Lithium amido complexes

Scheme2.1 Lithium amido complexes formed upon addition of 12-crown-4 a/ h/ c/ d, e, > f ...

Figure 2.1 Illustration of the monomeric primary amido complex [Li(NHMes )(tmeda)f showing the distorted trigonal planar geometry at the lithium ion. Selected bond lengths Li-NI 1.895(8) A, Li-N2 2.137(9) A and Li-N3 2.165(9)A...

Magnesium amides can form a wide range of mixed metal amido complexes with alkali metal ions (M2[Mg(NH2)4]) (M = K, Rb or Cs).These contain tetrahedral Mg-centered [Mg(NH2)4] ions connected in three-dimensional networks by coordination of the amido groups to the group 1 metal ions. The most common hetero metal is lithium and lithium amido magnesiates are readily accessible by the addition of a lithium amide to a magnesium amide. 

FIGLfRE 2. Calculated Gibbs free-energy values of unsolvated and solvated mixed complexes between a chiral lithium amido ether and methyllithium... 

Although these mixed complexes with chiral lithium amido sulfides appear promising structures for asymmetric addition reactions in general, it should be noted that they are only stable at low temperatures (<50 °C). At higher temperatures they readily decompose, most likely due to deprotonation of the acidic a-protons next to the sulfur. 

A fluorenyl-amido complex with an expanded bridge, [Ci3H8-GH2Si(Me2)NBut]TiCl2 (Scheme 270), has been prepared by reacting the lithium salt of the fluorenyl-amido ligand with TiCl4.694... 

The spiro bis-Cp-amido complex Ti[CsH4C(=CH2)N(SiMe3)]2 (Scheme 587) has been isolated in 81% yield by treatment of lithium [l-(lithio-N-trimethylsilylamido)ethenyl]cyclopentadienide with TiCl4(THF)2.983... 

The zirconocene bis(arylamido) complex 787 was obtained by the reaction of Cp2ZrCl2 with 2 equiv. of the lithium amide605 (Scheme 195). When the reaction is carried out in a 1 1 ratio, the monoamide zirconocene chloride is generated as the major product. Reaction of in situ-generated Cp 2Zr with 2-(methylmercapto)aniline yields monoamido zirconocene hydride 788, the spectroscopic data of which suggest an interaction between the S atom and the Zr center in this complex. The bis(amido) complex 787 serves as a precursor for the synthesis of amido rhodium and iridium complexes. 

In the course of a closely related study, a series of new functionalized amido complexes of ytterbium, [Cp2YbNHR]2 (R = 8-quinolyl (Qu), 2-pyridyl (Py), 2-aminophenyl, 3-amino-2-pyridyl, and Cp2Yb[NHC6H4(CH2NH2-2)], have been synthesized by metathesis of Cp2YbCl and the corresponding amido lithium salts. Their reactivity toward carbodiimides has been investigated, in which multiple N-H... 

S3mthetic routes to homoleptic early-metal-amido complexes are discussed in detail in the review by Lappert. The most convenient route to homoleptic early-metal-amido complexes was developed by Bradley and co-workers and involves treatment of the appropriate metal chloride with excess lithium amide (Equation 4.15). - ... 

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