Perfluorocarbon-hydrocarbon discrete intermolecular aggregates:: An exceptionally short N•••I contact

1-Iodoperfluoroheptane (1a) and tetramethylethylenediamine (2, TMEDA) form the 2:1 ratio stable aggregate 3a and a similar behaviour is shown by 1-iodoperfluoroalkanes 1b-e and iodopentafluorobenzene 1f. These aggregates have been characterised in solution by H-1/F-19-NMR spectroscopy and in the solid state through IR and single crystal X-ray diffraction. The determined structure of 3a (triclinic, a = 6.2283(10), b = 9.250(2), c = 15.098(3) Angstrom, alpha = 81.369(5), beta = 81.397(5), gamma = 86.010(5), V = 849.3(3) A(-3), T = 175(3) K, space group P-1 (No. 2), Z = 1; d(calc) = 2.167 g cm(-3); 4121 independent reflections, 3665 with I-o > 2(I-o); final refinement gave RI = 0.0400, wR2 = 0.0901) showed the second shortest N...I interaction found in the crystallographic literature [2.762(3) Angstrom] and the interdigitation of perfluorocarbon and hydrocarbon modules due to co-operative -CH...F-C- interactions. Calculations to quantify these latter interactions have been also performed.