Which one of the following methyl diboranes does not exist?
Di borane forms methyl diborane(B2H5(CH3)),dimethyl diborane(B2H4(CH3)2),trimethyl diborane(B2H3(CH3)3) ,tetra methyl diborane(B2H2(CH3)4).
So B2H(CH3)5 can not form, because in this compound we have to use bridge hydrogen for the formation of this compound ,that never happens.