The reaction of (CH3)2Si(NMe2)2 with BlOH14 Yields a polymer, BlOH12. Me2NSi(CH3)2NMe2n, whose pyrolysis in a stream of ammonia gives hexagonal boron nitride containing 'a' little silicon nitride. In contrast, CH3(H)Si(NMe2)2 reacts with BlOH14 to give 1,2-dimethyl-1,2-disila-closo-dodecaborane(12) (DMSB) , an air-sensitive solid, the structure of whose 1:1 benzene solvate was determined by X-ray diffraction. This compound crystallizes in the space group P ccn ( 56) with a 10.081(1) b = 10 ...