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|Section2= |Section3= |Section4= |Section5= |Section8= }} Methyldiborane, CH3B2H5, or monomethyldiborane is the simplest alkyldiborane, consisting of a methyl group substituted for a hydrogen in diborane. As with other boranes it exists in the form of a dimer with a twin hydrogen bridge that uses three-center two-electron bonding between the two boron atoms, and can be imagined as methyl borane (CH3BH2) bound to borane (BH3). Other combinations of methylation occur on diborane, including 1,1-dimethylborane, 1,2-dimethyldiborane, trimethyldiborane, tetramethyldiborane, and trimethylborane (which is not a dimer). At room temperature the substance is at equilibrium between these molecules.〔 The methylboranes were first prepared by H. I. Schlesinger and A. O. Walker in the 1930s.〔 〕 ==Formation== Methylboranes are formed by the reaction of diborane and trimethylborane. This reaction produces four different substitution of methyl with hydrogen on diborane. Produced is 1-methyldiborane, 1,1-dimethyldborane, 1,1,2-trimethyldiborane and 1,1,2,2-tetramethyldiborane.〔 The reaction is complex. At 0°C when diborane is in excess, monomethyldiborane is initially produced, coming to a steady but low level, and 1,1-dimethyldiborane level increases over a long time, until all trimethylborane is consumed. Monomethyldiborane ends up at equilibrium with a mixture of diborane and dimethyldiborane. At 0° the equilibrium constant for 2B2H5Me ←→ B2H6 + (BH2Me)2 is around 0.07, so monomethyldiborane will typically be the majority of the mixture, but there will still be a significant amount of diborane and dimethyldiborane present. Monomethyldiborane yield is best with a ratio of 4 of diborane to 1 of trimethylborane. The yield of trimethyldiborane is maximised with ratio of 1 of diborane to 3 of trimethylborane.〔 When methyllithium reacts with diborane, monomethyldiborane is produced in about a 20% yield.〔 〕 Tetramethyl lead can react 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-di, tridiborane. The other outputs of the reaction are hydrogen gas and lead metal. 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. 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. When trimethylgallium reacts with diborane at -45°, methyldiborane is produced along with dimethylgallium borohydride. :2(CH3)3Ga + B2H6 → (CH3)2GaBH4 + CH3B2H5. At room temperature trimethylgallium reacts with diborane to make a volatile substance that deccomposes to gallium metal along with methyldiborane. :(CH3)3Ga + 3B2H6 → Ga + 3CH3B2H5 +1.5H2.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Methyldiborane」の詳細全文を読む スポンサード リンク
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