The doubly lithiated aminals bis(lithiomethyl(methylamino))methane [LiCH2N(Me)]2CH2
(1a) and bis(lithiomethyl-isopropylamino)methane [LiCH2N(i-Pr)]2CH2 (1b) react with Cp-
and Cp*- (Cp* = C5Me5) substituted zirconocene chlorides in toluene to give
(2a, R = Me; 2c, R = i-Pr) and
(2b, R = Me;
2d, R = i-Pr). An interaction of the nitrogen atoms of the metallacycles with the zirconium
centers in the solid state (2a, 2b) and in solution (2a, 2c) is deduced from structural studies
and from the 1H NMR spectra at variable temperatures (ΔG
⧧ = 65.7 ± 0.6 kJ mol-1 for the
ring inversion process in 2c). Isonitriles CNR (R = t-Bu, Me) and CO insert in one of the
zirconium methylene σ-bonds of 2b and 2d and yield
(3a, R1 = Me, R2 = t-Bu; 3b, R1 = i-Pr, R2 = t-Bu; 3c, R1, R2 = Me) and the zirconium
enolates
(4a, R = Me; 4b, R = i-Pr), respectively.
Further insertion of isonitriles does not occur. Complexes 2a and 2c are unaffected by
isonitriles or CO. The molecular structures of 2a, 2b, and 3a have been studied by X-ray
diffraction. The resulting structural information of the complexes 2a and 2b provides
valuable insight into the nature of the Zr ← N interaction within the metallacycles, which
is discussed briefly.
The doubly lithiated aminal bis(lithiomethyl-(methylamino))methane, [LiCH 2 N(Me)] 2 CH 2 , reacts with bis(trimethylphosphine)nickel dichloride in diethyl ether to give the solvent-free dinickelate [Ni{[CH 2 N(Me)] 2 -CH 2 }Li 2 ] 2 (1) in good yield. The molecular structure of 1 has been studied by X-ray-crystallography.
A New Route to Sila-and Phosphaheterocycles: Nucleophilic Aminomethylation.-Doubly lithiation of the compounds (I) occurs by exclusive N-methyl metalation to give the lithiated aminals (II). They are used for nucleophilic aminomethylations at silicon and phosphorus centers forming compounds such as (IV), (VI), and (VIII). Side reactions often lower the yield. -(KARSCH, H. H.; SCHREIBER, K.-A.; HERKER, M.; Chem.
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