Quintuple bond formation

Compound 14 (Figure 6.26) was prepared from sequential reduction of a halide-free dinuclear chromium precursor [89]. The encapsulated potassium ions play a critical role in the formation of the Cr-Cr quintuple bond reaction of 14 with 1 equiv. of [18]crown-6 yields a mononuclear Cr(ll) compound. 

Five helical strands associate laterally leading to a quintuple helical braid (Figure 29). The authors [49] suggested that the formation of this supramolecular assembly may be due to edge-to-face interactions between the pyridine units and the phenyl groups in conjunction with van der Waals interactions. Finally, the quintuple helices associate laterally to form the crystal. In this supramolecular synthesis H-bonding plays a role only in the first level of the assembly process via a single-stranded H-bonded helical network. 

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