a theoretical approach

The role of Ti(II) sandwich complex, [Cp2Ti], generated by the combination of [Cp2TiCl2] and two equivalents of nBuLi, in situ, in toluene has been investigated theoretically for the release of H2 from a series of liquid organic hydrogen carriers (LOHCs), mainly alcohols or diols of low molecular weights. The compounds with hydroxyl functionality considered here are methanol, ethanol, isopropanol, methanediol, and ethylene glycol. Satisfactory results have also been obtained on applying the same mechanism to two other compounds with amino functionality, viz., methanediamine and ethylene diamine. The exploration has been carried out using density functional theory (DFT). Our findings reveal that the reaction is initiated with the formation of an adduct of the Ti center of sandwich complex, [Cp2Ti], with O/N atom of the compound under investigation. From the adduct thus formed, H2-release is possible via two routes. In one of the paths, O/N–H bond breaks first, followed by the cleavage of C–H bond, and in the other path, C–H bond breaking takes place prior to the scission of O/N–H bond. Our results show that the second path is thermodynamically and kinetically more preferable for the release of H2. Thus, [Cp2Ti] can be highly effective in releasing one equivalent of H2 from alcohols and compounds with amino functionalities, and more importantly, removal of two equivalents of H2 from methanediol is possible using [Cp2Ti], which is significant in terms of hydrogen storage purpose.

Method for the Synthesis of γ-PEGylated Folic Acid and Its Fluorescein-Labeled Derivative

This paper reports exclusive γ-conjugation of poly(ethylene glycol) (PEG) to folic acid (FA) and the synthesis of its fluorescein (Fl)-labeled derivative. FA is first reacted with 1 equiv of n-BuLi that forms the metal salt exclusively at the γ-position. Model reactions between γ-lithiated FA and bromo-alcohols were used to demonstrate exclusive γ-conjugation. γ-PEGylated FA was then synthesized by reacting γ-lithiated FA with a bromine-functionalized methoxy-PEG (Br-PEGM) that is prepared by Candida antarctica Lipase B (CALB)-catalyzed transesterification of ethyl 5-bromovalerate (EBV) with methoxy-PEG (HO-PEGM). Fl-labeled γ-PEGylated FA was also synthesized by CALB-catalyzed Michael addition of FA-γ-SH to acrylate-PEG-Fl that was made by a series of CALB-catalyzed transformations. NMR spectroscopy and MALDI-ToF spectrometry verified the structure and purity of the compounds. These lithiation-based methods are superior compared to both the currently used activated ester method that gives a mixture of γ,...

1,8‐Bis(borylamido)naphthalene Complexes of Lithium and Zinc(II) Including a Zinc(II) Isocyanide Adduct

The zinc coordination chemistry of a useful metal ion chelator, bis(borylamido)naphthalene ligand [1,8‐C10H6(NBNL)2]2–, which has two borylamido groups on a rigid naphthalene backbone, is presented. Deprotonation of N1,N8‐di(9‐bora‐bicyclo[3.3.1]nonan‐9‐yl)naphthalene‐1,8‐diamine, [1,8‐C10H6(NBNL)2]H2 (3) with two equivalents of nBuLi in Et2O afforded the lithium derivative, Li2(Et2O)2[1,8‐C10H6(NBNL)2] (4). Metathesis reaction of Li2(Et2O)2[1,8‐C10H6(NBNL)2] with (tBu2bipy)ZnCl2 (tBu2bipy = 4,4′‐di‐tert‐butyl‐2,2′‐bipyridine) in a 1:1 molar ratio gave [1,8‐C10H6(NBNL)2]Zn(tBu2bipy) (5), which features an all‐nitrogen coordination sphere at zinc. The reaction of 4 with ZnCl2, however, produced [1,8‐C10H6(NBNL)2]Zn(Et2O)(µ‐Cl)Li(Et2O)3 (6), which retains one of the chlorides as ClLi(Et2O)3 on zinc. Treatment of 6 with tBu2bipy or two equivalents of 2,6‐dimethylphenyl isocyanide completes the salt elimination and led to [1,8‐C10H6(NBNL)2]Zn(tBu2bipy) (5) or [1,8‐C10H6(NBNL)2]Zn(CNC6H3‐2,6‐Me2)2 (7), respectively. Compounds 3–7 have been characterized by several analytical methods including X‐ray crystallography. The zinc atoms of 5–7 are four‐coordinate and adopt a distorted tetrahedral geometry. The ν(NC) bands of 7 in the IR spectrum have been observed at 2203 and 2187 cm–1.

Preparation of Isocyanoaryllithiums via Halogen–Lithium Exchange Reaction and Their Reaction with Various Electrophiles

Treatment of 2-bromo-4,6-dimethylphenylisocyanide (1a) with 1.2 equiv of n-BuLi in THF at −78 °C provided an o-isocyanoaryllithium intermediate, which reacted with aldehydes, nitroalkenes, and trim...

Alkali-Metal- and Alkaline-Earth-Metal-Mediated C–O Activation of an Anisole-Substituted Phosphido–Borane Ligand

The reaction between {(Me3Si)2CH}PH(C6H4-2-OMe) (4) and 1 equiv of BH3·SMe2 yields the phosphine–borane {(Me3Si)2CH}PH(BH3)(C6H4-2-OMe) (5). Subsequent reaction between 5 and 1 equiv of n-BuLi in THF gives the phosphido–borane complex [{(Me3Si)2CH}P(BH3)(C6H4-2-OMe)]Li(THF) (6a), which was isolated as a colorless microcrystalline solid. Treatment of 5 with 1 equiv of PhCH2M yields the corresponding complexes [{(Me3Si)2CH}P(BH3)(C6H4-2-OMe)]ML (ML = Na(THF) (6b), K(pmdeta) (6c); pmdeta = N,N,N′,N″,N″-pentamethyldiethylenetriamine), after crystallization in the presence of the corresponding coligand. While compounds 6b,c are stable toward heat, compound 6a decomposes on heating to 50 °C in toluene to give the cluster [[{(Me3Si)2CH}PH(C6H4-2-O)]Li]6 (7) and the tertiary phosphine–borane {(Me3Si)2CH}P(BH3)(Me)(C6H4-2-OMe) (8). Related C–O cleavage reactions are observed when MgI2 is treated with 2 equiv of 6a and when CaI2 is treated with 2 equiv of [{(Me3Si)2CH}P(BH3)(C6H4-2-OMe)]K in THF, giving [{(Me3Si)2C...

Reactivity of 1,3-Disubstituted Indoles with Lithium Compounds: Substituents and Solvents Effects on Coordination and Reactivity of Resulting 1,3-Disubstituted-2-Indolyl Lithium Complexes.

Reactivity of 1,3-disubstituted indolyl compounds with lithium reagents was studied to reveal the substituents and solvent effects on coordination modes and reactivities resulting in different indolyl lithium complexes. Treatment of 1-alkyl-3-imino functionalized compounds 1-R-3-(R'N═CH)C8H5N [R = Bn, R' = Dipp (HL1); R = Bn, R' = tBu (HL2); R = CH3OCH2, R' = Dipp (HL3); Dipp = iPr2C6H3] with Me3SiCH2Li or nBuLi in hydrocarbon solvents (toluene or n-hexane) produced 1,3-disubstituted-2-indolyl lithium complexes [η1:(μ2-η1:η1)-1-Bn-3-(DippN═CH)C8H4NLi]2 (1), {[η1:(μ3-η1:η1:η1)-1-Bn-3-(tBuN═CH)C8H4N][η2:η1:(μ2-η1:η1)-1-Bn-3-(tBuN═CH)C8H4N][η1:(μ2-η1:η1)-1-Bn-3-(tBuN═CH)C8H4N]Li3} (2), and [η1:η1:(μ2-η1:η1)-1-CH3OCH2-3-(DippN═CH)C8H4NLi]2 (3), respectively. The bonding modes of the indolyl ligand were kept in 1 by coordination with donor solvent, affording [η1:(μ2-η1:η1)-1-Bn-3-(DippN═CH)C8H4NLi(THF)]2 (4). The trinuclear complex 2 was converted to dinuclear form with a change of bonding modes of the indolyl ligand by treatment of 2 with donor solvent THF, producing [η1:(μ2-η1:η1)-1-Bn-3-(tBuN═CH)C8H4NLi(THF)]2 (5). X-ray diffraction established that compounds 1, 3, 4, and 5 crystallized as dinuclear structures with the carbanionic sp2 carbon atoms of the indolyl ligands coordinated to lithium ions in a μ2-η1:η1 manner, while compound 2 crystallized as a trinuclear structure and the carbanionic atoms of the indolyl moieties coordinated to lithium ions in μ2-η1:η1 and μ3-η1:η1:η1 manners. When the lithiation reaction of HL1 with 1 equiv of nBuLi was carried out in THF, the monomeric lithium complex {η1:η1-1-Bn-3-(DippN═CH)-2-[1'-Bn-3'-(DippNCH)C8H5N]C8H4NLi(THF)} (6) having coupled indolyl moieties was obtained. The compound 6 can also be prepared by the reaction of 1 with 0.5 equiv of HL1 with a higher isolated yield. Accordingly, the lithium complexes [η1:η4-1-Bn-3-tBuN═CH-2-(1'-Bn-3'-tBuNCHC8H5N)C8H4NLi(L)] (L = THF, 7a; L = Et2O, 7b) with the coupled indolyl moieties in η4 mode were isolated by treatment of HL2 with 2 in THF or Et2O. All complexes were characterized by spectroscopic methods, and their structures were determined by X-ray diffraction study.

Homo- and Heteropolynuclear Clusters of Phosphine Triphenolates.

The synthesis and structural characterization of a series of homo- and heteropolynuclear clusters constructed with a potentially tetradentate phosphine triphenolate ligand are presented. Treatment of tris(3,5-di-tert-butyl-2-hydroxyphenyl)phosphine (H3[O3P]) with 3 equiv of nBuLi in diethyl ether at -35 °C affords hexanuclear Li6[O3P]2(OEt2)2 (1) as colorless crystals. In situ lithiation of H3[O3P] with 3 equiv of nBuLi in THF at -35 °C followed by metathetical reactions with MnCl2 or NiCl2(DME) gives crystals of forest green pentanuclear MnLi4[O3P]2(THF)3 (2) or dark brown tetranuclear Ni2Li2[O3P]2(THF)2 (3), respectively. Alkane elimination of ZnR2 (R = Me, Et) with H3[O3P] in THF at 25 °C generates high yields of colorless crystalline trinuclear Zn3[O3P]2(THF)2 (4). The cluster structures of 1-4 were all determined by single crystal X-ray diffraction studies. These molecules represent the first examples of metal complexes supported by phosphine triphenolate derivatives. The cluster 2 contains a paramagnetic core of high spin Mn(II) (S = 5/2) as indicated by solution and solid state magnetic susceptibility measurements.

Chromium Complexes with N,N,N-Tridentate Quinolinyl Anilido-Imine Ligand: Synthesis, Characterization, and Catalysis in Ethylene Polymerization

The treatment of 2-(ArN═CH)C6H4-HNC9H6N ([NQNANIMe]H, Ar = 2,6-Me2C6H3; [NQNANIEt]H, Ar = 2,6-Et2C6H3; [NQNANIiPr]H, Ar = 2,6-iPr2C6H3) with nBuLi and CrCl3(THF)3 achieves the hetero-dinuclear complexes [NQNANIR]CrCl(μ-Cl)2Li(THF)2 (1a, R = Me; 1b, R = Et; 1c, R = iPr) or bisligated complex κ5-[NQNANIiPr]2CrCl (2c) depending on the reactant ratios used. Reactions of these ligands with nBuLi and CrCl2(THF)2 could achieve the square-pyramidal complexes [NQNANIR]CrCl(THF) (3b, R = Et; 3c, R = iPr). Complex 3c can be oxidized by alkyl chloride to dimeric complex {[NQNANIiPr]CrCl}2(μ-Cl)2 (4) through a single-electron-transfer mechanism. Similar reaction of 2-(C9H6N)N═CHC6H4-HNAr ([NQNINAMe]H, Ar = 2,6-Me2C6H3; [NQNINAEt]H, Ar = 2,6-Et2C6H3; [NQNINAiPr]H, Ar = 2,6-iPr2C6H3) with nBuLi and CrCl3(THF)3 furnishes [NQNINAR]CrCl(μ-Cl)2Li(THF)2 (5a, R = Me; 5b, R = Et; 5c, R = iPr) in high yields. However, a chromium complex with a butyl-substituted ligand, [NQBuNINAiPr]CrCl2 (6), is obtained when 2 equiv of nBuLi is used. The molecular structures of 1c, 2c, 3c, 4, 5c, and 6 are confirmed by X-ray crystallography. Upon activation with MAO, the Cr(III) complexes (1a–1c, 4, and 5a–5c) show moderate catalytic activities (50 to 218 kg of PE·mol(Cr)−1·h–1) in ethylene polymerization, whereas the Cr(II) complexes 2c, 3b, and 3c are inert under the same conditions.

From Ferrocenecarbonitriles to Ferrocenylimines: Synthesis, Structure, and Reaction Chemistry

From the reaction of [PtCl2(N≡CMe)2] with FcC≡N (1) (Fc = Fe(η5-C5H4)(η5-C5H5)) complex [PtCl2(FcC≡N)(N≡CMe)] (2) was obtained, which on subsequent treatment with 1 gave trans-[PtCl2(N≡CFc)2] (trans-3). The latter complex and the appropriate cis isomer (cis-3) were also accessible when [PtCl2] or [PtCl2(N≡CMe)2] is reacted with a 2.6-fold excess of 1. Appropriate treatment of [PtCl2(N≡CMe)2] with two equivalents of 1-acetyl-1′-cyanoferrocene (4) produced trans-[PtCl2(Fe(η5-C5H4CN)(η5-C5H4C(O)Me))2] (trans-5). Coordination polymer [PtCl2(Fe(η5-C5H4CN)2)]n (7) was obtained by combining [PtCl2(N≡CPh)2] with [Fe(η5-C5H4CN)2] (6). However, when 7 was reacted with PPh3 for deaggregation, [PtCl2(PPh3)2] was formed. Addition of FcC≡CLi (8-Li) to trans-3 gave pentametallic trans-[Pt(C≡CFc)2(NH═CnBuFc)2] (10) via trans-[Pt(C≡CFc)2(N≡CFc)2] (9). When trans-3 is reacted with two equivalents of nBuLi in the absence of FcC≡CH (8), trans-[PtCl2(NH═CnBuFc)2] (11) was obtained, which decomposed to FcC(═NH)nBu (12), giving...

NHC Bis-Phenolate Aluminum Chelates: Synthesis, Structure, and Use in Lactide and Trimethylene Carbonate Polymerization

A novel family of Al(III) complexes supported by a tridentate, dianionic N-heterocyclic carbene bis-phenolate ligand ((OCO)2–) was prepared via various synthetic routes, and the derived compounds were all structurally characterized. The methane elimination reaction of the protio ligand N,N′-bis(2-hydroxy-3,5-di-tert-butylphenyl)-4,5-dihydroimidazolium chloride (1·H3Cl) with AlMe3 quantitatively led to the formation of the bis-phenolate imidazolinium Al zwitterion (1·H)Al(Me)(Cl) (2), whose formulation was established by X-ray diffraction studies. The deprotonation of species 2 with 1 equiv of lithium diisopropylamide (LDA) proceeded with the elimination of LiCl to afford the Al-NHC methyl derivative [(OCO)AlMe]2 (3), which was isolated as a dimer, as confirmed by X-ray diffraction studies. Alternatively, compound 3 may be accessed via a salt metathesis route involving the reaction of the NHC bis-phenolate Li salt 1·Li2, generated in situ via reaction of 1·H3Cl with 3 equiv of nBuLi (−40 °C, THF), with 1 equiv of MeAlCl2. The serendipitous hydrolysis of compound 3 allowed the X-ray characterization of the Al-oxo dinuclear species [(OCO)Al-O-Al-(OCO)] (3′), in which both Al(III) centers adopt a distorted-trigonal-monopyramidal geometry. The reaction of the salt 1·H3Cl with Al(OiPr)3 afforded the corresponding bis-phenolate imidazolinium Al zwitterion (1·H)Al(OiPr)(Cl) (4), which incorporates a four-coordinate tetrahedral Al center effectively κ2O,O-chelated by the two phenolate moieties of the OCO2– ligand. Compound 4 may be readily converted to the Al-NHC alkoxide derivative [(OCO)AlOiPr]2 (5) upon reaction with 1 equiv of LDA. Alternatively, the alcoholysis of the Al-NHC methyl species 3 with iPrOH also permitted access to the derived Al alkoxide 5 and proceeds via the formation of the kinetic product (1·H)Al(OiPr)(Me) (6) that may readily eliminate methane upon heating to produce species 5. The Al alkoxide species 5 was shown to efficiently polymerize rac-lactide and trimethylene carbonate in a highly controlled manner for the production of narrow disperse materials. The observed catalytic performances are in the range of the majority of those for group 13 metal based ROP catalysts developed thus far, and all data support the noninvolvement of the NHC moiety in these polymerization reactions.

High-Yield Syntheses and Reactivity Studies of 1,2-Diborylated and 1,2,4,5-Tetraborylated Benzenes

Treatment of 1,2-dibromobenzene (1,2-C6H4Br2) or 1,2,4,5-tetrabromobenzene (1,2,4,5-C6H2Br4) with 2 equiv or 4 equiv of n-BuLi in the presence of excess iso-propoxy(pinacol)borane ((i-PrO)Bpin) furnishes 1,2-C6H4(Br)(Bpin) (1) or 1,4,2,5-C6H2(Br)2(Bpin)2 (3) with excellent selectivity. The subsequent reaction of 1 or 3 with Mg turnings and more (i-PrO)Bpin gives the di- and tetraborylated benzenes 1,2-C6H4(Bpin)2 (2) and 1,2,4,5-C6H2(Bpin)4 (4) in overall yields of about 65%. For the Grignard transformation step, it is essential to continuously add 1 equiv (1) or 2 equiv (3) of 1,2-dibromoethane as an entrainer over a period of 1 h. Compounds 1 and 2 have been transformed into the ortho-functionalized trihydroborates Li[1,2-C6H4(Br)(BH3)] (Li[7]) and Li[1,2-C6H4(Bpin)(BH3)] (Li[8]) by means of 1 equiv of Li[AlH4]. Using 3 equiv of Li[AlH4], 2 can also be converted into the ditopic lithium trihydroborate Li2[1,2-C6H4(BH3)2] (Li2[9]); even the tetratopic derivative Li4[1,2,4,5-C6H2(BH3)4] (Li4[10]) is accessible from 4 and 4 equiv of Li[AlH4]. The compounds Li[7], Li[8], Li2[9], and Li4[10] have been crystallographically characterized as ether solvates, but still show Ar–BH3-η2-Li interactions as the dominant mode of coordination. In the cases of Li2[9] and Li4[10] an intricate three-dimensional network and a zigzag polymer, respectively, are established by the contact ion pairs in the crystal lattice.

A new anilido-imine compound containing o-OMe-anilinyl derived from an unexpected adduct: Synthesis, crystal structure and its coordination capability

A new compound, ortho-C6H4F[CH(NHC6H4OMe-2)2], 1, was obtained with ortho-flurobenzaldehyde and 2-methoxyaniline as the starting materials. Compound 1 was readily converted into ortho-C6H4(2-OMeC6H4)(CHNC6H4OMe-2) 2 after treatment with 1 equiv of n-BuLi. Treatment of compound 2 with 1.5 equiv of ZnEt2 afforded the trinuclear zinc complex 3 by alkyl elimination and alkylation of the imino group of the ligand. The molecular structures of two new organic compounds and of the trinuclear zinc complex were determined by single-crystal X-ray diffraction. The dianionic ONNO tetradentate ligands derived from compound 2 coordinate to zinc ions in four to five coordination modes, forming distorted tetrahedral and trigonal–bipyramidal geometry around three metal centers.

Synthesis and Structural Characterization of Phosphine–Borane-Stabilized Dicarbanions with either Rigid or Flexible Spacers

The reaction between 1,2-C6H4(CH2Cl)2 and 2 equiv of in situ generated [R2P(BH3)]Li in THF gives the corresponding o-phenylene-bridged bis(phosphine–boranes) 1,2-C6H4{CH2P(BH3)R2}2 (R = iPr (1a), Ph (2a), Cy (3a)). Treatment of 1a–3a with 2 equiv of nBuLi and 2 equiv of tmeda yields the corresponding phosphine–borane-stabilized carbanion (PBC) complexes [1,2-C6H4{CHP(BH3)R2}2][Li(tmeda)]2·nL (R = iPr, n = 0 (1b); R = Ph, nL = THF (2b); R = Cy, nL = 2PhCH3 (3b)). In contrast, treatment of 1a with 2 equiv of MeK, followed by 2 equiv of pmdeta, yields the monodeprotonation product [1,2-C6H4{CHP(BH3)iPr2}{CH2P(BH3)iPr2}][K(pmdeta)] (1c), due to a competing side reaction with the solvent. Treatment of 1a and 3a with the less aggressive metalating agent PhCH2K gives the corresponding dipotassium salts, the latter of which was isolated as the adduct [1,2-C6H4{CHP(BH3)Cy2}2][K(pmdeta)]2 (3c). X-ray crystallography reveals that 1b–3b adopt similar structures in which the lithium ions are coordinated by the carbani...

Syntheses and Crystal Structures of Novel Functionalized Lithium Silylamides R(4–n)Si(N(Li)CH2CH2NR'2)n (R = Me, Ph, R' = Me, iPr; n = 2, 3)

AbstractThe difunctional aminosilanes Ph2Si(NHCH2CH2NMe2)2 (1), Me2Si(NHCH2CH2NiPr2)2 (2) and Ph2Si(NHCH2CH2NiPr2)2 (3) were prepared by aminolysis of the chlorosilanes R2SiCl2 (R = Ph, Me) and the corresponding ethylenediamine derivatives H2NCH2CH2NR'2 (R' = Me, iPr). The trifunctional aminosilane MeSi(NHCH2CH2NiPr2)3 (4) was synthesized from MeSiCl3 and H2NCH2CH2NiPr2 in the presence of triethylamine as auxiliary base. Compounds 1–4 were obtained as pale yellow viscous oils that have been characterized by 1H, 13C and 29Si NMR spectroscopy. Treatment of the aminosilanes 1–3 with two equivalents and 4 with three equivalents of nBuLi in hexane led to the corresponding lithium salts, which were recrystallized from n‐hexane at –25 °C. The crystal structure analysis of Ph2Si(N(Li)CH2CH2NMe2)2 (5) and Me2Si(N(Li)CH2CH2NiPr2)2 (6) revealed dimeric molecules which contain a central Li4N4 heterocubane core. Additionally, the lithium atoms are coordinated intramolecularly by NR2 donor groups. For Ph2Si(N(Li)CH2CH2NiPr2)2 (7) dimers with Si2N4Li4 adamantane core were observed. MeSi(N(Li)CH2CH2NiPr2)3 (8) displays dimers with a rhombododecahedral Si2N6Li6 core. Like in compounds 5–7 the cluster structure is supported by intramolecular coordination of the NiPr2 donor group.