methylalane Dimethylborane, (CH3)2BH is the simplest dialkylborane, consisting of a methyl group substituted for a hydrogen in borane.

[2] Other combinations of methylation occur on diborane, including monomethyldiborane, trimethyldiborane, 1,2-dimethylborane, 1,1-dimethylborane and trimethylborane.

[12] The nuclear resonance shift for the bridge hydrogen is 8.90 ppm, compared to 10.49 for diborane.

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

[4] Atomic hydrogen converts trimethylborane on a graphene monolayer surface to dimethylborane which dimerises to tetramethyldiborane.

[15] Dimethylborane reacts with alkenes with the highest yield in ether to produce a dimethylalkylborane.

This requires heating to 150° with carbon monoxide under 50 bars of pressure, and then oxidation with hydrogen peroxide.

[16] Methylboranes such as tetramethyldiborane disproportionate in the gas phase to trimethylborane and diborane at room temperature.

[21] Acetonitrile reacts slowly with tetramethyldiborane at room temperature to form dimeric ethylideneaminodimethylborane (CH3CH=NB(CH3)2)2.

Tetramethyldiborane acts as a catalyst to enable the same results from trimethylborane: The tetramethylborate anion (CH3)4B− only has one boron atom.