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1,1-Dimethyldiborane

1,1-Dimethyldiborane
1,1-dimethyldiborane.svg
Names
IUPAC name
1,1-Dimethyldiborane
Other names
Unsymmetrical dimethyldiborane
Identifiers
3D model (JSmol)
Properties
(CH
3)
2B
2H
4
Molar mass 55.72 g mol−1
Appearance Colorless gas
Melting point −150.2 °C (−238.4 °F; 123.0 K)
Boiling point −4 °C (25 °F; 269 K)
Solubility in organic solvents Soluble in ether, pentane, tetrahydrofuran
Thermochemistry
-25 kcal/mol
Hazards
NFPA 704
Flammability code 2: Must be moderately heated or exposed to relatively high ambient temperature before ignition can occur. Flash point between 38 and 93 °C (100 and 200 °F). E.g., diesel fuel Health (blue): no hazard code Reactivity code 2: Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water. E.g., phosphorus Special hazards (white): no codeNFPA 704 four-colored diamond
Related compounds
Related alkyl boranes
Methyldiborane
Trimethyldiborane
Tetramethyldiborane
Trimethylborane
Diethyldiborane
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N (what is YesYN ?)
Infobox references

1,1-Dimethyldiborane is the organoboron compound with the formula (CH3)2B(μ-H)2BH2. A pair of related 1,2-dimethyldiboranes are also known. It is a colorless gas that ignites in air.

The methylboranes were first prepared by H. I. Schlesinger and A. O. Walker in the 1930s. Methylboranes are formed by the reaction of diborane and trimethylborane. This reaction produces four different substitution of methyl with hydrogen on diborane. Produced are 1-methyldiborane, 1,1-dimethyldborane, 1,1,2-trimethyldiborane, and 1,1,2,2-tetramethyldiborane.

Tetramethyl lead reacts with diborane in a 1,2-dimethoxyethane solvent at room temperature to make a range of methyl substituted diboranes, ending up at trimethylborane, but including 1,1-dimethyldiborane, and trimethyldiborane. The other outputs of the reaction are hydrogen gas and lead metal.

Other methods to form methyldiboranes include heating trimethylborane with hydrogen. Alternatively trimethylborane reacts with borohydride salts with in the presence of hydrogen chloride, aluminium chloride, or boron trichloride. If the borohydride is sodium borohydride, then methane is a side product. If the metal is lithium then no methane is produced. dimethylchloroborane and methyldichloroborane are also produced as gaseous products.

When Cp2Zr(CH3)2 reacts with borane dissolved in tetrahydrofuran, a borohydro group inserts into the zirconium carbon bond, and methyl diboranes are produced.

In ether dimethylcalcium reacts with diborane to produce dimethyldiborane and calcium borohydride:


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