No abstract

Employing modified sol-gel techniques, trialkoxysilanes bearing either epoxy or 1-propenyl ether functional groups can be condensed under well controlled conditions to yield a series of soluble multifunctional siloxane oligomers. The key to the success of this synthetic approach was the use of weakly acidic ion-exchange resins as catalysts. The novel multifunctional oligomers displayed exceptionally high reactivity in photoinitiated cationic polymerization using diaryliodonium salts as photoinitiators. Polymerization involved not only addition polymerization of the pendant epoxide or 1-propenyl ether groups but also acid-catalyzed hydrolysis and condensation of residual alkoxy groups along the siloxane backbone.

Surface modifications of colloidal silica by sol−gel techniques with trialkoxysilane coupling agents bearing cationically polymerizable epoxy and 1-propenyl ether groups were carried out under mild conditions. After dilution with difunctional epoxy and 1-propenyl ether monomers and the addition of an onium salt photoinitiator, the mixtures were irradiated with UV light to provide organic−inorganic hybrid matrixes. Photopolymerizations were uniformly rapid and proceeded to high conversions. Colorless, transparent, cross-linked films potentially useful as abrasion resistant coatings for plastic articles were produced.

The manganese carbonyl acyl complexes L(CO)4MnC(O)R (L = CO, R = CH3 (2a); L = CO, R = Ph (2b); L = PPh3, R = CH3 (2c)) are precatalysts for the PhSiH3 hydrosilation−deoxygenation of Cp(CO)2FeC(O)CH3 (1a) to Cp(CO)2FeCH2CH3 (6a). Thus, 2a (4%) and 1.1 equiv of PhSiH3 reduce 1a initially to a mixture of [Cp(CO)2FeCH(CH3)O]3 - x H x SiPh (x = 2 (3b), 1 (4b), and 0 (5b)) (7−8 h), which transforms to a mixture of 5b (62%) and 6a (35%) (12 h). Similarly, 2b and PhSiH3 transform 1a to a mixture containing 4% 3b, 22% 4b, 72% 5b, and 2% 6a (30 min), then up to 15−20% 6a (12 h). Use of 2c as the precatalyst selectively yields 71% 4b and 10% 6a (30 min), then up to 19% 6a (5 h). Both 4b and 5b were isolated by size-exclusion chromatography and characterized as mixtures of four stereoisomers, 4b as a pair of enantiomers having a prochiral center and two meso diastereoisomers with pseudoasymmetric centers and 5b as a diastereomeric pair of enantiomers. The PhSiH3 (1.6 equiv)/RhCl(PPh3)3 (3%) system conveniently transforms Cp(L)(CO)FeC(O)R to their alkyl derivatives Cp(L)(CO)FeCH2R. Seven iron acyl complexes were studied (Cp(CO)2FeC(O)R, R = Me, Ph, iPr, tBu; Cp(L)(CO)FeC(O)CH3, L = PPh3, P(OMe)3, and P(OPh)3), which gave 49−87% isolated yields of Cp(L)(CO)FeCH2R. Their modest yields correspond to the presence of byproducts, Cp(CO)2FeCHCH2 (32%) and 4b (14%) with 1a and 10−15% of the vinyl complexes with L = PPh3 and P(OPh)3.

A series of chemical vapor deposition (CVD) precursors have been synthesized by a single‐step reaction of 1,1,3,3‐tetramethylguanidine and a variety of silicon chlorides. The structures of the 1,1,3,3‐tetramethylguanidinate‐based compounds were verified by 1H NMR, 13C NMR, XPS, EI‐MS, and elemental analysis. The thermal stability, transport behavior, and vapor pressures of these compounds were evaluated by simultaneous thermal analyses (STA). These compounds are highly stable and those in liquid form are very volatile. Silicon carbonitride (SiCN) thin films were prepared by using bis (tetramethylguanidine)‐dimethyl‐silane as the precursor in helicon wave plasma chemical vapor deposition (HWP‐CVD). The properties of the films were investigated by SEM, AFM, and XPS. The results showed that the films have good uniformities, low friction coefficient, and high hardness, enabling the films for fabrication of semiconductor devices.