The mid infrared spectra of allene (C₃H₄) and boron trifluoride (BF₃) mixtures, dissolved in liquid argon (84–125 K) and in liquid nitrogen (80–113 K), are discussed. In all spectra, the formation of a 1:1 van der Waals complex C₃H₄·BF₃ was observed. From spectra recorded between 85 and 108 K, the complexation enthalpy in liquid argon, ΔH_LAr^°, was determined to be -9.2(3) kJ mol^-1. Using the self-consistent isodensity polarized continuum model to correct for the solvent influences, and applying statistical thermodynamics to account for zero-point vibrational and thermal influences, the gas phase complexation energy ΔE_c^exp was estimated to be -14.9(6) kJ mol^-1. The analysis was completed by carrying out abinitio calculations at the MP2/6-311++G(d,p), the MP2/6-311++G(3df,2pd)//MP2/6-311++G(d,p) and the MP2/aug-cc-PVTZ//MP2/6-311++G(d,p) level. At the latter level, the calculated complexation energy, -13.96 kJ mol^-1, closely agrees with the experimental value.