The aromaticity of three-membered monoheterocycles containing a group 14 or 4 element was investigated by using modern aromaticity criteria: structural, electronic (FBO), optical (vibrational spectroscopy), energetic (ISE), and magnetic (NICS-scan, GIMIC). The results of all methods used show that the group 14 compounds are aromatic, with cyclopropene exhibiting σ aromaticity, whereas sila-and germacyclopropenes X 2 EC 2 R 2 exhibit pseudo-π aromaticity due to the interaction of the CC π bond orbital with the low-lying vacant antibonding σ* orbital of the X 2 E fragment (E = Si, Ge). At the same time, the results of MO and magnetic descriptor calculations testify against the aromaticity of group 4 cyclopropenes Cp 2 MC 2 R 2 (M = Ti, Zr, Hf). Thus, a fundamental dissimilarity in bonding schemes and electronic structure was disclosed between 1-heterocyclopropenes containing E = C, Si, Ge atoms and those containing M = Ti, Zr, Hf atoms, the latter molecules being in essence π complexes of acetylene.

Poly(n-butyl-n-hexylsilylene) (PBHS) has been studied by UV and Raman spectroscopy as a function of temperature from 300 to 27 K. At room temperature, PBHS adopts a hexagonal columnar mesophase. Upon cooling to 250 K or below, a complex first-order phase transformation takes place, leading to three other forms:  a 7/3 helical form, an all-trans form, and an intermediate form with unknown conformation. The amount of each form depends on the thermal history of the sample. The final transformation, from 7/3 helical to the all-trans conformation, does not proceed to completion because equilibration ceases at the glass transition temperature, near 210 K.

A new approach towards nitronium salts via the reaction of CF3COONO2 (TFAN) with acids was developed. This method was applied to the syntheses of the following solid nitronium salts: NO2HSO4 (1), NO2HS2O7 (2), (NO2)2S2O7 (3), (NO2)(CF3CO)SO4 (4), NO2ClO4 (5), (NO2)CF3SO3 (6), (NO2)FSO3 (7), NO2IO4 (8), (NO2)(CF3CO)S2O7 (9), and NO2BF4 (10) (71–95%). Nitronium monosulfates 1 and 4 as well as compounds 8, 9 and NO2HS3O10 (11) were obtained for the first time. The structures of compounds 3 and 4 were confirmed by powder X‐ray diffraction.

The reaction of (CH&Si(NMe2)2 with B10H14 yields a polymer, -[BloH12.Me2NSi(CH3)2NMe2-ln, whose pyrolysis in a stream of ammonia gives hexagonal boron nitride containing a small amount of silicon nitride. In contrast, CH3(H)Si(NMe2)2 reacts with B10H14 to give 1,2-dimethyl-1,2-disila-closo-dodecaborane( 12) (DMSB), an air-sensitive solid, the structure of whose 1:l benzene solvate was determined by X-ray diffraction. This compound crystallizes in the space group Pccn (#56) with a = 10.081(1) A, b = 10.666(8) A, c = 16.130(5) A, V = 1734(2) A3, and Z = 4. Final R = 0.044 and R , = 0.058. The 'H, I3C, 29Si, and llB N M R spectra and mass spectrum of DSMB are reported.Its vibrational spectrum (Raman, 5-3600 cm-l; IR, 200-3600 cm-I) has been measured and compared with that of o-carborane. A study of its He(1) photoelectron spectrum led to the conclusion that DMSB is the most electron-rich cluster of type XYBloHlo with two adjacent main group element centers known.

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