Triply hydrogen bonded van der Waals complexes: CH<subscript>2</subscript>F<subscript>2</subscript>⋯CF<subscript>2</subscript>=CH<subscript>2</subscript> and CH<subscript>2</subscript>F<subscript>2</subscript>⋯CF<subscript>2</subscript>=CHF.

The results of molecular beam Fourier transform microwave (FTMW) investigations of the van der Waals complexes of difluoromethane with 1,1-difluoroethene (DFE) and trifluoroethene (TFE) are reported. The rotational parameters of the complexes have been interpreted in terms of a C s geometry with the two H or F atoms of CH2F2 lying out of the σ v symmetry plane of the complexes. The complexes are bound by three hydrogen bonds, of which one is the stronger C–F⋯H–C type, and two are the weaker C–H⋯F⋯H–C or C–F⋯H⋯F–C types for DFM–DFE or DFM–TFE, respectively. The most notable difference in the two complexes is that the out of plane atoms are two hydrogens for DFM–DFE, but are two fluorines for DFM–TFE. Additional information on the structure and hydrogen bonding has been obtained from ab initio calculations. [Copyright &y& Elsevier]