Chelating TMEDA ligands

The zinc atom is pseudo-tetrahedrally surrounded by the cyclopentadienyl and methyl groups and the chelating TMEDA ligand, while the dimethylpyrrole pendant is not coordinated to the metal. The zinc-methyl bond (1.985(2) A) and the (vO-bound cyclopentadienyl ligand (2.185(2) A) are both slightly elongated, possibly due to the steric crowding about zinc. 

Trimethylacetophenone forms a dimeric sodium enolate with two chelating TMEDA ligands (6). There is significant jt-electron interaction of the metal ion with the olefinic carbons but no evidence of jt-bonding with the aromatic rings. ... 

Lithium 2-diisopropylamino-2-boratanaphthalene (cf. 28) with Me2-NCH2CH2NMe2 (TMEDA) forms a crystalline derivative Li(TMEDA) (C9H7BNPr 2) which has been characterized by X-ray structure determination (102). The lithium cation is situated above the center of the boratabenzene moiety of the anion and, in addition, is chelated by one TMEDA ligand. Thus, the crystal consists of discrete tight ion-pair molecules. 

The reactions of a benzylzinc chloride TMEDA adduct with either benzyllithium or benzyl(trimethylsilyl)lithium TMEDA adduct yielded both homoleptic dibenzylzinc (37, Figure 16) and heteroleptic monobenzylzinc compounds as TMEDA adducts. The heteroleptic diorganozinc compounds do not disproportionate as long as TMEDA is present, but removal of the chelating nitrogen ligand in the gas phase does cause disproportionation. 

The first iron-containing silsesquioxanes which appeared in the literature were compounds containing ferrocenyl units as side-groups.However, these are not within the scope of this review as iron is not part of the metallasilsesquioxane skeleton. Meanwhile, several ferrasilsesquioxane complexes have been synthesized. The first iron(III) compound of this type was prepared in our laboratory according to Scheme 56. ° In 161, the coordination sphere of iron is completed by TMEDA (N,N,N, N -tetramethylethylenediamine) as a chelating amine ligand. Pale yellow, crystalline 161 was isolated in 80% yield and structurally characterized by X-ray diffraction. This compound was later used by Maxim et to prepare iron... 

The reaction of magnesium bromide with potassium 3,5-di-tert-butylpyrazolate, K[Bu 2pz], in toluene affords Mg2(Bu 2pz)4 in THF the product is Mg2(Bu 2pz)4(THF)2." Both of these are dinuclear complexes with two bridging pyrazolato and two chelating ry -pyrazolato ligands. TMEDA binds to the unsolvated compound or displaces THF from the solvate to give Mg(Bu 2pz)2 (TMEDA), which is a mononuclear species with two ry -pyrazolates and chelating TMEDA. 

Nickel(O) complexes undergo oxidative addition reactions with alkynes to give nickelacyclopentadienes and also react under certain conditions with carbon dioxide or isocyanates to form oxanickelacyclopentenones (87) " or azanickelacyclopentenones (88) (Scheme 30). In both cases the chelating basic ligand TMEDA (tetramethylethylenediamine) influences the reaction strongly. 

Cu(py)2(PhenCat)(PhenBQ) (2), including the unusually short C-O bond lengths (1.315(5), 1.316(5)A) for the chelated PhenCat ligand. The EPR spectrum of Cu(tmeda)(PhenCat) in solution is solvent dependent (Figure 5). In acetonitrile spectra show evidence for the... 

Mg center. The two terminal Na atoms are linked to the five-membered ring of the indolyl systems via electrostatic cation Jt-interactions in a t] -manner with the C2 (deprotonated) and C3 (proton-bearing atoms. Each Na atom is additionally solvated by a chelating TMEDA donor ligand completing their tetrahedral coordination spheres. This hi order magnesium ate complex represents the first example of a structure of a C-magnesiate indolyl system. 

Fig. 38). In this complex, benzene has been converted to a 1,4-dianion. Comparing this complex to compounds like 57, it seems that the addition of TMEDA has resulted in the formation of a molecule akin to an open inverse crown molecule (with the extrusion of neutral NaTMP). The TMEDA ligands chelate to the Na cations. 

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