Organozinc amides, structure

Tris(trimethylsilyl)methylzinc bis(trimethylsrlyl)amide (178) is the only example of an organozinc amide in which the zinc atom is two-coordinate, of which the structure has been determined in the solid state (Figure 89). The Zn—C bond distance [1.944(2) A] is as expected for a a-bonded zinc atom. The C—Zn—N bond angle [177.8(1)°] is close to linear. The Zn—N distance is extremely short [1.846(2) A], but this is a logical consequence of the sp-hybridization of the zinc atom and the sp -hybridization of the amide-nitrogen atom. The latter is indicated by the fact that the sum of the bond angles around this nitrogen atom is 359.7°. 

The solid state structures of the organozinc amides 198 ", 199 4 200 (Figure 97),... 

FIGURE 103. Schematic structures of the trimeric organozinc amides 220-223... 

A recent report on the first structurally characterized organozinc amide enolate has appeared, and the observations are consistent with ours. Hlavinka, M.L. Hagadom, J.R. Organometallics 2005,24,4116. Although drawn as monovalent in Equation 20.2 for clarity, it is assumed that lithium is tetracoordinate, and 12-crown-4 is displacing other hgands hound to lithium, such as THE. 

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