An improved method has been devised for the preparation of (HSiOs/2)s. The previously unknown higher homologs (HSiOi/,)i0-i6 have also been prepared and characterized. They were isolated from a soluble, silanol-free resin obtained by a rather unusual hydrolysis and condensation procedure whereby water is generated via the sulfonation of an aromatic solvent such as benzene. Evidence for the existence of structural isomerism in the larger cage systems was obtained from nmr studies; i.e., only the octamer and decamer exhibit simple single-line spectra. Despitethe attention accorded to prismatic silsesquioxane oligomers [(RSiOy2)8,10,12] in recent years,1 relatively little information is available concerning the oligomeric forms of the simplest member of

Silicone polymers (polydimethylsiloxanes, or PDMS) are used in numerous personal care and household products, eventually enter wastewater treatment plants, and are later applied to the land as a component of sludge. The fate of silicones in soil is largely unknown, but this study shows that in a moist (0.2 MPa = 12% moisture) Londo sandy clay loam, 200 centi‐stoke (cs)14C‐labeled PDMS degraded slowly over six months to yield about 3% of applied 14C as low‐molecular‐weight, water‐soluble products. When the soil was allowed to dry in one week from 12 to 3% moisture, the degradation rate was much more rapid, and after several days at 3 % moisture about half of the applied 14C was water desorbable. HPLC‐GPC of tetrahydrofuran (THF) soil extracts showed that PDMS had been degraded to low‐molecular‐weight molecules of the general formula HO‐[Si(CH3)2O]n‐H. The range of moistures in this experiment was measured in a field of Londo sandy clay loam during the summer of 1992, indicating that PDMS should be unstable in the soil environment. Further work on the identification and biological degradation of these small products is ongoing.

Silatranes are pentacoordinate silicon derivatives formed from the reaction of trialkanolamines such as triethanolamine with trifunctional silanes such as RSi(OMe)3. This paper describes the synthesis of a number of unusual silatranes bearing halo, acyloxy, siloxy, and hydroxy substituents at the apical silicon site. An effort is made to rationalize the sometimes exceptional chemistry of silatranes and to account for some of the apparent structural requisites for stable transannular dative bonding of nitrogen to silicon. The convenient preparation of polymeric modifications from epoxy functional precursors is also described.

The aqueous solubility of several low mlecular weight linear, cyclic, and branched permethylsiloxanes was determined at room temperature. A method for preparing molecularly dispersed, colloid‐free saturated aqueous solutions is described. Solubilities, decreasing with increased molecular weights, ranged downward from one part per million to mere parts per trillion. The cyclic oligomers were slightly more soluble than their linear analogues. While the effect of branching was mixed, polar groups such as phenyl and hydroxyl moities sharply increased aqueous solubility. Semilog plots of the solubility/molecular weight yielded linear regressions, the extrapolation of which indicate the absence of any environmentally relevant water solubility (< 1 ppt) for the conventional higher molecular weight polydimethylsiloxanes of commerce.

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Table . Metal-Promoted Isomerizations of l-Methyltricyclo[4. .1.0.0* '7]heptane Catalyst Conditions temp, time, solvent a ch3 11 -% yield of products-,ch3 cc d ch3 12 13 CH, 'to 14 [Rh(CO)iCl]i 25°, 15 min, CHC1, 96 [Ir(CO)sCl]i 25°, 14 hr, CHC1, 93

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