Structurally, it is related to diborane, but with methyl groups replacing terminal hydrides on each boron.

[2] 1,2-Dimethyldiborane is an easily condensed, colorless gas that ignites spontaneously in air.

[7] Other methods to form methyldiboranes include treating hydrogen with trimethylborane between 80 and 200 °C under pressure, or treating a metal borohydride with trimethylborane in the presence of hydrogen chloride, aluminium chloride or boron trichloride.

[12] Gas chromatography can be used to determine the amounts of the methyl boranes in a mixture.

The order of elution are: diborane, monomethyldiborane, trimethylborane, 1,1-dimethyldiborane, 1,2-dimethyldiborane, trimethyldiborane, and last tetramethyldiborane.

[14] Methylborane shows little tendency to disproportionate (redistribute) at room temperature.

[15] Methylborane hydrolyzes to methylboronic acid:[6] Symmetrical dimethyldiborane reacts with trimethylamine to yield a solid adduct trimethylamine-methylborane (CH3)3N·BH2CH3.

[6] When dimethyldiborane is combined with ammonia and heated, B-methyl borazoles are produced.