Reactions of laser-ablated boron atoms with monomethylamine in argon produce two new iminoboranes, CH3BNH and CH3NBH, as well as the related isomer, CH2BNH2. Boron reactions with dimethylamine also generate these products and a third new iminoborane, CH3BNCH3. These molecules are identified by matching observed matrix infrared and MP2 calculated B-10/B-11 isotopic frequency ratios. In these reactions, the observed products indicate that the primary reaction mechanisms involve boron insertion into either the C-N or N-H bonds, instead of into the C-H bonds.