The microwave spectrum of the van der Waals complex NCCN-BF//3 has been obtained by molecular beam electric resonance spectroscopy. This molecule is shown to be a symmetric rotor. The rotational constants for the **1**1B and **1**0B species are B//0 equals 672. 2 (2) and 675. 6 (2) MHz, respectively. These values are consistent with a B-N bond length of 2. 647 (3) A. Radio-frequency and microwave transitions of the complex CO//2 multiplied by (times) BF//3 have been observed and establish that this molecule is an asymmetric rotor. One radio-frequency transition observed for N//2O multiplied by (times) BF//3 suggests an asymmetric structure for this complex as well.