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 1 H/ 19 F-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) Å, f =81.369(5), g =81.397(5), n = 86.010(5), V =849.3(3) A m 3 , T =175(3) K, space group P-1 (No. 2), Z =1; d (calc)=2.167 g cm m 3 ; 4121 independent reflections, 3665 with I o >2( I o ); final refinement gave R1=0.0400, wR2=0.0901) showed the second shortest N > I interaction found in the crystallographic literature [2.762(3) Å] and the interdigitation of perfluorocarbon and hydrocarbon modules due to co-operative -C-H > F-C- interactions. Calculations to quantify these latter interactions have been also performed.