Lithiated alpha-cyanophosphonates: self-assembly of two-dimensional molecular sheets composed of interconnected twenty-four membered rings

摘要

Reaction of the phosphonates (RO)(2)P(O)CH2CN (R=Et I or Pr-i II) with one molar equivalent of LiNPr2i in THF gave the metallated complexes [(RO)(2)P(O)CHCNLi . THF](infinity) (R=Et 1 or Pr-i 2). Crystallographic analyses of them reveal that they form dimeric Li-2(O=P)(2) units, which further aggregate through inter-dimer association via the nitrile of the phosphonate to form cross-linked, polymeric network structures. These sheets align in the crystals to form a 'patchwork' arrangement of molecular channels. The carbanionic centres of the phosphonates are devoid of Li-C contacts and almost perfectly planar. In solution, the dimeric units most likely remain intact but the nitrile is involved in chelation to a metal centre via intra-dimer association. Theoretical calculations show that chelation of the nitrile unit is a viable mode of bonding. [References: 64]