Polymeric ladder structure lithium amides

By using a combination of gas-phase synthesis and millimeter/submillimeter-wave spectroscopy, LiNH2 was found to be a monomeric unsolvated planar molecule. The lithium amide [H2NCH2CH2N(H)Li]co has a polymeric ladder structure with two types of (NLi)2 ring which alternate throughout its infinite length. ... 

Dimeric and higher aggregate lithium amides can generally be classified into the coordination motifs illustrated in Scheme 2.2. The four-membered (LiN)2 ring is ubiquitous in lithium amide chemistry and is observed both in discrete dimeric structures in either planar (Scheme 2.2, A) or non-planar (Scheme 2.2, B) geometries as well as in oligomeric and polymeric (ladder) frameworks (Scheme 2.2, C). Trimeric six-membered (LiN), ring... 

The ladder structures formed by lithium amides and their heavier group 15 analogues stand in contrast to those formed by the related lithium alkyls which generally prefer aggregates with three-dimensional or one-dimensional polymeric structures. 

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