Sila-metalation Route to Hydrido(trialkylsilyl)silyllithiums

Iwamoto, Takeaki; Okita, Junichiro; Kabuto, Chizuko; Kira, Mitsuo

doi:10.1021/ja026705d

Cited by 45 publications

(31 citation statements)

References 12 publications

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“…The silyllithium 4 is dimeric in the solid state, although the structure is different from that of the unsolvated dimer [(Me 3 Si) 3 Si(µ-Li)] 2 . [8d] Two lithium atoms bridge two anionic silicon atoms, and each lithium atom is coordinated by one THF molecule with an O(1)ϪLi (1) [8d] [tBu 3 Si(µ-Li)] 2 , [17] [(PhMe 2 Si) 2 MeSi(µ-Li)] 2 , [18] [(Me 3 Si) 2 PhSi(µ-Li)] 2 , [18] [(Me 3 SiMe 2 Si) 3 Si(µ-Li)] 2 , [19] and [(tBuMe 2 Si) 2 HSi(µ-Li·THF)] 2 , [20] all of them containing planar four-membered rings consisting of two anionic silicon and two cationic lithium atoms. However, the silyllithium 4 possesses a folded four-membered ring.…”

Section: Resultsmentioning

confidence: 99%

Tris(trimethylsilyl)‐Substituted Heavy Group 14‐Element‐Centered Anions: Unsolvated Trimeric Germyllithium and Solvated Dimeric Silyl‐ and Stannyllithiums

Nanjo

Mochida

2004

Eur J Inorg Chem

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Tris(trimethylsilyl)‐substituted group 14‐element‐centered anion monomers [LiE(SiMe3)3·3THF] (E = Si, Ge, and Sn) can be distilled under reduced pressure to give dimeric silyllithium 4 and stannyllithium 6, and trimeric germyllithium 5 without pyrolysis products such as dilithiometallanes. The molecular structures of 4, 5, and 6 were unequivocally determined by X‐ray diffraction. Dimer 4 has a symmetrical bent four‐membered‐ring structure consisting of two anionic silicon atoms and two cationic lithium atoms with coordinated THF molecules. Dimer 6 has an unsymmetrical distorted four‐membered‐ring structure consisting of two anionic tin atoms, a bridged unsolvated lithium atom, and a bridged lithium atom solvated by a THF molecule. Interestingly, 6 aggregates to form dimers of dimers by an intermolecular CH3···Li interaction. Trimeric germyllithium 5 forms an equilateral triangular lithium cluster without solvation. Compound 5 has a crystallographic threefold axis with three anionic germanium atoms and three cationic lithium atoms lying in the same plane. The lithium atoms in 5 are stabilized by an intramolecular CH3···Li interaction. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

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Section: Resultsmentioning

confidence: 99%

Tris(trimethylsilyl)‐Substituted Heavy Group 14‐Element‐Centered Anions: Unsolvated Trimeric Germyllithium and Solvated Dimeric Silyl‐ and Stannyllithiums

Nanjo

Mochida

2004

Eur J Inorg Chem

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“…Deprotonation of 2-(dimethylsilyl)indene (1a, 2-DMS-Ind) and 2-(trimethylsilyl)indene (1b, 2-TMS-Ind) was achieved by n-butyllithium in pentane at room temperature or -90°C, respectively. In spite of the nonpolar solvent, deprotonation at lower temperatures provided hydride substitution products for 1a, as observed by Kira et al [4] Alternatively deprotonation can be achieved with potassium hydride at room temperature.…”

Section: Ligand Synthesesmentioning

confidence: 56%

“…The slight excess of n-butyllithium used in the reaction could be traced by deScheme 2. Reactivity of 1-isopropyl-2-(trimethylsilyl)indene (4). a) nBuLi, pentane; b) potassium hydride, THF; c) 2-Iodopropane, diethyl ether/THF (n.i.…”

Section: Ligand Synthesesmentioning

confidence: 99%

Synthetic Explorations Towards Sterically Crowded 1,2,3‐Substituted Bis(indenyl)zirconium(IV) Dichlorides

et al. 2005

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The systematic synthesis of 1,3-dialkyl-substituted 2-silylindenes and their suitability as zirconocene ligands is discussed. Unexpected reactivities rendered a number of substitution patterns unfeasible, especially for alkyl groups other than methyl in 2-(trimethylsilyl)indene derivatives, and essentially for all derivatives of 2-(dimethylsilyl)indene. The syntheses of rac/meso-bis [1-methyl-2-(trimethylsilyl)indenyl]zirconium(IV) dichloride (12) and bis [1,3-dimethyl-2-(trimethylsilyl)indenyl]zirconium(IV) dichloride (13b) are de- IntroductionThe field of metallocene-catalyzed olefin polymerization has achieved significant improvements on polymer properties. The ligandϪtacticity relationship is well understood and, apart from tailor-made stereocontrol, co-monomer incorporation and block length have been emphasized as keys to innovative materials.[1] The detailed polymerization mechanism with all its variations is complicated and the choice of appropriate polymerization conditions to favor one monomer over the other still requires vast and tedious sets of experiments. An outline of the extensive efforts made within this area can be found in the various review articles. [2] Previous work from our laboratory addressed unbridged zirconocene dichloride with silyl substituents in the 1 or 2 position.[3] Reports on trisubstituted indenyl ligands, i.e. substituents in the 1, 2, and 3 positions, are still quite uncommon. It may be expected that steric congestion in such complexes is significant and that overall polymerization activity may be negatively influenced. In this study, we wish to present our results on a systematic study of 1,3-dialkyl-2-silyl-trisubstituted indene ligands for the synthesis of zirconocene dichlorides. Results and Discussion Ligand SynthesesThe introduction of alkyl groups in the 1 and 3 position of 2-silylindenes should be feasible in a straight forward manner by simple double alkylation of indenyllithium salts. Deprotonation of 2-(dimethylsilyl)indene (1a, 2-DMS-Ind) and 2-(trimethylsilyl)indene (1b, 2-TMS-Ind) was achieved by n-butyllithium in pentane at room temperature or -90°C, respectively. In spite of the nonpolar solvent, deprotonation at lower temperatures provided hydride substitution products for 1a, as observed by Kira et al.[4] Alternatively deprotonation can be achieved with potassium hydride at room temperature.Methylation of the lithium salt of 1a with methyl iodide at -40°C in diethyl ether yielded exclusively 3-Me-2-DMSInd (2a), while 1-Me-2-TMS-Ind (2b) was obtained likewise from 2-TMS-Ind. Repetition of the deprotonationϪmethyl-ation sequence afforded a 1:4 mixture of the 1,1-dimethyl and 1,3-dimethyl isomers for both, 3a and 3b. Deprotonation and washing with pentane provided pure lithium salts of the 1,3-dimethyl-2-silylindenes 3a and 3b (Scheme 1). 3a exhibits diastereotopic methyl resonances of the silyl group in a 1:1 ratio due to the presence of the chiral C(1) atom.In order to determine whether bulkier alkyl substituents could be placed in the 1,3 positions, studies ...

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“…[18] Main-group derivatives are limited to [{(tBuMe 2 Si) 2 HGeLi} 2 ], obtained by the reaction of (tBuMe 2 Si) 2 GeH 2 with tBuLi in THF, [19] and [M 2 {Ge(H)Ar'} 2 ] (M= Li, Na, K; Ar' = C 6 H 3--2,6-(C 6 H 3--2,6-iPr 2 ) 2 ), prepared by the treatment of Ar'(H)GeGe(H)Ar' with the metals in toluene. [20] We here present the first family of discrete alkali metal germyl derivatives.…”

Section: Introductionmentioning

confidence: 99%

“…The same is observed in a dimeric hydrido-A C H T U N G T R E N N U N G (trialkylsilyl) germyllithium, in which GeÀH distances of 1.57 are observed. [19] Theoretical studies Quantum chemical calculations were employed to study the unexpected GeH 3 À binding orientations in contact structures 1 and 4. In the absence of crystal interactions, a cationGeH 3 À structure would be expected to conform to either that of the vant Hoff arrangement, with the anionic Ge lone pair in direct contact with the metal cation, or the GeH 3 À -inverted variant, in which the three H atoms of the anion bind symmetrically to the cation.…”

Section: Introductionmentioning

confidence: 99%

Synthetic, Structural, and Theoretical Investigations of Alkali Metal Germanium Hydrides—Contact Molecules and Separated Ions

Teng

Allis

Ruhlandt‐Senge

2007

Chemistry A European J

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The preparation of a series of crown ether ligated alkali metal (M=K, Rb, Cs) germyl derivatives M(crown ether)nGeH3 through the hydrolysis of the respective tris(trimethylsilyl)germanides is reported. Depending on the alkali metal and the crown ether diameter, the hydrides display either contact molecules or separated ions in the solid state, providing a unique structural insight into the geometry of the obscure GeH3- ion. Germyl derivatives displaying M--Ge bonds in the solid state are of the general formula [M([18]crown-6)(thf)GeH3] with M=K (1) and M=Rb (4). The compounds display an unexpected geometry with two of the GeH3 hydrogen atoms closely approaching the metal center, resulting in a partially inverted structure. Interestingly, the lone pair at germanium is not pointed towards the alkali metal, rather two of the three hydrides are approaching the alkali metal center to display M--H interactions. Separated ions display alkali metal cations bound to two crown ethers in a sandwich-type arrangement and non-coordinated GeH3- ions to afford complexes of the type [M(crown ether)2][GeH3] with M=K, crown ether=[15]crown-5 (2); M=K, crown ether=[12]crown-4 (3); and M=Cs, crown ether=[18]crown-6 (5). The highly reactive germyl derivatives were characterized by using X-ray crystallography, 1H and 13C NMR, and IR spectroscopy. Density functional theory (DFT) and second-order Møller-Plesset perturbation theory (MP2) calculations were performed to analyze the geometry of the GeH3- ion in the contact molecules 1 and 4.

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Sila-metalation Route to Hydrido(trialkylsilyl)silyllithiums

Cited by 45 publications

References 12 publications

Tris(trimethylsilyl)‐Substituted Heavy Group 14‐Element‐Centered Anions: Unsolvated Trimeric Germyllithium and Solvated Dimeric Silyl‐ and Stannyllithiums

Tris(trimethylsilyl)‐Substituted Heavy Group 14‐Element‐Centered Anions: Unsolvated Trimeric Germyllithium and Solvated Dimeric Silyl‐ and Stannyllithiums

Synthetic Explorations Towards Sterically Crowded 1,2,3‐Substituted Bis(indenyl)zirconium(IV) Dichlorides

Synthetic, Structural, and Theoretical Investigations of Alkali Metal Germanium Hydrides—Contact Molecules and Separated Ions

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