Jean-Marc Frances

Synthesis and thermal decomposition of substituted [2-(acyloxy)alkyl]diorganotin compounds, Bu2Sn(X)CH2 CHR1OCOR2 (X halogen 2,4-pentanedionate or OCOR), potential sources of organotin catalysts

Halido-, (2,4-pentadionato-O,O′) and (acyloxy[2-(acyloxy)ethyl]dibutylstannanes, Bu2Sn(X)CH2CHR1OCOR2 (X  halogen, 2,4- pentanedionate, or OCOR) have been prepared, either by hydrostannation of vinyl esters or by condensation of stannyllithium compounds with epoxides followed by esterification. These thermally unstable compounds are easily decomposed in diorganotin compounds with two heteroatom donors. Some are good catalyst sources for silicone curing and polyurethane preparation.

Nonhydrolytic synthesis and structural study of methoxyl-terminated polysiloxane D/Q resins

Low-viscosity, methoxylated polysiloxane resins incorporating Me 2 SiO 2/2 (D) and SiO 4/2 (Q) units were prepared using nonhydrolytic condensation between Si-Cl and Si-OMe groups with the formation of MeCl, catalyzed by a Lewis acid. With the commonly used catalysts, condensation between two Si-OMe groups, with formation of Me 2 O, also took place to a large extent, hindering the control of the degree of condensation of the resins. Several catalysts were tested by monitoring the formation of MeCl and Me 2 O using sealed NMR tubes and 1 H-NMR spectroscopy. The best compromise between reactivity and selectivity was obtained with ZrCl 4 . Resins with various compositions were prepared in the absence of solvent by condensation between Me 2 SiCl 2 and Si(OMe) 4 at 130°C, catalyzed by 1 mol % ZrCl 4 . They were characterized using viscosimetry, gas chromatography coupled with mass-spectrometry (GC-MS), and quantitative 29 Si-NMR spectroscopy. The resins consisted of a complicated mixture of oligomers, linear or branched (n > 1) and cyclic (n > 3), with a high degree of D/Q bonding. The distribution of Si-OMe and Si-OSi bonds and the bonding between D and Q units were found to be nearly random. This was ascribed to the occurrence of Si-OSi/Si-OMe and Si-OSi/Si-OSi redistribution reactions that reached equilibrium during the synthesis.