Terminally Dimetalated Tetramethylethylenediamine (TMEDA) Compounds

Tian, Xin; Fröhlich, Roland; Pape, Tania; Mitzel, Norbert W.

doi:10.1021/om0504405

Cited by 21 publications

(6 citation statements)

References 29 publications

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“…The Ga-O distance of 1.901( 6) A ˚and the O-N distance of 1.431(8) A ˚are similar to those of the heteronorbornane 1 [1.929(4) and 1.433(6) A ˚, respectively]. The length of the endocyclic Ga-N dative bond of 3a of 2.058(7) A ˚is remarkably shorter than that of 1 [2.257(5) A ˚] and even shorter than in the reference compounds 1,2,2,4,5,5-hexamethyl-1,4-diaza-2,5-digallabicyclo[2.2.2] octane [2.077(2) A ˚] and 2,2,5,5-tetra-tert-butyl-1,4-dimethyl-1,4-diaza-2,5-digallabicyclo[2.2.2]octane (2.106(2)), 11 which are both also heterobicyclooctanes, but with isoelectronic CH 2 instead of O units as compared to 3a. 1(3) • and 79.2(2) • , respectively].…”

Section: Spectroscopic and Structural Characterisationmentioning

confidence: 99%

Structural diversity in bishydroxylamine complexes of gallium

et al. 2008

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Reactions of bishydroxylamines of the type HON(R)CH2CH2N(R)OH (R=Me, tBu) with trimethyl- and triisopropylgallium gave bicyclic metalla cages of the formula R'2GaO(R)NCH2CH2N(R)OGaR'2 [R'=Me, R=Me (), tBu (); R'=iPr, R=Me (), tBu ()] with six-membered Ga2O2N2-rings. While the complexes show the same core constitution in the solid state, NMR spectra reveal the steric influence of the isopropyl substituent of the compounds / on its behaviour in solution. The reaction of the sterically more demanding substituted tri-tert-butylgallium with HON(Me)CH2CH2N(Me)OH yielded a heterodimeric complex O'-[HON(Me)CH2CH2NH(Me)O(tBu2Ga)]-cyclo-(tBu2Ga)-O,N'-[ON(Me)CH2CH2N(Me)O] () with two gallium atoms of different surrounding and two different bishydroxylamine ligands, one doubly deprotonated and one protonated, but at one end in its tautomeric aminoxide form. Further condensation of was observed to give a tricyclic compound cyclo-[(tBuGa)ON(Me)CH2CH2N(Me)O]2 () with a central Ga2O2N2 ring resulting from two Ga-N donor-acceptor bonds.

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Section: Spectroscopic and Structural Characterisationmentioning

confidence: 99%

Structural diversity in bishydroxylamine complexes of gallium

et al. 2008

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“…The central gallium atom is pseudotetrahedrally coordinated to the methyl ligand [Ga−C(Me), 1.949(8) Å], the NMe 2 sidearm [Ga−N, 2.100(5) Å], and the C 2 B 3 plane of the dicarbollyl ligand [Ga−C 2 B 3 (centroid), 1.862 Å]. The Ga−N distance is consistent with a regular Ga−N( sp 3 ) single bond and confirms that the N-donor atom is coordinated to the metal in a strain-free manner. The C 2 B 3 ligand is η 5 -coordinated to the gallium metal center, but rather unsymmetrically with short Ga−B and long Ga−C distances …”

Section: Resultsmentioning

confidence: 76%

Dicarbollylamine Ligand as a Tunable Template for σ,σ- and π,σ-Bonding Modes: Syntheses, Structures, and Theoretical Studies of η⁵:η¹-Coordinated Constrained-Geometry Group 13 Metal Complexes

Lee

Kim

et al. 2008

J. Am. Chem. Soc.

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A series of group 13 main group complexes with pi,sigma-type bonding interaction of the formula [{(eta (5)-RC 2B 9H 9)(CH 2)(eta (1)-NMe 2)}MMe] (M = Al, R = H 5, Me 6; Ga, R = H 7, Me 8; In, R = H 9, Me 10) was produced by the reaction of group 13 metal alkyls (MMe 3; M = Al, Ga, In) with the dicarbollylamine ligands, nido-8-R-7,8-C 2B 9H 10-7-(CH 2)NHMe 2 (R = H 1, Me 2). The reactions of 1 and 2 with AlMe 3 in toluene initially afforded tetra-coordinated aluminum complexes with sigma,sigma-type bonding interaction, [{(eta (1)-RC 2B 9H 10)(CH 2)(eta (1)-NMe 2)}AlMe 2] (R = H 3, Me 4), which readily underwent further methane elimination to yield the corresponding constrained geometry complexes (CGCs, 5 and 6) of aluminum with pi,sigma-bonding interaction. However, the reactions between 1 and 2 and MMe 3 (M = Ga, In) in toluene produced gallium and indium pi,sigma-CGCs of 7 and 10 directly, not proceeding through sigma,sigma-intermediates. The structures of group 13 metal CGCs were established by X-ray diffraction studies of 5, 6, and 8, which authenticated a characteristic eta (5):eta (1)-coordination mode of the dicarbollylamino ligand to the group 13 metals. A similar pi,sigma-bonding interaction was also established in ethylene-bridged dicarbollylethylamine series. Thus, aluminum pi,sigma-CGCs of dicarbollylethylamine, [{(eta (5)-RC 2B 9H 9)(CH 2) 2(eta (1)-NBz 2)}AlMe] (R = H 17, Me 18), were prepared by the trans-metalation of the [{(eta (5)-RC 2B 9H 9)(CH 2) 2(eta (1)-NBz 2)}Ti(NMe 2) 2] (R = H 15, Me 16) with AlMe 3. However, only sigma,sigma-bonded complexes of the formula [{(eta (1)-RC 2B 9H 9)(CH 2) 2(eta (1)-NBz 2)}AlMe 2] (R = H 13, Me 14) were isolated by the reaction between [ nido-7-8-R-7,8-C 2B 9H 10-(CH 2) 2HNBz 2] (R = H 11, Me 12) and AlMe 3. When methane-elimination reactions between metal alkyls and dicarbollylamines were carried out with either the gallium atom or monobenzyl aminoethyl tethered ligands, [ nido-7-H 2NBz(CH 2) 2-8-R-7,8-C 2B 9H 10] (R = H 21, Me 22), desired pi,sigma-CGCs, [{(eta (5)-RC 2B 9H 9)(CH 2) 2(eta (1)-NBz 2)}GaMe] (R = H 19, Me 20) or [{(eta (5)-RC 2B 9H 9)(CH 2) 2(eta (1)-NHBz)}AlMe] (R = H 23, Me 24), were generated, respectively. DFT calculation on 5 provides evidence of existence of pi,sigma-bonding of dicarbollylamine ligand to the aluminum atom: pi-bonding interaction of a dicarbollyl unit becomes intensified in the presence of a weak sigma-bonding amine-tethered group. Furthermore, preference for the formation of pi,sigma-bonding was predicted by optimizing a reaction profile including sigma,sigma- and pi,sigma-structures as well as transition state structures for each methylene- and ethylene-spaced ligand system, 3-5 and 14- 18, to reveal that pi,sigma-bonding interaction is more favorable in the case of a methylene-tethered ligand system.

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“…larly deprotonated a to nitrogen, which generally is a position challenging to metalate in tertiary amines. [18] Having successfully applied this intramolecular alumination trapping methodology to both added organic substrates and in their absence attached neutral caps, we pondered whether it could be extended to the considerably more taxing challenge of deprotonating an attached anion. This task proved surprisingly straightforward in practice.…”

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confidence: 99%