Low temperature infrared spectral data are given for the adducts H3BC(O)N(CH3)3, D3BC(O)N(CH3)3, H3BC(O)N(CD)3)3)D3BC(O)N(CD3)3 over the range 3000 to 300 cm−1. Boron-11 NMR data are given for H3BCO and H3BC(O)N(CH3)3. The spectra allow the assignment of the structure of the adducts as [Formula: see text]