Serendipity and the Search for Short N---I Halogen Bonds
The X-ray structure of the complex formed between N,N-dimethylaminopyridine (DMAP) and 1,2-bis(iodoethynyl)benzene is reported. The N---I halogen bond lengths are 2.654 and 2.662 Ã…, approximately 75% of the sum of the van der Waals radii. On the basis of literature precedent and electrostatic potential calculations, a series of fluorosubstituted iodophenylacetylenes were prepared and individually complexed with dimethylaminopyridine in a search for shorter halogen bonds. A N---I halogen bond distance of 2.680 Ã… was observed in the DMAP complex with 3,5-difluoro(iodoethynyl)benzene, and halogen bond distances of 2.622, 2.676, 2.700, and 2.705 Ã… were observed in the complex of 4-fluoro(iodoethynyl)benzene with DMAP. These N---I bond distances range from 74.3 to 76.6% of the sum of the van der Waals radii.